Animal Cell (Leaving Cert Biology): Revision Notes
Animal Cell
Cell Organelle
- Cell Membrane
- Cytoplasm
- Nucleus
- Ribosomes
- Mitochondria
1. Cell Membrane
Function:
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Retains the cell contents.
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Controls what enters and leaves the cell.
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It is selectively permeable. Composition:
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Made up of a thin layer of lipids and proteins.
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Two layers of phospholipid molecules form a lipid bilayer.
Selectively permeable means the cell membrane allows certain molecules to pass through while blocking others. For example, oxygen can pass into an animal cell.
Cell Membrane
2. Cytoplasm
Function:
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A jelly like substance that suspends cell organelle
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Chemical reactions occur here. Composition:
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Includes sugars, which are needed for diffusion and osmosis to occur.
Cytosol: the cytoplasm minus organelles.
Quick Definition Review! Diffusion: The movement of substances from an area of high concentration to an area of low concentration.
Osmosis: The movement of water molecules from an area of high water concentration to an area of low water concentration across a semi-permeable membrane.
3. Nucleus
Function:
- The control centre of the cell.
- Responsible for DNA replication and cell division.
DNA: Deoxyribonucleic Acid
Composition:
- Surrounded by a double membrane with nuclear pores.
- Contains DNA which is organised into chromosomes.
Chromosomes are composed of DNA and protein. When a cell isn't dividing, the chromosomes are usually in a thin, thread-like form called chromatin.
4. Ribosomes
Function:
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Protein synthesis (make protein) Composition:
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Made of protein and RNA (ribonucleic acid).
5. Mitochondria
Function:
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Aerobic respiration occurs here. Composition:
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A double membrane with inner folding of cristae.
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These increase surface area, allowing more energy-producing reactions to occur.
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For example, mitochondria in the legs are heavily folded, as they require lots of energy.
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The number of mitochondria in a cell depends on its energy needs.
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Cells requiring more energy (like leg muscles) have more mitochondria.
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Mitochondria contain their own DNA.
