AP Bio: Cellular Energetics

What is the purpose of enzymes and what types of reactions can they facilitate?

Enzymes speed up chemical reactions by lowering activation energy and can facilitate both catabolic (breaking down) and anabolic (building up) reactions.

What are most enzymes made of?

Most enzymes are made of proteins.

Why is an enzyme’s structure important to its function?

The specific 3D shape of an enzyme determines how it binds to its substrate and performs its catalytic function.

What is a substrate?

A substrate is the reactant molecule that an enzyme binds to and acts upon in a chemical reaction.

What is the significance of the active site to an enzyme?

The active site is the region of the enzyme where the substrate binds and the chemical reaction takes place.

Why can enzymes be reused?

Enzymes are not consumed in the reactions they catalyze, so they can be used repeatedly.

What is activation energy?

Activation energy is the minimum amount of energy needed for a chemical reaction to occur.

How do enzymes speed up chemical reactions?

Enzymes lower the activation energy required, allowing reactions to occur faster.

What is denaturation, what factors can cause it, and what is the result?

Denaturation is the unfolding or structural alteration of a protein, caused by factors such as temperature, pH, or chemicals, which results in loss of its function.

How do temperature, pH, and substrate/enzyme concentration affect the rate of enzyme-catalyzed reactions?

Temperature and pH can increase reaction rate up to an optimal point but extreme values can denature enzymes, while higher substrate or enzyme concentration generally increases reaction rate until saturation occurs.

What is the difference between an acid and a base in terms of H+ concentration and the pH scale?

Acids have higher H+ concentration and lower pH, while bases have lower H+ concentration and higher pH.

How can you calculate rate from a graph?

Rate can be calculated using the slope of a line on a graph, typically using change in product or reactant over time.

What is the difference between competitive and noncompetitive (allosteric) enzyme inhibitors?

Competitive inhibitors bind to the active site and block substrate binding, while noncompetitive inhibitors bind elsewhere (allosteric site), changing the enzyme’s shape and reducing its activity.

What is the second law of thermodynamics?

The second law of thermodynamics states that energy transfer increases the entropy (disorder) of a system, meaning some energy is always lost as heat.

How is energy released from ATP and transferred to other molecules?

Energy is released when ATP is hydrolyzed to ADP and inorganic phosphate, and this energy is used to drive other cellular reactions.

What is energy coupling?

Energy coupling is the use of energy released from exergonic reactions (like ATP hydrolysis) to drive endergonic reactions that require energy.

What is a metabolic pathway?

A metabolic pathway is a series of linked chemical reactions within a cell, where the product of one reaction becomes the substrate for the next.

Who were the first photosynthetic organisms and what important role did they play?

The first photosynthetic organisms were cyanobacteria, which produced oxygen as a byproduct, leading to the oxygenation of Earth’s atmosphere.

What is the balanced equation of photosynthesis and its overall purpose?

The balanced equation is 6 CO₂ + 6 H₂O → C₆H₁₂O₆ + 6 O₂, and its purpose is to convert light energy into chemical energy stored in glucose.

What is the function of pigments in photosynthesis?

Pigments, such as chlorophyll, absorb light energy to drive the reactions of photosynthesis.

What are the roles of the light-dependent reactions and the Calvin cycle?

Light-dependent reactions capture light energy to produce ATP and NADPH, while the Calvin cycle uses ATP and NADPH to fix carbon dioxide into glucose.

What is the structure of the chloroplast?

Chloroplasts have a double membrane, with internal stacks of thylakoids called grana where light-dependent reactions occur, and a fluid-filled stroma where the Calvin cycle takes place.

What is the difference between oxidation and reduction?

Oxidation is the loss of electrons, while reduction is the gain of electrons.

Which reactants do the products of photosynthesis come from?

Oxygen comes from water, and glucose comes from carbon dioxide fixed in the Calvin cycle.

Why do pigments appear a specific color and why is it advantageous for photosynthetic organisms to have a variety of pigments?

