Cell membranes and Molecular movement Flashcards
Cell membrane (what it is and structure)
-semi-permeable barrier that separates the inside of the cell with the outside
Structure
- phospholipid bilayer
- contains proteins
- contains cholesterol (animal cells)
- contains carbohydrates
- dynamic
Phospholipid bilayer
- phosphate+glycerol+2 fatty acid tails
- hydrophilic head, hydrophobic tails
Contains proteins (types and functions)
types:
- peripheral: inner or outer surface of membrane
- integral: embedded in membrane
- transmembrane: penetrate membrane completely
Functions:
- transport (channels)
- recognition (name tags)
- receptor (communication)
- adhesion (attachment/ support)
- enzymes (workers)
Contains cholesterol (function and what happens in extreme temps)
function: regulates fluidity
- cold –> prevents from becoming too rigid
- hot –> prevents from moving too much
Contains carbohydrates (what it is and functions (3))
- glycocalyx: carbohydrate coat
- functions: adhesion, barrier, recognition
Dynamic
fluid mosaic model
Cell membrane (functions and example)
- allows each cell to act as its own unit
- regulates movement of molecules in and out of the cell (selective permeability based on size, charge, shape, lipid solubility)
- provide an anchor for enzymes to coordinate cell activities
ex: ATP production
Membrane transport (what it is and types)
-allows nutrients, waste, water, etc in and out of the cell in a controlled manner
Types: passive transport, active transport
Passive transport (what it is and types)
- does not require energy
- movement of molecules from high to low concentration
Types:
- simple diffusion
- facilitated diffusion
- osmosis
Simple diffusion aka dialysis (what it is and examples)
- movement of solutes across a membrane from high to low concentration
ex: lipid soluble compound, dissolved gasses
Types of facilitated diffusion
carrier mediated and protein channels
Carrier Mediated (what it is and example)
-transported protein facilitates movement of a solute from high to low concentration
-usually specific, 1 transporter –> 1 molecule
EX: glucose carrier protein
Protein channels (what it is and example)
-transmembrane proteins –> channels allowing molecules to move through
-passage depends on size and charge
EX: water soluble compounds, ions
Osmosis
movement of water across a membrane from a high to low concentration of water
Osmotic pressure (what it is and when it happens)
- the force of water generated by a solute concentration
- When? solutes: not permeable, water: freely permeable
A closer look at osmotic pressure
- measure of how strong a solution draws in water
- high osmotic pressure=more water draw
Osmolality (what it is, units, determined by)
-the measure of osmotic pressure
- Units
- osmole: 1 mole of solute dissolved into 1 liter of water
- mole: 6.02x10^23 particles
- determined by the number of particles not concentration
- osmolality= concentration x # of particles
Driving force for passive transport
-electrochemical
- Electrical
- membrane potential: difference in electrical potential across membranes
- like charges repel, opposite charges attract
- Chemical
- concentration gradients
factors affecting diffusion rates
- distance: shorter –> faster
- gradient size: larger distance –> faster
- molecular size: smaller –> faster
- Temperature: hotter –> faster
Active transport (what is required, direction molecules move, types)
- requires energy (ATP) and a transporter protein
- movement of molecules from low –> high concentration
- Types:
- primary active transport
- secondary active transport
Primary active transport
- uses ATP and transporter to move molecules against concentration gradient
- EX: Na+/K+ pump
Na+/K+ pump
- uses 1 ATP
- moves 3 Na+ out and 2 K+ in
Secondary Active transport
- uses a concentration gradient (generated by primary active transport) to move molecules against their concentration gradient
- EX: Na+ concentration gradient produced by Na+/K+ pump drives glucose transport
Cotransport
Same direction
Countertransport
opposite direction
Transporter proteins
Ion pumps: move ions (Na+/K+)
Exchange pumps: move 2 types of molecules at the same time
