Cell Membranes, Transport, and Organelles - Vocabulary Flashcards

Vocabulary flashcards covering membrane structure, transport mechanisms, and cellular organelles as discussed in the lecture notes.

Phospholipid bilayer

Phospholipids spontaneously form a double layer in water with hydrophilic heads facing the water on both sides and hydrophobic tails tucked inside, creating the cell membrane.

Hydrophilic head

The water-loving, polar region of a phospholipid facing the aqueous environment (outside or inside the cell).

Hydrophobic tail

The water-fearing, nonpolar region of a phospholipid that faces inward, away from water.

Channel protein

A membrane protein that allows substances to pass through the membrane down their concentration gradient (passive transport).

Pump protein

A membrane protein that uses energy (often ATP) to move substances against their concentration gradient (active transport).

Passive transport

Movement of molecules down their concentration gradient without the input of cellular energy.

Active transport

Movement of molecules against their concentration gradient that requires energy, typically from ATP or another energy source.

Concentration gradient

A difference in the amount of a substance across a membrane that drives diffusion or transport.

Membrane protein

Proteins embedded in or associated with the cell membrane, including channels, pumps, receptors, and adhesion proteins.

Receptor

A membrane protein that binds signaling molecules (like hormones) and triggers a cellular response.

Adhesion protein

A membrane protein that helps cells attach to each other or to the extracellular matrix, aiding tissue formation.

Endocrine signaling

Hormone signaling where hormones are released into the bloodstream to reach distant target cells.

MHC (Major Histocompatibility Complex)

Molecules on cell surfaces that present protein fragments to T cells to distinguish self from non-self.

Self protein / Self antigen

Normal cellular proteins recognized as 'self' by the immune system; non-self proteins indicate infection.

Autoimmune disease

A condition in which the immune system attacks the body's own tissues due to misrecognition of self.

Cytosol

The jelly-like fluid inside the cell, excluding organelles; ribosomes can be free-floating here.

Cytoplasm

Cytosol plus all organelles (excluding the nucleus); the cell’s interior minus the nucleus.

Nucleus

Organelle where genetic information is housed and transcription occurs (DNA to RNA).

Transcription

Process of copying DNA into messenger RNA (mRNA); occurs in the nucleus with RNA polymerase.

RNA polymerase

Enzyme that synthesizes RNA from a DNA template during transcription.

Ribosome

Molecular machine that translates mRNA into protein; free in the cytosol or bound to the rough ER.

Rough endoplasmic reticulum (RER)

ER studded with ribosomes; synthesizes proteins destined for membranes or secretion.

Smooth endoplasmic reticulum (SER)

ER without ribosomes; stores calcium (especially in muscle) and metabolizes/detoxifies substances.

Golgi apparatus

Cellular sorting center that receives vesicles from the rough ER and directs proteins to their destinations.

Vesicle

Membrane-bound sac that transports proteins between organelles or to the cell membrane.

Kinesin

Motor protein that walks vesicles along microtubules toward the cell membrane; each step uses energy, often described as two ATP per step.

Mitochondrion

Powerhouse of the cell; produces ATP via glycolysis (cytosol) and oxidative phosphorylation; double membrane with inner/outer membranes.

Intermembrane space (IMS)

Space between the inner and outer mitochondrial membranes.

70S ribosome

Prokaryotic-like ribosome found in mitochondria (evidence for endosymbiotic origin).

Endosymbiotic theory

Idea that mitochondria originated as free-living bacteria that were taken in by ancestral eukaryotic cells.

Lysosome

Organelle containing proteolytic enzymes and low pH; degrades damaged proteins and organelles; involved in apoptosis when ruptured.

Lysis

Breaking open a cell; often refers to rupture of lysosomes releasing contents.

Peroxisome

Organelle that breaks down reactive oxygen species (peroxides) to protect the cell.

Peroxide

Reactive oxygen species (H2O2) produced during metabolism; highly reactive and detoxified by peroxisomes.