Unit 3: Cellular Energetics

What is the function of enzymes?

Enzymes are proteins that act as catalysts, speeding up biochemical reactions by lowering the activation energy required.

What is an active site?

The active site is the specific region on an enzyme where the substrate binds and the reaction takes place.

Describe the induced fit model.

The induced fit model suggests that the active site of an enzyme changes shape slightly to fit the substrate more snugly, enhancing enzyme activity.

What is feedback inhibition?

Feedback inhibition is when the end product of a metabolic pathway inhibits an enzyme involved in that pathway to regulate and conserve resources.

What are catabolic and anabolic pathways?

Catabolic pathways break down molecules and release energy (e.g., cellular respiration), while anabolic pathways build molecules and require energy (e.g., protein synthesis).

How do enzymes lower activation energy?

Enzymes lower the activation energy needed for reactions, allowing them to proceed faster without consuming the enzyme itself.

What types of energy are important in cells?

Cells use kinetic energy (motion), thermal energy (heat), and potential energy (stored energy, like in molecular bonds).

Explain the First Law of Thermodynamics.

The First Law of Thermodynamics states that energy cannot be created or destroyed, only transformed from one form to another.

What is the Second Law of Thermodynamics?

The Second Law of Thermodynamics states that energy transformations increase entropy (disorder), often releasing heat as a byproduct.

Define spontaneous and nonspontaneous processes.

Spontaneous processes occur without added energy, moving systems toward stability, while nonspontaneous processes require energy input.

What factors influence enzyme activity?

Temperature, pH, and substrate concentration affect enzyme activity, with extreme conditions potentially causing enzyme denaturation.

What are competitive and noncompetitive inhibitors?

Competitive inhibitors block the active site, preventing substrate binding, while noncompetitive inhibitors bind elsewhere, altering enzyme shape and reducing activity.

What is ATP and why is it important?

ATP (Adenosine Triphosphate) is the cell's main energy currency, providing energy for cellular work such as chemical, transport, and mechanical functions.

What is the equation for photosynthesis?

Photosynthesis equation: 6CO₂ + 6H₂O + light energy → C₆H₁₂O₆ + 6O₂.

What happens in the light reactions of photosynthesis?

During the light reactions, solar energy splits water, releasing oxygen and creating ATP and NADPH for the Calvin Cycle.

What is the Calvin Cycle?

The Calvin Cycle uses CO₂, ATP, and NADPH to produce G3P, which can be used to form glucose, in three phases: carbon fixation, reduction, and regeneration.

What is cellular respiration and its equation?

Cellular respiration is the process of breaking down glucose to produce energy, with the equation: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + ATP.

What are the three stages of cellular respiration?

Glycolysis (cytoplasm), Krebs Cycle (mitochondrial matrix), and Electron Transport Chain (mitochondrial membrane).

Describe glycolysis.

Glycolysis breaks down glucose into two molecules of pyruvate, producing a small amount of ATP and NADH.

What occurs in the Krebs Cycle?

In the Krebs Cycle, acetyl CoA is broken down, releasing CO₂, producing ATP, NADH, and FADH₂.

Explain the Electron Transport Chain (ETC) in cellular respiration.

The ETC transfers electrons from NADH and FADH₂, pumping protons to create a gradient used by ATP synthase to generate ATP in oxidative phosphorylation.

What is anaerobic respiration?

Anaerobic respiration generates ATP without oxygen, using processes like fermentation.

What is lactic acid fermentation?

Lactic acid fermentation converts pyruvate to lactate in muscles when oxygen is low, producing minimal ATP and causing muscle fatigue.

What is alcoholic fermentation?

Alcoholic fermentation, used by yeast, converts pyruvate to ethanol and CO₂, a process used in baking and alcohol production.