Cell Organelles

including mitochondria, nucleus, ribosomes, lysosomes, microvilli, cytoplasm, endoplasmic reticulum, chloroplasts...

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Mitochondrion

-In cytoplasm

-Different amount in different cells

-Generate most of the cell's ATP

-Used for cell differentiation, cell death and signalling

-Protein based outer membrane allows diffusion

-Inner membrane is highly impermeable to molecules

-Not found in fat cells

-Matrix is a liquid within the organellewhich contains enzymes

-Respiration happens in mitochondria

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Nucleus

-Controls eating, movement and reproduction

-Knows what is going on inside the cell

-Not always in the centre, but can't be too close to the edge - danger of damage

-Appears as a dark spot in the cytoplasm

-Nucleolus in the centre of the nucleus is DNA

-Spherical - large volume, small surface area

-Pores to allow proteins and molecules in/out

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Ribosomes

-Small granules in the cytoplasm or on RER

-2 types - 80S (eukaryotic) and 70S (prokaryotic)

-80S are bigger than 70S and have more RNA molecules and more proteins

-One big and one small subunit containing ribosome DNA

-mRNA come between the subunits

-Ribosomes read mRNA

-Ribosomes help protein synthesis

-Attach to RER because it has a large surface area for protein synthesis

-Ribosomes are close to the nucleus

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Lysosomes

-Membrane-bound, in the cytoplasm

-Contain various hydrolytic enzymes which function in intercellular digestion

-Break down ingested material (e.g. in white blood cells)

-Release enzymes to destroy material around the cell

-Digest worn out organelles so useful chemicals can be re-used

-Break down dead cells

-Contain enzymes which are proteins manufactured by ribosomes in the RER and packaged by Golgi apparatus inside the membraneous vesicles that make up lysosomes.

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Microvilli

-Increase the surface area for more effective absorption

-On the epithelial cells in the small intestine

-Has a dense bundle of cross linking Actin filaments

-Takes starch molecules into the blood

-No other organelles within the microvilli

-Actin is a type of protein which keeps the microvilli from falling down

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Cytoplasm

-The fluid that fills the cell

-Thick, gel-like, semi-transparent, in both plant and animal cells

-Organelles are suspended in cytosol (fluid part of cytoplasm)

-Cytosol is mainly water, dissolved ions, small molecules ans large water-soluble molecules (proteins)

-Microfilaments and microtubules set up a "skeleton" of the cell (to stop it collapsing) and cytosol fills the spaces

-Cytoplasm has fatty acids, sugars and amino acids dissolved in it

-Waste products are dissolved

-Uses dissolved enzymes to break larger molecules into products used by other organelles

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Endoplasmic Reticulum (ER)

-Spreads through cytoplasm, continuous outer membranes holding flattened sacs called Cisternae

-Forms a network of tubules, vesicles and cisternae

-In plant and animal cells

Rough Endoplasmic Reticulum

-RER is a complex membrane; surface is covered with ribosomes

-RER is a pathway for the transport of materials such as proteins and glycoproteins

-Ribosomes only bind to the RER when it begins to synthesise a protein for sorting

-Free ribosomes synthesise a protein until a signal recognises the amino acids

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Endoplasmic Reticulum (ER)

Smooth Endoplasmic Reticulum

-SER has few or no ribosomes attached and has a tubular appearance

-SERs synthesise lipids and store and transport carbohydrates and lipids

-SER has an increased surface area

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Chloroplasts

-In plant cells, responsible for photosynthesis, disc-shaped

-Chloroplast envelope - plasma with double membrane surrounding chloroplasts

-100s of disc-like grana make up thylakoids which contain chlorophyll

-Stroma - fluid filled tissue containing other structure such as starch grains

-Photosynthesis - 1st stage happens in Grana and Thylakoids, 2nd stage in Stroma

-Chloroplasts catch sunlight for photosynthesis

-Grana membranes have a large surface area

-Fluid in stroma contains enzymes neede for photosynthesis

-Contain DNA and ribosomes to easily manufacture proteins needed for photosynthesis

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