Transport Of Ions And Small Molecules Flashcards
Diffusion
Random molecular motion of solute down a chemical or electrochemical gradient
How move across membrane
Osmosis
Diffusion of water across a semipermeable membrane
Protein mediated transport
More rapid than simple diffusion
Substrate for molecule movement
Saturation kinetics and chemical specificity and stereospecificy because only certain molecules are transported
Saturation kinetics
Rate of transport increases until it reaches a point at which is stabilizes
There’s a limit only so many proteins so can only move so many molecules
Facilitated vs. simple diffusion
Simple is linear
Facilitated if add proteins rate will increase
Allosteric binding sites
To control conformation of proteins and regulates transport
Glucose binding is competitive inhibition
Competitive inhibition
Is molecule binds site instead of glucose it blocks glucose binding to the protein and suppresses glucose transport
Lots of therapeutic agents, ex is antihistamines
Types of protein mediated transport
Facilitated transport
Active transport
Facilitated transport
Not linked to metabolic energy because moves down gradient and not blocked by substrate
Cannot move against electrical potential because requires energy
Cannot move uncharged particles against a gradient
Transported molecule may alter transport by producing conformational change in the transport protein
Active transport
ATP required, hydrolysis is needed to move against gradient, foundation of membrane potential
Metabolic inhibitors can block
Substances can move against concentration gradients
Membrane potential
Requires active transport
Types of transport proteins
Carrier proteins which bind molecules and move across membrane via conformational change
Channel proteins which have pores that open and close transmitting certain molecules across the membrane
Uniport
One type of molecule is transported across the membrane
Symport
Two different molecules transported in same direction
Antiport
Two different molecules transported in different directions
Types of channels
Open, closed, active transport, conformational transformation
ATP pump, ion channel which has greatest rate of transport and transporter
Carrier proteins
Can be active of facilitated transport
Uniporter, symporter, antiporter
Na, K ATPase
Most important ion transport via carrier proteins in the body
Maintains Low Na and high K in the cell by active transport and is responsible for membrane potential
3 Na out and 2 K in for each ATP hydrolyzed to ADP
2/3 of neurons energy needed here
Phosphorylation and dephosphorylation regulates
Chemical potential energy created and used to drive other systems ex: kidney
1 gate open at time creates specificity
Ca ATPase
Important in muscle
Na Ca Antiporter
Important in the heart
Na H antiport
PH of cytoplasm
Chloride bicarbonate antiporter
Important for pH
Na K Cl symporter
All at the same time
LasX binds to chloride symporter
Ion transport channels
Transmembrane alpha helicopter
b subunit forms a physical gate on outside of cell which opens to activate channel
Specificity not just dependent on molecule itself, ex: Na smaller than K but transports with water so cannot fit through K channel
Voltage gated channel
Ion transport channel
Activated by changes in membrane potential
Exist for Na, K and Ca
Different channels can be activated by depolarization or hyperpolarization
Ligand gated channel
Activated by ligand binding receptor which then opens the gate
Ketamine blocks this for Na and Cl which is activated by glutamate
Ketamine Blocks depolarization (making +) so no generation of action potential
