Study guide - Tagged

Passive

Passive

no need for energy (ATP or GTP),

molecules are moving high to low (downhill) concentration.

Example: facilitated diffusion, ion channels (Na+ channel), and carrier molecules (glucose transporter)

Active

uses energy to move molecules from low to high (uphill) concentration; an example is Na+/K+ pump

Na+/K+ pump

primary active transport,

pumps out (of the cells) 3Na+ and pumps in 2K+,

keeps up high extracellular Na+ cc.,

reset ion-distribution at the end of the action potential

Co-transporters

secondary active transport,

the (downhill) diffusion of one molecule provides energy for the uphill (against the concentration gradient) movement of another molecule.

It can be symporter and antiporter

Na+/glucose symporter

Na+ entering the cell (), and that energy is used to move glucose into the cell uphill. This is a co-transport; more specifically, it is a symporter

symporter

(“piggy-back,” same direction)
– SGLT: sodium-dependent glucose transporters
• into intestinal and renal cells
– sodium-dependent amino acid transporters
• into intestinal and renal cells

antiport

“see-saw,” opposite directions)
– Na+-Ca2+ exchanger
• cardiac muscle
– Na+-H+ exchanger
• renal tubular cells

simple diffusion

Downhill movement”
 net movement from area of higher concentration to area of lower
concentration
-across lipid bilayer
 size,  lipid solubility  permeability
ions < glucose < H2O << nonpolar molecules < CO2, O2, N2

diffusion through channels

 aquaporins (water channels)
 ion channels

movement via transporters

 facilitated diffusion
 active transport

channels

simpler mechanism

transporters

more complex mechanisms, intermediate complex formed during transport

ion channels

leak channels and gated channels

leak channels

some are always open(open and close randomly)

gated channels

stimulus operates the channel

types of gated channels

voltage-gated, ligand-gated, mechanically-gated

voltage-gated

open/close due to changes in membrane

ligand-gated

open/close due to binding of chemical signals

mechanically-gated

open/close due to mechanical stimulus

driving forces of resting membrane potentail

1. Concentration gradient
2. Electrical gradient

K+

150-5.5-goes out

Ca++

2.5-0.0001-goes in

Na+

150-15-goes in

local potential

step 1- Depolarization to Threshold
• depolarization produced by the stimulus
chemical, electrical, mechanical
• depolarization due to what’s done to
(received by) this part of the membrane

threshold

step 2

The production of an action potential is an all-or-none response

depolarization

step 3,4-

• depolarization produced in
response to the stimulus
• depolarization due to what this
part of the membrane does

Acceleration indicates a process that has positive feedback. Depolarization continues and reaches peak at about +35 mV

Repolarization

step 5 Membrane potential returns to resting level

hyperpolarization

step 6

Membrane potential becomes even more negative, falling a little bit below resting membrane potential, and then gradually returns back to resting level

IPSP

into the cell or K+ out of the cell, The inside of the cell is becoming more negative

local potentails

Excitatory (depolarizing, aka EPSP) or Inhibitory (hyperpolarizing, aka IPSP)

EPSP

Na+ into the cell or Ca++ into the cell. The inside is becoming less negative

Exocytosis

the process by which intracellular secretory vesicles release their contents to the outside of the cell (the extracellular space [ECS])

Endocytosis

the process by which cells internalize contents from the ECS

what does exocytosis move

macromolecules (proteins, lipids)contained in an intracellular vesicle are released to the extracellular space after the vesicle fuses with the plasma membrane

Mechanism of receptor-mediated endocytosis-

1)Receptor binding,

2) recruitment of adaptor protein, clathrin, and dynamin to the activated receptor,

3) formation and pinch off of vesicle,

4) early endosome

5) late endosome/fusion with the lysosome.

6) Recirculation of receptor and either degradation or transcytosis of ligand

exocytosis

trafficking, fusion, opening/rupture, release

types of exocytosis

constitutive and regulated

constitutive

need to surviv

regulated

need to adapt

endocytosis

invaginates, pinches, closure, separates

types of endocytosis

eating, drinking, sleeping

phagocytosis

cell eating

pinocytosis

cellular drinking

receptor-mediated

cell sleeping

receptor mediated endocytosis

requires Clathrin-Coated Pit formation & adaptor proteins (e.g., dynamin, AP) to internalize cell surface receptors

3 main fates of receptors

(1) degradation (2) recycling to the cell surface & (3) transcytotic release

vesicle transport

defined by the Coat Proteins that surround them

common coat proteins

Clathrin, COPI, COPII, Caveolin

Coat proteins determine vesicle’s ________

(1) destination (2) formation & (3) target specificity