Diffusion And Co Transport

Question 1

Definition of diffusion

Answer 1

• a passive movement of molecules from an area of high concentration to an area of low concentration until equilibrium is reached

Question 2

How does simple diffusion work?

Answer 2

• only occur in gas and liquid
• molecules move by its KE that already possess = so can move constantly
• the motion is random
• only lipid soluble and small molecules can diffuse through the membrane
• a passive process

Question 3

3 factors affect rate of diffusion

Answer 3

• concentration gradient
• surface area
• thickness of membrane ( distance)

Question 4

Facilitated diffusion

Answer 4

• uses proteins of membrane to transport molecules e.g. water soluble ions + large molecules

Question 5

How does channel proteins help in F. Diffusion

Answer 5

• it forms a water filled hydrophilic tubes = allow water soluble (polar) ions to diffuse in membrane
• it is selective which only open to certain ions when they bind to them = so have control over enter or exit of ions

Question 6

How does carrier proteins help in F. Diffusion ?

Answer 6

• it binds with large molecules e.g. glucose = cause a change in shape of the protein = enable to diffuse through

Question 7

What law use in measuring rate of diffusion?

Answer 7

Fick’s Law

Question 8

Formula of fick’s law

Answer 8

Rate of diffusion = SA x difference in conc. / membrane thickness

Question 9

defintion of osmosis

Answer 9

• the passive net movement of water from an area of higher water potential to an area of lower w.p across a partial permeable membrane

Question 10

What is water potential ?

Answer 10

• pressure created by water molecules
• kPa

Question 11

Trend of water potential

Answer 11

• more solute in the solution ( higher conc.) = lower water potential
• water move from high w.p (less negative ) to lower w.p (more negative )

Question 12

Isotonic meaning

Answer 12

• when the w.p of the solution is the same with the w.p of the cell

Question 13

Animal cell in different condition of water

Answer 13

• hypotonic = burst
• hypertonic = shrivelled
• isotonic = balance equilibrium

Question 14

Plant cell in different water condition

Answer 14

• hypotonic = turgid
• hypertonic = plasmalysed
• vacuole will get smaller / bigger as water enter / exit the cell

Question 15

Active transport

Answer 15

• the movement of molecules in or out of the cell from an area of lower conc. to higher conc. using ATP and carrier proteins

Question 16

ATP role in active transport

Answer 16

• directly moving molecules
• co transport - move molecules individually using conc. gradient

Question 17

How does ions/ other molecules pass through A.T ?

Answer 17

• ATP binds to carrier proteins = change shape = enable pass through
• certain molecules bind to receptor site on C.P = ATP bind protein in the inner membrane, hydrolysis to ADP + Pi = protein change shape, Pi then released from protein

Question 18

What is the process used to get Na and glucose from ileum to epithelial cell ?

Answer 18

Co transport using facilitated diffusion through a carrier protein

Question 19

What is the role of villi in co transport ?

Answer 19

• provide large SA for CT to happen, thin membrane walls for transportation and rich network of blood capillaries

Question 20

What is the full process of Na + G to blood in order ?

Answer 20

1) AT from epithelial cell to blood = bring Na to blood
2) epithelial cell stay low conc.
3) CO transport = to get Na with glucose from ileum to epithelial cell using carrier protein
4) facilitated diffusion used to get Na + G from e.c to blood to maintain high conc of glucose in blood stream or respiration