Metabolism & Energy
What is the difference between catabolic and anabolic pathways?
Catabolic pathways break down molecules and release energy; anabolic pathways build molecules and consume energy.
What is the role of enzymes in metabolism?
Enzymes speed up chemical reactions by lowering activation energy.
What are the three main stages of cellular respiration?
Glycolysis, Citric Acid Cycle (Kreb cycle), and Oxidative Phosphorylation (ETC)
What is the overall equation for photosynthesis?
6CO₂ + 6H₂O + light → C₆H₁₂O₆ + 6O₂
What macromolecule class does ATP belong to?
ATP is a nucleotide, part of the nucleic acid macromolecule group.
Which type of energy is stored in chemical bonds—kinetic or potential?
Potential energy is stored energy (e.g., in chemical bonds); kinetic energy is energy of motion.
What is the induced-fit model of enzyme function?
The induced-fit model suggests the enzyme changes shape slightly to fit the substrate better.
Where does glycolysis occur in the cell?
Glycolysis occurs in the cytoplasm.
Where do the light reactions occur?
Light reactions occur in the thylakoid membranes.
Why is ATP considered the energy currency of the cell?
ATP stores energy in its phosphate bonds and releases it when hydrolyzed.
What does a negative ΔG indicate about a reaction?
A negative ΔG means the reaction is spontaneous and releases free energy.
How does temperature affect enzyme activity?
Enzyme activity increases with temperature up to an optimal point, then decreases due to denaturation. (enzymes are made up of proteins)
What is the role of NAD⁺ in respiration?
NAD⁺ accepts electrons and becomes NADH, carrying energy to the electron transport chain.
What is the role of rubisco in the Calvin cycle?
Rubisco fixes CO₂ by attaching it to RuBP in the Calvin cycle.
What happens during ATP hydrolysis?
ATP hydrolysis breaks a phosphate bond, releasing energy and forming ADP + Pi.
Define an exergonic reaction and give an example.
An exergonic reaction releases energy (e.g., cellular respiration).
What’s the difference between competitive and noncompetitive inhibition?
Competitive inhibitors bind to the active site; noncompetitive inhibitors bind elsewhere and change enzyme shape.
Compare oxidative phosphorylation and substrate-level phosphorylation.
How is photophosphorylation similar to oxidative phosphorylation?
Both use chemiosmosis and ATP synthase; mitochondria use food energy, chloroplasts use light energy.
Why do bubbles form in a beer bottle when you open it?
Bubbles form due to fermentation, a process where yeast breaks down sugars anaerobically (without oxygen). During this process, ethanol (alcohol) is produced, and carbon dioxide (CO₂) is released as a byproduct. The CO₂ dissolves under pressure in the sealed bottle forming those bubbles.
Explain how the first and second laws of thermodynamics apply to living systems.
Allosteric regulators bind to sites other than the active site to activate or inhibit enzyme activity.
How do allosteric regulators control enzyme activity?
Explain how the electron transport chain creates a proton gradient.
The ETC pumps protons into the intermembrane space, creating a gradient used by ATP synthase to make ATP.
Trace the path of electrons from water to G3P.
Water → P680 → ETC → P700 → NADP⁺ → NADPH → Calvin cycle → G3P.
Interpret a free energy diagram of an endergonic reaction.
In an endergonic reaction, free energy increases (ΔG > 0), and the products have more energy than the reactants.