Cell Theory & Structure
Cell theory has three basic generalizations, according to the University of California at Davis. These generalizations state that all organisms are composed of one or more cells, the cell is the smallest unit that has properties of life, and life continues as a result of division and growth of single cells.
The Facts
Cell theory is often referred to as cell doctrine. The concept that all organisms are made up of similar units called cells was originally formulated by Matthias Jakob Schleiden and Theodor Schwann in 1839. This theory was developed prior to other important theories in biology including Charles Darwin's theory of evolution in 1859.
History
In 1838, Schleiden, a botanist, and Schwann, a zoologist, had a conversation regarding their respective studies of cells. According to Charles Mallery of the Department of Biology, University of Miami, Schwann saw similarities between plant cells that Schleiden discussed and his own observations of animal tissue cells. They proceeded to Schwann's lab and wrote a book about plant and animal cells the following year.
Features
Schwann and Schleiden's conclusions regarding cells stated that cells are a unit of structure, organization and physiology in living things. Furthermore, the cell acts as both a unique entity and as a building block in organism construction, and cells result from free-cell formation that is similar to crystals. Today, biologists know that their first two statements are true, however the third it incorrect. In fact, it was Rudolph Virchow who suggested a more accurate description of cell generation by stating that "all cells only arise from pre-existing cells."
Considerations
While the three generalizations listed in the overview are the core tenets, cell theory has three other statements that add to a more complete picture of cell structure. These tenets state that cells contain hereditary information that passes on from cell to cell during cell division. Furthermore, all cells are considered of the same chemical composition and all energy flow of life (particularly metabolism and biochemical reactions) occur within the cells.
Structure
All cells are considered to have three things in common. Cells have a cell membrane that selects which materials are allowed to pass into and out of the cell. They also have cytoplasm, which is the part of the cell that is enclosed by the cell membrane, and DNA, which is the genetic material of the cell. Furthermore, cells are divided into two types, prokaryotic (simple cells like bacteria) or eukaryotic (more complex cells like plants).
Wednesday, July 7, 2010
Cell Theory
Cell Theory
The discovery of the cell was made possible by the invention of the microscope, which was made possible by improved lens-grinding techniques. Antoni van Leeuwenhoek (1632-1723), a Dutch tradesman, learned to grind lenses and assemble them into simple microscopes. His contemporary Robert Hooke (1635-1703) used such an instrument to observe cork cells, sketches of which appeared in his 1665 publication "Micrographia." Inspired by Hooke's work, Leeuwenhoek began making microscopic examinations of his own. In 1678, he reported to the Royal Society that he had discovered "little animals" -- bacteria and protozoa -- in various samples. The society asked Hooke to confirm Leeuwenhoek's findings, and he did.
protozoaAaron Bell/Visuals Unlimited/Getty ImagesIn 1678, Antoni van Leeuwenhook reported that he had observed "little animals" -- protozoa -- through a microscope.
This paved the way for wide acceptance that a hidden world existed just beyond the limits of human vision and encouraged many scientists to take up the microscope in their investigations. One such scientist was German botanist Matthias Jakob Schleiden (1804-1881), who looked at numerous plant samples. Schleiden was the first to recognize that all plants, and all the different parts of plants, are composed of cells. While having dinner with zoologist Theodor Schwann (1810-1882), Schleiden mentioned his idea. Schwann, who came to similar conclusions while studying animal tissues, quickly saw the implications of their work. In 1839, he published "Microscopic Investigations on the Accordance in the Structure and Growth of Plants and Animals," which included the first statement of the cell theory: All living things are made up of cells.
Then, in 1858, Rudolf Virchow (1821-1902) extended the work of Schleiden and Schwann by proposing that all living cells must rise from pre-existing cells. This was a radical idea at the time because most people, scientists included, believed that nonliving matter could spontaneously generate living tissue. The inexplicable appearance of maggots on a piece of meat was often given as evidence to support the concept of spontaneous generation. But a famous scientist by the name of Louis Pasteur (1822-1895) set out to disprove spontaneous generation with a now-classic experiment that both firmly established the cell theory beyond doubt and solidified the basic steps of the modern scientific method.
The discovery of the cell was made possible by the invention of the microscope, which was made possible by improved lens-grinding techniques. Antoni van Leeuwenhoek (1632-1723), a Dutch tradesman, learned to grind lenses and assemble them into simple microscopes. His contemporary Robert Hooke (1635-1703) used such an instrument to observe cork cells, sketches of which appeared in his 1665 publication "Micrographia." Inspired by Hooke's work, Leeuwenhoek began making microscopic examinations of his own. In 1678, he reported to the Royal Society that he had discovered "little animals" -- bacteria and protozoa -- in various samples. The society asked Hooke to confirm Leeuwenhoek's findings, and he did.
protozoaAaron Bell/Visuals Unlimited/Getty ImagesIn 1678, Antoni van Leeuwenhook reported that he had observed "little animals" -- protozoa -- through a microscope.
This paved the way for wide acceptance that a hidden world existed just beyond the limits of human vision and encouraged many scientists to take up the microscope in their investigations. One such scientist was German botanist Matthias Jakob Schleiden (1804-1881), who looked at numerous plant samples. Schleiden was the first to recognize that all plants, and all the different parts of plants, are composed of cells. While having dinner with zoologist Theodor Schwann (1810-1882), Schleiden mentioned his idea. Schwann, who came to similar conclusions while studying animal tissues, quickly saw the implications of their work. In 1839, he published "Microscopic Investigations on the Accordance in the Structure and Growth of Plants and Animals," which included the first statement of the cell theory: All living things are made up of cells.
