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Organelle
sub-cellular structure with specific function
Eukaryotic cell
cytoplasm contains membrane-bound organelles
so DNA is enclosed in a nucleus
Function of nucleus
Contains DNA which contains genes which codes for proteins (transcribed into mRNA)
Nucleolus makes ribosomes
Nuclear pores allow substances to move between nucleus and cytoplasm
Structures of a nucleus
Nuclear envelope, nucleolus, nucleoplasm, linear DNA
Nuclear envelope
Double membrane containing nuclear pores
Nuclear pores
Allow the passage of large molecules (mRNA) out of the nucleus.
Nucleoplasm
Granular, jelly like material which takes up the bulk of the nucleus.
DNA
Protein bound (histone), linear DNA in two forms:
chromatin: condensed
chromosome: highly condensed
Nucleolus
Small spherical region within the nucleoplasm which is the site of rRNA production and makes ribosomes. (May be more than one)
Types of Endoplasmic reticulum
Rough and smooth
Function of rough endoplasmic reticulum
Site of protein synthesis, transport proteins in RER, transport proteins to Golgi apparatus in vesicles
Function of smooth endoplasmic reticulum
Synthesise and processes lipids (e.g. cholesterol/steriod hormones)
Structure of rough endoplasmic reticulum
Ribosomes, cisternae, large surface area and ability to form shuttle vesicles.
Structure of smooth endoplasmic reticulum
Cisternae, large surface area and ability to form shuttle vesicles.
Cisternae (endoplasmic reticulum)
Corridors that control the transport of polypeptides throughout the cell through compartmentalisation.
Large surface area (endoplasmic reticulum)
Fits a lot of ribosomes for maximised area for polypeptide synthesis
Ability to form shuttle vesicles (endoplasmic reticulum)
Transports polypeptides to Golgi apparatus.
Ribosomes
Site of protein synthesis
Made of 2 subunits (large and small subunit)
Can be found on RER or floating in the cytoplasm.
Function of Golgi Apparatus
Flattened membrane sac that:
Modifies proteins from RER (e.g. protein + carbohydrate → glycoprotein)
Packages proteins into Golgi vesicles
Forms lysosomes.
Structure of Golgi apparatus
Cisternae/membrane bound cavities, enzymes in cisternae, ability to form Golgi vesicles, ability to form lysosomes.
Cisternae/membrane bound cavities (Golgi apparatus)
Compartmentalise the different reactions for the modification of polypeptides into proteins.
Enzymes (Golgi apparatus)
Catalyze the reactions needed for the modification of polypeptides into proteins.
Golgi vesicles
Small membrane-bound sac that transports proteins/lipids to required destination (e.g. cell surface membrane)
Lysosomes
Membrane-bound sac/vesicle that release lysozymes (hydrolytic enzymes)
To hydrolyse pathogens/worn-out organelles
Function of mitochondrion
Site of aerobic respiration to produce ATP for energy release.
Structure of mitochondrion
Cristae, matrix, independent ribosomes/circular DNA, double membrane system.
Cristae
Holds enzymes involved in catalysing the reactions involved in aerobic respiration.
Folded providing larger surface area for reactions.
Matrix
Solution within double membrane of mitochondria containing small ribosomes and circular DNA.
Independent ribosomes/circular DNA in mitrochondria
Manufactures independent proteins within the mitochondria speeding up rate of reaction as the proteins necessary for aerobic reactions made in the mitochondria.
Double membrane system
Compartmentalises substances between membranes (e.g. CO2 of O2)
Why does the mitochondrion look circular in some images?
The mitochondrion have been sectioned at different orientations.
Function of chloroplasts
Absorbs light energy for photosynthesis to produce organic substance e.g. carbohydrates and lipids.
Structure of chloroplasts
double membrane, stroma, thylakoid membrane, grana small ribosomes, circular DNA, starch granules, lipid droplets, lamella
Double membrane in chloroplasts
Compartmentalises the reactions in photosynthesis.
Stroma
Solution within the chloroplast making up the bulk of the cell containing independent ribosomes and DNA, encircling the grana and thylakoids.
Thylakoid membranes/granas
Granas are stacks of thylakoid membranes which provide large surface area to store large amounts of enzymes and chlorophyll needed for photosynthesis.
Independent ribosomes/DNA in the stroma
Manufactures independent proteins within the chloroplast speeding up rate of reaction as the proteins necessary for photosynthesis are made in the chloroplast itself.
Function of starch grains
Store glucose in a cell without affecting cells water potential.
Structure of starch grains
Compact, insoluble, large and easy to hydrolyse.
Compact starch
Maximise amount of carbohydrates stored.
Insoluble starch
Doesn’t affect cells water potential.
Large starch
Cannot diffuse out of the cell.
Easy to hydrolyse starch
Can be quickly used as a source of glucose for respiration.
Lipid droplets
Can be used to make micelles and phospho-lipid bilayer in cell membrane.
Function of Cellulose cell wall
Formed outside the cell surface membrane providing mechanical strength to the cell so prevents osmotic lysis (although is permeable to most substances)
Structure of Cellulose cell wall
Cellulose microfibrils in pectin matrix, permeable, middle lamella, pits and plasmodesmata.
Cellulose microfibrils in pectin matrix
Provides strong composite structure to support plant cell.
Permeable cell wall
Allow passage of important substances into the cell.
Middle lamella
Made of pectin to hold cells together as an adhesive.
Pits and plasmodesmata
Connects cells together.
What are fungal cell walls made out of?
Chitin- a monosaccharide with an amine group
Function of Vacuole
Membrane bound storage area for cell sap (organic and inorganic substances e.g. waste) and maintains turgor pressure.
Structure of Vacuole
Tonoplast, high hydrostatic pressure, coloured pigments, large volume relative to cell.
Tonoplast
Compartmentalises what comes in and out of the vacuole.
High hydrostatic pressure
Pushes chloroplasts to the edge of the cell for easy access to CO2 diffusing into the cell.
Coloured pigments
In some species, for pollution/seed disposal/mating)
Large volume relative to the cell
Maintain turgidity to push chloroplasts
Tissue
Group of specialised cells with similiar structure working together to perform specific function.
Organ
Groups of tissues working together to perform specific functions.
Organ system
Group of organs working together to perform specific functions.
Adaptation of white blood cells/glands
Needs high rate of protein production (antibodies/hormones)
Many ribosomes/RER
For high rate of protein synthesis
Adaptation of muscles cells
High rate of ATP production (due to higher metabolic rate)
So have many mitochondria
For high rate of aerobic respiration/ATP production