Biology Paper 2 November 2016

1. AThe glycocalyx carbohydrate chains attached to the outer surface of the membrane
2. BThe peripheral proteins loosely attached to the inner face of the membrane
3. CThe hydrophilic phosphate heads, which face the aqueous cytoplasm and are thought to actively draw polar substances inward
4. DThe hydrophobic fatty acid tails, which form a non-polar core that repels polar molecules

1. AIt anchors ribosomes to the inner surface of the membrane during protein synthesis
2. BIt provides receptor and antigen sites that must face outward so other cells and molecules can detect them
3. CIt increases the flexibility of the inner leaflet so cytoskeleton filaments can attach more securely to the inner membrane surface
4. DIt regulates the opening of ion channels from inside the cytoplasm

1. ACholesterol molecules in the membrane bind directly to glucose and hold it in place
2. BMembrane-bound enzymes break glucose down into smaller, more lipid-soluble molecules before it can reach and cross the membrane
3. CThe hydrophobic core formed by the phospholipid fatty-acid tails repels polar molecules such as glucose
4. DThe glycocalyx forms a physical barrier that traps glucose outside the cell

Answer this when you sit the paper.

1. APlant cells have an extra glycocalyx layer that stiffens the membrane surface
2. BPlant cells have a rigid cellulose cell wall outside the membrane that prevents it from folding outward
3. CPlant cells have a permanent central vacuole that flattens the membrane tightly against the surrounding cell wall, preventing outward folding
4. DPlant cells contain chloroplasts that restrict how much the membrane can curve

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1. AThe enzyme catalase becomes denatured by the heat released as the reaction proceeds, which stops any further catalytic activity from occurring
2. BOxygen gas re-dissolves back into the hydrogen peroxide solution at the same rate it is produced
3. CThe hydrogen peroxide substrate has been used up, so the reaction rate falls even though enzyme is still present
4. DThe falling pH of the reaction mixture inactivates the catalase enzyme

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1. AThe increased H+ ion concentration disrupts the ionic bonds maintaining the enzyme's active site shape, denaturing catalase
2. BThe acid lowers the temperature of the reaction mixture, slowing the rate of molecular collisions
3. CThe acid molecules temporarily occupy the active site and block hydrogen peroxide from binding, without changing the enzyme's overall shape at all
4. DThe acid reacts directly with hydrogen peroxide, converting it into water without releasing any oxygen

Answer this when you sit the paper.

1. AThey are insoluble in water, forming long, parallel polypeptide chains crosslinked into fibres
2. BThey fold into a compact, roughly spherical shape stabilised by many different types of bonds
3. CThey are highly soluble in water because their hydrophilic groups face outward on a folded surface
4. DThey function mainly as enzymes, each with a specific active site for a substrate

Answer this when you sit the paper.

Answer this when you sit the paper.

1. APhosphodiester bonds between the terminal ends of the polypeptide chain
2. BPeptide bonds linking the carboxyl group of one amino acid to the amino group of the next amino acid in the chain only
3. CGlycosidic bonds between sugar residues attached along the polypeptide backbone
4. DHydrogen bonds, ionic bonds, disulphide bonds, and hydrophobic interactions between R groups