Chapter 3- Enzymes, Photosynthesis, and Cellular Respiration

What are mitochondria?

Mitochondria are membrane-bound organelles found in eukaryotic cells that are responsible for producing ATP through cellular respiration.

What is glycolysis?

Glycolysis is a biochemical pathway that occurs in the cytosol, converting glucose into pyruvate, producing ATP and NADH in the process.

What is the Krebs cycle?

The Krebs cycle, also known as the citric acid cycle, takes place in the mitochondrial matrix and generates ATP, NADH, and FADH2 by oxidizing acetyl-CoA.

What is the electron transport chain (ETC)?

The electron transport chain is a series of protein complexes located in the inner mitochondrial membrane that transfers electrons from NADH and FADH2 to oxygen, forming water and establishing a proton gradient.

What is oxidative phosphorylation?

Oxidative phosphorylation is the process of generating ATP using the energy derived from the transfer of electrons through the electron transport chain and the flow of protons back through ATP synthase.

What is chemiosmosis?

Chemiosmosis is the movement of protons across a membrane that drives the synthesis of ATP from ADP and inorganic phosphate through ATP synthase.

Define fermentation. What are its products?

Fermentation is a metabolic process that allows glycolysis to occur in the absence of oxygen, resulting in products like lactic acid or alcohol, depending on the organism.

What is lactic acid fermentation?

Lactic acid fermentation is a pathway that occurs in some cells (like muscle cells) where glucose is converted into lactic acid, regenerating NAD+ for glycolysis.

What is alcoholic fermentation?

Alcoholic fermentation is a process by which yeasts convert glucose into alcohol and carbon dioxide, regenerating NAD+ for glycolysis.

What is the purpose of the Krebs Cycle?

The purpose of the Krebs cycle is to harvest high-energy electrons from carbon compounds while releasing carbon dioxide as a waste product.

Compare oxidative phosphorylation and photophosphorylation.

Both processes generate ATP using chemiosmosis, but oxidative phosphorylation occurs in mitochondria using oxygen as a terminal electron acceptor, while photophosphorylation occurs in chloroplasts using light energy and NADP+ as a terminal electron acceptor.

What are the main components of aerobic cellular respiration?

The main components include glycolysis, the Krebs cycle, the electron transport chain, and oxidative phosphorylation.

What is the purpose of glycolysis?

Glycolysis converts glucose into pyruvate while producing ATP and NADH, and occurs in the cytosol.

Where does the Krebs cycle occur?

The Krebs cycle occurs in the mitochondrial matrix.

What are the inputs and outputs of the Krebs cycle?

Inputs are acetyl-CoA, NAD+, FAD, and ADP; outputs are CO2, NADH, FADH2, and ATP.

What initiates the electron transport chain?

The electron transport chain is initiated by electrons carried by NADH and FADH2.

What is oxidative phosphorylation?

Oxidative phosphorylation is the process of ATP formation involving electron transport chain and chemiosmosis.

How do protons create a gradient in the inner mitochondrial membrane?

Electrons passing through the electron transport chain lead to the pumping of protons into the intermembrane space, creating a gradient.

What distinguishes aerobic respiration from anaerobic processes?

Aerobic respiration requires oxygen as the terminal electron acceptor, while anaerobic processes do not.

What organisms perform lactic acid fermentation?

Lactic acid fermentation occurs in muscle cells and some bacteria.

What is the main purpose of fermentation?

The main purpose of fermentation is to regenerate NAD+ so glycolysis can continue in the absence of oxygen.

What are the products of alcoholic fermentation?

Alcoholic fermentation produces ethanol and carbon dioxide.

In what part of the cell does chemiosmosis occur?

Chemiosmosis occurs across the inner mitochondrial membrane or thylakoid membrane in chloroplasts.

What is the role of ATP synthase in cellular respiration?

ATP synthase synthesizes ATP from ADP and inorganic phosphate using the energy from the proton gradient.

What happens during the electron transport chain?

Electrons are transferred from NADH and FADH2 through a series of proteins to the terminal electron acceptor, oxygen.

How is heat generated in cellular respiration?

Heat is generated when oxidative phosphorylation is decoupled from electron transport.

What is photophosphorylation?

Photophosphorylation is the process of generating ATP using light energy in photosynthesis.

What is the difference between NADH and FADH2?

NADH and FADH2 are both electron carriers, but NADH donates electrons earlier in the electron transport chain than FADH2.

What is the significance of the proton gradient in energy production?

The proton gradient is crucial for driving ATP synthesis through ATP synthase.

Photosynthesis

The process by which organisms capture energy from the sun to produce sugars.

Prokaryotic photosynthesis

Photosynthesis that first evolved in prokaryotic organisms, particularly cyanobacteria, which contributed to an oxygenated atmosphere.

Light-Dependent Reactions

A series of reactions in eukaryotic photosynthesis that capture light energy to produce ATP and NADPH.

Chlorophylls

Pigments that absorb light energy and boost electrons to a higher energy level during photosynthesis.

Photosystems I and II

Complexes of proteins and chlorophyll that are involved in the light-dependent reactions.

Electron Transport Chain (ETC)

A sequence of reactions where higher energy electrons are transferred between molecules, creating an electrochemical gradient.

Proton Gradient

An increase in hydrogen ions (H+) across a membrane, linked to ATP synthesis.

ATP Synthase

An enzyme that synthesizes ATP from ADP and inorganic phosphate using the energy from the proton gradient.

Calvin Cycle

The process where ATP and NADPH are used to produce carbohydrates from carbon dioxide.

Stroma

The fluid-filled space in chloroplasts where the Calvin cycle occurs.

