Biology Paper 4 June 2004

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1. ABubbles form in the mixture but the splint does not relight.
2. BNo bubbles form in the mixture but the splint still relights.
3. CThe mixture bubbles vigorously, exactly as it did before boiling, and the splint relights when it is inserted.
4. DNo bubbles form in the mixture and the splint does not relight.

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1. ABoiling increased the catalase's activity so much that all of the hydrogen peroxide had already reacted before the glowing splint could even be inserted into the tube.
2. BThe cooling step under running tap water washed all of the hydrogen peroxide out of the tube before any reaction with the yeast could begin.
3. CThe catalase in the boiled sample was denatured by the heat because it is a protein, so it could no longer catalyse the breakdown of hydrogen peroxide.
4. DThe yeast suspension in tube B had already been killed by the cold tap water before it was ever placed into the boiling water bath at all.

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1. AThe reaction has reached true chemical equilibrium and has therefore stopped producing any further oxygen gas.
2. BA factor other than substrate concentration, such as the fixed amount of enzyme present, has become limiting.
3. CHydrogen peroxide concentration remains the only factor limiting the rate at every concentration that was tested.
4. DThe catalase enzyme has been permanently and irreversibly denatured by the high substrate concentration itself.

1. ATo allow the glowing splint enough time to cool down completely before it was inserted into the tube.
2. BTo allow the initial, uneven burst of bubble production to settle into a steady, countable rate.
3. CTo allow the boiling water bath enough time to fully return to its normal, full boiling temperature again.
4. DTo let enough of the hydrogen peroxide evaporate out of the tube so the bubbles could be counted safely.

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1. AFacilitated diffusion
2. BActive transport
3. COsmosis
4. DSimple diffusion

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1. AHigher sucrose concentrations dissolve the cell wall directly, which causes plasmolysis in a larger proportion of the cells.
2. BSucrose molecules actively diffuse into the cells and replace the water content that was originally present there.
3. CThe water potential gradient between the cell and the solution becomes steeper, so more water leaves the cells by osmosis.
4. DHigher sucrose concentrations increase the rate of active transport of water molecules into the cells themselves.

1. ADifferent cells contain different amounts and types of solutes, since their metabolic activity varies from cell to cell.
2. BAll cells within a single piece of tissue always have identical solute potential, unless the tissue has been physically damaged.
3. CSolute potential depends mainly on a cell's physical size rather than on the solutes that the cell contains.
4. DOnly the outermost cells of a piece of tissue are able to differ in solute potential from the cells beneath them.

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1. AIt functions as an endocrine gland for a short time and then undergoes regression and degeneration.
2. BIt is expelled from the body together with the unfertilised secondary oocyte during menstruation.
3. CIt remains permanently active in the ovary, continuing to secrete hormones for the rest of a woman's life.
4. DIt immediately develops back into a new primary follicle, ready for the next ovarian cycle.