CO-TRANSPORT

Question 1

What are co-transporters a type of

Answer 1

carrier protein

Question 2

What do co-transporters do

Answer 2

bind 2 molecules at a time

Question 3

How do co-transporters work

Answer 3

they use to concentration gradient of one of the molecules to move the other against its own concentration gradient

Question 4

How are sodium and glucose co-transported

Answer 4

sodium ions move into the cell down their concentration gradient and glucose moves into the cell against concentration gradient

Question 5

What is the role of diffusion in absorption

Answer 5

proteins & carbohydrates are being digested continuously, so there is a greater conc of glucose & amino acids in the ilium than blood, so glucose moves down the conc gradient from the ilium to the blood which is moved away via circulation, maintaining the conc gradient.

Question 6

How can you increase the rate of movement across membranes (2 points)

Answer 6

1) increased surface area (villi/microcilli)

2) increased number of protein channels/carrier proteins

Question 7

What are villi

Answer 7

projections of the wall of the illium

Question 8

What are microvilli

Answer 8

projections of the cell-surface membrane of the epithelial cells that line the wall off the illium

Question 9

What method are amino acids and glucose absorbed from the small intestine into the blood

Answer 9

co-transported

Question 10

What molecule is glucose/amino acid co-transported into the blood with

Answer 10

sodium

Question 11

How is glucose/amino acid co-transported from small intestine (5 points)

Answer 11

1) sodium ions are actively transported out of the epithelial cells into the blood through the sodium-potassium pump (takes place in one type of protein-carrier molecule in the cell surface membrane of epithelial cells)
2) this maintains a higher concentration gradient of the sodium ions in the lumen of the intestine than the inside the epithelial cells
3) sodium ions diffuse down this conc gradient through a different type of protein carrier (sodium-glucose co-transporter protein), carrying either amino acid or glucose molecules into the cell with them as they diffuse
4) the conc of amino acids/glucose increases
5) so amino acids/glucose diffuses out of the cell into the blood down conc gradient through protein channel by facilitated diffusion

Question 12

What conc gradient does sodium & amino acid/glucose move along in co-transport

Answer 12

sodium = down
glucose = against

Question 13

What type of active transport is co-transport of sodium & amino acid/glucose (indirect/direct)

Answer 13

indirect

Question 14

Why is the co-transport of sodium & amino acid/glucose an indirect form of active transport

Answer 14

the energy comes from the sodium ion concentration gradient rather than ATP

Question 15

What is a treatment for diarrhoea

Answer 15

oral rehydration therapy

Question 16

What are the causes of diarrhoea (3 points)

Answer 16

1) damage to the epithelial cells lining the intestine
2) loss of microvilli due to toxins
3) excessive secretion of water due to toxins (e.g cholera toxin)

Question 17

What is the result of diarrhoea

Answer 17

dehydration

Question 18

Why is just drinking water ineffective for curing diarrhoea (2 points)

Answer 18

1) water is not being absorbed from the intestine

2) drinking water does not replace the electrolytes (ions) being lost from the intestinal cells

Question 19

What ‘drink’ (rehydration solution) can be made to help diarrhoea

Answer 19

one that contains a suitbale mixture of substances that will be absorbed by the small intestine

Question 20

How does the ‘drink’ (rehydration solution ) work if the small intestine is not absorbing water

Answer 20

it uses the alternative pathways of the other type of carrier protein in the plasma membrane of epithelial cells that absorbs sodium ions

Question 21

What does the rehydration solution need to contain (5 points)

Answer 21

1) water
2) sodium ions
3) glucose
4) potassium ions
5) other electrolytes

Question 22

Why is water required in the rehydration solution

Answer 22

to rehydrate tissues

Question 23

Why are sodium ions required in the rehydration solution

Answer 23

to replace the sodium ions lost from epithelium of intestine, and optimise use of althernative carrier proteins

Question 24

Why is glucose required in the rehydration solution

Answer 24

to stimulate the uptake of sodium ions from the intestine, and provide energy

Question 25

Why are potassium ions required in the rehydration solution

Answer 25

to replace lost potassium ions and stimulate appetite

Question 26

Why are other electrolytes required in the rehydration solution

Answer 26

to help prevent electrolyte imbalance, and a condition called metabolic acidosis

Question 27

What are examples of the other electrolytes required in the rehydration solution (2 points)

Answer 27

chloride ions, citrate ions

Question 28

Does oral rehydration therapy cure diarrhoea

Answer 28

no

Question 29

Were there any side effects and what were they caused by

Answer 29

yes especially in children, caused by excess sodium

Question 30

What was tested to overcome the side effects, and what was the issue created

Answer 30

solutions with lower sodium ion content and higher glucose, the extra glucose lowered the water potential in the lumen of the ilium so that it started drawing more water from the epithelial cells

Question 31

What was tested to overcome the issues created with the solution to the side effects

Answer 31

use starch in place of glucose

Question 32

Why was starch a choice for overcoming the issues created with the solution to the side effects

Answer 32

it is steadily broken down into glucose monomers by amylase and maltase

Question 33

Which type of starch was favoured for tested overcoming the issues created with the solution to the side effects and why (2 reasons)

Answer 33

rice starch

1) readily available in many parts of the world (espeically those diarrhoea is common)
2) provides other nutrients such as amino acids, that are nutritionally valuable & help uptake of sodium ions

Question 34

How many stages of testing drugs are there usually

Answer 34

4

Question 35

What are the 4 stages of testing drugs

Answer 35

1) small numer (20-80) of healthy people given a tiny amount of the drug which may be increased gradually over 6 months
2) drug given to slightly more people (100-300), stage takes up to 2 years
3) large-scale trail, many given placebo, takes up to may years
4) if passes, drug granted license