Cell Membranes

Page 25 Application1a) to keep enzymes needed for photosynthesis in one placeb) to increase surface area available for photosynthesis to take placec) to control what substances enter/leave the cell2) through carrier proteins - facilitated diffusion3) 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 content4) 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 recall1) lets some molecules through membrane but not others2) a- glycoprotein b- glycolipid c- cholesterol d- channel protein e- phospholipid3) hydrophilic - attracted to water, hydrophobic - repels water4) as the centre is hydrophobic, so it repels any water-soluble molecules trying to pass through membrane5) cholesterol - hydrophobic regions to create barrier to polar substances, proteins allow passage of large molecules that would otherwise be too large to pass through membrane6a) stabilityb) stability and receptors7) phospholipid bilayer starts to breakdown, proteins denature, losing their structure, increased permeability of membrane, water inside expands putting pressure on membrane.

Page 28 Application1) 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 place2)  as it's shape is no longer complementary to the messenger molecule, so the messenger molecule can no longer bind to it triggering a response3) as the specific receptor for the messenger molecule is only found on the surface of liver cells

Page 31 Application1) the ink molecules are moving from an area of high concentration - the ink, to an area of low concentration - the water2a) water molecules from the human cheek cells will move into the salt solutionb) water will move into the apple slicesc) there will be no net movement of water as the solutions are isotonic3a) as the solution has moved by osmosis into the potato cells, swelling the vacuole making turgidb) 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 Application1a) vesicleb) vesicle pinches off from golgi sacs with substance inside, vesicle moves into plasma membrane and fuses with it, releasing contents outside of neurone 1c) by facilitated diffusion using carrier/channel proteins2a) linearb) 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 tooc) 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 recall1) the net movement of substances from an area of higher concentration to an area of lower concentration2) passive3) water, non polar4) facilitated is of larger molecules and uses carrier/channel proteins to diffuse them across membrane5) the net movement of water molecules from an area of higher water potential to an area of lower water potential6) the likelihood of water molecules to move in/out of a cell by osmosis7a) burstb) become turgidc) flaccid and plasmolysed8) similarities - uses carrier/channel proteins, is of large molecules, down concentration gradientdifferences - active uses energy from ATP against concentration gradient9a) carrier proteins - molecule attaches, protein changes shape in membrane, releases molecule on opposite side of membranechannel proteins - form pores in membrane to allow substances to diffuse through10) part of plasma membrane surrounds substance, and pinches off forming a vesicle with substance inside

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