Chapter 5 - Entropy and Electricity Flashcards
Factors affecting the diffusion of a substance across a membrane
1) temperature— directly prop.
2) molecular weight— inversely prop.
3) surface area— directly prop.
4) gradient— directly prop.
5) membrane permeability— directly prop.
6) distance— inversely prop.
Diffusion (def)
The movement of a substance from an area of high substance concentration to an area of low substance concentration due to random thermal molecular motion (no energy)
Flux (def)
The amount of substance that crosses a defined surface area per unit time
Diffusion equilibrium (def)
State in which the diffusion fluxes in opposing direction are equal, resulting in a net flux of zero
Most molecules in the body are
Lipophobic and/or charged and so will not pass readily through the bilayer
Types of molecules that pass through phospholipid bilayer
Small, non charged substances, often nonpolar (CO2 and O2)
Types of Passive transport and definitions and types of molecules
Simple diffusion: diffusion directly through the membrane— CO2 and O2, small hydrophobic
Facilitated: diffusion through membrane proteins
Types of facilitated diffusion
Channels: small, hydrophilic molecules
Open or gated
Gated: regulated by the cell
stimulus-gated: respond to ligand binding
(neurotransmitters, hormones)
voltage-gated: respond to changes in membrane
potential (action poten.)
mechanosensitive: respond to physical distortion
(tactile)
Carrier-mediated transport: medium, hydrophilic molecules
Uniport carriers: single ion in direction of the gradient
Cotransporter: moves 2 ions (symport=same direction, antiport=opposite)
Types of Active transport
1) Primary active: small molecules
4 types of ATPase
1) Na-K maintains membrane potential
2) Ca plasma membrane and organelles, important for muscle contraction
3) H mitochondria and plasma membrane
4) H-K plasma membranes (stomach)
2) Secondary Active: medium molecules
3) Vesticular transport: large molecules
1) Endocytosis:
phagocytosis “cell eating”
pincocytosis “cell drinking”
2) exocytosis
Osmosis (def)
The movement of water from an area of high water (low solute) concentration to an area of low water (high solute) concentration due to random thermal molecular motion
Osmolarity (def)
Concentration of a solution expressed as number of solutes per liter (regardless of solute type)
Hyper, hypo, iso osmotic definitions
Hyper: higher solute concentration
Hypo: lower solute concentration
Iso: equal solute concentration
Electrical potential (def)
Voltage difference between two points (E)
Electricity
oppositely charged particles come together it can perform work
Voltage (def)
Measure of potential (separated charges to do work (units of potential) (V)
