full notes hitting all areas of specification for unit 1 of AQA A Level biology
consisting from cell structure to cell recognition and the immune system
with diagrams and definitions
highlighted key information
Nucleus
Contains chromosomes that are linear strands of DNA associated with histone proteins and
one or more nucleoli.
The nuclear envelope has nuclear pores to control exchange between the nucleus and
cytoplasm.
Contains chromatin and a nucleolus that is the site of ribosome production.
The nucleus controls gene expression and mediates the replication of dna during cell cycle
Cell surface membrane
Thin phospholipid bilayer that surrounds the cell and controls the exchanges between the
cell and its environment
Rough endoplasmic reticulum
Is an extended system of membrane sacs that is encrusted with ribosomes
Synthesises proteins
Smooth endoplasmic reticulum
Similar to the rough endoplasmic reticulum but
with no ribosomes
Synthesizes lipids, steroids and hormones
Synthesises, stores and transports
carbohydrates
Golgi apparatus
Consists of stacks of flattened membranes
Modifies proteins
Makes lysosomes
Collects,transports and sorts molecules that are then transported by vesicles to other parts
of the cell or secreted out of the cell
Lysosomes
A golgi vesicle that releases lysozyme and contains other hydrolytic enzymes
Mitochondria
Has a smooth outer membrane with a highly folded inner membrane into cristae
Contains a matrix on the inside containing all the enzymes needed to respiration
Carries out aerobic respiration and synthesises ATP
Ribosomes
80s in eukaryotic cells
Site of protein synthesis
, Chloroplasts
Contains disc-like thylakoid membranes arranged in stacks called grana with an internal fluid
called stroma
Light-dependent reactions of photosynthesis takes place on the thylakoid membranes and
the light-independent reactions of photosynthesis take place in the stroma
Cell wall
Is composed of mainly cellulose in plants, chitin in fungi, and/or glycoproteins in algae
Provides strength whilst remaining permeable
Vacuoles
Contains sap and supports the cell
Prokaryotic + virus structure
Cytoplasm
Lacks membrane-bound organelles
Smaller ribosomes
70s
No nucleus
They have a circular loop of dna that is free in the
cytoplasm and has no associated proteins
Cell wall
Contains murien
Some have:
One or more plasmids
Small circular dna molecules that only contains a few genes
Are more accessible for proteins required for gene expression and therefore contain genes
that are required often or in emergencies
Usually where the gene for antibiotic resistance are found
Capsule
Which helps the cell to retain moisture and adhere to
surfaces
Flagella
hair-like structures which attach to other bacterial cells
Virus
Acellular and non-living
Consist of nucleic acid enclosed in a protective protein
coat sometimes contained in a lipid envelope
Attachment proteins are essential to allow the virus to identify and attach to a host cell
Cell structure role
capsule protects bacterium from other cells and helps groups of bacteria to
stick together for further protection
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