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SingaporeBiology

Energy and Equilibrium

8 dot points across 8 inquiry questions. Click any dot point for a focused answer with worked past exam questions where available.

Why is ATP described as the universal energy currency of the cell, and how does its structure suit this role?

Describe the structure of ATP and explain its role as the immediate energy source for cellular processes
A focused answer to the H2 Biology Energy and Equilibrium outcome on ATP. The structure of ATP, the hydrolysis and synthesis cycle with ADP and inorganic phosphate, and why ATP is the immediate, universal energy currency of the cell.
8 min answer →

How do competitive and non-competitive inhibitors reduce enzyme activity, and how is inhibition used to control metabolism?

Distinguish competitive and non-competitive enzyme inhibition and explain end-product inhibition in metabolic control
A focused answer to the H2 Biology Energy and Equilibrium outcome on enzyme inhibition. Competitive inhibitors binding the active site, non-competitive inhibitors binding elsewhere, the effect of substrate concentration on each, and end-product inhibition as feedback control.
8 min answer →

How do enzymes catalyse biochemical reactions, and what does the induced fit model add to the lock and key idea?

Explain how enzymes act as biological catalysts by lowering activation energy, and describe the lock and key and induced fit models
A focused answer to the H2 Biology Energy and Equilibrium outcome on enzymes. How enzymes lower activation energy, the enzyme-substrate complex, the lock and key and induced fit models, and the meaning of specificity.
8 min answer →

How do temperature, pH, substrate concentration and enzyme concentration affect the rate of an enzyme-catalysed reaction?

Explain the effects of temperature, pH, substrate concentration and enzyme concentration on the rate of enzyme activity
A focused answer to the H2 Biology Energy and Equilibrium outcome on enzyme kinetics. The effect of temperature (including the optimum and denaturation), pH, substrate concentration (the plateau at saturation) and enzyme concentration, with the reasoning behind each graph.
9 min answer →

How is glucose broken down in glycolysis and the link reaction, and what are the products of each stage?

Describe glycolysis and the link reaction, including the products and the role of substrate-level phosphorylation
A focused answer to the H2 Biology Energy and Equilibrium outcome on the first stages of respiration. Glycolysis in the cytoplasm, the net yield of ATP, NADH and pyruvate, and the link reaction producing acetyl coenzyme A, with the role of substrate-level phosphorylation.
9 min answer →

How do the light-dependent reactions of photosynthesis capture light energy and convert it into ATP and reduced NADP?

Describe the light-dependent reactions of photosynthesis, including photophosphorylation and the photolysis of water
A focused answer to the H2 Biology Energy and Equilibrium outcome on the light-dependent stage of photosynthesis. Light absorption by chlorophyll, the photolysis of water, the electron transport chain and chemiosmosis in the thylakoid, and the production of ATP and reduced NADP.
9 min answer →

How does the Calvin cycle use ATP and reduced NADP to fix carbon dioxide into carbohydrate?

Describe the Calvin cycle (light-independent reactions), including carbon fixation, reduction and the regeneration of the carbon dioxide acceptor
A focused answer to the H2 Biology Energy and Equilibrium outcome on the light-independent reactions. Carbon fixation by rubisco, the reduction of glycerate phosphate to triose phosphate using ATP and reduced NADP, and the regeneration of the carbon dioxide acceptor.
9 min answer →

How do the Krebs cycle and the electron transport chain complete the oxidation of glucose and generate most of the cell's ATP?

Describe the Krebs cycle and oxidative phosphorylation, including chemiosmosis and the role of oxygen as the final electron acceptor
A focused answer to the H2 Biology Energy and Equilibrium outcome on the final stages of aerobic respiration. The Krebs cycle in the matrix, the electron transport chain and chemiosmosis on the inner membrane, the role of oxygen, and the overall ATP yield.
10 min answer →