ap biology unit 3

What is the primary role of enzymes in biological reactions?

They act as biological catalysts to speed up chemical reactions by lowering the activation energy.

The specific region on an enzyme where the substrate binds is called the _.

active site

What model describes the interaction where an enzyme changes its shape slightly to bind more snugly to its substrate?

The induced fit model.

How does increasing substrate concentration initially affect the rate of an enzyme-catalyzed reaction?

It increases the reaction rate because of more frequent collisions between substrate and enzyme molecules.

What happens to the reaction rate when an enzyme becomes saturated with substrate?

The reaction rate plateaus because all enzyme active sites are occupied, and the enzyme is working at its maximum velocity.

Define denaturation in the context of an enzyme.

"The disruption of an enzyme's protein structure, often by extreme temperature or pH, which eliminates its catalytic ability."

"A _ inhibitor binds to the active site of an enzyme

competitive

How does a noncompetitive inhibitor affect an enzyme's function?

It binds to an allosteric site, causing a conformational change in the active site that prevents the substrate from binding effectively.

What is feedback inhibition in a metabolic pathway?

A regulatory mechanism where the end product of a pathway binds to and inhibits an enzyme that acts early in the pathway.

What is the term for the totality of an organism's chemical reactions?

Metabolism.

Metabolic pathways that release energy by breaking down complex molecules into simpler compounds are called _ pathways.

catabolic

What type of metabolic pathway consumes energy to build complex molecules from simpler ones?

Anabolic pathways.

What does the first law of thermodynamics, the principle of conservation of energy, state?

Energy can be transferred and transformed, but it cannot be created or destroyed.

The second law of thermodynamics states that every energy transfer or transformation increases the _ of the universe.

entropy (disorder)

A chemical reaction that proceeds with a net release of free energy is called a(n) _ reaction.

exergonic

A chemical reaction that absorbs free energy from its surroundings is called a(n) _ reaction.

endergonic

What molecule functions as the primary energy currency for cells?

Adenosine triphosphate (ATP).

What are the three components of an ATP molecule?

Adenine (a nitrogenous base), ribose (a five-carbon sugar), and three phosphate groups.

How does ATP release energy to power cellular work?

Energy is released when the terminal phosphate bond is broken by hydrolysis, converting ATP to ADP and inorganic phosphate

The use of an exergonic process to drive an endergonic one is known as _.

energy coupling

What is the general chemical equation for photosynthesis?

6CO2 + 6H2O + Light Energy → C6H{12}O6 + 6O2

"In photosynthesis, $CO_2$ is _____ to form glucose, and $H_2O$ is _____ to form oxygen.

reduced

What are the two main stages of photosynthesis?

The light-dependent reactions and the Calvin cycle (light-independent reactions).

Where do the light-dependent reactions of photosynthesis occur in a eukaryotic cell?

In the thylakoid membranes of the chloroplast.

What are the primary products of the light-dependent reactions?

ATP, NADPH, and oxygen

What is the fluid-filled space within the chloroplast where the Calvin cycle occurs?

The stroma.

What are the inputs for the Calvin cycle?

Carbon dioxide ($CO_2$), ATP, and NADPH.

What is the primary output molecule of the Calvin cycle that is used to synthesize glucose?

Glyceraldehyde 3-phosphate (G3P).

What is the role of chlorophyll and other pigments in photosynthesis?

They absorb light energy, which excites electrons to a higher energy level, initiating the light reactions.

Which photosystem functions first in the light reactions and is responsible for splitting water?

Photosystem II (PS II).

The process of splitting water using light energy during photosynthesis is called _.

photolysis

What is the function of the electron transport chain (ETC) in the light reactions of photosynthesis?

It uses the energy from excited electrons to pump protons ($H^+$) from the stroma into the thylakoid space, creating a proton gradient.

What is photophosphorylation?

The process of generating ATP from ADP and phosphate, driven by the flow of protons through ATP synthase during the light reactions of photosynthesis.

Which enzyme catalyzes the first step of the Calvin cycle, fixing carbon dioxide to RuBP?

RuBisCO (Ribulose-1,5-bisphosphate carboxylase/oxygenase).

What is the overall chemical equation for aerobic cellular respiration?

$C6H{12}O6 + 6O2 \rightarrow 6CO2 + 6H2O + \text{Energy (ATP + heat)}$

In cellular respiration, glucose ($C_6H_{12}O_6$) is _____ and oxygen ($O_2$) is _____.",oxidized

reduced

What are the four main stages of aerobic cellular respiration?

Glycolysis, pyruvate oxidation, the citric acid cycle (Krebs cycle), and oxidative phosphorylation.

Where in a eukaryotic cell does glycolysis occur?

In the cytoplasm (cytosol).

What are the net products of glycolysis from one molecule of glucose?

