Week 4 - Lipids & Membranes Flashcards
(26 cards)
Intergral Membrane Protein
Embedded in the bilayer; spans the membrane (transmembrane).
Peripheral Membrane Protein
Attached to surface of the membrane (not embedded).
Channel Proteins
Provide pores/tunnels for passive transport (often gated).
Carrier Proteins
Bind specific molecules, change shape, and shuttle them across the membrane.
Cis-Unsaturated Fatty Acids
Double bond creates a kink; liquid at room temp (like oils).
Trans-Unsaturated Fatty Acids
Double bond but no kink; behaves more like saturated fat; often artificially made.
Saturated Fatty Acids
No double bonds; straight, tightly packed; solid at room temp (like butter).
Gap Junction
Channels between animal cells allowing ions and small molecules to pass; enable communication.
Desmosome
Strong anchoring junction that connects cytoskeletons of neighboring cells; adds mechanical strength.
Hemidesmosomes
Anchor epithelial cells to the extracellular matrix (like basement membrane); half of a desmosome.
Phospholipid
A lipid with a hydrophilic head and two hydrophobic fatty acid tails; forms bilayers in water.
Sterol
A type of lipid with a 4-ring structure; cholesterol is the most common in animals.
Cholesterol
A sterol that stabilizes membranes, maintaining fluidity at different temperatures.
Fluid Mosaic Model
Describes the membrane as fluid, with proteins floating in or on the phospholipid bilayer.
Micelle
A sphere of phospholipids with tails inward, heads outward—used in fat digestion.
Bilayer
Double layer of phospholipids that forms cell membranes; tails face inward, heads face water.
Amphipathic
Molecule with both hydrophilic and hydrophobic parts (like phospholipids).
Simple Diffusion
Movement of small/nonpolar molecules directly through the membrane from high → low concentration.
Facilitated Diffusion
Movement of molecules through a protein (channel or carrier) from high → low concentration; no energy needed.
Active Transport
Movement against the gradient (low → high); requires energy (usually ATP).
Secondary Active Transport
Uses energy from a gradient created by active transport (like Na⁺) to move other substances.
Osmosis
Passive movement of water across a semipermeable membrane from low → high solute concentration.
Hypotonic
Solution has less solute than the cell → water enters the cell (cell may swell).
Hypertonic
Solution has more solute than the cell → water leaves the cell (cell may shrink).
