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United StatesBiology

Unit 3: Cellular Energetics

6 dot points across 6 inquiry questions. Click any dot point for a focused answer with worked past exam questions where available.

How do cells obtain, store and use energy, and what makes a reaction favorable?

Topic 3.4 Cellular Energy: explain how cells use free energy, ATP and coupled reactions to drive endergonic processes, and how energy flows into and out of biological systems.
A focused answer to AP Biology Topic 3.4, covering free energy, exergonic and endergonic reactions, ATP as the energy currency, energy coupling, and why living systems require a constant input of free energy.
9 min answer →

How do cells release the chemical energy in glucose to make ATP?

Topic 3.6 Cellular Respiration: explain how glycolysis, the Krebs cycle and oxidative phosphorylation release energy from glucose to make ATP, and how fermentation allows ATP production without oxygen.
A focused answer to AP Biology Topic 3.6, covering glycolysis, the Krebs cycle, oxidative phosphorylation, chemiosmosis, the role of oxygen, and fermentation, with the link back to photosynthesis.
10 min answer →

How do temperature and pH change the rate of an enzyme-catalyzed reaction?

Topic 3.3 Environmental Impacts on Enzyme Function: explain how changes in temperature and pH affect enzyme structure and the rate of an enzyme-catalyzed reaction, including denaturation and optimum conditions.
A focused answer to AP Biology Topic 3.3, covering the optimum temperature and pH of enzymes, why activity rises then falls with temperature, denaturation, and how to read enzyme-rate graphs.
9 min answer →

How do enzymes speed up reactions, and what controls the rate of an enzyme-catalyzed reaction?

Topic 3.2 Enzyme Catalysis: explain how enzymes lower activation energy and how substrate concentration, enzyme concentration and inhibitors affect the rate of an enzyme-catalyzed reaction.
A focused answer to AP Biology Topic 3.2, covering activation energy, the transition state, saturation, the effect of substrate and enzyme concentration, and competitive versus noncompetitive inhibition, with a worked rate calculation.
10 min answer →

How does the structure of an enzyme determine which reaction it catalyzes?

Topic 3.1 Enzyme Structure: describe the structure of enzymes, the role of the active site, and how the structure of an enzyme determines its specificity for a substrate.
A focused answer to AP Biology Topic 3.1, covering enzymes as protein catalysts, the active site, the induced-fit model, enzyme-substrate specificity, and how three-dimensional shape determines which reaction is catalyzed.
9 min answer →

How does photosynthesis capture light energy and store it as chemical energy in sugars?

Topic 3.5 Photosynthesis: explain how the light-dependent reactions and the Calvin cycle capture light energy and use it to fix carbon dioxide into sugar.
A focused answer to AP Biology Topic 3.5, covering the light-dependent reactions, the electron transport chain, chemiosmosis, the Calvin cycle, and how light energy is converted to the chemical energy of sugars.
10 min answer →