Cells Flashcards
Nucleus, nuclear envelope, nucleolus
structure
nucleus surrounded by double membrane (nuclear envelope), contain pores
nucleolus contains RNA, no membrane
chromatin is genetic material, DNA wound round histone proteins
cell not dividing: chromatin spread out/extended
about to divide:chromatin condenses, coils tightly into chromosomes - make up organism’s genome
nuclear envelope function
separates contents of nucleus from rest of cell
some regions: outer, inner nuclear membranes fuse together - dissolved substances (ribosomes) pass
pores enable larger substances (mRNA) out, steroid hormones from cytoplasm in.
nucleolus function
where ribosomes are made
chromosomes contain genome
nucleus function
control centre
stores organism’s genome
transmits genetic info
provides instructions for protein synthesis
RER structure
system of membranes
contain fluid-filled cavities (cisternae)
coated with ribosomes
RER function
intracellular transport system: cisternae form channels for transporting substances around cell
large SA for ribosomes - assemble amino acids into proteins, pass through membrane into cisternae, transported to Golgi apparatus
SER structure
contains fluid-filled cavities (cisternae)
no ribosomes
SER function
contains enzymes - catalyse reactions involved with lipid metabolism
absorption, synthesis, transport of lipids
Golgi apparatus structure
stack of membrane-bound flattened sacs
have secretory vesicles - transport materials to and from GA
Golgi apparatus function
modifies proteins
proteins packaged into vesicles, pinched off, stored in cell/incorporated in plasma membrane/exported out cell
Mitochondria structure
2-5 μm long
outer and inner membrane (fluid between)
inner folded into cristae
inner=fluid filled matrix
Mitochondria function
site of ATP production = aerobic respiration
self-replicating
lots metabolic activity = lots mitochondria
chloroplasts structure
4-10 μm long in palisade mesophyll layer double membrane inner membrane = stacks of flattened membrane sacs (thylakoids) - contain chlorophyll stack of thylakoids = granum fluid-filled matric = stroma contain loops of DNA and starch grains
chloroplasts function
1st stage of photosynthesis, in grana: light energy trapped by chlorophyll make ATP
water split - supply hydrogen ions
2nd, in stroma:energy from ATP - hydrogen reduces carbon dioxide to make carbohydrates
Vacuole structure
contains fluid
surrounded by tonoplast (membrane)
Vacuole function
maintains cell stability
pushes cell wall = supports, cell turgid
filled with water and solutes
Lysosomes structure
formed from GA
small bags surrounded by membrane
contain hydrolytic enzymes (digestive)
Lysosomes function
keep powerful enzymes from rest of cell
ingest, digest pathogens
engulf old organelles and foreign matter
return digested components to cell for reuse
Cilia and Undulipodia structure
protrusions from cell
surrounded by cell surface membrane
contains microtubules
formed from centrioles
Cilia and Undulipodia function
in epithelial cells lining airways to move mucus
acts as antenna - contains receptors - cell detects signals about env.
Ribosomes structure
20nm diameter
made of ribosomal RNA (rRNA)
remain in cytoplasm or attach to ER
Ribosomes function
in RER: synthesising proteins - exported out cell
free in cytoplasm: assemble proteins - used in cell
Centrioles structure
2 bundles of microtubules at right angles
microtubules made from tubulin protein subunits into cylinder
Centrioles function
before cell division - threads of tubulin (spindle) forms from centrioles
chromosomes attach to middle of spindle
motor proteins walk along tubulin threads = pull chromosomes opposite ends of cell
formation of cilia, undulipodia (from microtubules)
Cytoskeleton structure
network of protein structures within cytoplasm
rod-like microfilaments, intermediate filaments, striahgt cylindrical microtubules
cytoskeletal motor proteins; myosins, kinesins, dyneins =molecular motors, and enzymes, allows hydrolysis of ATP as energy source
Cytoskeleton function
support, strength to cell’s shape, cell movement
help organelles move through cytoplasm
form track along which motor proteins walk
form spindle before cell divides (chromosomes moved)
intermediate filaments = anchor nucleus, extend between cells - signalling
Cellulose cell wall structure
made of bundles of cellulose fibres
Cellulose cell wall function
prevent cells from bursting when turgid
strength, support, maintain shape
permeable, allows solutions to pass
Prokaryotic cells
Plasma membrane Cytoplasm Ribosomes DNA RNA
smaller, less developed cytoskeleton, no centrioles,
