Concept 9.1: Catabolic pathways yield energy by oxidizing organic fuels

Flashcards from Concept 9.1 of Pearson's Campbell Biology, Twelfth Edition.

Cellular respiration

The process by which plant and animal cells break down organic molecules within mitochondria

• Uses O₂ and organic molecules to make ATP with waste CO₂ and H₂O

• Includes aerobic and anaerobic respiration

Photosynthesis

The use of light, CO₂, and H₂O to make organic molecules and O₂

Catabolic pathways

Chains of exergonic reactions that release stored energy by breaking down complex molecules using electron transfers from food molecules

• Only linked to work by ATP as they do not power work

Fermentation

A partial degradation of sugars that occurs without oxygen; is a type of anaerobic respiration

Aerobic respiration

Process that utilizes oxygen and organic molecules to yield ATP

• Represented by the equation: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + Energy

• Energy takes the form of ATP and heat

Electron transfer

The transfer of electrons during chemical reactions to release stored energy in organic molecules for ATP synthesis

Redox reactions (reduction-oxidation reactions)

Chemical reactions that transfer electrons between reactants

• Some electrons are shared via covalent bonds in these

• Oxygen atoms attract electrons and do not share them equally; this still constitutes one of these

Oxidation

The loss of electrons from a substance in a redox reaction

Reduction

The addition of electrons to a substance in a redox reaction

• Refers to the positive charge

Reducing agent

The electron donor in a redox reaction

• Reduces the electron acceptor

• Seen with food molecules in cellular respiration due to their high abundance of hydrogen

Oxidizing agent

The electron acceptor in a redox reaction

• Oxidizes the electron donor

• Seen with oxygen during cellular respiration

Electronegativity

The attraction of electrons toward an atom; higher levels of this attract more electrons

• Electrons lose potential energy when shifting to atoms with higher levels of this, releasing kinetic energy for ATP synthesis

Nicotinamide adenine dinucleotide (NAD+)

A coenzyme that functions as an electron carrier and oxidizing agent during cellular respiration

NADH

The reduced form of NAD+, representing stored energy tapped to synthesize ATP

• Passes electrons to the electron transport chain through a series of redox reactions, releasing a small amount of energy

Electron transport chain

A series of molecules built into the inner membrane of the mitochondria to break the fall of electrons to oxygen in several energy-releasing steps

Oxygen

The final electron acceptor in the electron transport chain that captures electrons and hydrogen nuclei to form H₂O

• Yields energy through the attraction of electrons in redox reactions

Glycolysis

The first step of cellular respiration, breaking down one molecule of glucose into two molecules of pyruvate

Citric acid cycle

The second step of cellular respiration with pyruvate oxidation, completing the breakdown of glucose to CO₂

Oxidative phosphorylation

The closing of cellular respiration and the electron transport chain to facilitate synthesis of 90% of the cell’s ATP

• Powered by redox reactions

Substrate-level phosphorylation

The formation of some ATP in glycolysis and the citric acid cycle after an enzyme transfers a phosphate group directly from a substrate to ADP