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BIOLOGY - CELL STRUCTURE AND DIVISION > CO-TRANSPORT > Flashcards

Flashcards in CO-TRANSPORT Deck (35)
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1

What are co-transporters a type of

carrier protein

2

What do co-transporters do

bind 2 molecules at a time

3

How do co-transporters work

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

4

How are sodium and glucose co-transported

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

5

What is the role of diffusion in absorption

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.

6

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

1) increased surface area (villi/microcilli)
2) increased number of protein channels/carrier proteins

7

What are villi

projections of the wall of the illium

8

What are microvilli

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

9

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

co-transported

10

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

sodium

11

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

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

12

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

sodium = down
glucose = against

13

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

indirect

14

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

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

15

What is a treatment for diarrhoea

oral rehydration therapy

16

What are the causes of diarrhoea (3 points)

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)

17

What is the result of diarrhoea

dehydration

18

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

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

19

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

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

20

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

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

21

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

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

22

Why is water required in the rehydration solution

to rehydrate tissues

23

Why are sodium ions required in the rehydration solution

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

24

Why is glucose required in the rehydration solution

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

25

Why are potassium ions required in the rehydration solution

to replace lost potassium ions and stimulate appetite

26

Why are other electrolytes required in the rehydration solution

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

27

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

chloride ions, citrate ions

28

Does oral rehydration therapy cure diarrhoea

no

29

Were there any side effects and what were they caused by

yes especially in children, caused by excess sodium

30

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

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