2.5 cell membranes

Question 1

no. membranes around nucleus

Answer 1

2

Question 2

no. membranes around ER

Answer 2

1

Question 3

no. membranes around GOLGI

Answer 3

1

Question 4

no. membranes around LYSOSOME

Answer 4

1

Question 5

no. membranes around CHLOROPLAST

Answer 5

2

Question 6

no. membranes around MITOCHONDRIA

Answer 6

2

Question 7

partially permeable defintion

Answer 7

allows some substances to pass through but not all

Question 8

purpose of plasma membrane

Answer 8

1. BARRIER : controls movement of substances in and out of the cell (cell membrane)
2. Compartmentalisation (golgi apparatus)
3. cell signalling (receptors on csm)
4. electrical communication (nerve csm)
5. attachment site for enzymes (inner membrane of mitochondria)

Question 9

phopholipid properties

Answer 9

• hydrophilic head (charged)
• hydrophobi tails (uncharged)

Question 10

phospholipid bilayer orientation

Answer 10

orientate so that hypdrophilic heads are faced towards water and hydrophobic tails away from water
- can form a micelle (sphere) HPI heads outside and in the middle

Question 11

7 components of CSM

Answer 11

1. glycoprotein
2. glycoplipid
3. phospholipid bilayer
4. cholestrol
5. channel / carrier protein
6. extrinsic protein
7. actin microfilament

Question 12

fluid mosaic model

Answer 12

• phospholipid bilayer
• hydophilic heads facing external environment
• hydophobic tails away from external environment
• proteins free to move inside membrane
• proteins randomly arranged throughouy

Question 13

cholestrol

Answer 13

• 4 carbon rings
• regulates fluidiity of membrane
• ONLY IN EUKARYOTIC
• high temp: binds to tails of phospholipids, increasing packing reducing fluidity

Question 14

channel proteins

Answer 14

• ALLOW facilitated diffusion to happen
• only specific substances can diffuse through

Question 15

carrier proteins

Answer 15

• change shape to allow specific substances through
• facilitated diffusion AND active transport

Question 16

glycoproteins and glycolipids

Answer 16

• polysaccharaide chain attached to lipid or protein
• act as antigens for cell recognition (tissue formation)
• receptors for cell signalling

Question 17

temperature effect on membranes

Answer 17

• as temp increaes, KE increases
• membrane bceoms more fluid
• gaps created
• more permeable

Question 18

organisms in COLD environments membranes

Answer 18

• MORE cholestrol to prevent membrane freezing
• more UNSATURATED and SHORTER fatty acid tails to make it more fluid

Question 19

organisms in HOT environments membrane adaptation

Answer 19

• more SATURATED and LONGER fatty acid tails to make membrane less fluid

Question 20

role of membrane bound receptors for hormones and drugs to bind

Answer 20

1. glycoprotein or glycolipid receptors on the outer surface of csm has a BINDING SITE complementary in shape to the hormone or drug
2. hormone or drug is primary messenger. binds to the receptor activating g proteins -> adenyl cyclase ->atp to camp
3. camp secondary messenger, activates proteins by activating pka, phosphorylates. binding can also change shape

Question 21

what can diffuse across with simple diffusion?

Answer 21

• small
• non polar
• FAT SOLUBLE (eg lipid) molecules

Question 22

channel proteins are involved in

Answer 22

facilitated diffusion

Question 23

carrier proteins are involved in

Answer 23

(facilitated diffusion) AND active transport

Question 24

endocytosis transports …

Answer 24

bulk transport of materials into the cell

Question 25

describe endocytosis

Answer 25

1. molecule binds to specific comp receptor (glycprotein or glycolipid) on cell surface membrane and folds in around the substance 2. fuses with itself and pinches off, forming a vesicle 3. vesicle moves through cytoplasm 4. USES ATP

Question 26

how does the active transport using proteins work

Answer 26

- carrier protein changes shape using ATP - AT pump (protein) is shaped so that the molecule being carried fits to one side only

Question 27

how to describe permeability when using the proteins

Answer 27

selectively permeable

Question 28

extrinsic proteins

Answer 28

proteins held on the outer surface of the membrane

Question 29

2 examples of what cannot go across by simple diffusion

Answer 29

- water - ions

Question 30

how does cholestrol work

Answer 30

- fits between the tails of phospholipids - inhibits their movement, reducing fluidity

Question 31

waht happens if the temp is too high

Answer 31

- loses mechanical stability - fully permeable - proteins denature

Question 32

effect of solvents like alcohol

Answer 32

- dissolve fatty substances by inserting into bilayer and breaking IMFs

Question 33

OTHER use of cholestrol

Answer 33

steroid hormones - make vitamin D - make bile salts

Question 34

3 example of active transport

Answer 34

- mineral ions into root hair cells - h+ out of companion cells - sucrose out of sieve tube at sink

Question 35

freezing effect on permeability

Answer 35

increases

Question 36

how does x pass through membrane

Answer 36

- non-polar lipid - soluble in the phospholipid bilayer so can pass through

Question 37

why is rate of transport not constant in active transport

Answer 37

- uses carrier proteins - proteins become saturated

Question 38

exocytosis

Answer 38

bulk transport of substances OUT of the cell - component packaged into vesicle - vesicle fuses w cell surface membrane - released outside - requires ATP