NCEA Level 2 Biology 91156 Cellular life processes: past papers, practice and marking
- NCEA Level 2
- Biology
- AS91156
- 4 credits
- External exam
About 91156
AS91156, Demonstrate understanding of life processes at the cellular level. Photosynthesis in both phases and what limits it, aerobic and anaerobic respiration and why an active animal needs both, enzymes and what changes their activity, diffusion, osmosis, facilitated diffusion and active transport, and DNA replication, mitosis and cell size: the 4-credit external, in the six question types it keeps reusing.
What 91156 covers
- PhotosynthesisWord and symbol equations, how water and carbon dioxide enter, chlorophyll, the light-dependent phase in the thylakoids (water split, oxygen released, ATP and hydrogen passed on) and the light-independent phase in the stroma (carbon dioxide fixed into glucose, enzyme-controlled), chloroplast structure suited to function, comparing cells
- Limiting factorsLight intensity, temperature, carbon dioxide and water availability, the idea of a limiting factor, rate across a day from sunrise to night, sun and shade leaves, why carbon dioxide limits aquatic plants more than land plants
- RespirationReleasing energy from glucose as ATP; aerobic in the mitochondria with oxygen, 36–38 ATP, no toxic by-product; anaerobic in the cytoplasm, 2 ATP, fast, lactic acid in animals and ethanol and carbon dioxide in yeast; mitochondrion structure; why an active animal uses both
- EnzymesBiological catalysts, protein with an active site, enzyme-substrate complex, lower activation energy, lock and key and induced fit; temperature (collisions, optimum, denaturing), pH, substrate concentration, co-factors and co-enzymes, inhibitors
- Membrane transportDiffusion, osmosis, facilitated diffusion and active transport: passive or active, with or against the concentration gradient, protein channels, carriers and pumps, ATP; applied to roots, fish, muscle and plant tissue data
- MitosisSurface area to volume ratio falling as a cell grows, why cells divide, semi-conservative replication with complementary base pairing and antiparallel strands, mitosis giving two genetically identical cells for growth and repair, high division rates
91156 past papers
Open a 91156 past paper beside your own Ako page, then get it marked, part by part.
Work through a past paper All NCEA Level 2 Biology past papers
Practice questions
Question 1: Photosynthesis
A student wrote in their notes: "The light-independent phase happens at night, in the cytoplasm, because it does not need light."
- State where the light-independent phase really takes place.(up to Achieved)
- Describe what the light-independent phase uses and what it makes.(up to Achieved)
Check your answer
Part a: what gets the marks
- The light-independent phase takes place in the stroma of the chloroplast.
A full answer: In the stroma of the chloroplast, not the cytoplasm.
Part b: what gets the marks
- The light-independent phase uses carbon dioxide, hydrogen and ATP, and makes glucose.
A full answer: It uses carbon dioxide, plus hydrogen and ATP from the light-dependent phase. It fixes the carbon from carbon dioxide and makes glucose.
What gets each grade
Question 2: Photosynthesis
In a famous kind of experiment, scientists gave a plant water whose oxygen atoms were a heavy form of oxygen that can be traced. The carbon dioxide they supplied contained ordinary oxygen. The heavy oxygen turned up in the oxygen gas the plant gave off, and not in the glucose it made.
- State where in the chloroplast the light-dependent phase takes place.(up to Achieved)
- Describe what happens in the light-dependent phase.(up to Achieved)
Check your answer
Part a: what gets the marks
- The light-dependent phase takes place in the thylakoid membranes, which are stacked into grana.
A full answer: In the thylakoid membranes, which are stacked into grana.
Part b: what gets the marks
- Chlorophyll in the thylakoid membranes absorbs light energy.
- The absorbed light energy splits water into oxygen and hydrogen.
- Oxygen is released as a by-product, and ATP and hydrogen are made and passed to the stroma.
A full answer: Chlorophyll in the thylakoid membranes absorbs light energy. This energy is used to split water molecules into oxygen and hydrogen. The oxygen is released from the leaf as a by-product. Energy is also used to make ATP. The hydrogen and the ATP are passed on to the stroma for the light-independent phase.
What gets each grade
Question 3: Photosynthesis
A palisade mesophyll cell just under the upper surface of a pūriri leaf contains about 50 chloroplasts. Spongy mesophyll cells deeper in the leaf contain far fewer.
- Name the part of the chloroplast where the light-independent phase takes place, and describe what this phase uses and makes.(up to Achieved)
- Explain why the palisade cells near the upper surface of the pūriri leaf have many more chloroplasts than the cells deeper in the leaf.(up to Merit)
Check your answer
Part a: what gets the marks
- The light-independent phase takes place in the stroma, where carbon dioxide is used with ATP and hydrogen to make glucose.
A full answer: The light-independent phase takes place in the stroma. It uses carbon dioxide with ATP and hydrogen from the light-dependent phase to make glucose.
Part b: what gets the marks
- Chloroplasts contain chlorophyll, which absorbs the light energy needed for photosynthesis.
- The upper surface receives the most light, so packing many chloroplasts into the palisade cells there means more chlorophyll catches the light before it is absorbed or scattered deeper in the leaf, so more light energy is captured and more glucose is made.
A full answer: Chloroplasts contain chlorophyll, which absorbs light energy. The palisade cells sit just under the upper surface, where most light reaches the leaf, so many chloroplasts there capture the most light energy before it is absorbed or scattered deeper down. More light captured means more water split and more ATP and hydrogen for making glucose.