Then, in 1858, Rudolf Virchow (1821-1902) extended the work of Schleiden and Schwann by proposing that all living cells must rise from pre-existing cells. This was a radical idea at the time because most people, scientists included, believed that nonliving matter could spontaneously generate living tissue. The inexplicable appearance of maggots on a piece of meat was often given as evidence to support the concept of spontaneous generation. But a famous scientist by the name of Louis Pasteur (1822-1895) set out to disprove spontaneous generation with a now-classic experiment that both firmly established the cell theory beyond doubt and solidified the basic steps of the modern scientific method.
Brain Anatomy
Brain Anatomy
The cerebellum is the portion of the brain that is responsible for the coordination of movement. It is located just above the brainstem, beneath the occipital lobes at the base of the skull. Similar to the cerebrum, the cerebellum contains several folded bulges which add to its surface area and therefore increases the quantity of information that can be processed.
The cerebellum controls movement by processing and coordinating sensory input, then sending the information to the motor nerves. Whenever we perform a physical task, the cerebellum records the information so that we don't forget it. That is why we don't have to re-learn how to walk, run or ride a bike. Think you know all about the cerebellum and the brain? Take the Human Brain Quiz and test your knowledge of human brain anatomy.
The cerebellum is the portion of the brain that is responsible for the coordination of movement. It is located just above the brainstem, beneath the occipital lobes at the base of the skull. Similar to the cerebrum, the cerebellum contains several folded bulges which add to its surface area and therefore increases the quantity of information that can be processed.
The cerebellum controls movement by processing and coordinating sensory input, then sending the information to the motor nerves. Whenever we perform a physical task, the cerebellum records the information so that we don't forget it. That is why we don't have to re-learn how to walk, run or ride a bike. Think you know all about the cerebellum and the brain? Take the Human Brain Quiz and test your knowledge of human brain anatomy.
Bacteriophage
Bacteriophage
A bacteriophage (from 'bacteria' and Greek φᾰγεῖν phagein "to eat") is any one of a number of viruses that infect bacteria. Bacteriophages are among the most common biological entities on Earth. The term is commonly used in its shortened form, phage.
Typically, bacteriophages consist of an outer protein capsid enclosing genetic material. The genetic material can be ssRNA, dsRNA, ssDNA, or dsDNA ('ss-' or 'ds-' prefix denotes single-strand or double-strand) long with either circular or linear arrangement. Bacteriophages are much smaller than the bacteria they destroy.
Phages are estimated to be the most widely distributed and diverse entities in the biosphere. Phages are ubiquitous and can be found in all reservoirs populated by bacterial hosts, such as soil or the intestines of animals. One of the densest natural sources for phages and other viruses is sea water, where up to 9×108 virions per milliliter have been found in microbial mats at the surface, and up to 70% of marine bacteria may be infected by phages. They have been used for over 60 years as an alternative to antibiotics in the former Soviet Union and Eastern Europe. They are seen as a possible therapy against multi drug resistant strains of many bacteria.
A bacteriophage (from 'bacteria' and Greek φᾰγεῖν phagein "to eat") is any one of a number of viruses that infect bacteria. Bacteriophages are among the most common biological entities on Earth. The term is commonly used in its shortened form, phage.
Typically, bacteriophages consist of an outer protein capsid enclosing genetic material. The genetic material can be ssRNA, dsRNA, ssDNA, or dsDNA ('ss-' or 'ds-' prefix denotes single-strand or double-strand) long with either circular or linear arrangement. Bacteriophages are much smaller than the bacteria they destroy.
Phages are estimated to be the most widely distributed and diverse entities in the biosphere. Phages are ubiquitous and can be found in all reservoirs populated by bacterial hosts, such as soil or the intestines of animals. One of the densest natural sources for phages and other viruses is sea water, where up to 9×108 virions per milliliter have been found in microbial mats at the surface, and up to 70% of marine bacteria may be infected by phages. They have been used for over 60 years as an alternative to antibiotics in the former Soviet Union and Eastern Europe. They are seen as a possible therapy against multi drug resistant strains of many bacteria.
Diploid
Diploid
The basic set of chromosomes in an organism is called the monoploid number. This number is indicated by x. In an organism, the ploidy of cells can vary. Humans and almost all mammals, have diploid cells. The gametes or sex cells (egg and sperm) are haploid cells. In this article, we shall understand what is a diploid cell. You can read more on biology.
What is a Diploid Cell?
According to the diploid cell definition, it is an organism or cell that contains double set of chromosome (2n), one inherited from the mother and one inherited from father. Another diploid cell definition also includes an individual that contains a double set of chromosome per cell. The somatic tissues of higher plants and animals contain diploid chromosome content.
Almost all animals have diploid number of cells. All the organisms that produce sexually, have two copies of chromosomes that have different origins, that is, paternal and maternal. This help in mixing of genes that gives rise to better progeny.
There are a few species that have haplodiploid cells. Here, one sex (mostly male) contains haploid cells and the other sex (female) has diploid cells. The male have developed from unfertilized eggs and the females develop from fertilized eggs. Thus, they have a complete set of chromosome. The diploid cell example in such a case, includes insects like ants, bees and wasps, where the queen has diploid number of chromosome. You can read more on human genetics.
