Citric Acid Cycle and Cellular Respiration

These flashcards include key vocabulary and concepts related to the citric acid cycle, cellular respiration, and metabolic pathways.

Citric Acid Cycle

A metabolic furnace that further oxidizes organic fuel derived from pyruvate and completes the breakdown of glucose.

Oxidation of Acetyl CoA

The process that converts acetyl CoA to carbon dioxide in the citric acid cycle.

Substrate-level phosphorylation

A process that generates 1 ATP per turn of the citric acid cycle.

NAD+

A coenzyme that acts as an electron carrier in the citric acid cycle.

FAD

A coenzyme that accepts electrons during the citric acid cycle, converting to FADH2.

NADH

The reduced form of NAD+, which shuttles high-energy electrons to the electron transport chain.

FADH2

The reduced form of FAD, which carries electrons to the electron transport chain.

Oxaloacetate

A four-carbon molecule that combines with acetyl CoA in the first step of the citric acid cycle.

Citrate

The six-carbon molecule formed when acetyl CoA combines with oxaloacetate.

Isocitrate

The isomer of citrate formed after the conversion of citrate in the citric acid cycle.

a-Ketoglutarate

A five-carbon molecule formed from the oxidation of isocitrate in the citric acid cycle.

Succinyl CoA

A four-carbon molecule that is formed from the oxidation of a-ketoglutarate.

Succinate

The four-carbon molecule formed after the conversion of succinyl CoA.

Fumarate

The four-carbon molecule produced from the oxidation of succinate.

Malate

The four-carbon molecule formed from the hydration of fumarate.

ATP

A molecule that stores and transfers energy within cells.

GTP

A molecule similar to ATP that can be converted to ATP in the citric acid cycle.

Carbon dioxide (CO2)

A waste product generated by the citric acid cycle.

Electron Transport Chain (ETC)

A collection of protein complexes in mitochondria that transfer electrons, driving ATP synthesis.

Proton motive force

The H+ gradient created by the electron transport chain that drives ATP synthesis.

Chemiosmosis

Process where the movement of protons across a membrane is coupled to ATP synthesis.

ATP synthase

The enzyme that synthesizes ATP by using the energy from the proton gradient.

Obligate anaerobes

Organisms that can only carry out anaerobic respiration or fermentation.

Facultative anaerobes

Organisms that can switch between aerobic respiration and fermentation based on oxygen availability.

Pyruvate oxidation

The process by which pyruvate is converted to acetyl CoA before entering the citric acid cycle.

Fermentation

A metabolic process that produces ATP without oxygen, involving glycolysis and substrate-level phosphorylation.

Alcohol fermentation

A type of fermentation that converts pyruvate into ethanol, releasing CO2.

Lactic acid fermentation

A type of fermentation that converts pyruvate directly into lactate.

Beta oxidation

The metabolic process that breaks down fatty acids into two-carbon fragments for the citric acid cycle.

Phosphofructokinase

An important enzyme in glycolysis that regulates the speed of cellular respiration.

Glycolysis

The first step in the breakdown of glucose, producing pyruvate and a net gain of 2 ATP.

Anaerobic respiration

A type of respiration that occurs without oxygen, using an alternative final electron acceptor.

Energy yield from glucose

Up to 32 ATP can be produced through cellular respiration per glucose molecule.

Deamination

The process of removing amino groups from amino acids before they enter metabolic pathways.

Fatty acids

Long hydrocarbon chains that are digested and metabolized in the citric acid cycle.

Mitochondrion

The cell organelle where the citric acid cycle and oxidative phosphorylation occur.

Cofactors

Non-protein chemical compounds that assist enzymes and are essential for their catalytic activity.

Coenzyme A (CoA)

A molecule that carries acyl groups in metabolic reactions, crucial for the citric acid cycle.

Oxidative phosphorylation

The final step in cellular respiration where ATP is produced using the energy from electrons.

Inner mitochondrial membrane

The membrane where the electron transport chain is localized in mitochondria.