Molecular Variation

Variation at the molecular level that allows organisms to respond to environmental stimuli.

Thylakoid Membrane

The location of light-dependent reactions in chloroplasts.

Photon

A particle of light energy that is captured in the light-dependent reactions.

Photolysis

The process of splitting water molecules in light-dependent reactions.

RuBisCo

An enzyme that catalyzes the first step of the Calvin cycle, making CO2 usable.

3-PGA

A 3-carbon molecule produced during the first phase of the Calvin cycle after carbon fixation.

G3P

A 3-carbon molecule that is produced from 3-PGA and used to regenerate RuBP.

RuBP

A 5-carbon molecule that combines with CO2 in the Calvin cycle to initiate the formation of carbohydrates.

NADP+

A molecule that serves as an electron acceptor in the light-dependent reactions, being reduced to NADPH.

Oxidation

The loss of electrons during a chemical reaction.

Reduction

The gain of electrons during a chemical reaction.

Cyclic Electron Flow

A process where electrons from PSI are recycled back into the electron transport chain in the absence of NADP+.

Oxygen Production

O2 is produced as a byproduct during the light-dependent reactions from the splitting of water.

ATP

A high-energy molecule produced during the light-dependent reactions, used in the Calvin cycle.

NADPH

A reduced electron carrier produced during the light-dependent reactions, used in the Calvin cycle.

Light Energy

Energy from sunlight that is captured by chlorophyll and used in photosynthesis.

Electrochemical Gradient

A gradient formed when protons are pumped across the thylakoid membrane, driving ATP synthesis.

Hydrogen Ions (H+)

Ions released during the photolysis of water that contribute to the proton gradient.

PSI (Photosystem I)

The second photosystem in the light-dependent reactions that absorbs light to energize electrons.

PSII (Photosystem II)

The first photosystem in the light-dependent reactions that captures light energy and initiates electron flow.

Phosphorylation

The process of adding a phosphate group to ADP to form ATP.

Calvin Cycle Phase 1

The carbon fixation phase where RuBisCo combines CO2 with RuBP.

Calvin Cycle Phase 2

The reduction phase where ATP and NADPH convert 3-PGA to G3P.

Calvin Cycle Phase 3

The regeneration phase where G3P is used to regenerate RuBP, consuming ATP.

Photosynthetic Pigments

Molecules in plants that absorb specific wavelengths of light necessary for photosynthesis.

Environmental Stimuli

Changes in the environment that organisms respond to through molecular variation.

Eukaryotic Photosynthesis

Photosynthesis that occurs in eukaryotic organisms, utilizing chloroplasts.

Cyanobacterial Photosynthesis

Photosynthesis conducted by cyanobacteria that contributed to the development of an oxygen atmosphere.

ATP Production

The synthesis of ATP during light-dependent reactions as a result of proton flow.

Respiration

The process by which cells convert sugars into energy, complementary to photosynthesis.

Glucose

A simple sugar produced by the Calvin cycle that serves as an energy source for organisms.

Biological Processes

Processes necessary for the survival of organisms, including energy capture and storage.

Photosynthetic Pathways

The series of biochemical processes that different organisms use to capture light and convert it to energy.

Enzymes

Biological catalysts that speed up reactions without being consumed.

Cofactor

Inorganic molecules (like metals or ions) that assist enzymes in their function.

Coenzyme

Carbon-based molecules that help enzymes function.

Active Site

The specific region of an enzyme where the substrate binds.

Specificity

Enzymes are specific for their substrate, meaning each enzyme fits a particular substrate.

Lock and Key Model

A model that illustrates the specificity of enzymes and substrates.

Induced Fit Model

A more accurate model than the lock and key, describing a conformational change of the enzyme when the substrate binds to the active site.

Denaturation

The process in which enzymes or proteins lose their functional shape due to changes in pH, temperature, or salinity.

Optimal Conditions

The specific pH, temperature, and salinity that allow enzymes to function most effectively.

Competitive Inhibition

A type of inhibition where a molecule competes with the substrate for the active site.

Non-competitive Inhibition

A type of inhibition where a molecule binds to the enzyme, not at the active site, causing a shape change.

Saturation

The point at which all active sites of an enzyme are occupied, resulting in maximum reaction rate.

Reversible Inhibition

Inhibition where the inhibitor can be removed from the enzyme.

Irreversible Inhibition

Inhibition where the inhibitor cannot be removed from the enzyme, often covalently bound.

Allosteric Site

A site on an enzyme where an inhibitor can bind, causing a change in enzyme shape.

Enzyme Activators

Molecules that bind to enzymes and enhance their activity.

Hydrogen Bonds

Weak bonds that can be disrupted during denaturation, affecting protein structure.

Kinetic Energy

Energy that increases with temperature, leading to more molecular collisions.

Optimal Temperature

The temperature at which enzyme activity is highest before denaturation occurs.

Biological Function

The role that enzymes play in facilitating biological reactions.

R Group Interactions

Interactions between the side chains of amino acids that help maintain protein structure.

Substrate Concentration

The amount of substrate present that can affect the rate of enzyme-catalyzed reactions.

Penicillin

An antibiotic that blocks an enzyme used by bacteria to build their cell wall.

Tamiflu

A drug that blocks an enzyme allowing flu viruses to enter cells.

Cyanide

A molecule that blocks a critical enzyme in cellular respiration by binding outside of the active site.

Molecular Collisions

Interactions between enzyme and substrate that lead to reactions.

pH

A measure of acidity or alkalinity that can affect enzyme activity.

Temperature

A factor that can increase or slow down enzyme reactions based on its optimal conditions.