Pigments absorb specific wavelengths of light and reflect others, appearing colored

What are the roles of light, NADP+, NADPH, ATP, chlorophyll, electrons, photosystems I and II, thylakoids, electron transport chain, hydrogen ions, ATP synthase, water, and oxygen in the light-dependent reactions?

Light excites electrons in chlorophyll, which move through photosystems and the electron transport chain in thylakoid membranes

What are the roles of ATP, NADPH, carbon dioxide, stroma, and glucose in the Calvin cycle?

ATP and NADPH provide energy and electrons, carbon dioxide is fixed in the stroma, and the cycle produces glucose.

What are the uses for the glucose produced through photosynthesis?

Glucose can be used for cellular respiration to produce ATP, stored as starch, or used to make other organic molecules like cellulose and lipids.

Which organisms perform cellular respiration and/or fermentation?

All organisms perform cellular respiration to extract energy from glucose, and some can perform fermentation under anaerobic conditions.

What is the balanced equation of cellular respiration and its overall purpose?

The equation is C₆H₁₂O₆ + 6 O₂ → 6 CO₂ + 6 H₂O + ATP, and its purpose is to convert glucose into usable chemical energy (ATP).

What do the terms aerobic and anaerobic mean?

Aerobic means requiring oxygen, while anaerobic means occurring without oxygen.

What are the steps of cellular respiration?

The steps are glycolysis, pyruvate oxidation, the Krebs cycle, and the electron transport chain.

What is the structure of the mitochondria and what is the significance of the cristae?

Mitochondria have a double membrane, with the inner membrane folded into cristae to increase surface area for ATP production during oxidative phosphorylation.

Which reactants do the products of cellular respiration come from?

Carbon dioxide comes from glucose, water comes from oxygen, and ATP is produced from the energy released during glucose breakdown.

What are the roles of glucose, cytosol, ATP, NAD+, NADH, ADP, phosphate, and pyruvate in glycolysis?

Glucose is broken down in the cytosol

What are the roles of the mitochondrial matrix, NADH, carbon dioxide, pyruvate, and acetyl CoA in pyruvate oxidation?

Pyruvate enters the mitochondrial matrix, is converted to acetyl CoA, NAD+ is reduced to NADH, and carbon dioxide is released as a waste product.

What are the roles of acetyl CoA, mitochondrial matrix, NADH, FADH2, carbon dioxide, and ATP in the Krebs (citric acid) cycle?

Acetyl CoA enters the cycle in the mitochondrial matrix

What are the roles of NADH, FADH2, oxygen, hydrogen ion gradient, inner mitochondrial membrane, ETC, ATP synthase, and water in oxidative phosphorylation?

NADH and FADH2 donate electrons to the ETC in the inner mitochondrial membrane, creating a proton gradient

How does the pH of the mitochondrial matrix compare to the inner membrane space during oxidative phosphorylation?

The matrix is more basic (higher pH) due to lower proton concentration, while the inner membrane space is more acidic (lower pH) due to proton accumulation.

How does oxidative phosphorylation compare and contrast with photophosphorylation?

Both use an electron transport chain and proton gradient to produce ATP, but oxidative phosphorylation uses energy from glucose, while photophosphorylation uses energy from sunlight.

Where do electron transport chains occur in prokaryotes?

In prokaryotes, electron transport chains are located in the plasma (cell) membrane.

What is the result of decoupling in oxidative phosphorylation?

Decoupling prevents the proton gradient from driving ATP synthesis, so energy is released as heat instead of forming ATP.

How does aerobic cellular respiration compare and contrast with anaerobic cellular respiration?

Both break down glucose to produce ATP, but aerobic respiration uses oxygen as the final electron acceptor and produces more ATP, while anaerobic respiration uses another molecule and produces less ATP.

How does aerobic cellular respiration compare and contrast with fermentation?

Both begin with glycolysis, but aerobic respiration continues with pyruvate oxidation, the Krebs cycle, and oxidative phosphorylation to produce more ATP, while fermentation regenerates NAD+ to allow glycolysis to continue, producing less ATP.

How does fermentation allow glycolysis to continue in the absence of oxygen?

Fermentation regenerates NAD+ from NADH, ensuring glycolysis can continue producing ATP when oxygen is not available.