Cellular Respiration: Pathways and Processes

Catabolic pathways

Breakdown molecules to harvest energy for ATP

Anabolic pathways

Synthesize larger molecules using ATP energy

Cell respiration

Series of oxidation reactions producing ATP

Redox reactions

Chemical reactions involving electron transfer

Oxidation

Loss of electron(s) in a reaction

Reduction

Gain of electron(s) in a reaction

Electron carriers

Molecules that shuttle electrons in reactions

NAD+

Oxidized form of nicotinamide adenine dinucleotide

NADH

Reduced form of NAD+, carries electrons

Aerobic respiration

Respiration using oxygen to produce ATP

Anaerobic respiration

Respiration that does not require oxygen

Glycolysis

Splitting glucose into two pyruvate molecules

Energy investment phase

Initial phase using 2 ATP in glycolysis

Energy payoff phase

Phase producing 4 ATP and NADH in glycolysis

Substrate-level phosphorylation

Direct transfer of phosphate to ADP for ATP

NET yield from glycolysis

2 ATP, 2 NADH, 2 pyruvate produced

Pyruvate oxidation

Conversion of pyruvate to Acetyl CoA

Citric acid cycle

Cycle occurring in mitochondrial matrix for ATP

Acetyl CoA

Key molecule entering the citric acid cycle

ATP synthase

Enzyme using proton gradient to produce ATP

Oxaloacetate

Molecule that combines with Acetyl CoA in cycle

Free energy

Energy released during glucose oxidation process

C6H12O6 + 6 O2

Glucose and oxygen reactants in aerobic respiration

2 CO2

Waste product from pyruvate oxidation

2 NADH (from pyruvate)

Electrons carried to ETC from pyruvate conversion

Citric Acid Cycle

Series of reactions producing energy carriers.

FADH2

Another electron carrier produced in the cycle.

GTP

Energy molecule produced in the citric acid cycle.

ATP Yield

2 ATP produced per acetyl CoA in cycle.

Electron Transport Chain

Membrane proteins transferring electrons to O2.

Chemiosmosis

Process using H+ gradient to synthesize ATP.

Proton Gradient

Difference in H+ concentration across membranes.

Oxidative Phosphorylation

Major ATP production phase in cellular respiration.

Anaerobic Respiration

Uses non-oxygen molecules as electron acceptors.

Fermentation

Process generating ATP without oxygen present.

Lactic Acid Fermentation

Occurs in muscle cells under low oxygen.

Alcohol Fermentation

Occurs in yeast, producing ethanol and CO2.

Feedback Inhibition

Regulation mechanism by NADH and ATP levels.

ATP Synthase

Enzyme converting ADP to ATP using H+ flow.

Energy Yield

Theoretical 36 ATP for eukaryotes per glucose.

Methanogens

Archaea using CO2 as electron acceptor.

Sulfur Bacteria

Reduce sulfate to hydrogen sulfide.

Glucose Oxidation

Complete breakdown of glucose to CO2.

NAD+ Regeneration

Essential for continuing glycolysis and respiration.

Proton-Motive Force

Energy stored in H+ gradient for ATP synthesis.

Actual ATP Yield

~30 ATP per glucose for eukaryotes.

Leaky Membrane

Causes reduced ATP yield in eukaryotes.