Cells 1
- Created by: Nicola Carter
- Created on: 08-12-12 11:06
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- Cells
- Cytoskeleton - network of fibres made of protein
- These fibres keep the cell's shape stable by providing n internal framework
- Actin filaments - are like fibres found in muscle cells. They are able to move against each other.
- Cause the movement seen in some white blood cells. Also move organelles around the cell
- Microtubules - other fibres made of a protein called tubulin
- Cylinders are 25nm in diameter.
- May be used to move microorganims through a liquid, or to waft a liquid past the cell
- Proteins present on the microtubles move organelles and other cell contents along the fibres.
- How chromosomes are moved during mitosis
- How vesicles move from the endoplasmic reticulum to the Golgi apparatus
- These proteins are known as microtuble motors - ATP to drive these movements
- Flagella and cilia
- Flagella also known as undulipodia
- Structurally the same - hair-like extensions that stick out from the surface of cells
- Each one is made up of a cylinder that contains 9 microtubles arranged in a circle with 2 mircrotubles in the centre
- Flagella forms the tail of the sperm cell
- Cilia move substances such as mucus across the surface of the cell
- Can move because the microtubules use ATP
- Flagella usually occur in ones and twos on a cell
- Cilia often occur in large numbers on a cell
- Vesicles and Vacuoles
- Vesicles are membrane bound sacs found in cells. Used to carry many different substances around the cell.
- In plant cells, the large cell vaculole maintains cell stability. Is filled with water and solutes, so it pushes the cytoplasm against the cell wall, making the cell turgid
- Plant cell walls- outside of the plant cell plasma membranes. Made of cellulose - forms a sieve like network of strands that makes the wall strong.
- Division of Labour
- Some of the cells within some organisms produce hormones
- The instructions to make the hormone are in the DNA in the nucleus
- The specific instruction to make a hormone is called a gene
- The nucleus copies the instructions in the DNA into a molecule called mRNA
- The mRNA molecule leaves the nucleus through a nuclear pore and attaches to a ribosome
- The ribosome is attached to rough ER
- The ribosome reads the instructions and uses the codes to assemble the hormone
- The assembled protein inside the rough ER is pinched off in a vesicle and transported to Golgi appartus
- The Golgi apparatus packages the protein and may also modify it so that it is ready for release. The protein is now packaged into a vesicle and moved to the cell surface membrane, where it is secreted outside
- The assembled protein inside the rough ER is pinched off in a vesicle and transported to Golgi appartus
- The mRNA molecule leaves the nucleus through a nuclear pore and attaches to a ribosome
- The nucleus copies the instructions in the DNA into a molecule called mRNA
- The specific instruction to make a hormone is called a gene
- Eukaryotes
- The cells described so far all contain organelles, some of which are bound by membrane.
- This gives these cells a complicated internal structure, where each organelle performs a specific role, these are called eukaryotic cell
- Have a true nuclueus
- This gives these cells a complicated internal structure, where each organelle performs a specific role, these are called eukaryotic cell
- The cells described so far all contain organelles, some of which are bound by membrane.
- Prokaryotes
- Features
- Only one membrane - no membrane bound organelles
- Surrounded by a cell wall
- Outside cell wall there is often a slippery protective layer called the capsule
- Contain small ribosomes
- Single loop of DNA
- DNA not surrounded by a membrane
- Features
- Cytoskeleton - network of fibres made of protein
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