Eduqas A Level Biology Component 1: Energy for Life Exam Questions

About Eduqas A Level Biology Component 1: Energy for Life

Component 1 of Eduqas A Level Biology, Energy for Life, follows energy from the sun into ATP and through ecosystems. It starts with chemiosmosis and the structure of ATP, then moves through the light-dependent and light-independent reactions of photosynthesis, the stages of aerobic and anaerobic respiration, culturing and counting microorganisms, population growth and energy flow, and finally how humans affect ecosystems. It builds directly on AS work on enzymes, membranes and organelles. Examiners like data interpretation on limiting factors, calculations of efficiency and respiratory quotient, serial dilution counts, and extended answers that link the biochemistry of energy release to whole ecosystems.

What you need to know

• 1.1 ATP is a phosphorylated nucleotide whose hydrolysis to ADP and inorganic phosphate releases energy in small, usable amounts. It is made by substrate-level phosphorylation and by chemiosmosis, where protons flow through ATP synthase down an electrochemical gradient across a membrane.
• 1.2 In the light-dependent stage, photosystems I and II absorb light, water is photolysed and ATP and reduced NADP are produced. In the Calvin cycle, rubisco fixes carbon dioxide with RuBP to form GP, which is reduced to triose phosphate using ATP and reduced NADP; most TP regenerates RuBP.
• 1.3 Aerobic respiration runs through glycolysis (cytoplasm), the link reaction and Krebs cycle (matrix) and the electron transport chain (inner mitochondrial membrane), with oxygen as the final electron acceptor. Anaerobic pathways regenerate NAD only, giving lactate in mammals and ethanol plus carbon dioxide in yeast. RQ = CO2 produced / O2 used.
• 1.4 Bacteria are classified by shape and Gram staining. Cultures need aseptic technique, and population size is estimated by serial dilution and plate counts (viable counts) or by haemocytometer and turbidity (total counts).
• 1.5 Populations follow a growth curve limited by density-dependent and density-independent factors. Energy transfer between trophic levels is inefficient, and carbon and nitrogen cycles depend on microorganisms (nitrogen fixation, nitrification, denitrification, ammonification). Succession leads to a climax community.
• 1.6 Human activities such as deforestation, overfishing, agricultural intensification and pollution reduce biodiversity. Conservation uses sustainable management, quotas, protected areas and seed banks, and eutrophication follows nutrient run-off into water.

Common mistakes in Component 1: Energy for Life

• Saying ATP stores a large amount of energy. It releases a small, manageable amount on hydrolysis and is an immediate energy source, not a long-term store.
• Placing the Krebs cycle in the cytoplasm or the electron transport chain in the matrix. Glycolysis is in the cytoplasm, link reaction and Krebs cycle in the matrix, and the ETC on the cristae.
• Writing that light is used directly in the Calvin cycle. The light-independent stage uses the ATP and reduced NADP made in the light-dependent stage and stops soon after light is removed.
• Forgetting to multiply by the dilution factor and divide by the volume plated in serial dilution calculations. Number of colonies divided by volume plated, multiplied by the dilution factor, gives cells per cm3 of the original culture.
• Saying nitrifying bacteria fix nitrogen. Nitrogen fixation converts N2 to ammonia (for example Rhizobium); nitrification oxidises ammonium to nitrite then nitrate.

Try three Component 1: Energy for Life exam-style questions