Summary
Summary Cell Structure Notes - CIE A-level Biology
- Module
- Unit 1 - A Cell Structure
- Institution
- CIE
Unit 1 Cell Structure, AS, for papers 1-3
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1 | cell structureeukaryotes
cell surface membrane
partially permeable
controls entry and exit of substances
nucleus
nuclear envelope, double membrane
outer membrane continuous with ER
nuclear pores → controls entry and exit of substances
chromatin
coiled threads
DNA + histones
contains genetic material
control activities of cell
nucleolus
contains DNA
endoplasmic reticulum
network of flattened sacs
site of metabolic processes, separated from cytoplasm
rough ER
covered with ribosomes → site of protein synthesis
proteins modified as they move through
vesicles break off and join to form Golgi
smooth ER
makes lipids
stores calcium ions
ribosomes
on rough ER or free in cytoplasm
made of RNA and protein
large and small subunits
site of protein synthesis
Golgi apparatus
stack of flattened sacs (cisternae)
1 | cell structure 1
, max 1 in each cell
constantly being formed at one end from vesicles, broken down at the other end to form Golgi
vesicles
collects and processes molecules, modifies proteins and packages them into vesicles/lysosomes
molecules transported in Golgi vesicles to other parts of the cell or out of the cell
lysosomes
spherical sacs
single membrane
no internal structure
contain hydrolases (digestive enzymes)
destroys unwanted cell components
autolysis, endocytosis, exocytosis
mitochondria
2 membranes
inner membrane folded to form cristae (finger-like projections), projected into the matrix
cells that require more energy have more mitochondria
site of aerobic respiration
cytoskeleton
made up of microtubules and microfilaments
cell scaffolding
microtubules
long, rigid, hollow tubes
α-tubulin and β-tubulin form dimers
dimers form protofilaments
13 protofilaments line up in a ring to form a microtubule
cell support
intracellular transport system, cell components can be moved along the outside surfaces
microtubule organising centres MTOCs
control formation of microtubules from tubulin
centrioles
2 lie at right angles to each other
9 triplets of microtubules in each
in centrosome (main MTOC, not centrioles)
can act as MTOCs at bases of cilia and flagella
centrioles and centrosomes absent in most plant cells
1 | cell structure 2
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