Study guide for test 2

Kinetic energy

The energy of motion.

Potential energy

Stored energy that has the potential to do work.

Thermodynamics

The study of energy transformations.

Kilocalorie (kcal)

A unit used to measure food energy, where 1 kcal = 1000 calories.

Photosynthesis

The process by which plants, algae, and certain bacteria convert light energy into chemical energy.

Oxidation

The loss of an electron.

Reduction

The gain of an electron.

First Law of Thermodynamics

Energy cannot be created or destroyed, only changed from one form to another.

Chemical energy

Energy stored in the bonds of molecules that can be converted into different forms.

Entropy

A measure of disorder or randomness in a system.

Second Law of Thermodynamics

Energy transformations increase the total entropy of a system.

Exergonic reactions

Reactions that release energy (G

Endergonic reactions

Reactions that absorb energy (G>0) and are non-spontaneous.

Activation energy

The energy required to initiate a chemical reaction.

Catalysts

Substances that lower the activation energy required to start a reaction without being consumed.

ATP

A molecule that stores and provides energy for cellular processes; often referred to as the "energy currency" of the cell.

Hydrolysis of ATP

The process that breaks down ATP, releasing energy when the phosphate bonds are broken.

Structure of ATP

Comprised of a ribose sugar, adenine, and three phosphate groups.

Phosphate bonds

Bonds in ATP that store energy, especially between the last two phosphate groups.

Endergonic processes

Processes that require energy to proceed, which ATP helps to drive.

ATP cycle

The continuous recycling of ATP in cells from ADP and inorganic phosphate.

Glycolysis

The metabolic process that converts glucose into two pyruvate molecules, producing ATP and NADH.

Priming phase of glycolysis

The initial phase where glucose is phosphorylated using 2 ATP to become more reactive.

Cleavage phase of glycolysis

The phase where the modified glucose splits into two 3-carbon molecules.

Energy payoff phase of glycolysis

The phase where ATP and NADH are produced from the oxidized 3-carbon molecules.

Aerobic respiration

A type of cellular respiration that uses oxygen as the final electron acceptor.

Fermentation

A metabolic process that converts glucose to energy without oxygen using organic molecules as final electron acceptors.

NAD+

An electron carrier molecule that accepts electrons and protons to form NADH.

Pyruvate oxidation

The process that converts pyruvate into acetyl-CoA, producing CO2 and NADH.

Citric Acid Cycle

A series of biochemical reactions that processes acetyl-CoA to produce ATP, NADH, and FADH2.

Electron Transport Chain (ETC)

A series of protein complexes in the mitochondria that transfer electrons and create a proton gradient.

Chemiosmosis

The process by which protons flow back into the mitochondrial matrix through ATP synthase, driving ATP production.

ATP Synthase

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

Competitive inhibition

A type of enzyme inhibition where an inhibitor competes with substrates for the active site.

Noncompetitive inhibition

A type of inhibition where an inhibitor binds to an enzyme away from the active site, altering its function.

Anabolic reactions

Metabolic pathways that construct molecules, requiring energy input.

Catabolic reactions

Metabolic pathways that break down molecules, releasing energy.

Feedback inhibition

A regulatory mechanism where the final product of a metabolic pathway inhibits an early step.

Autotrophs

Organisms that produce their own organic molecules through photosynthesis.

Heterotrophs

Organisms that consume organic compounds produced by other organisms.

Cellular respiration

A series of metabolic reactions that extract energy from organic molecules.

Dehydrogenation

The process where lost electrons are accompanied by protons.

Electron carriers

Molecules that transport electrons during redox reactions and play a critical role in ATP production.

Final electron acceptor

The molecule that receives electrons at the end of the electron transport chain, e.g., oxygen in aerobic respiration.

P/O ratio

The amount of ATP synthesized per molecule of oxygen consumed.

Oxidation without O2

The process occurring during anaerobic respiration and fermentation, using inorganic or organic molecules as electron acceptors.

Methanogens

Organisms that reduce CO2 to methane, found in environments such as the guts of cattle.

Sulfur-reducing prokaryotes

Organisms that reduce inorganic sulfate to hydrogen sulfide during anaerobic respiration.

Lactic acid fermentation

A process where pyruvate is converted into lactic acid to regenerate NAD+ in the absence of oxygen.

Ethanol fermentation

A process in yeast where pyruvate is converted into ethanol to regenerate NAD+.

Feedback inhibition in glycolysis

The inhibition of phosphofructokinase by ATP and/or citrate when energy supplies are ample.

Control points in the Citric Acid Cycle

Sites where key enzymes like pyruvate dehydrogenase and citrate synthase are regulated by high levels of NADH and ATP.

Substrate-level phosphorylation

Direct transfer of a phosphate group from a substrate to ADP to form ATP.

Oxidative phosphorylation

The production of ATP via ATP synthesis powered by the proton gradient formed during electron transport.

