Intracellular Components and Protein Transport Overview

Membrane-enclosed organelles

Organelles surrounded by lipid membranes in cells.

Protein sorting

Process of directing proteins to specific locations.

Nuclear pores

Gateways in nuclear membrane for macromolecule transport.

Vesicles

Small membrane-bound sacs transporting proteins and materials.

Signal sequences

Short peptide sequences guiding protein localization.

Nuclear localization signal

Sequence directing proteins to the nucleus.

GTP hydrolysis

Energy-releasing reaction driving nuclear transport.

Mitochondrial precursor proteins

Unfolded proteins imported into mitochondria.

TOM complex

Translocator of outer mitochondrial membrane for protein import.

TIM complex

Translocator of inner mitochondrial membrane for protein import.

Endoplasmic reticulum (ER)

Extensive membrane network modifying and transporting proteins.

Signal recognition particle (SRP)

Ribonucleoprotein directing ribosomes to the ER.

SRP receptor

Protein binding SRP for ribosome entry into ER.

Signal peptidase

Enzyme cleaving signal sequences from proteins.

Single pass transmembrane proteins

Proteins anchored by a single hydrophobic sequence.

Double pass transmembrane proteins

Proteins anchored by two hydrophobic sequences.

Clathrin

Protein forming vesicle coats during endocytosis.

Adaptin proteins

Proteins binding clathrin to cargo for vesicle formation.

COPI proteins

Coat proteins involved in retrograde vesicular transport.

COPII proteins

Coat proteins facilitating anterograde vesicular transport.

Exocytosis

Process of vesicle fusion with plasma membrane.

Endocytosis

Process of vesicle formation to internalize substances.

Clathrin

Protein forming vesicle outer shell with adaptin.

COPI proteins

Facilitate vesicular transport in retrograde direction.

COPII proteins

Facilitate vesicular transport in anterograde direction.

Rab proteins

Mediators of vesicle docking to target membranes.

SNARE proteins

Catalyze fusion of vesicles with target membranes.

Unfolded protein response

Reaction to accumulation of misfolded proteins.

Glycosylation

Covalent modification of proteins with sugars.

Disulfide bonds

Covalent linkages stabilizing protein structure.

Secretory vesicles

Store and release proteins via exocytosis.

Constitutive secretion

Continuous protein release without external signals.

Regulated secretion

Protein release triggered by specific extracellular signals.

Endocytosis

Process of internalizing substances into the cell.

Phagocytosis

Ingestion of large particles by specialized cells.

Receptor-mediated endocytosis

Specific uptake via membrane receptors.

Low density lipoprotein (LDL)

Cholesterol carrier linked to cardiovascular issues.

High density lipoprotein (HDL)

Cholesterol carrier beneficial for cardiovascular health.

Transcytosis

Transport of materials across a cell.

Autophagy

Cellular process for degrading and recycling components.

Macroautophagy

Bulk degradation of cellular components.

Chaperone-mediated autophagy

Selective degradation requiring chaperone proteins.

Microautophagy

Direct engulfment of cytoplasmic material by lysosomes.

Lysosomes

Organelles containing hydrolytic enzymes for degradation.

Vesicular transport

Dynamic process for cellular trafficking of materials.

Endocytosis

Mechanism for cellular uptake of substances.

ER

Organelle for lipid and protein synthesis.

Golgi apparatus

Organelle for modifying and sorting proteins.

Glycolysis

Process converting glucose into pyruvate and ATP.

ATP

Energy currency of the cell, produced during metabolism.

NADH

Electron carrier produced during glycolysis and citric acid cycle.

Citric acid cycle

Pathway for oxidizing acetyl CoA to produce energy.

Pyruvate

End product of glycolysis, converted to acetyl CoA.

Acetyl CoA

Key substrate for the citric acid cycle.

Fermentation

Process generating ATP without oxygen, producing lactate or ethanol.

Hexokinase

Enzyme phosphorylating glucose in glycolysis.

Aldolase

Enzyme cleaving fructose 1,6-bisphosphate in glycolysis.

GAP

Glyceraldehyde 3-phosphate, a glycolysis intermediate.

NAD+

Oxidized form of NADH, used in fermentation.

Phosphorylation

Addition of phosphate group to a molecule.

Oxidative phosphorylation

Process producing ATP using electron transport chain.

GTP

Energy produced in the citric acid cycle.

FADH2

Electron carrier produced in the citric acid cycle.

Citrate

First product of the citric acid cycle.

Isomerization

Conversion of a molecule into its isomer.

2-phosphoglycerate

Intermediate formed in glycolysis before phosphoenolpyruvate.

Isocitrate

Converted to α-ketoglutarate in citric acid cycle.

α-Ketoglutarate

Converted to succinyl CoA; produces NADH and CO2.

Succinyl CoA

Catalyzed to succinate by succinyl CoA synthetase.

Succinate

Converted to fumarate by succinate dehydrogenase.

Fumarate

Converted to malate in the citric acid cycle.

Malate

Converted to oxaloacetate; produces NADH.

Oxaloacetate

Regenerated for the next cycle of citric acid.

NADH

Main energy carrier produced during citric acid cycle.

FADH2

Produced in citric acid cycle; energy carrier.

GTP

Generated from succinyl CoA conversion to succinate.

Oxidative phosphorylation

Generates majority of ATP in cells.

Glycolysis

Breaks down glucose into pyruvate, producing ATP.

Fermentation

Produces ATP under oxygen-limited conditions.

Mitochondria

Organelles involved in ATP production and metabolism.

Matrix

Innermost compartment of mitochondria.

Inner membrane

Site of electron transport chain in mitochondria.

Outer membrane

Surrounds mitochondria; permeable to small molecules.

Intermembrane space

Space between inner and outer mitochondrial membranes.

Chemiosmotic coupling

Mechanism linking electron transport to ATP synthesis.

Electron transport chain

Series of complexes transferring electrons to oxygen.

Proton gradient

Energy stored for ATP synthesis by ATP synthase.

Reactive oxygen species

Byproducts of mitochondrial metabolism; can cause damage.

Proton Pumping

Creates electrochemical proton gradient in mitochondria.

Electrochemical Proton Gradient

Drives ATP synthesis and transport across membranes.

ATP Synthase

Enzyme that produces ATP using proton gradient energy.

ATP/ADP Ratio

High ratio maintained by rapid ADP to ATP conversion.

Chemiosmotic Coupling

Links electron flow with proton pumping for ATP synthesis.

Energy Carriers

NADH and FADH2 supply electrons in mitochondria.

Electron Transport Chain

Series of complexes transferring electrons in mitochondria.

Photosystems

Multiprotein complexes in chloroplasts containing chlorophyll.

Light Reactions

Stage 1 of photosynthesis producing ATP and NADH.

Photosystem II

Generates ATP via photosynthetic proton pump.

Water-Splitting Enzyme

Catalyzes electron extraction from water in photosystem II.

Photosystem I

Transfers high-energy electrons to produce NADH.