Cell Bio Ch 12: Neurons

What goes through the lipid bilayer easily?

small, hydrophobic, nonpolar, and uncharged atoms

ex) CO2, O2, hormones, N2

What goes through the lipid bilayer slowly?

small, uncharged, polar

ex) H2O, ethanol, glycerol

What cannot go through the lipid bilayer?

Large, uncharged, polar

ex) amino acids, nucleosides, glucose

Ions (tiny + charged)

2 types of membrane proteins

Transporters

Channels

both are amphipathic

Very specific

Lock and key

transmembrane proteins

Transporter

Changes shape to let 1 thing through

think of a turnstile (loopy doors)

VERY SELECTIVE

each cell has its own set

Channels

multiple things can get through!

normal gate (open once and let many in)

Diffusion

High to low concentration

Chemical Gradient (in every cell)

Passive Transport

Going with the concentration gradient

high to low

chill and no extra energy

Active transport

Goes against concentration gradient

3 types : ATP, Light, and coupled reactions

You need extra stuff

High → low

Coupled Reaction

Active transport

both work together

ex) an unfavorable protein will bind to a favorable protein to make it past the concentration gradient . still high to low

ATP Active Transport

Energy carrier → breaks bonds for energy

We are most used to this

Light Active Transport

Bacteria and ectogenetics

Is the membrane charged or uncharged?

it is charged on the outside and uncharged on the inside

When the electrochemical agrees

High to low concentration of protons (+) → wants to be inside to be alone (-)

DRIVING FORCE IS HUGE → STEEP GRADIENT

ex) Sodium/Na+

Sodium / Na+

agrees with electrochemical gradient → very fast, dissolves very quick, steep concentration gradient

Low inside cell. High outside cell

When they disagree with the electrochemical gradient

high → low

inside → outside

The electric side and the chemical sides of the gradient will try go opposite ways → whichever is stronger will go in their respective direction (so only 1 direction in the end)

LOW concentration gradient

ex) Potassium / K+

Potassium / K+

disagrees with electrochemical gradient →potassium slowly leaves cell, little net movement

High in cell, low outside of cell (which is why it leaves slowly)

Cellular Ion Concentrations

tightly regulated! Na and K

Na+ - K+ Pump

Glucose-Sodium (Na+) Symport

Ca2+ Pump

Na+ - K+ Pump (Sodium-Potassium Pump)

Creates electrochemical gradient !!!

takes sodium in while pushing potassium out

goes against gradient

uses ATP as energy (active)

\the NA outside the cell = HUGE ENERGY SOURCE

10 miliseconds

Glucose-Sodium Symport

Low to high

USES ELECTROCHEMICAL GRADIENT AS ENERGY (active transport)

Uses Na+ to move glucose → coupled reaction

• Na+ is coupled with the electrochemical gradient

• Na+ = unfavorable

• Gradient = favorable

Transporter

VERY specific

BIG DRIVING FORCE !!!

Ca2+ Pump

Transorter