High-Energy Bonds

Bonds between the last two phosphate groups in ATP that store significant energy.

G3P

Glyceraldehyde-3-phosphate, a 3-carbon molecule formed during glycolysis.

Coenzyme A

A molecule that carries acetyl groups into the citric acid cycle.

Oxaloacetate

A four-carbon molecule that combines with acetyl-CoA to form citrate in the citric acid cycle.

Malate

A four-carbon intermediate in the citric acid cycle that forms after the addition of water to fumarate.

Citrate

A six-carbon molecule formed from acetyl-CoA and oxaloacetate in the citric acid cycle.

Fumarate

A four-carbon intermediate in the citric acid cycle that is oxidized to regenerate oxaloacetate.

Isocitrate

An isomer of citrate that is formed in the citric acid cycle before it is oxidized.

Succinyl-CoA

A four-carbon intermediate formed during the citric acid cycle after the second oxidation step.

Feedback inhibition

A mechanism where the end product of a metabolic pathway inhibits an earlier step in the pathway.

Acetyl-CoA

The entry molecule into the citric acid cycle produced from the oxidation of pyruvate.

Pyruvate dehydrogenase

An enzyme complex that catalyzes the conversion of pyruvate to acetyl-CoA.

NADH

An electron carrier that stores energy by carrying high-energy electrons.

FADH2

A reduced form of FAD, an electron carrier used in cellular respiration.

GTP

A molecule similar to ATP that serves as an energy currency in cells.

ATP production yield

The total number of ATP molecules produced from one glucose molecule.

ATP synthase

A key enzyme that synthesizes ATP using energy from proton gradients.

Proton gradient

A difference in proton concentration across a membrane that drives ATP synthesis.

Allosteric site

A site on an enzyme where a molecule can bind and influence the enzyme's activity.

Transition state

The state during a reaction where reactants are transformed into products, often stabilized by enzymes.

Hydrolysis

The chemical breakdown of a compound due to reaction with water, commonly seen in ATP breakdown.

Cellular respiration stages

The four stages are glycolysis, pyruvate oxidation, citric acid cycle, electron transport chain.

Facilitated diffusion

The process by which molecules diffuse across membranes with the assistance of special proteins.

Steps of Glycolysis

Glycolysis consists of three phases: Priming phase, Cleavage phase, and Energy payoff phase.

Priming phase of Glycolysis

Involves the phosphorylation of glucose to become more reactive, using 2 ATP.

Cleavage phase of Glycolysis

Glucose splits into two 3-carbon molecules, each being converted to a glyceraldehyde-3-phosphate (G3P).

Energy payoff phase of Glycolysis

ATP and NADH are produced from the oxidation of G3P.

Pyruvate Oxidation

Converts pyruvate into acetyl-CoA, producing CO2 and NADH before entering the Citric Acid Cycle.

Citric Acid Cycle (Krebs Cycle) Steps

Includes condensation, isomerization, oxidation, decarboxylation, and substrate-level phosphorylation steps.

Final Electron Transport Chain (ETC) Process

Electrons are transferred through protein complexes, creating a proton gradient for ATP synthesis.

Chemiosmosis process

Protons flow back into the mitochondrial matrix through ATP synthase to generate ATP.

ATP Yield from Glycolysis

Net gain of 2 ATP and 2 NADH from one glucose molecule during glycolysis.

Role of NADH in Cellular Respiration

NADH carries electrons to the electron transport chain to facilitate ATP production.

Oxygen in Electron Transport Chain

Acts as the final electron acceptor, forming water and preventing the backup of the electron chain.

Substrate-level Phosphorylation

The direct transfer of a phosphate group from a substrate to ADP

Photosynthesis

The process by which plants, algae, and certain bacteria convert light energy into chemical energy (glucose) using carbon dioxide and water.

Chloroplast

The organelle where photosynthesis occurs, containing thylakoid membranes and stroma.

Light-dependent reactions

Reactions that require light, occurring in the thylakoid membranes, producing ATP and NADPH.

Calvin Cycle

The light-independent reactions that synthesize organic molecules from CO2 using ATP and NADPH.

Chlorophyll

The main pigment in plants that absorbs blue and red light, necessary for photosynthesis.

Thylakoid membrane

Internal membranes in chloroplasts that contain chlorophyll and are the site of light-dependent reactions.

Grana

Stacks of thylakoids in chloroplasts where light-dependent reactions occur.

Stroma

The semi-liquid matrix surrounding thylakoids in chloroplasts, where the Calvin cycle takes place.

Cyclic photophosphorylation

A process in photosynthesis that generates additional ATP without producing NADPH.

Noncyclic photophosphorylation

A process that produces both ATP and NADPH during light-dependent reactions.

Carbon fixation

The initial phase of the Calvin cycle where CO2 is fixed into a 3-carbon compound.