Aerobic Metabolism

The total set of chemical reactions in cells that generate energy for cellular processes and use that energy (along with organic precursors) to synthesize complex molecules

Metabolism

One of the two main branches of metabolism; it consists of degradative reactions that break down complex molecules into simpler ones to release energy (often captured as ATP)

Catabolism

One of the two main branches of metabolism; it consists of biosynthetic reactions that build complex molecules from smaller ones, requiring an energy input (usually from ATP)

Anabolism

The primary energy currency of the cell, used to store and release energy for cellular functions

ATP

Nitrogenous base in ATP

Adenine

Sugar in ATP

Ribose

ATP contains ____ phosphate groups

Three

In ATP, energy is stored in the high-energy bonds between ________ groups

Phosphate

The process where ATP releases energy by reacting with water; breaks down into ADP and inorganic phosphate, releasing usable energy

ATP Hydrolysis

Contains ribose sugar and three phosphate groups; used for energy transfer and RNA synthesis

ATP

Contains deoxyribose sugar; used strictly for genetic storage

DNA Nucleotide

A mechanism where cells link energy-releasing (exergonic) reactions with energy-consuming (endergonic) reactions; this allows unfavorable reactions to proceed using energy from favorable ones

Coupled reactions

ATP hydrolysis drives macromolecule _______

Synthesis

The portion of a system’s energy that can perform work at constant temperature and pressure; it determines the spontaneity of reactions

Gibbs free energy

The difference in free energy between products and reactants

Change in Gibbs free energy

A negative change in Gibbs free energy indicates a _________ reaction (exergonic, energy released)

Spontaneous

A positive change in Gibbs free energy indicates a _________ reaction (endergonic, energy required)

Non-spontaneous

A spontaneous reaction where change in Gibbs free energy is negative; energy is released, and the reaction proceeds without external energy input

Exergonic

The formation of many metabolites occurs _________ and is heavily favored

Spontaneously

A non-spontaneous reaction where the change in Gibbs free energy is positive; energy input is required, and the reaction does not proceed on its own

Endergonic

Biological reactions are generally considered ________, where the energy input of the forward reaction equals the energy output of the reverse reaction

Reversible

Breaks down subunits (sugars, fatty acids, amino acids) —> releases energy —> generates ATP

Catabolism

Uses ATP —> builds macromolecules (carbohydrates, proteins, lipids, nucleic acids)

Anabolism

A catabolic process where cells extract free energy from glucose; glucose is converted to CO2 and H2O

Glucose oxidation

Cells do not release all energy from glucose in a single explosive step; instead, energy is captured in usable form (ATP) through a ________ process

Multistep

Converts glucose to pyruvate

Glycolysis

Converts pyruvate to acetyl-CoA

Pyruvate oxidation

Converts Acetyl-CoA to CO2 and high-energy electrons

TCA cycle

Converts electrons to ATP via oxidative phosphorylation

Electron transport chain

Converts chemical energy in food into ATP to power movement, biosynthesis, and cellular maintenance

Cellular respiration

The separation of opposing metabolic pathways into distinct cellular areas to prevent interference and optimize regulation

Cellular compartmentalization

The site of DNA replication and mRNA synthesis

Nucleus

The site of the TCA cycle and fatty acid oxidation

Mitochondria

The site of glycolysis and fatty acid synthesis

Cytosol

Systems that regulate movement across membranes to control concentrations of enzymes, substrates, and cofactors and maintain metabolic efficiency and directionality

Transport systems

The “powerhouse of the cell” and the primary site of ATP production via aerobic respiration

Mitochondria

The boundary layer of the mitochondrion

Outer membrane

The membrane that houses the ETC and ATP Synthase

Inner membrane

Folds of the inner mitochondrial membrane that function to increase the surface area for energy production

Cristae

The innermost compartment of the mitochondrion; site of the TCA cycle and Pyruvate oxidation

Mitochondrial matrix

Electron carriers which donate electrons to the ETC

NADH and FADH2

Acts as the final electron acceptor to form water (H2O)

Oxygen

A metabolic process that converts glucose and oxygen into usable energy (ATP), carbon dioxide, and water

Cellular respiration

Inputs for cellular respiration

Glucose and oxygen

Outputs for cellular respiration

ATP, CO2, and water

The process where most metabolic energy is produced via oxidation-reduction reactions in the mitochondria; it relies on electron transport to oxygen and mitochondrial compartmentalization

Oxidative metabolism

_____ yield the most energy per gram compared to other fuels like carbohydrates

Fats

The loss of electrons or hydrogen; often involves the gain of oxygen

Oxidation

In respiration, glucose is ______

Oxidized

The gain of electrons or hydrogen; often involves the loss of oxygen

Reduction

In respiration, oxygen is _______

Reduced

Molecules that store energy by accepting electrons during fuel oxidation

Electron carriers

An electron carrier derived from Niacin (Vitamin B3)