Another, diploid cell example is the human race. Humans contain 2 set of chromosomes in their cells. The somatic cells or non-sex cells contains 46 chromosomes each. There are 22 sets of autosomal chromosomes and 1 set of sex chromosome. This brings the total to 23 sets of chromosomes. After fertilization, the somatic cells receive 23 chromosomes from each parent making the number of chromosomes in the cell 46.
The basic set of chromosomes in an organism is called the monoploid number. This number is indicated by x. In an organism, the ploidy of cells can vary. Humans and almost all mammals, have diploid cells. The gametes or sex cells (egg and sperm) are haploid cells. In this article, we shall understand what is a diploid cell. You can read more on biology.
What is a Diploid Cell?
According to the diploid cell definition, it is an organism or cell that contains double set of chromosome (2n), one inherited from the mother and one inherited from father. Another diploid cell definition also includes an individual that contains a double set of chromosome per cell. The somatic tissues of higher plants and animals contain diploid chromosome content.
Almost all animals have diploid number of cells. All the organisms that produce sexually, have two copies of chromosomes that have different origins, that is, paternal and maternal. This help in mixing of genes that gives rise to better progeny.
There are a few species that have haplodiploid cells. Here, one sex (mostly male) contains haploid cells and the other sex (female) has diploid cells. The male have developed from unfertilized eggs and the females develop from fertilized eggs. Thus, they have a complete set of chromosome. The diploid cell example in such a case, includes insects like ants, bees and wasps, where the queen has diploid number of chromosome. You can read more on human genetics.
Another, diploid cell example is the human race. Humans contain 2 set of chromosomes in their cells. The somatic cells or non-sex cells contains 46 chromosomes each. There are 22 sets of autosomal chromosomes and 1 set of sex chromosome. This brings the total to 23 sets of chromosomes. After fertilization, the somatic cells receive 23 chromosomes from each parent making the number of chromosomes in the cell 46.
Lysosome
Lysosome
Structure
The human body comprises of about 50 to 75 trillion cells. The cell is the smallest unit of life and is often called the building block of life. A single cell is made up of many different organelles, that have specific functions, such as the nucleus, Golgi bodies, mitochondria, peroxisomes and lysosomes. In this article, we shall learn about lysosome structure, its function and its importance in the cell.
Lysosomes
Lysosomes are membrane bound organelles that are found in the cytoplasm of both plant and animal cells. The word lysosome was derived from two Greek words, 'lysis' which means destruction or dissolution and 'soma' which means 'body'. Lysosomes were discovered in 1949, by a Belgian cytologist, Christian de Duve.
Lysosome StructureLysosomes are actually membranous sacs filled with enzymes. They are found in all eukaryotic cells and act as 'garbage disposal' or the 'digester' of the cell. Lysosomes are spherical bag like structures that are bound by a single layer membrane, however, the lysosome shape and size may vary to some extent in different organisms. The lysosome size ranges between 0.1 to 1.2μm. The membrane that surrounds the lysosome, protects the rest of the cell from the hydrolytic or digestive enzymes that are contained in the lysosomes.
Lysosomes are manufactured by the Golgi apparatus, by budding, in the cell and the various digestive enzymes, that are present in the lysosomes are produced in the endoplasmic reticulum. These enzymes are then transported to the Golgi apparatus and are distributed to the lysosomes. Some examples of enzymes present in the lysosomes include nucleases, proteases, lipases and carbohydrases. These enzymes are used to dissolve nucleic acids, proteins, lipids and carbohydrates, respectively. All these enzymes are typically hydrolytic and can digest cellular macromolecules. Lysosomes are acidic, with a pH of 4.8. This acidic pH is maintained by pumping protons, from the cytosol that has a pH of 7.2. The protons are pumped across the membrane via proton pumps and chloride ion channels. The membrane thus acts as a protective barrier, that protects the cytosol and the rest of the cell from the hydrolytic enzymes within the lysosome.
Lysosome Function
Lysosomes act as disposal system of the cell. They break down complex proteins, carbohydrates, lipids and other macromolecules into simpler compounds. These simple compounds are returned to the cytoplasm and are used as new cell building materials. They are used for digestion of cellular waste products, dead cells or extracellular material such as foreign invading microbes, that pose a threat to the cell by phagocytosis process. However, phagocytosis is just one process that helps to get rid of unwanted material in the cell. Lysosomes are also involved in other digestive processes including endocytosis and autophagy. Another interesting function of the lysosomes is to repair the damage to the plasma membrane. They serve as membrane patch and help in sealing the wound in the plasma membrane. Lysosomes are also involved in programmed cell death, or autolysis, which is a catabolic process involving degradation of the cell's own components. This is the reason why lysosomes are often called as 'suicide sacs'. Read more on lysosomes function.
Lysosome Defects
Any malfunctioning of the lysosomes or any of the digestive proteins, results in lysosomal storage diseases, such as Tay-Sachs disease and Pompe's disease. These diseases are caused by defective function of the lysosomes or in absence of any of the digestive proteins or lysosomal hydrolytic enzymes.
Structure
The human body comprises of about 50 to 75 trillion cells. The cell is the smallest unit of life and is often called the building block of life. A single cell is made up of many different organelles, that have specific functions, such as the nucleus, Golgi bodies, mitochondria, peroxisomes and lysosomes. In this article, we shall learn about lysosome structure, its function and its importance in the cell.
Lysosomes
Lysosomes are membrane bound organelles that are found in the cytoplasm of both plant and animal cells. The word lysosome was derived from two Greek words, 'lysis' which means destruction or dissolution and 'soma' which means 'body'. Lysosomes were discovered in 1949, by a Belgian cytologist, Christian de Duve.
