Cell structure
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- Created by: eliseefowler
- Created on: 11-01-16 16:36
Cell structure
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Nucleus
Nuclear envelope
- Double membrane surrounding the nucleus
- Outer membrane has ribosomes on the surface
- Controls the entry and exit of materials in and out of the nucleus
Nuclear pores
- Allows the passage of molecules out of the nucleus
Nucleoplasm
- Jelly-like material that makes up most of the nucleus
Nucleolus
- It manufactures ribosomes
Functions of the nucleus
- Controls activities of the cell
- Collects the genetic material
- Makes ribosomes
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Mitochondria
Double membrane
- The inner membrane folds to form extensions called cristae
Cristae
- Provides a large surface area for the attachment of enzymes and other proteins
Matrix
- Contains proteins, lipids, ribosomes and DNA that allows mitochondria to produce its own proteins
- Many enzymes involved in respiration are found in the matrix
Functions of mitochondria
- To produce ATP- an energy carrier molecule from respiratory substrates
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Chloroplasts
Chloroplast envelope
- Double plasma membrane that surrounds the chloroplast
- It's very selective in what it allows in and out of the chloroplast
The granum
- Stacks of disc-like structures called thylakoids
- It's where the first stage of photosynthesis occurs (light absorption)
The stroma
- Fluid-filled matrix where the second stage of photosynthesis occurs (synthesis of sugars)
The chloroplasts adaptations for photosynthesis
- The double membrane provides a large surface area for the attachment of chlorophyll, electron carriers and enzymes
- The fluid in the stroma has the enzymes needed to make sugars for the second stage of photosynthesis
- They contain DNA and ribosomes so they can make proteins needed for photosynthesis
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Endoplasmic reticulum
Rough endoplasmic reticulum (RER)
- Has ribosomes on the surface
- Provides a large surface area for protein synthesis
- Provides a pathway for transport of materials
- The double membrane folds to form sacs called cisternae
Smooth endoplasmic reticulum (SER)
- Hasn't got ribosomes on the surface
- More tubular in appearance
- It synthesises, stores and transports lipids and carbohydrates
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Golgi apparatus
Cisternae
- Has small rounded, hollow structures called vesicles
Proteins and lipids
- The endoplasmic reticulum produces them and then they're transported to the golgi apparatus
- The golgi apparatus modifies the proteins by adding non-protein components (eg: carbohydrates)
- It labels the proteins so that they can be sent to the right destinations
- They're then sent to the golgi vesicles, then the cell surface where they fuse with the membrane and release the contents
Functions of the golgi apparatus
- To add carbohydrates to proteins to form glycoproteins
- To produce secretory enzymes
- To secrete carbohydrates
- To transport, modify and store lipids
- Form lysosomes
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Lysosomes
-Formed from the golgi apparatus
- Has lysozymes which is an enzyme that hydolyses the cell walls of certain bacteria
Functions of lysosomes
- To hydrolyse materials ingested by phagocytic cells (eg: white blood cells)
- Release enzymes to destroy material around the cell
- Digest worn out organelles so that useful chemicals can be re-used
- Breaks down cells after they have died
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Ribosomes
70s ribosomes
- They're slightly smaller
- Found in prokaryotic cells, mitochondria and chloroplasts
80s ribosomes
- Found in eukaryotic cells
Function of ribosomes
- Protein synthesis
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Cell wall
- Consists of microfibrils of cellulose that are embedded in a matrix
- Microfibrils have good strength, so it strengthens the cell wall
The middle lamella
- Thin layer
- Marks the boundary between adjacent cell walls and brings them together
Cell walls of fungi
- Doesn't contain cellulose
- Has a mixture of chitin, glycan and glycoproteins
Cell walls of algae
- Made of cellulose or glycoproteins or both
Functions of cell walls
- Provide strength to prevent osmotic lysis
- To allow water to pass through
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Vacuole
- It's a fluid-filled sac bounded by a single membrane- The single membrane is called the tonoplast
Plant vacuole
- Contains a solution of mineral salts, sugars and amino acids
Functions
- Sugars and amino acids can act as temporary food
- The pigments can colour petals to attract pollinating insects
- They support herbaceous plants by making them turgid
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Prokaryotic cells
- They're smaller and they have no nucleus
- Instead of a nucleus, they have circular DNA and they may have smaller strands called plasmids
- Has no membrane-bounded organelles
- Has 70s ribosomes
- The cell wall is made of murein
- May have an outer mucilaginous layer called a capsule
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