Ubiquinone (Q)

A mobile electron carrier in the electron transport chain that transfers electrons.

Cytochrome

An iron-containing protein that plays a key role in electron transport and energy transfer.

Heat energy in respiration

The energy not captured in ATP during cellular respiration that is released as heat.

Acetyl group

A two-carbon fragment from acetyl CoA that enters the citric acid cycle.

High-energy electrons

Electrons that are transferred from NADH and FADH2 during cellular respiration.

Electrons transport

The flow of electrons through the electron transport chain, leading to the production of ATP.

Regulation of respiration

The control of enzyme activity to modulate the rate of cellular respiration based on energy needs.

Yeast fermentation

Alcohol fermentation process conducted by yeast producing ethanol and CO2.

Sulfate ion (SO4 ²⁻)

An alternative electron acceptor used in anaerobic respiration.

NAD+ recycling

The process of regenerating NAD+ from NADH during aerobic conditions via the electron transport chain.

Hydrolysis of starch

The breakdown of starch into glucose in the digestive tract for energy.

Nitrogenous waste

The byproduct of amino acid metabolism, excreted as ammonia or urea.

Fats and ATP production

Fats produce more ATP upon oxidation compared to carbohydrates.

Exergonic flow

The energy-releasing process during electron transport in the electron transport chain.

Glycogen metabolism

The process of breaking down glycogen to glucose between meals for respiration.

Energy flow in respiration

The sequence: glucose → NADH → electron transport chain → ATP.

Respiration efficiency

The percentage of chemical energy in glucose converted to ATP, estimated at 34%.

Citric acid cycle yield

The cycle produces 6 NADH, 2 FADH2, and 2 ATP per glucose molecule processed.

Oxidation state of electron carriers

Electron carriers in the ETC alternate between reduced and oxidized states.

Mitochondrial cristae

Inner membrane folds in mitochondria that increase surface area for ATP synthesis.

Functional similarities of chloroplasts and mitochondria

Both organelles use electron transport chains and ATP synthase complexes in energy conversion.

Feedback mechanisms

Biological processes allowing cells to adjust metabolic pathways based on energy needs.

Substrate-level phosphorylation yield

A net gain of 4 ATP produced during glycolysis and the citric acid cycle.

Electron transport in complex 1

Electrons are transferred from NADH to the first molecule in the electron transport chain.

Cytochrome's role

Cytochromes are key electron carriers in the electron transport chain, containing iron.

Heat as byproduct

The energy lost as heat during the conversion of glucose to ATP.

Glycerol conversion into G3P

The process by which glycerol is metabolized for entry into glycolysis.

Caloric value of carbohydrates

Carbohydrates produce less ATP per gram than fats when metabolized.

Mitochondrial matrix

The compartment within mitochondria where the citric acid cycle takes place.

Hydrophobic ubiquinone

Ubiquinone is a small, hydrophobic electron carrier within the electron transport chain.

Reactive oxygen species

Potentially harmful compounds produced during electron transport, needing regulation.

Substrates of glycolysis

Glycolysis can process glucose and various carbohydrates as fuel.

Importance of NAD+

NAD+ is crucial for accepting electrons during glycolysis and other metabolic processes.

Cellular concentration of ATP

High ATP levels slow down respiration, regulating energy production needs.

Withdrawal of energy from glucose

Energy extraction from glucose mainly occurs through glycolysis and the citric acid cycle.

Pyruvate to lactate conversion

Occurs in lactic acid fermentation, regenerating NAD+ without CO2 release.

Acetyl CoA's dual role

Acetyl CoA enters the citric acid cycle or can be used for fatty acid synthesis.

Difference in energy pathways

Fermentation and anaerobic respiration differ in electron acceptor usage.

ATP from FADH2

FADH2 generates less ATP than NADH when transferring electrons to the ETC.

Hydrolysis of proteins

Proteins are broken down into amino acids before entering metabolic pathways.