Cellular Respiration Flashcards

A set of flashcards covering vocabulary and processes of cellular respiration based on the lecture notes.

Cellular Respiration

A process in mitochondria where organic molecules and $O_2$ are used to produce ATP, $CO_2$, and $H_2O$.

Photosynthesis

A process in chloroplasts that uses $CO_2$ and $H_2O$ to produce organic molecules and $O_2$.

Cellular Respiration Equation

$$C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O + ENERGY$$

Oxidation reaction

A reaction that takes an electron from an atom in a compound.

Reduction reaction

A reaction involving the addition of an electron to a compound.

Redox Reactions

Chemical reactions involving the shift of electrons from one compound to another, altering their potential energy.

Electron carriers

Shuttles that bind and carry high-energy electrons between compounds in biochemical pathways.

Reducing agents

Compounds that are oxidized by losing electrons.

Oxidizing agents

Compounds that are reduced by accepting electrons.

Nicotinamide adenine dinucleotide (NAD)

An important electron carrier in cellular respiration that exists in oxidized and reduced forms.

NAD+

The oxidized form of Nicotinamide adenine dinucleotide.

NADH

The reduced form of Nicotinamide adenine dinucleotide that has accepted a hydrogen ion and 2 electrons.

Flavin adenine dinucleotide (FAD+)

The oxidized form of an important electron carrier in cellular respiration.

FADH2

The reduced form of Flavin adenine dinucleotide.

Adenosine triphosphate (ATP)

The energy currency of the cell.

ATP hydrolysis

The reaction $ATP \rightarrow ADP + Pi + energy$.

Phosphorylation

The addition of a phosphate group to ADP to make ATP.

ATP regeneration

The reaction $ADP + Pi + energy \rightarrow ATP$.

Substrate-level phosphorylation

ATP production where a phosphate group is removed from an intermediate reactant and added to ADP; it generates only a few ATP molecules.

Oxidative phosphorylation

The production of ATP through the process of chemiosmosis, generating 90% of ATP during glucose catabolism.

Chemiosmosis

The movement of ions across a plasma membrane via integral proteins to generate ATP.

Oxidative phosphorylation location (prokaryotes)

The plasma membrane.

Oxidative phosphorylation location (eukaryotes)

The mitochondria.

Glycolysis

The first step in the breakdown of glucose, which is anaerobic and occurs in the cytoplasm.

Anaerobic

A process that occurs without the need for oxygen.

Glycolysis starting and ending molecules

Begins with a 6-carbon ring glucose and ends with two 3-carbon pyruvate molecules.

Hexokinase

The enzyme in Glycolysis Step 1 that phosphorylates glucose using ATP to create glucose-6-phosphate.

Glucose-6-phosphate

The product of the first step of glycolysis after glucose is phosphorylated.

Isomerase (Glycolysis Step 2)

The enzyme that converts glucose-6-phosphate into its isomer, fructose-6-phosphate.

Fructose-6-phosphate

The isomer of glucose-6-phosphate formed in the second step of glycolysis.

Phosphofructokinase

The enzyme in Glycolysis Step 3 that phosphorylates fructose-6-phosphate to fructose-1,6-bisphosphate; it provides feedback inhibition.

Feedback inhibition of Phosphofructokinase

The enzyme is active when ATP is low and less active when ATP is high.

Fructose-1,6-bisphosphate

The product formed in Glycolysis Step 3 after a second ATP molecule is used as a phosphate source.

Aldolase

The enzyme that cleaves fructose-1,6-bisphosphate into two 3-carbon isomers: dihydroxyacetone phosphate and glyceraldehyde-3-phosphate.

Dihydroxyacetone phosphate

One of the two 3-carbon isomers produced by aldolase in Step 4 of glycolysis.

Glyceraldehyde-3-phosphate

The 3-carbon isomer that continues through the energy-releasing phase of glycolysis.

Isomerase (Glycolysis Step 5)

The enzyme that converts dihydroxyacetone phosphate into its isomer glyceraldehyde-3-phosphate.

Net investment of Glycolysis Phase 1

2 ATPs molecules used per one glucose.

Glycolysis Step 6

The oxidation of glyceraldehyde-3-phosphate, producing NADH and adding a phosphate to form 1,3-bisphosphoglycerate.

1,3-bisphosphoglycerate

The sugar intermediate formed in Step 6 of glycolysis that does not require ATP for its second phosphorylation.

Phosphoglycerate kinase

The enzyme in Glycolysis Step 7 that allows 1,3-bisphosphoglycerate to donate a phosphate to ADP, forming ATP and 3-phosphoglycerate.

3-phosphoglycerate

The 3-carbon product formed after the first ATP is generated in the energy-releasing phase of glycolysis.

Rate limiting factor (Glycolysis Step 7)

The availability of NAD+.

Mutase

The enzyme in Glycolysis Step 8 that catalyzes the conversion of 3-phosphoglycerate to 2-phosphoglycerate.

2-phosphoglycerate

An intermediate in glycolysis formed when a phosphate group is moved to another carbon by mutase.

