Transport

Question 1

Factors affecting rate of diffusion

Answer 1

•Temperature
•Concentration gradient
•Surface area
•Diffusion distance
•Size of molecule
•Stirring / moving of molecules

Question 2

What are the 2 types transport across membranes?

Answer 2

Passive transport
Active transport

Question 3

Define diffusion

Answer 3

The net movement of particles from a region of high concentration to a region of lower concentration until evenly distributed (DOWN a concentration gradient)

Question 4

What does facilitated diffusion use?

Answer 4

Channel or carrier proteins

Question 5

Define active transport

Answer 5

The movement of particles into or out of a cell from a region of lower concentration to a region of higher concentration (AGAINST its concentration gradient) using ATP and carrier proteins.

Question 6

Process of active transport

Answer 6

1. The molecule or ion to be transported across the membrane binds to specific carrier proteins on one side of the membrane (at binding site)
2. On the inside of the membrane, ATP binds to the carrier protein, causing it to hydrolyse (bond breaks) into ADP + Pi (releasing the ADP).
3. This causes the carrier protein to change shape and open to the opposite side of the membrane (releasing the molecule or ion to the opposite side).
4. The inorganic phosphate is released from the carrier protein causing it to revert back to its original shape
5. The process can then be repeated

Question 7

What is co-transport?

Answer 7

More than one molecule or ion may be moved across the membrane together (a type of active transport)

Question 8

Define osmosis

Answer 8

The passive movement (diffusion) of water from a region of higher water potential to a region of lower water potential, through a selectively permeable membrane.

Question 9

What is water potential?

Answer 9

A measure of how free water molecules are to move (their potential to do osmosis)

Question 10

What is water potential measured in?

Answer 10

Units of pressure e.g kPa

Question 11

What happens under isotonic conditions in animal cells?

Answer 11

No net movement of water

Question 12

What happens to an animal cell in hypotonic solution?

Answer 12

Water enters the cell which may burst (lysis)

Question 13

What happens to an animal cell in hypertonic solution?

Answer 13

Water leaves the cell which shrivels (crenation)

Question 14

What happens to a plant cell in isotonic solution?

Answer 14

No net movement of water - incipient plasmolysis

Question 15

What happens to a plant cell in hypotonic solution?

Answer 15

Vacuoles fill with water, turgor pressure develops , chloroplasts seen next to cell wall

Question 16

What happens to a plant cell in hypertonic solution?

Answer 16

Vacuoles lose water, cytoplasm shrink(plasmolysis) and chloroplasts are seen in the centre of the cell