Electron Transport Chain, Fermentation & DNA Structure Lecture

Vocabulary flashcards covering key terms from the lecture on respiration, fermentation, and DNA structure.

Electron Transport Chain (ETC)

Membrane-embedded series of proteins that pass electrons from NADH/FADH₂ to a terminal electron acceptor while pumping protons across the membrane.

Oxidative Phosphorylation

ATP synthesis powered by an electron transport chain and the resulting proton motive force rather than by direct substrate transfer.

Proton Motive Force (PMF)

Electrochemical gradient of H⁺ ions across a membrane that stores energy for ATP production and other work.

ATP Synthase

Rotary enzyme that allows protons to flow down the PMF and couples this movement to phosphorylation of ADP forming ATP.

Chemiosmosis

Diffusion of protons back across a membrane through ATP synthase, driving ATP formation.

Terminal Electron Acceptor

Molecule that receives electrons exiting the ETC; oxygen in aerobic respiration, alternatives like nitrate or sulfate in anaerobic respiration.

NADH

Reduced electron carrier produced in glycolysis and the Krebs cycle; donates electrons to the ETC.

FADH₂

Reduced electron carrier generated in the Krebs cycle that feeds electrons into the ETC.

NAD⁺

Oxidized form of NADH; must be regenerated (e.g., by ETC or fermentation) to keep glycolysis running.

Aerobic Respiration

Respiratory pathway that uses O₂ as the terminal electron acceptor, yielding water and high ATP output.

Anaerobic Respiration

Respiration that uses a terminal electron acceptor other than O₂ (e.g., NO₃⁻, SO₄²⁻); produces less ATP than aerobic respiration.

Fermentation

Anaerobic process that oxidizes NADH by transferring its electrons to an organic molecule (often pyruvate) to regenerate NAD⁺ without an ETC.

Glycolysis

Cytoplasmic pathway that splits glucose into two pyruvate, making 2 ATP and reducing NAD⁺ to NADH.

Krebs Cycle (Citric Acid Cycle)

Series of reactions that fully oxidizes acetyl-CoA to CO₂, producing NADH, FADH₂ and a small amount of ATP.

Oxidation

Loss of electrons (or increase in oxidation state) by a molecule.

Reduction

Gain of electrons (or decrease in oxidation state) by a molecule.

Pyruvate

Three-carbon end product of glycolysis; serves as a substrate for the Krebs cycle or as an electron acceptor in fermentation.

Lactic Acid

Reduced product formed when pyruvate accepts electrons during homolactic fermentation.

Ethanol

Alcohol produced when yeast reduce an acetaldehyde intermediate derived from pyruvate during alcoholic fermentation.

Homolactic Bacteria

Microbes (e.g., Streptococcus, Lactobacillus) that convert glucose mainly into lactic acid through fermentation.

Genome

Complete set of an organism’s genetic material (all its DNA or, in some viruses, RNA).

Plasmid

Small, circular, independently replicating DNA molecule found in many prokaryotes and some eukaryotes.

Phenotype

Observable traits or characteristics of a cell/organism that result from gene expression.

Nucleotide

DNA (or RNA) monomer consisting of a deoxyribose sugar, phosphate group, and nitrogenous base.

Deoxyribose

Five-carbon sugar in DNA lacking an oxygen at the 2′ position.

Nitrogenous Base

Variable component of a nucleotide; adenine, thymine, guanine or cytosine in DNA.

Sugar-Phosphate Backbone

Repeating chain of deoxyribose sugars linked by phosphates that forms the structural framework of DNA strands.

Chargaff’s Rule

Observation that in any DNA sample %A = %T and %G = %C, reflecting specific base pairing.

Base Pairing

Hydrogen-bonded pairing of A with T (2 bonds) and G with C (3 bonds) in double-stranded DNA.

Antiparallel Strands

Orientation of the two DNA strands running in opposite 5′→3′ directions.

5′ End

Terminus of a DNA strand with a free phosphate attached to the 5′ carbon of deoxyribose.

3′ End

Terminus of a DNA strand with a free hydroxyl group on the 3′ carbon; site where new nucleotides are added.

Double Helix

Right-handed coiled structure formed by two complementary, antiparallel DNA strands.

Adenine (A)

Purine nitrogenous base that pairs with thymine in DNA via two hydrogen bonds.

Thymine (T)

Pyrimidine nitrogenous base that pairs with adenine in DNA via two hydrogen bonds.

Guanine (G)

Purine nitrogenous base that pairs with cytosine in DNA via three hydrogen bonds.

Cytosine (C)

Pyrimidine nitrogenous base that pairs with guanine in DNA via three hydrogen bonds.