Lysosome StructureLysosomes are actually membranous sacs filled with enzymes. They are found in all eukaryotic cells and act as 'garbage disposal' or the 'digester' of the cell. Lysosomes are spherical bag like structures that are bound by a single layer membrane, however, the lysosome shape and size may vary to some extent in different organisms. The lysosome size ranges between 0.1 to 1.2μm. The membrane that surrounds the lysosome, protects the rest of the cell from the hydrolytic or digestive enzymes that are contained in the lysosomes.
Lysosomes are manufactured by the Golgi apparatus, by budding, in the cell and the various digestive enzymes, that are present in the lysosomes are produced in the endoplasmic reticulum. These enzymes are then transported to the Golgi apparatus and are distributed to the lysosomes. Some examples of enzymes present in the lysosomes include nucleases, proteases, lipases and carbohydrases. These enzymes are used to dissolve nucleic acids, proteins, lipids and carbohydrates, respectively. All these enzymes are typically hydrolytic and can digest cellular macromolecules. Lysosomes are acidic, with a pH of 4.8. This acidic pH is maintained by pumping protons, from the cytosol that has a pH of 7.2. The protons are pumped across the membrane via proton pumps and chloride ion channels. The membrane thus acts as a protective barrier, that protects the cytosol and the rest of the cell from the hydrolytic enzymes within the lysosome.
Lysosome Function
Lysosomes act as disposal system of the cell. They break down complex proteins, carbohydrates, lipids and other macromolecules into simpler compounds. These simple compounds are returned to the cytoplasm and are used as new cell building materials. They are used for digestion of cellular waste products, dead cells or extracellular material such as foreign invading microbes, that pose a threat to the cell by phagocytosis process. However, phagocytosis is just one process that helps to get rid of unwanted material in the cell. Lysosomes are also involved in other digestive processes including endocytosis and autophagy. Another interesting function of the lysosomes is to repair the damage to the plasma membrane. They serve as membrane patch and help in sealing the wound in the plasma membrane. Lysosomes are also involved in programmed cell death, or autolysis, which is a catabolic process involving degradation of the cell's own components. This is the reason why lysosomes are often called as 'suicide sacs'. Read more on lysosomes function.
Lysosome Defects
Any malfunctioning of the lysosomes or any of the digestive proteins, results in lysosomal storage diseases, such as Tay-Sachs disease and Pompe's disease. These diseases are caused by defective function of the lysosomes or in absence of any of the digestive proteins or lysosomal hydrolytic enzymes.
Animal Cell
Animal Cell
Animal Cell ModelAs the name signifies, an animal cell is an advanced, eukaryotic type of cell isolated from animal species. If you have learned plant and animal cell differences, you might be already aware that the latter type is nearly circular in shape. An animal cell lacks the protective cell wall, hence the shape of the cell is framed by a plasma membrane. Inside the cell, there are various membrane bound organelles, each of which is responsible for specific functions.
Topics concerning plant cell vs animal cell and their similarities are introductory chapters in science subjects. They provide information about the types and functions of cells. However, demonstrating cell models is a better way to understand the lessons precisely and also, in an interactive manner. Thus, in biology experiments, students are often given assignments to prepare an animal cell model or diagram.
How to Make an Animal Cell Model?
Before you get involved in making an animal cell model, try to understand the anatomy and parts of a typical eukaryotic cell. A better alternative is to examine the shapes and structures of the organelles in a labeled animal cell diagram. This will help you in coming up with innovative ideas for your project. With a little creativity and forethought, you can prepare an animal cell model with less effort.
Following is a step by step procedure for building a labeled animal cell model:
Required Materials and Supplies
* Colorful animal cell picture
* Styrofoam balls
* Playdough (or modeling clay)
* Cardboard for base
* Pipe cleaners
* T - Pins
* Duct tape or regular tape
* Glue or adhesive
* Ruler
* Box cutter
* Knife and scissors
Steps for Building an Animal Cell
Step # 1
Gather the required supplies for building an animal cell model. Select a large and detailed animal cell picture with colorful parts. For the cell nucleus part, you can purchase a small ball or Styrofoam block from the garden supplier. You can make remaining cell organelles from this block or playdough.
Step # 2
It is better to make the individual organelles before and stick to the cardboard base with adhesive pr pins. Otherwise, working directly on the model will make the job more tedious and messy. Accordingly, prepare a list of the cell parts, which you are supposed to build. Remember to make appropriate sized organelles with respect to the model size.
Step # 3
Lay the cardboard base and start building an animal cell model. To create plasma membrane, you can use a large rubber band or paint with a brush. Then, stick the nucleus (round plastic ball or Styrofoam ball) in the center with the help of duct tape or glue. For chromatin structures, you can use pipe cleaners in a random manner.
Step # 4
Cut out different shapes of Styrofoam that resemble cell organelles and color each of them with different shades. With reference to the labeled animal cell diagram, attach the colored pieces to the cardboard one by one, making sure that they occupy the correct positions in the animal cell model.
Step # 5
For better understanding, prepare a key on a paper sheet and illustrate the various cell parts. Ensure that the spellings are correct and if possible, explain their main functions in one or two lines. Finally, document the steps of making animal cell model, especially if you are presenting in a science fair project.
So, isn't making animal cell model interesting? After completion of the task, you will be familiar with the functions of the organelles. You can look out for different animal cell model ideas and choose the best for your project. Be accurate with the cell shape, structure and organelles to get good scores. Next time, learn about plant cell structure and parts and portray your understandings by building a plant cell model.