Enolase

The enzyme in Glycolysis Step 9 that removes water from 2-phosphoglycerate to create phosphoenolpyruvate (PEP).

Phosphoenolpyruvate (PEP)

A high-energy intermediate in glycolysis formed by a double bond after water is removed from 2-phosphoglycerate.

Pyruvate kinase

The enzyme in Glycolysis Step 10 that removes a phosphate group from PEP to produce pyruvate and another ATP.

Net Gains per Glucose in Glycolysis

2 ATPs and 2 NADH.

Glycolysis Rate Limiting Enzyme

Pyruvate kinase.

Aerobic respiration

A process that moves forward if oxygen is available, involving the transport of pyruvate into the mitochondria.

Oxidation of Pyruvate (Step 1)

The removal of a carboxyl group from pyruvate, releasing $CO_2$ and leaving a 2-carbon hydroxyethyl group.

Oxidation of Pyruvate (Step 2)

The oxidation of the hydroxyethyl group to an acetyl group, where electrons are picked up by NAD+ to form NADH.

Oxidation of Pyruvate (Step 3)

The transfer of the acetyl group to CoA to form acetyl CoA.

Citric Acid Cycle (TCA cycle)

A closed-loop series of reactions in the mitochondrial matrix where the last step regenerates the compound used in the first step.

Citrate

The first compound formed in the Citric Acid Cycle when Acetyl CoA reacts.

Isocitrate

The product formed after citrate is converted in the second step of the Citric Acid Cycle.

Alpha-ketoglutarate

The product of the oxidation of isocitrate, producing 1 $CO_2$ and 1 NADH.

Succinyl CoA

The product formed from alpha-ketoglutarate, producing 1 $CO_2$ and 1 NADH during its formation.

Succinate

The compound produced from succinyl CoA, generating 1 GTP or 1 ATP.

Fumarate

The compound formed when succinate dehydrates, producing 1 FADH2.

Malate

The compound formed when fumarate is hydrolyzed.

Oxaloacetate

The final compound in the Citric Acid Cycle, formed by the oxidation of malate (producing 1 NADH), which regenerates the cycle.

Citric Acid Cycle Net Gains (per pyruvate)

2 $CO_2$, 3 NADH, 1 FADH2, and 1 GTP/ATP.

Electron Transport Chain (ETC)

A series of redox reactions in which electrons are passed through four protein complexes to reduce molecular oxygen to water.

Final Electron Acceptor

Oxygen ($O_2$).

Complex I

The first protein complex in the ETC that receives NADH and pumps $H+$ ions.

Complex II

The protein complex in the ETC that receives FADH2 directly and passes electrons to Complex III.

Complex III

The protein complex in the ETC that uses iron to pass electrons and pumps $H+$ ions.

Complex IV

The complex that pumps $H+$ and holds $O_2$ until it is reduced by 2 electrons and combines with 2 $H+$ to form $H_2O$.

ATP synthase

An integral protein that acts like a tiny generator, using the force of diffusing $H+$ to add a phosphate to ADP to make ATP.

Dinitrophenol (DNP)

A historical weight-loss drug that made the mitochondrial membrane leaky to protons, disrupting oxidative phosphorylation.

Proton-motive Force

The potential energy resulting from the electrochemical gradient of $H+$ ions across the mitochondrial membrane.

ATP yield from 1 NADH

2.5 ATP.

ATP yield from 1 FADH2

1.5 ATP.

Total Gain of ATP from Glycolysis (Net)

2 ATP.

Total NADH Gain from Citric Acid Cycle (per Glucose)

6 NADH.

Total FADH2 Gain from Citric Acid Cycle (per Glucose)

2 FADH2.

Total Net Gain of ATP per Glucose molecule

32 ATP.

Metabolic connection of 5-carbon sugars

Sugars that form nucleic acids are created from intermediates in glycolysis.

Metabolic connection of amino acids

Nonessential amino acids can be made from intermediates of both glycolysis and the citric acid cycle.

Anaerobic cellular respiration

Energy conversion in the absence of oxygen, used by methanogens and certain sulfate-reducing bacteria.

Methanogens

A group of archaeans that reduce $CO_2$ to methane to oxidize NADH.

Fermentation

A process that uses an organic molecule to regenerate NAD+ from NADH in the absence of oxygen.

Lactic acid fermentation equation

$$Pyruvic acid + NADH \rightleftharpoons lactic acid + NAD+$$

Lactate dehydrogenase (LDH)

The enzyme used in lactic acid fermentation to catalyze the reaction.

Facultative anaerobes

Organisms that can switch between aerobic respiration and fermentation depending on oxygen supply.

Obligate anaerobes

Organisms that must live in the absence of oxygen.

Pyruvate decarboxylase

The enzyme in alcohol fermentation that removes a carboxyl group from pyruvate to release $CO_2$.

Alcohol dehydrogenase

The enzyme in alcohol fermentation that oxidizes NADH to NAD+ and reduces acetaldehyde to ethanol.

Alcohol fermentation equation

$$Pyruvic acid + H+ \rightarrow CO_2 + acetaldehyde + NADH + H+ \rightarrow ethanol + NAD+$$