2 pyruvate, 2 ATP, and 2 NADH.

Is oxygen required for glycolysis to occur?

No, glycolysis is an anaerobic process.

What happens during pyruvate oxidation and where does it take place?

Each pyruvate molecule is converted into acetyl CoA, producing $CO_2$ and NADH; this occurs in the mitochondrial matrix.

The _ cycle completes the breakdown of glucose by oxidizing acetyl CoA in the mitochondrial matrix.

citric acid (or Krebs)

For each turn, what does the citric acid cycle produce?

1 ATP, 3 NADH, 1 $FADH_2$, and 2 $CO_2$.

What stage of cellular respiration generates the vast majority of ATP?

Oxidative phosphorylation.

What is the role of NADH and $FADH_2$ in oxidative phosphorylation?

They donate high-energy electrons to the electron transport chain.

Where is the electron transport chain for cellular respiration located in eukaryotes?

In the inner mitochondrial membrane.

What is the final electron acceptor in the electron transport chain of aerobic respiration?

Oxygen ($O_2$), which is reduced to form water ($H_2O$).

What is chemiosmosis in the context of cellular respiration?

The process where the energy stored in a proton gradient across the inner mitochondrial membrane is used to drive ATP synthesis by ATP synthase.

The ATP produced during glycolysis and the citric acid cycle is generated by _.

substrate-level phosphorylation

What is the main purpose of fermentation?

To regenerate $NAD^+$ from NADH, allowing glycolysis to continue producing ATP in the absence of oxygen.

What are the two common types of fermentation?

Alcohol (ethanol) fermentation and lactic acid fermentation.

In alcohol fermentation, pyruvate is converted into _____ and _____.

ethanol; carbon dioxide ($CO_2$)

What is the end product of lactic acid fermentation?

Lactate (lactic acid).

How does the net ATP yield of fermentation compare to aerobic respiration?

Fermentation yields only 2 ATP per glucose (from glycolysis), while aerobic respiration yields approximately 30-32 ATP.

Autotroph

An organism that produces its own food, usually via photosynthesis (photoautotroph) or chemosynthesis (chemoautotroph).

Heterotroph

An organism that obtains energy and organic molecules by consuming other organisms.

What are cofactors and coenzymes?

Cofactors are non-protein enzyme helpers (e.g., inorganic ions), while coenzymes are organic cofactors (e.g., vitamins, NAD+).

How do environmental temperatures above the optimum range affect enzyme activity?

They cause the enzyme to denature, rapidly decreasing its activity.

In photosynthesis, the high concentration of protons ($H^+$) is established in the _____.

thylakoid space (lumen)

In cellular respiration, the high concentration of protons ($H^+$) is established in the _____.

intermembrane space

The process of decoupling oxidative phosphorylation from electron transport generates _ instead of ATP.

heat

Organisms such as yeast that can survive using either fermentation or cellular respiration are known as _.

facultative anaerobes

What evidence supports the claim that glycolysis is a very ancient metabolic process?

It is conserved across all domains of life and does not require oxygen, which was scarce in Earth's early atmosphere.

The green color of leaves is due to chlorophyll _ green light.

reflecting and transmitting

What is the difference between an absorption spectrum and an action spectrum for photosynthesis?

An absorption spectrum shows which wavelengths a pigment absorbs, while an action spectrum shows which wavelengths are most effective at driving photosynthesis.

What are the three stages of the Calvin cycle in order?

1. Carbon Fixation, 2. Reduction, 3. Regeneration of the $CO_2$ acceptor (RuBP).

In eukaryotes, the enzymes for the citric acid cycle are located in the _____, while the enzymes for the ETC are located in the _____.

mitochondrial matrix; inner mitochondrial membrane

The energy from the exergonic flow of electrons down the ETC is used to perform what work?

Pumping protons ($H^+$) against their concentration gradient from the matrix to the intermembrane space.

What is the name of the electron carrier that functions in photosynthesis?

$NADP^+$ / NADPH

What are the names of the two primary electron carriers that function in cellular respiration?

$NAD^+$ / NADH and FAD / $FADH_2$

The transfer of a phosphate group from ATP to another molecule, making it more reactive, is called _____.

phosphorylation

How many turns of the Calvin cycle are required to produce one net molecule of G3P?

Three turns, fixing three molecules of $CO_2$.

How many molecules of acetyl CoA are produced from a single glucose molecule?

Two, because glycolysis splits one 6-carbon glucose into two 3-carbon pyruvate molecules.

What type of organisms were first responsible for producing the oxygenated atmosphere on Earth?

Prokaryotic photoautotrophs, specifically cyanobacteria.

How does ATP synthase harness the energy of the proton-motive force?

It uses the kinetic energy from the diffusion of protons ($H^+$) down their electrochemical gradient to power the phosphorylation of ADP to ATP.