Animal Cell ModelAs the name signifies, an animal cell is an advanced, eukaryotic type of cell isolated from animal species. If you have learned plant and animal cell differences, you might be already aware that the latter type is nearly circular in shape. An animal cell lacks the protective cell wall, hence the shape of the cell is framed by a plasma membrane. Inside the cell, there are various membrane bound organelles, each of which is responsible for specific functions.
Topics concerning plant cell vs animal cell and their similarities are introductory chapters in science subjects. They provide information about the types and functions of cells. However, demonstrating cell models is a better way to understand the lessons precisely and also, in an interactive manner. Thus, in biology experiments, students are often given assignments to prepare an animal cell model or diagram.
How to Make an Animal Cell Model?
Before you get involved in making an animal cell model, try to understand the anatomy and parts of a typical eukaryotic cell. A better alternative is to examine the shapes and structures of the organelles in a labeled animal cell diagram. This will help you in coming up with innovative ideas for your project. With a little creativity and forethought, you can prepare an animal cell model with less effort.
Following is a step by step procedure for building a labeled animal cell model:
Required Materials and Supplies
* Colorful animal cell picture
* Styrofoam balls
* Playdough (or modeling clay)
* Cardboard for base
* Pipe cleaners
* T - Pins
* Duct tape or regular tape
* Glue or adhesive
* Ruler
* Box cutter
* Knife and scissors
Steps for Building an Animal Cell
Step # 1
Gather the required supplies for building an animal cell model. Select a large and detailed animal cell picture with colorful parts. For the cell nucleus part, you can purchase a small ball or Styrofoam block from the garden supplier. You can make remaining cell organelles from this block or playdough.
Step # 2
It is better to make the individual organelles before and stick to the cardboard base with adhesive pr pins. Otherwise, working directly on the model will make the job more tedious and messy. Accordingly, prepare a list of the cell parts, which you are supposed to build. Remember to make appropriate sized organelles with respect to the model size.
Step # 3
Lay the cardboard base and start building an animal cell model. To create plasma membrane, you can use a large rubber band or paint with a brush. Then, stick the nucleus (round plastic ball or Styrofoam ball) in the center with the help of duct tape or glue. For chromatin structures, you can use pipe cleaners in a random manner.
Step # 4
Cut out different shapes of Styrofoam that resemble cell organelles and color each of them with different shades. With reference to the labeled animal cell diagram, attach the colored pieces to the cardboard one by one, making sure that they occupy the correct positions in the animal cell model.
Step # 5
For better understanding, prepare a key on a paper sheet and illustrate the various cell parts. Ensure that the spellings are correct and if possible, explain their main functions in one or two lines. Finally, document the steps of making animal cell model, especially if you are presenting in a science fair project.
So, isn't making animal cell model interesting? After completion of the task, you will be familiar with the functions of the organelles. You can look out for different animal cell model ideas and choose the best for your project. Be accurate with the cell shape, structure and organelles to get good scores. Next time, learn about plant cell structure and parts and portray your understandings by building a plant cell model.
Angiosperms and Gymnosperms
Angiosperms and Gymnosperms
The seed bearing plants are broadly divided into a single class known as Sprematophyta, which is further sub-divided into angiosperms and gymnosperms. The word gymnosperm is derived from Greek word gymnospermos, meaning 'naked seed'. Angiosperms and gymnosperms are both seed bearing plants. Although, differences are more distinct, the points mentioned below are some of the similarities between them.
* They are capable of producing pollen for fertilization and their fertilization is siphonogamous, i.e through a pollen tube. Gymnosperms mostly depend on wind pollination and some angiosperms are also dependent on the same agent.
* The sporophyte of angiosperms and gymnosperm is differentiated into root, stem and leaves. * Apart from primary growth, their stem undergoes expansion by secondary growth.
* Like angiosperms, gymnosperms also have vessels and companion cells. The vascular system is common for the both of them consisting of conjoint and vascular bundles (open and collateral).
* Ovules of angiosperms and gymnosperms develop into seeds. The mode of seed germination is epigeal and hypogeal or both.
* One distinct similarity is, reduced gametophytic phase of both angiosperms and gymnosperms.
* Polyembryony, a common feature of gymnosperms is also prevalent in some angiosperms and a suspensor is formed during the embryo development phase.
The seed bearing plants are broadly divided into a single class known as Sprematophyta, which is further sub-divided into angiosperms and gymnosperms. The word gymnosperm is derived from Greek word gymnospermos, meaning 'naked seed'. Angiosperms and gymnosperms are both seed bearing plants. Although, differences are more distinct, the points mentioned below are some of the similarities between them.
* They are capable of producing pollen for fertilization and their fertilization is siphonogamous, i.e through a pollen tube. Gymnosperms mostly depend on wind pollination and some angiosperms are also dependent on the same agent.
* The sporophyte of angiosperms and gymnosperm is differentiated into root, stem and leaves. * Apart from primary growth, their stem undergoes expansion by secondary growth.
* Like angiosperms, gymnosperms also have vessels and companion cells. The vascular system is common for the both of them consisting of conjoint and vascular bundles (open and collateral).
* Ovules of angiosperms and gymnosperms develop into seeds. The mode of seed germination is epigeal and hypogeal or both.
* One distinct similarity is, reduced gametophytic phase of both angiosperms and gymnosperms.
* Polyembryony, a common feature of gymnosperms is also prevalent in some angiosperms and a suspensor is formed during the embryo development phase.
