Transport across Cell membranes

Question 1

diffusion def

Answer 1

diffusion is the net movement of particles from an area of high concentration to an area of low concentration.

• diffusion is a passive process- does not require energy

Question 2

what 4 things affect rate of diffusion?

Answer 2

1) concentration gradient
2) thickness of exchange surface (diffusion distance)
3) surface area
4) temperature- particles have more kinetic energy, so can move faster

Question 3

what is facillitated diffusion

Answer 3

Diffusion with the help of carrier proteins or channel proteins.

• carrier proteins: 4 big molecules/ions
• channel proteins: 4 small particles or small charged particles

-Passive process

Question 4

how do CARRIER proteins work

Answer 4

1) large molecule attaches onto a carrier protein in the membrane
2) Carrier Protein changes shape
3) releasing the molecule onto the other side

Question 5

How do CHANNEL proteins work

Answer 5

1) Form pores in the membrane for charged particles to diffuse through
THATS IT!!!???
NANNIIII

Question 6

what is active transport

and why is it a weirdo

Answer 6

moves molecules and ions across a plasma membrane…
AGAINST THE CONCENTRATION GRADIENT
low-> high basically

Active process- requires ATP
to move the substance against its concentration

Question 7

what is endocytosis and when/why can it be used over diffusion

Answer 7

when cells TAKE IN THINGS

endocytosis is used to take in molecules that are too large for carrier proteins (Eg proteins, lipids)

Question 8

endocytosis process

Answer 8

1) cell surrounds a substance
2) membrane PINCHES OFF to form a vesicle inside the cell containing the ingested substances.

EG white blood cells use endocytosis to take in microorganisms and dead cells to destroy them

endocytosis is an active process
requires ATP for energy

Question 9

excocytosis ( when cells SECRETE THINGS) process

Answer 9

1) vesicles containing the substances( eg hormones) released from the cell PINCH OFF from the sacs of the golgi apparatus, and move towards the plasma membrane.
2) the vesicle fuses with the plasma membrane and releases its contents outside the cell

however if you want to secrete something like a membrane protein that wont be secreted- instead they are inserted straight into the plasma membrane

• excocytsis is an active process and requires energy from ATP