Cell Membrane Flashcards
Cell Membrane (Phospholipid Bilayer) Components
Fats: phospholipids, cholesterol, glycolipids (smaller amount) Protein: Enzymes, signal transductors and transporters, Carbohydrates: attached to lipids and proteins
Phospholipid Bilayer Creation
Self forming biomolecular sheet. Hydrophobic hydrocarbon tails hydrophobic reactions repel tail away from water. Phosphate hydrophilic head is held in H bond with water. Bi-layer is self-sealing
Types of proteins in cell membrane (integral)
Alpha-Helix (receptors), Helical Bundle (enzymes, receptors), Beta-Barrel Channel proteins
Peripheral Proteins
Enzymes attach to cell receptors. Don’t enter hydrophobic part of bilayer but can push into peripheral regions. Attaches to integral proteins
Cell Membrane Carbohydrates
Glycoproteins, glycolipids, proteoglycans. Forms glycolax layer outside of membrane
Glycocalyx Functions
Barrier for cell from surroundings, holds cell shape against external forces, mediator for cell - cell interactions + involved in disease development
Cell Membrane Functions
Barrier, Holds molecules inside/outside cell, maintains cell internal environment pH and receptors, structural support
Fluid Mosaic Model
Membranes are 2D solutions of oriented globular proteins and lipids. Sea of lipids
Types of movement across cellular membrane
Passive diffusion, facilitated diffusion and active transport
Passive Diffusion
Unaided transport of solute molecules down concentration gradient. Until equilibrium is reached on both sides of membrane
Facilitated Diffusion
Diffusion mediated by integral proteins. Moves down concentration gradient, no energy required
3 Types of integrated protein ports
Uniport, Symport, Antiport
Non-specific transporter
1 continuous channel through protein
Specific Transporter
Binding sight of specific shape. Chanels 1 specific protein
Active Transport
Uses energy, goes against concentration gradient. 2 Types
Primary Active Transport (eg Na and K chanel) Outline
ATP molecule attaches to protein, 3 Na molecules bind to their active sites, ATP molecule splits (ADP and Phosphate), Phosphorylation of protein, confirmational changes occur, Na ions released to extracellular fluid + 2 K ions bind to binding sites, ATPase is dephosphorylised, reverts back to previous formation, K+ ions released
Secondary Active Transport
Symport moves specific substance across concentration gradient. Movement of 1st pulls 2nd substance along with it (energy only spent on 1)
Endocytosis Def.
Bringing molecules into cell
Exocytosis Def.
Bringing molecules out of cell