Kingston Computing Expert Charts Amputees' Rehabilitation
Kingston Computing Expert Charts Amputees' Rehabilitation
New Kingston University research could reduce the recovery time for lower limb amputees by helping health professionals chart patients' progress more easily. Tom Geake, from Kingston's Mobile Information and Network Technologies Research Centre, has designed a new method of interpreting results from the locomotor capabilities index, used by clinicians to assess amputees' improvement in the four-week period after they have been fitted with a socket and artificial limb.
Using the index, amputees are set goals at the start of their rehabilitation programme which are later reviewed to see how much progress has been made. Patients are assessed on 14 activities, ranging from basic tasks such as rising from a chair to more advanced tasks such as walking outside on uneven ground. Their capability is recorded on a scale of 0-3. Until now there had been no simple method for therapists to analyse the data gathered, Mr Geake said. His research has produced a new system using colour and shape on patients' charts to improve the process. "Time is scarce in the NHS, so the faster a clinician can assess a person's rehabilitation the better," Mr Geake said. "Rather than having to think about what each figure tells them, the system allows the therapist to see at a glance which goals have been reached from the colour and shape they see on the chart. They can draw conclusions more easily about the patient's progress and, if necessary, suggest changes to their individual recovery programme." Another advantage is that patients can also understand the contents. "Seeing which activities they need to concentrate on to achieve their goals helps them become more motivated - a key factor in their rehabilitation," Mr Geake said.
The research was commissioned by Dr Rajiv Hanspal, a consultant in rehabilitation medicine at the Royal National Orthopaedic Hospital. Dr Hanspal's colleague, senior physiotherapist Jennifer Fulton, and Dr David Wertheim from the University's School of Computing and Information Systems were also involved in the project.
Mr Geake presented the research at the National Scientific Meeting of the International Society for Prosthetics and Orthotics, where he was awarded the British Limbless Ex-Servicemen's Association prize. He is due to outline his findings to NHS representatives with a view to further trials of the system.
Beyond genes: Mapping the “brave new world” of the epigenome
With the human genome — the “Book of Life” — in hand, scientists are trying to fill the pages of an anthology of closely related volumes that explain how simple chemical modifications to DNA and its packaging proteins turn genes on and off in ways that impact human health. Those companion tomes involve the human “epigenome,” the topic of the cover story in the current issue of Chemical & Engineering News, ACS’ weekly newsmagazine.
C&EN contributing editor Laura Cassiday notes in the article that the basic DNA sequence in the genome remains relatively constant throughout a person’s life. Epigenomic changes, however, can cause dramatic alterations how genes work without altering the underlying gene sequence. Studies link some of those changes to aging, cancer, certain birth defects, autoimmune diseases and other health problems.
The article describes ongoing epigenomics research and notes that the field is getting a boost from the National Institutes of Health Roadmap Epigenomics Program. It will fund more than $190 million in research over the next five years to support development of new technologies for mapping the epigenome. “With a brave new world awaiting exploration beyond the genome, it’s not surprising that epigenetics has risen from near obscurity to one of the hottest fields in biology,” the article notes.
C&EN contributing editor Laura Cassiday notes in the article that the basic DNA sequence in the genome remains relatively constant throughout a person’s life. Epigenomic changes, however, can cause dramatic alterations how genes work without altering the underlying gene sequence. Studies link some of those changes to aging, cancer, certain birth defects, autoimmune diseases and other health problems.
The article describes ongoing epigenomics research and notes that the field is getting a boost from the National Institutes of Health Roadmap Epigenomics Program. It will fund more than $190 million in research over the next five years to support development of new technologies for mapping the epigenome. “With a brave new world awaiting exploration beyond the genome, it’s not surprising that epigenetics has risen from near obscurity to one of the hottest fields in biology,” the article notes.
DNA
DNA
(DNA) is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms and some viruses. The main role of DNA molecules is the long-term storage of information. DNA is often compared to a set of blueprints, like a recipe or a code, since it contains the instructions needed to construct other components of cells, such as proteins and RNA molecules. The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in regulating the use of this genetic information.
Chemically, DNA consists of two long polymers of simple units called nucleotides, with backbones made of sugars and phosphate groups joined by ester bonds. These two strands run in opposite directions to each other and are therefore anti-parallel. Attached to each sugar is one of four types of molecules called bases. It is the sequence of these four bases along the backbone that encodes information. This information is read using the genetic code, which specifies the sequence of the amino acids within proteins. The code is read by copying stretches of DNA into the related nucleic acid RNA, in a process called transcription.
Within cells, DNA is organized into long structures called chromosomes. These chromosomes are duplicated before cells divide, in a process called DNA replication. Eukaryotic organisms (animals, plants, fungi, and protists) store most of their DNA inside the cell nucleus and some of their DNA in organelles, such as mitochondria or chloroplasts.[1] In contrast, prokaryotes (bacteria and archaea) store their DNA only in the cytoplasm. Within the chromosomes, chromatin proteins such as histones compact and organize DNA. These compact structures guide the interactions between DNA and other proteins, helping control which parts of the DNA are transcribed.
Deoxyribonucleic (DNA) is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms and some viruses. The main role of DNA molecules is the long-term storage of information. DNA is often compared to a set of blueprints, like a recipe or a code, since it contains the instructions needed to construct other components of cells, such as proteins and RNA molecules. The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in regulating the use of this genetic information.
