Cell Membranes And Transport (chapter 4) Flashcards
Phospholipid
Hydrophilic head
Hydrophobic tail
Hydrophobic
Water hating - fat loving
Hydrophilic
Water loving - fat hating
Bilayer
Phospholipid bilayer
Amphipathic
One end hydrophilic, other end hydrophobic
Unsaturated hydrocarbon
Degree of Unsaturation (double bonds) in tail (more = more fluid)
Unsaturated hydrocarbons - tails with kinks
Saturated hydrocarbon
Length of fatty acid tail (longer = more viscous)
Saturated hydrocarbon tails = no kinks, straight
Desaturase
Desaturase enzyme makes double bonds (kink)
Cholesterol
- Cholesterol is in the membrane of animal cells
- Cholesterol counters the effects of temperature extremes:
• high temps, reduces membrane fluidity by restraining movement of lipids
• low temps, increases membrane fluidity by preventing lipids from ordering
Integral membrane (transmembrane) proteins
Contains hydrophobic domains that cross the bilayer
Peripheral proteins
Sit on the surface and form non-covalent bonds with lipids and membrane proteins
Passive transport
Transport from high to low concentration is driven by increase in entropy
1. Diffusion
2. Facilitated diffusion
Active transport
Transport against the concentration gradient (from low to high concentration) requires energy
1. Primary - uses ATP
2. Secondary - uses electrochemical gradients
Diffusion
Things move from high to low concentration “down their concentration gradient”
(Non-polar molecules) (small uncharged polar molecules)
Osmosis
Movement of a solvent from high to low concentrations
Hypotonic solution
Solution concentration < cell concentration
Volume increases (water moves into the cell)
Hypertonic solution
Solution concentration > cell concentration
Volume decreases (water moves out of the cell)
Isotonic solution
Solution concentration = cell concentration
Volume stays the same (stays the same)
Simple diffusion
Small and uncharged molecules diffuse rapidly
Facilitated diffusion - channel proteins
A. Channel protein
B. Gated channel protein
C. Carrier proteins
Channel protein
From hydrophilic channels in the membrane through which water and ions can move
Channel protein: Aquaporin
An aquaporin is a water channel. Water molecules move through channel by being handed off to a succession of hydrogen-bonding sites in the channel
Gated channel proteins: K+ voltage-gated channel
Normal voltage across membrane, activation gate of K+ closed (no movement)
Response to voltage change across membrane, activation gate of K+ opens up for movement
Carrier protein
- In conformation so that binding site is exposed toward region of higher concentration
- Solute molecule binds to carrier protein
Primary active transport (example: sodium-potassium pump)
- moves sodium ions (NA+) out of cell
- moves potassium ions (K+) into cell
- the transporter uses ATP to do this
Both ions are moved against their concentration gradient so energy is needed
Secondary active transport
- does not use ATP
- uses ion gradients (electrochemical) for energy
- energy is released as an ion moves with its concentration gradient is used to drive movement of a solute against its concentration gradient
Symport
The transported solute moves in the same direction as the gradient of the driving ion
Antiport
The transported solute moves in the direction opposite from the gradient of the driving ion
Micelle
Micelle is water forms an aggregate with the hydrophilic “head” regions in contact with surrounding solvent. Hydrophobic single-tail regions in the centre on the micelle
Selective permeability
Polymeric membrane that will allow certain molecules or ions to pass through by osmosis
Uniport
Membrane transport protein that transports a single substrate across a cell membrane
Electrochemical gradient
Gradient of electrochemical potential
