BIO111 Quiz 3 Review: Membrane Transport, Energy, and Cellular Respiration

Comprehensive vocabulary review flashcards for BIO111 Quiz 3 covering Membrane Structure and Transport, Energy and Reaction Thermodynamics, and the stages of Glucose Oxidation / Aerobic Respiration.

Overview of Glucose Oxidation (Aerobic Respiration)

A cellular respiration pathway diagram depicting Glycolysis in the cytoplasm, Pyruvate Transformation and the Krebs cycle in the mitochondrial matrix, and Oxidative phosphorylation on the mitochondrial inner membrane generating ATP from electrons removed from fuel molecules.

Phospholipid

An amphipathic molecule composed of a hydrophilic head and two hydrophobic fatty acid tails, forming the fundamental structural unit of biological membranes.

Lipid bilayer

A two-layered sheet of phospholipids where hydrophobic fatty acid tails face inward away from water and hydrophilic heads face outward toward the aqueous cytoplasm and extracellular space.

Selective Permeability

The property of a biological membrane that allows certain molecules to cross while restricting or preventing the movement of others.

Concentration gradient

A region along which the density or concentration of a chemical substance increases or decreases across a space or membrane.

Diffusion

The spontaneous net movement of particles from a region of higher concentration to a region of lower concentration down a concentration gradient.

Facilitated diffusion

Passive transport of polar or charged substances across a membrane down their concentration gradient assisted by specific transmembrane proteins (channels or carriers).

Primary active transport

A form of active transport that directly hydrolyzes ATP to move solutes across a membrane against their concentration gradient.

$Na^+/K^+$ pump

A primary active transport membrane protein that uses ATP hydrolysis to export three sodium ions ($Na^+$) out of the cell and import two potassium ions ($K^+$) into the cell against their electrochemical gradients.

Secondary active transport

A transport process driven by the potential energy stored in an electrochemical gradient established by primary active transport, rather than the direct hydrolysis of ATP.

Uniport

A membrane carrier protein that transports a single solute molecule or ion in one direction across a membrane.

Symport

A coupled cotransport protein that moves two different solutes across a biological membrane simultaneously in the same direction.

Antiport

A coupled transport protein that moves two different solutes across a biological membrane simultaneously in opposite directions.

1st Law of Thermodynamics

The law of conservation of energy stating that energy can be transferred and transformed from one form to another, but cannot be created or destroyed.

Free energy ($G$)

The portion of a thermodynamic system's total energy that is available to perform work under conditions of constant temperature and pressure.

Exergonic

A spontaneous chemical reaction characterized by a negative change in free energy ($\Delta G < 0$) that releases energy to the surroundings.

Endergonic

A non-spontaneous chemical reaction characterized by a positive change in free energy ($\Delta G > 0$) that requires an input of free energy.

Activation energy

The initial investment of energy required to start a chemical reaction by contorting reactant bonds into an unstable transition state.

Transition State

A high-energy, unstable molecular configuration formed during a chemical reaction where reactant bonds are in the process of breaking and product bonds are forming.

Reaction coupling

The thermodynamic pairing of an exergonic reaction, such as ATP hydrolysis, to drive forward an unfavorable endergonic reaction.

Oxidation

The loss of one or more electrons ($e^-$) or hydrogen atoms by a chemical substance during a redox reaction.

Reduction

The gain of one or more electrons ($e^-$) or hydrogen atoms by a chemical substance during a redox reaction.

Glycolysis

A cytoplasmic pathway that breaks down one six-carbon glucose molecule into two three-carbon pyruvate molecules, comprising an energy investment phase and an energy payoff phase yielding a net $2\,\text{ATP}$ and $2\,\text{NADH}$.

Pyruvate Oxidation

The reaction in the mitochondrial matrix that converts pyruvate into acetyl CoA while reducing $\text{NAD}^+$ to NADH and releasing a molecule of $CO_2$.

Citric Acid Cycle

A cyclical series of reactions in the mitochondrial matrix that oxidizes acetyl CoA to release $CO_2$, producing ATP, NADH, and $FADH_2$.

Electron transport chain (ETC)

A collection of protein complexes and electron carrier molecules embedded in the mitochondrial inner membrane that transfer electrons down energy levels to pump protons ($H^+$) across the membrane.

Proton gradient

An electrochemical difference in proton ($H^+$) concentration established across the inner mitochondrial membrane between the intermembrane space and matrix, storing potential energy to power ATP synthesis.

ATP synthase

A membrane-spanning enzyme complex in the inner mitochondrial membrane that utilizes the flow of protons ($H^+$) down their electrochemical gradient to synthesize ATP from ADP and inorganic phosphate.

Final $e^-$ acceptor

Molecular oxygen ($O_2$), which combines with electrons ($e^-$) and protons ($H^+$) at the end of the electron transport chain to form water ($H_2O$).