Chemically, DNA consists of two long polymers of simple units called nucleotides, with backbones made of sugars and phosphate groups joined by ester bonds. These two strands run in opposite directions to each other and are therefore anti-parallel. Attached to each sugar is one of four types of molecules called bases. It is the sequence of these four bases along the backbone that encodes information. This information is read using the genetic code, which specifies the sequence of the amino acids within proteins. The code is read by copying stretches of DNA into the related nucleic acid RNA, in a process called transcription.
Within cells, DNA is organized into long structures called chromosomes. These chromosomes are duplicated before cells divide, in a process called DNA replication. Eukaryotic organisms (animals, plants, fungi, and protists) store most of their DNA inside the cell nucleus and some of their DNA in organelles, such as mitochondria or chloroplasts. In contrast, prokaryotes (bacteria and archaea) store their DNA only in the cytoplasm. Within the chromosomes, chromatin proteins such as histones compact and organize DNA. These compact structures guide the interactions between DNA and other proteins, helping control which parts of the DNA are transcribed.
Types of RNA
Types of RNA
Messenger RNA (mRNA) is the RNA that carries information from DNA to the ribosome, the sites of protein synthesis (translation) in the cell. The coding sequence of the mRNA determines the amino acid sequence in the protein that is produced. Many RNAs do not code for protein however (about 97% of the transcriptional output is non-protein-coding in eukaryotes ).
These so-called non-coding RNAs ("ncRNA") can be encoded by their own genes (RNA genes), but can also derive from mRNA introns. The most prominent examples of non-coding RNAs are transfer RNA (tRNA) and ribosomal RNA (rRNA), both of which are involved in the process of translation. There are also non-coding RNAs involved in gene regulation, RNA processing and other roles. Certain RNAs are able to catalyse chemical reactions such as cutting and ligating other RNA molecules, and the catalysis of peptide bond formation in the ribosome;[3] these are known as ribozymes
Messenger RNA (mRNA) carries information about a protein sequence to the ribosomes, the protein synthesis factories in the cell. It is coded so that every three nucleotides (a codon) correspond to one amino acid. In eukaryotic cells, once precursor mRNA (pre-mRNA) has been transcribed from DNA, it is processed to mature mRNA. This removes its introns—non-coding sections of the pre-mRNA. The mRNA is then exported from the nucleus to the cytoplasm, where it is bound to ribosomes and translated into its corresponding protein form with the help of tRNA. In prokaryotic cells, which do not have nucleus and cytoplasm compartments, mRNA can bind to ribosomes while it is being transcribed from DNA. After a certain amount of time the message degrades into its component nucleotides with the assistance of ribonucleases.
Transfer RNA (tRNA) is a small RNA chain of about 80 nucleotides that transfers a specific amino acid to a growing polypeptide chain at the ribosomal site of protein synthesis during translation. It has sites for amino acid attachment and an anticodon region for codon recognition that binds to a specific sequence on the messenger RNA chain through hydrogen bonding. Ribosomal RNA (rRNA) is the catalytic component of the ribosomes. Eukaryotic ribosomes contain four different rRNA molecules: 18S, 5.8S, 28S and 5S rRNA. Three of the rRNA molecules are synthesized in the nucleolus, and one is synthesized elsewhere. In the cytoplasm, ribosomal RNA and protein combine to form a nucleoprotein called a ribosome. The ribosome binds mRNA and carries out protein synthesis. Several ribosomes may be attached to a single mRNA at any time. rRNA is extremely abundant and makes up 80% of the 10 mg/ml RNA found in a typical eukaryotic cytoplasm.
Transfer-messenger RNA (tmRNA) is found in many bacteria and plastids. It tags proteins encoded by mRNAs that lack stop codons for degradation and prevents the ribosome from stalling.
Regulatory RNAs
Several types of RNA can downregulate gene expression by being complementary to a part of an mRNA or a gene's DNA. MicroRNAs (miRNA; 21-22 nt) are found in eukaryotes and act through RNA interference (RNAi), where an effector complex of miRNA and enzymes can break down mRNA which the miRNA is complementary to, block the mRNA from being translated, or accelerate its degradation. While small interfering RNAs (siRNA; 20-25 nt) are often produced by breakdown of viral RNA, there are also endogenous sources of siRNAs. siRNAs act through RNA interference in a fashion similar to miRNAs. Some miRNAs and siRNAs can cause genes they target to be methylated, thereby decreasing or increasing transcription of those genes. Animals have Piwi-interacting RNAs (piRNA; 29-30 nt) which are active in germline cells and are thought to be a defense against transposons and play a role in gametogenesis. Many prokaryotes have CRISPR RNAs, a regulatory system similar to RNA interference. Antisense RNAs are widespread; most downregulate a gene, but a few are activators of transcription. One way antisense RNA can act is by binding to an mRNA, forming double-stranded RNA that is enzymatically degraded. There are many long noncoding RNAs that regulate genes in eukaryotes, one such RNA is Xist which coats one X chromosome in female mammals and inactivates it.
An mRNA may contain regulatory elements itself, such as riboswitches, in the 5' untranslated region or 3' untranslated region; these cis-regulatory elements regulate the activity of that mRNA.The untranslated regions can also contain elements that regulate other genes. In RNA processingUridine to pseudouridine is a common RNA modification.