NAD+

NAD+ is the _______ form

Oxidized

NADH is the ________ form

Reduced

In NAD+, electron transfer occurs due to the ____, which creates a “charged ring” that acts as an electron sink

N+

Electron carrier derived from Riboflavin (Vitamin B2)

FAD

Site of redox activity in FAD (accepts/donates electrons)

Isoalloxazine ring

Fuels (carbs/fats) are oxidized to produce _______ coenzymes

Reduced

Coenzymes are _________ to release energy, donating 2 electrons each to the ETC to generate ATP

Oxidized

Electron carriers donate ____ electrons to the ETC

Two

The breakdown of glucose into pyruvate in the cytoplasm

Glycolysis

Inputs are glucose, 2 ATP, and 2 NAD+

Glycolysis

Outputs are 2 pyruvate, 2 NADH, and net 2 ATP

Glycolysis

_____ is used in glycolysis to activate glucose

ATP

Stage of glycolysis that splits the 6-carbon sugar into two 3-carbon molecules

Cleavage

Stage of glycolysis where electrons are transferred to NAD+ and ATP is generated

Oxidation

The process that prepares carbon units for entry into the TCA cycle in the mitochondrial matrix

Pyruvate oxidation

Inputs are 2 pyruvate, 2 CoA, and 2 NAD+

Pyruvate oxidation

Outputs are 2 Acetyl-CoA, 2 CO2, and 2 NADH

Pyruvate oxidation

Completes the oxidation of carbon fuels and generates high-energy electron carriers in the mitochondrial matrix

TCA cycle

Inputs are 2 Acetyl-CoA, 2 ADP, 6 NAD+, and 2 FAD

TCA cycle

Outputs are 4 CO2, 2 ATP, 6 NADH, and 2 FADH2

TCA cycle

Electrons from NADH and FADH2 pass through protein complexes in the inner membrane and this electron flow establishes a ______ ________ across the membrane

Proton gradient

Uses proton gradient to convert ADP and Pi into ATP

ATP Synthase

Acts as the final electron acceptor to form water

Oxygen

Location for ETC

Inner mitochondrial membrane

Inputs are NADH, FADH2, and O2

ETC

Outputs are ATP, NAD+, FAD, and H2O

ETC

Main purpose is to generate ATP via oxidative phosphorylation

ETC

________ donates electrons to Complex I

NADH

________ donates electrons to Complex II

FADH2

The theory stating that electron flow through complexes I-IV drives proton pumping, creating a proton gradient across the inner mitochondrial membrane. This gradient drives oxidative phosphorylation

Chemiosmotic model

Protons are actively pumped “uphill” from the mitochondrial matrix to the intermembrane space creating a concentration and charge gradient

Proton gradient

Non-heme iron centers found within ETC complexes that are essential for electron transfer

Iron-Sulfur Complexes

Undergo one-electron redox reactions, alternating between ferric and ferrous states

Iron-Sulfur Complexes

A lipid-soluble molecule that acts as a central electron relay; shuttles electrons from Complex I and Complex II to Complex III

Coenzyme Q10

Accepts electrons from mitochondrial flavoproteins and undergoes a three step reduction to form QH2

Coenzyme Q10

A small heme protein located on the outer surface of the inner membrane that transfers electrons from Complex III to Complex IV

Cytochrome c

NADH dehydrogenase

Complex I

A flavoprotein using FMN and Fe-S centers; transfers 2 electrons from NADH to FMN to Coenzyme Q; pumps 4 protons from the matrix to the intermembrane space

Complex I

Succinate-Q Reductase

Complex II

Oxidizes succinate to fumarate and transfers electrons to Coenzyme Q, reducing it to QH2; contains FAD, heme groups, and Fe-S centers

Complex II

This complex does NOT pump protons across the membrane

Complex II

QH2-Cytochrome c Reductase

Complex III

Contains cytochrome c and Fe-S centers; accepts electrons from QH2 and transfers them to 2 cytochrome c molecules; pumps 4 protons into the intermembrane space per QH2 (takes 2 protons from matrix)

Complex III

Contains 2 copper (Cu) ions; accepts electrons from 4 cytochrome c molecules and transfers them to oxygen to form H2O; pumps 4 protons into the intermembrane space per O2

Complex IV

Spans the inner membrane of ATP synthase; allows proton flow

F0 domain

ATP synthase component located in the matrix; catalyzes ATP formation

F1 domain

Protons enter the ____ domain, causing the rotation of the stalk

F0