Cell Membranes

Seite 1

Page 25 Application

1a) to keep enzymes needed for photosynthesis in one place

b) to increase surface area available for photosynthesis to take place

c) to control what substances enter/leave the cell

2) through carrier proteins - facilitated diffusion

3) as energy releasing organelles require a lot of substances to travel through their membranes, some substances will require help from proteins to get across membranes, so these will have a higher protein content

4) as the low temperature denatures the proteins in the membrane, increasing permeability , as the temp increases the membrane is partially permeable as phospholipids are able to move so water molecules can diffuse out

Page 26 Fact recall

1) lets some molecules through membrane but not others

2) a- glycoprotein b- glycolipid c- cholesterol d- channel protein e- phospholipid

3) hydrophilic - attracted to water, hydrophobic - repels water

4) as the centre is hydrophobic, so it repels any water-soluble molecules trying to pass through membrane

5) cholesterol - hydrophobic regions to create barrier to polar substances, proteins allow passage of large molecules that would otherwise be too large to pass through membrane

6a) stability

b) stability and receptors

7) phospholipid bilayer starts to breakdown, proteins denature, losing their structure, increased permeability of membrane, water inside expands putting pressure on membrane.

Page 28 Application

1) the drug binds to the membrane bound receptor as it has a complementary shape, it is specific to that receptor. This means the messenger molecule can no longer bind as the drug is taking it's place

2) as it's shape is no longer complementary to the messenger molecule, so the messenger molecule can no longer bind to it triggering a response

3) as the specific receptor for the messenger molecule is only found on the surface of liver cells

Page 31 Application

1) the ink molecules are moving from an area of high concentration - the ink, to an area of low concentration - the water

2a) water molecules from the human cheek cells will move into the salt solution

b) water will move into the apple slices

c) there will be no net movement of water as the solutions are isotonic

3a) as the solution has moved by osmosis into the potato cells, swelling the vacuole making turgid

b) both potato cells in solutions will become flaccid from losing water and the potato cell in solution 3 will become plasmolysed as it will lose a lot of water

Page 34 Application

1a) vesicle

b) vesicle pinches off from golgi sacs with substance inside, vesicle moves into plasma membrane and fuses with it, releasing contents outside of neurone 1

c) by facilitated diffusion using carrier/channel proteins

2a) linear

b) sodium ion active transport requires energy from ATP, aerobic respiration must also increase in order to produce more ATP, so the rate of oxygen consumption must increase too

c) none, facilitated diffusion doesn't require energy from ATP, so there is no need for the rate of oxygen consumption to increase

Page 36 Face recall

1) the net movement of substances from an area of higher concentration to an area of lower concentration

2) passive

3) water, non polar

4) facilitated is of larger molecules and uses carrier/channel proteins to diffuse them across membrane

5) the net movement of water molecules from an area of higher water potential to an area of lower water potential

6) the likelihood of water molecules to move in/out of a cell by osmosis

7a) burst

b) become turgid

c) flaccid and plasmolysed

8) similarities - uses carrier/channel proteins, is of large molecules, down concentration gradient

differences - active uses energy from ATP against concentration gradient

9a) carrier proteins - molecule attaches, protein changes shape in membrane, releases molecule on opposite side of membrane

channel proteins - form pores in membrane to allow substances to diffuse through

10) part of plasma membrane surrounds substance, and pinches off forming a vesicle with substance inside

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