Cell BIo Exam 2 (for Final)

Glyceraldehyde‑3‑phosphate dehydrogenase reaction

Oxidation of G3P producing NADH and 1,3-bisphosphoglycerate (1,3-BPG)

Pinocytosis

Nonspecific uptake of extracellular fluid and dissolved solutes via small vesicles

Clathrin‑coated pit

Membrane indentation where adaptor proteins recruit clathrin to initiate vesicle formation

Succinyl‑CoA synthetase reaction

Conversion of succinyl‑CoA to succinate with simultaneous synthesis of GTP

Nuclear localization signal (NLS)

Basic amino‑acid motif that targets proteins for import into the nucleus

Citrate synthase reaction

Condensation of acetyl‑CoA with oxaloacetate to produce citrate

pH‑dependent ligand release

Mechanism whereby acidic endosomal conditions lower receptor affinity

Membrane ruffling

Dynamic actin‑mediated protrusions that can lead to macropinocytic vesicle formation

Energy investment phase

Early steps of glucose breakdown that consume two ATP to activate the substrate

Transcytosis

Vesicular transport that carries molecules across epithelial cells from one surface to the opposite

COPI

Coat complex that mediates retrograde transport from the Golgi back to the endoplasmic reticulum

Substrate-level phosphorylation

Direct synthesis of ATP from a high-energy intermediate during metabolic reactions

Clathrin

Coat protein that forms a lattice around budding vesicles during receptor‑mediated endocytosis

Receptor‑mediated endocytosis

Clathrin‑dependent internalization of specific ligands bound to cell‑surface receptors

Succinate dehydrogenase reaction

Oxidation of succinate to fumarate

Glycolysis

Cytosolic pathway that converts one glucose molecule into two pyruvate molecules

Warburg effect

Preference of cancer cells for aerobic glycolysis over oxidative phosphorylation

Protein translocase of the outer membrane (TOM)

Channel that imports nuclear‑encoded mitochondrial proteins across the outer membrane

Sec23/24 complex

Core component of the COPII coat that selects cargo for ER‑to‑Golgi transport

Unfolded Protein Response (UPR)

Cellular program that up‑regulates chaperones and reduces translation when misfolded proteins accumulate in the ER

COPII

Coat complex that packages cargo for transport from the endoplasmic reticulum to the Golgi apparatus

Transferrin receptor pathway

Iron‑binding protein‑receptor complex is endocytosed

Protein translocase of the inner membrane (TIM)

Complex that moves proteins into the mitochondrial matrix or inserts them into the inner membrane

Lysosome

Acidic (~pH 5) organelle containing hydrolytic enzymes for macromolecule degradation

FADH₂

Reduced flavin adenine dinucleotide that delivers electrons to complex II of the electron transport chain

Golgi trans‑face (TGN)

Region where sorting of cargo into secretory

Fermentation

Process that regenerates NAD+ from NADH in the absence of oxygen

Karyopherin

Transport receptor (importin/exportin) that binds cargo bearing an NLS and mediates passage through nuclear pores

Pyruvate kinase reaction

Final glycolytic step that generates ATP by converting phosphoenolpyruvate to pyruvate

Rab5

Rab GTPase that regulates early endosome fusion and sorting

Lactate fermentation

Conversion of pyruvate to lactate coupled with NAD+ regeneration

Macropinocytosis

Actin‑driven uptake of extracellular fluid into large vesicles called macropinosomes

SNARE complex

Pairing of vesicle‑ (v‑SNARE) and target‑ (t‑SNARE) proteins that drives membrane fusion

GTP

High‑energy guanosine triphosphate formed in the TCA cycle

Ran‑GTP system

GTP‑binding protein cycle that provides directionality for nuclear import and export

Dynamin

GTPase that constricts the neck of budding vesicles to facilitate scission

LDL receptor pathway

Sequence where low‑density lipoprotein binds its receptor

Phagocytosis

Actin‑driven engulfment of large particles or cells into intracellular vesicles

Endoplasmic reticulum-associated degradation (ERAD)

Process by which misfolded proteins are retro‑translocated to the cytosol for ubiquitination and proteasomal degradation

Golgi cis‑face

Side of the Golgi apparatus that receives vesicles from the endoplasmic reticulum

Viral exploitation of endocytosis

Viruses bind surface receptors to trigger vesicle formation

Cristae

Folded inner mitochondrial membrane structures that increase surface area for oxidative phosphorylation

Familial hypercholesterolemia

Genetic disorder caused by defective LDL receptors

COPII versus COPI function

COPII mediates forward ER‑to‑Golgi transport

Tay‑Sachs disease

Lysosomal storage disorder due to deficiency of a specific hexosaminidase enzyme

Glycolytic net ATP yield

Two molecules of ATP are produced per glucose after subtracting the two ATP invested early in the pathway

Isocitrate dehydrogenase reaction

Oxidative decarboxylation of isocitrate yielding NADH and α‑ketoglutarate

NADH

Reduced nicotinamide adenine dinucleotide that donates electrons to the electron transport chain

KDEL retention signal

C‑terminal tetrapeptide that keeps soluble proteins within the endoplasmic reticulum

Rab GTPase

Small GTP‑binding protein that ensures vesicles tether to the correct target membrane

Rab7

Rab GTPase that controls late endosome‑to‑lysosome trafficking

Adaptor protein complex (AP‑2)

Connects cargo‑sorting motifs to clathrin during plasma‑membrane endocytosis

Phosphofructokinase‑1 reaction

Key regulatory step that uses ATP to convert fructose‑6‑phosphate into fructose‑1

Phosphoglycerate kinase reaction

Substrate‑level phosphorylation that transfers a phosphate to ADP

Energy payoff phase

Later steps that generate four ATP and two NADH

Acetyl-CoA

Two‑carbon molecule that enters the citric acid cycle after decarboxylation of pyruvate

α‑Ketoglutarate dehydrogenase reaction

Second oxidative decarboxylation that forms NADH

Alcoholic fermentation

Two-step conversion of pyruvate to ethanol and CO₂

Malate dehydrogenase reaction

Oxidation of malate to oxaloacetate

Coatomer complex

Protein assembly that forms COPI vesicles for retrograde Golgi‑to‑ER traffic

Fumarase reaction

Hydration of fumarate to generate malate

Electron transport chain

Series of membrane‑embedded complexes that use NADH/FADH₂ electrons to generate a proton gradient for ATP synthesis

V‑ATPase

Multi‑subunit pump that acidifies lysosomes and endosomes by translocating protons into the lumen

Oxidative phosphorylation

ATP production driven by the flow of protons back into the mitochondrial matrix through ATP synthase

Hexokinase reaction

Phosphorylation of glucose using one ATP to form glucose‑6‑phosphate

Citric Acid Cycle

Series of eight mitochondrial matrix reactions that oxidize acetyl‑CoA to CO₂ while producing NADH

ER stress response

Cellular signaling cascade (UPR) activated by accumulation of unfolded proteins in the endoplasmic reticulum

Signal sequence

Short N‑terminal peptide that directs nascent proteins to specific cellular compartments