Cells

Question 1

Nucleus, nuclear envelope, nucleolus

structure

Answer 1

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

Question 2

nuclear envelope function

Answer 2

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.

Question 3

nucleolus function

Answer 3

where ribosomes are made

chromosomes contain genome

Question 4

nucleus function

Answer 4

control centre
stores organism’s genome
transmits genetic info
provides instructions for protein synthesis

Question 5

RER structure

Answer 5

system of membranes
contain fluid-filled cavities (cisternae)
coated with ribosomes

Question 6

RER function

Answer 6

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

Question 7

SER structure

Answer 7

contains fluid-filled cavities (cisternae)

no ribosomes

Question 8

SER function

Answer 8

contains enzymes - catalyse reactions involved with lipid metabolism
absorption, synthesis, transport of lipids

Question 9

Golgi apparatus structure

Answer 9

stack of membrane-bound flattened sacs

have secretory vesicles - transport materials to and from GA

Question 10

Golgi apparatus function

Answer 10

modifies proteins

proteins packaged into vesicles, pinched off, stored in cell/incorporated in plasma membrane/exported out cell

Question 11

Mitochondria structure

Answer 11

2-5 μm long
outer and inner membrane (fluid between)
inner folded into cristae
inner=fluid filled matrix

Question 12

Mitochondria function

Answer 12

site of ATP production = aerobic respiration
self-replicating
lots metabolic activity = lots mitochondria

Question 13

chloroplasts structure

Answer 13

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

Question 14

chloroplasts function

Answer 14

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

Question 15

Vacuole structure

Answer 15

contains fluid

surrounded by tonoplast (membrane)

Question 16

Vacuole function

Answer 16

maintains cell stability
pushes cell wall = supports, cell turgid
filled with water and solutes

Question 17

Lysosomes structure

Answer 17

formed from GA
small bags surrounded by membrane
contain hydrolytic enzymes (digestive)

Question 18

Lysosomes function

Answer 18

keep powerful enzymes from rest of cell
ingest, digest pathogens
engulf old organelles and foreign matter
return digested components to cell for reuse

Question 19

Cilia and Undulipodia structure

Answer 19

protrusions from cell
surrounded by cell surface membrane
contains microtubules
formed from centrioles

Question 20

Cilia and Undulipodia function

Answer 20

in epithelial cells lining airways to move mucus

acts as antenna - contains receptors - cell detects signals about env.

Question 21

Ribosomes structure

Answer 21

20nm diameter
made of ribosomal RNA (rRNA)
remain in cytoplasm or attach to ER

Question 22

Ribosomes function

Answer 22

in RER: synthesising proteins - exported out cell

free in cytoplasm: assemble proteins - used in cell

Question 23

Centrioles structure

Answer 23

2 bundles of microtubules at right angles

microtubules made from tubulin protein subunits into cylinder

Question 24

Centrioles function

Answer 24

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)

Question 25

Cytoskeleton structure

Answer 25

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

Question 26

Cytoskeleton function

Answer 26

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

Question 27

Cellulose cell wall structure

Answer 27

made of bundles of cellulose fibres

Question 28

Cellulose cell wall function

Answer 28

prevent cells from bursting when turgid
strength, support, maintain shape
permeable, allows solutions to pass

Question 29

Prokaryotic cells

Answer 29

Plasma membrane 
Cytoplasm
Ribosomes 
DNA
RNA

smaller, less developed cytoskeleton, no centrioles,