2B Diffusion, Osmosis & Active Transport

Question 1

Define diffusion.

Answer 1

NET MOVEMENT of particles from an area of HIGHER concentration to an area of LOWER concentration - the particles diffuse DOWN a concentration gradient

Question 2

Is diffusion a passive or active process?

Answer 2

Passive

Question 3

What is an active process?

Answer 3

Requires energy to happen

Question 4

What is a passive process?

Answer 4

No energy is required for it to happen

Question 5

What are the three factors that affect diffusion?

Answer 5

Surface area, concentration gradient and the thickness of diffusion pathway

Question 6

How does the concentration gradient affect diffusion?

Answer 6

> HIGHER conc. grad. = HIGHER RATE of diffusion
However, diffusion SLOWS down ove time as the difference in concentration DECREASES with movement until an EQUILIBRIUM is reached

Question 7

How does the surface area affect diffusion?

Answer 7

> The LARGER the surface area, the FASTER the rate of diffusion

Question 8

How does the thickness of the diffusion pathway affect diffusion?

Answer 8

> The SMALLER the diff. path. width, the FASTER the rate of diffusion

Question 9

Define facilitated diffusion.

Answer 9

The NET MOVEMENT of particles across a SEMI-PERMEABLE MEMBRANE from an area of HIGHER conc. to and area of LOWER conc. through a CARRIER/CHANNEL protein

Question 10

Is facilitated diffusion an active or passive process?

Answer 10

passive

Question 11

What is a carrier protein and how does it work?

Answer 11

> A protein in the membrane that moves LARGE molecules across it
a molecule ATTACHES to a carrier protein which causes it to CHANGE SHAPE
The molecule is then released on the OPPOSITE side of the membrane

Question 12

What is a channel protein and how does it work?

Answer 12

> A protein that forms PORES in the membrane for CHARGED molecules to diffuse through
Different charged particles diffuse through different channel proteins

Question 13

What two factors affect facilitated diffusion?

Answer 13

Concentration gradient and the number of channel/carrier proteins

Question 14

How does the number of channel/carrier proteins affect the rate of facilitated diffusion?

Answer 14

> Once all proteins are in use, F.D can’t increase the rate even if there is an increase in the concentration gradient
The GREATER the number, the FASTER the rate of F.D

Question 15

Define osmosis.

Answer 15

The diffusion of WATER MOLECULES across a PARTIALLY PERMEABLE MEMBRANE from an area of HIGH WATER POTENTIAL to an area of LOW WATER POTENTIAL

Question 16

What is the potential of pure water?

Answer 16

0

Question 17

What is the meaning of isotonic?

Answer 17

The water potentials of two solutions are equal so neither will lose/gain any water

Question 18

Define hypotonic.

Answer 18

A solution with a water potential that is HIGHER than INSIDE the cell causing the cell to SWELL

Question 19

Define hypertonic.

Answer 19

A solution with a water potential that is LOWER than INSIDE the cell causing the cell to SHRINK

Question 20

What are the factors that affect the rate of osmosis?

Answer 20

Water potential gradient, thickness of exchange surface, SA of exchange surface

Question 21

How does the water potential gradient affect the rate of osmosis?

Answer 21

> The HIGHER the gradient, the FASTER the rate of osmosis

> As osmosis occurs, the water potential gradient DECREASES so the rate of osmosis LEVELS off over time

Question 22

Define active transport.

Answer 22

The use of ENERGY to move molecules and ions across PLASMA MEMBRANES using CARRIER PROTEINS and CO-TRANSPORTERS

Question 23

What is the role of carrier proteins in active transport?

Answer 23

> Molecules ATTACH to the protein, it CHANGES SHAPE and causes the molecule to be RELEASED on the OPPOSITE side of the membrane
They usually move molecules from a LOW to a HIGH concentration
The movement requires ENERGY in the form of ATP - it is an active process

Question 24

What is the role of co-transporters in active transport?

Answer 24

> they are a type of CARRIER PROTEIN that BIND to 2 molecules at one time
the concentration gradient of ONE molecule is used to move the other AGAINST its own conc. grad.

Question 25

What three factors affect the rate of active transport?

Answer 25

Speed of individual carrier proteins, the number of carrier proteins, rate of cellular respiration and the availability of ATP

Question 26

Define water potential

Answer 26

Liklihood of water molecules to diffuse out of or into a solution

Question 27

Describe the chemical reaction the occurs to release energy from ATP

Answer 27

> A HYDROLYSIS reaction that breaks ATP down into ADP and an INORGANIC PHOSPHATE
It is the breaking of the HYDROGEN BOND that releases the energy

Question 28

Why are sodium ions important in the transport of glucose from the ileum into the blood?

Answer 28

> Sodium ions diffuse from the LUMEN of the ILEUM into the INTESTINAL EPITHELIUM CELLS DOWN their conc. grad. through a sod.-gluc. co-transporter protein.
At the same time, the co-transporter carries glucos into the EPITHELIUM CELL AGAINST its conc. grad.
GLUCOSE is then able to DIFFUSE into BLOOD from the EPITHELIAL CELL