Many RNAs are involved in modifying other RNAs. Introns are spliced out of pre-mRNA by spliceosomes, which contain several small nuclear RNAs (snRNA),or the introns can be ribozymes that are spliced by themselves.RNA can also be altered by having its nucleotides modified to other nucleotides than A, C, G and U. In eukaryotes, modifications of RNA nucleotides are generally directed by small nucleolar RNAs (snoRNA; 60-300 nt),found in the nucleolus and cajal bodies. snoRNAs associate with enzymes and guide them to a spot on an RNA by basepairing to that RNA. These enzymes then perform the nucleotide modification. rRNAs and tRNAs are extensively modified, but snRNAs and mRNAs can also be the target of base modification. RNA genomes
Like DNA, RNA can carry genetic information. RNA viruses have genomes composed of RNA, and a variety of proteins encoded by that genome. The viral genome is replicated by some of those proteins, while other proteins protect the genome as the virus particle moves to a new host cell. Viroids are another group of pathogens, but they consist only of RNA, do not encode any protein and are replicated by a host plant cell's polymerase. In reverse transcription
Reverse transcribing viruses replicate their genomes by reverse transcribing DNA copies from their RNA; these DNA copies are then transcribed to new RNA. Retrotransposons also spread by copying DNA and RNA from one another, and telomerase contains an RNA that is used as template for building the ends of eukaryotic chromosomes. Double-stranded RNA
Double-stranded RNA (dsRNA) is RNA with two complementary strands, similar to the DNA found in all cells. dsRNA forms the genetic material of some viruses (double-stranded RNA viruses). Double-stranded RNA such as viral RNA or siRNA can trigger RNA interference in eukaryotes, as well as interferon response in vertebrates.
Comparison with DNA
Comparison with DNA
RNA and DNA are both nucleic acids, but differ in three main ways. First, unlike DNA which is double-stranded, RNA is a single-stranded molecule in most of its biological roles and has a much shorter chain of nucleotides. Second, while DNA contains deoxyribose, RNA contains ribose (there is no hydroxyl group attached to the pentose ring in the 2' position in DNA). These hydroxyl groups make RNA less stable than DNA because it is more prone to hydrolysis. Third, the complementary base to adenine is not thymine, as it is in DNA, but rather uracil, which is an unmethylated form of thymine.
Like DNA, most biologically active RNAs, including mRNA, tRNA, rRNA, snRNAs and other non-coding RNAs, contain self-complementary sequences that allow parts of the RNA to fold and pair with itself to form double helices. Structural analysis of these RNAs has revealed that they are highly structured. Unlike DNA, their structures do not consist of long double helices but rather collections of short helices packed together into structures akin to proteins. In this fashion, RNAs can achieve chemical catalysis, like enzymes. For instance, determination of the structure of the ribosome—an enzyme that catalyzes peptide bond formation—revealed that its active site is composed entirely of RNA.
RNA and DNA are both nucleic acids, but differ in three main ways. First, unlike DNA which is double-stranded, RNA is a single-stranded molecule in most of its biological roles and has a much shorter chain of nucleotides. Second, while DNA contains deoxyribose, RNA contains ribose (there is no hydroxyl group attached to the pentose ring in the 2' position in DNA). These hydroxyl groups make RNA less stable than DNA because it is more prone to hydrolysis. Third, the complementary base to adenine is not thymine, as it is in DNA, but rather uracil, which is an unmethylated form of thymine.
Like DNA, most biologically active RNAs, including mRNA, tRNA, rRNA, snRNAs and other non-coding RNAs, contain self-complementary sequences that allow parts of the RNA to fold and pair with itself to form double helices. Structural analysis of these RNAs has revealed that they are highly structured. Unlike DNA, their structures do not consist of long double helices but rather collections of short helices packed together into structures akin to proteins. In this fashion, RNAs can achieve chemical catalysis, like enzymes. For instance, determination of the structure of the ribosome—an enzyme that catalyzes peptide bond formation—revealed that its active site is composed entirely of RNA.
Ribonucleic acid (RNA)
Ribonucleic acid (RNA)
Ribonucleic acid (RNA) is a biologically important type of molecule that consists of a long chain of nucleotide units. Each nucleotide consists of a nitrogenous base, a ribose sugar, and a phosphate. RNA is very similar to DNA, but differs in a few important structural details: in the cell, RNA is usually single-stranded, while DNA is usually double-stranded; RNA nucleotides contain ribose while DNA contains deoxyribose (a type of ribose that lacks one oxygen atom); and RNA has the base uracil rather than thymine that is present in DNA. RNA is transcribed from DNA by enzymes called RNA polymerases and is generally further processed by other enzymes. RNA is central to protein synthesis. Here, a type of RNA called messenger RNA carries information from DNA to structures called ribosomes. These ribosomes are made from proteins and ribosomal RNAs, which come together to form a molecular machine that can read messenger RNAs and translate the information they carry into proteins. There are many RNAs with other roles – in particular regulating which genes are expressed, but also as the genomes of most viruses.
Ribonucleic acid (RNA) is a biologically important type of molecule that consists of a long chain of nucleotide units. Each nucleotide consists of a nitrogenous base, a ribose sugar, and a phosphate. RNA is very similar to DNA, but differs in a few important structural details: in the cell, RNA is usually single-stranded, while DNA is usually double-stranded; RNA nucleotides contain ribose while DNA contains deoxyribose (a type of ribose that lacks one oxygen atom); and RNA has the base uracil rather than thymine that is present in DNA. RNA is transcribed from DNA by enzymes called RNA polymerases and is generally further processed by other enzymes. RNA is central to protein synthesis. Here, a type of RNA called messenger RNA carries information from DNA to structures called ribosomes. These ribosomes are made from proteins and ribosomal RNAs, which come together to form a molecular machine that can read messenger RNAs and translate the information they carry into proteins. There are many RNAs with other roles – in particular regulating which genes are expressed, but also as the genomes of most viruses.
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