2.1 describe the levels of organisation within organisms: organelles, cells, tissues, organs and systems
b) Cell Structure
2.2 recognise cell structures, including the nucleus, cytoplasm, cell membrane, cell wall, chloroplast and vacuole
2.3 describe the functions of the nucleus, cytoplasm, cell membrane, cell wall, chloroplast and vacuole
2.4 describe the differences between plant and animal cells
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| Animal cell |
- A cell membrane is like a sieve, it controls what goes in and out of the cell.
- The cytoplasm is where the chemical reactions take place, the mitochondria in the cytoplasm is where respiration takes place to release energy. The cytoplasm also contains enzymes that control the chemical reactions.
- The nucleus is like the 'brain' of the cell, it controls the cell, telling it what to do. It also contains DNA which is important when the cell reproduces.
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| Plant cell |
Plant cells have extra features:
- They have a cell wall, this is made of cellulose. It gives the cell shape and structure and provides support. It also means the cell can't burst, it becomes turgid when it is full of water. (The cell walls are actually impermeable to water, which is why they have small gaps in them called plasmodesmata which allow water to enter via osmosis..)
- They have chloroplasts which contain chlorophyll-the green pigment that allows it to absorb light energy and convert it to chemical energy during photosynthesis. Plants are autotrophs-they can make their own food.
- Plant cells have a permanent vacuole that contains cell sap, it provides support. It is also basically a storage and removes waste, and provides/maintains the cell structure.
Feature
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Animal
Cell
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Plant
Cell
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Nucleus
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Yes
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Yes
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Cytoplasm
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Yes
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Yes
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Cell
Membrane
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Yes
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Yes
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Mitochondria
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Yes
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Wednesday, 4 April 2012Nature and Variety
The specification for section 1 pretty much says it all, I didn't really add anything:
a) Characteristics of living organisms
1.1 recall that living organisms share the following basic characteristics:
b) Variety of living organisms
1.2 describe the common features shared by organisms within the following main groups, plants, animals, fungi, bacteria, protoctists and viruses, and for each group describe examples and their features as follows (details of life cycle and economic importance are not required).
Plants: These are multicellular organisms; they contain chloroplasts and are able to carry out photosynthesis; they have cellulose cell walls; and they store carbohydrates as starch or sucrose.
Examples include flowering plants, such as a cereal (for example maize) and a herbaceous legume (for example peas or beans).
Animals: These are multicellular organisms; they do not have chloroplasts and are not able to carry out photosynthesis; they have no cell walls; they usually have nervous coordination and are able to move from one place to another; they often store carbohydrates as glycogen.
Examples include mammals (for example humans) and insects (for example housefly and mosquito).
Fungi: These are organisms that are not able to carry out photosynthesis; their body is usually organised into a mycelium made from thread-like structures called hyphae, which contain many nuclei; some examples are single-celled; they have cell walls made of chitin; they feed by extracellular secretion of digestive enzymes onto food material and absorption of the organic products; this is known as saprotrophic nutrition; they may store carbohydrates as glycogen.
Examples include Mucor, which has the typical fungal hyphal structure, and yeast which is single-celled.
Bacteria: These are microscopic single-celled organisms; they have a cell wall, cell membrane, cytoplasm and plasmids; they lack a nucleus but contain a circular chromosome of DNA; some bacteria can carry out photosynthesis but most feed off other living or dead organisms.
Examples include Lactobacillus bulgaricus, a rod-shaped bacterium used in the production of yoghurt from milk, and Pneumococcus, a spherical bacterium that acts as the pathogen causing pneumonia.
Protoctists: These are microscopic single-celled organisms. Some, like Amoeba, that live in pond water, have features like an animal cell, while others, like Chlorella, have chloroplasts and are more like plants. A pathogenic example is Plasmodium, responsible for causing malaria.
Viruses: These are small particles, smaller than bacteria; they are parasitic and can reproduce only inside living cells; they infect every type of living organism. They have a wide variety of shapes and sizes; they have no cellular structure but have a protein coat and contain one type of nucleic acid, either DNA or RNA.
Examples include tobacco mosaic virus that causes discolouring of the leaves of tobacco plants by preventing the formation of chloroplasts, the influenza virus that causes 'flu' and the HIV virus that causes AIDS.
1.3 Recall the term 'pathogen' and know that pathogens may be fungi, bacteria, protoctists or viruses.
Monday, 26 March 2012Cell DivisionSpecification:
Mitosis:
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