4.5-CO-TRANSPORT AND ABSORPTION OF GLUCOSE IN THE ILEUM Flashcards Preview

B4- TRANSPORT ACROSS CELL MEMBRANES > 4.5-CO-TRANSPORT AND ABSORPTION OF GLUCOSE IN THE ILEUM > Flashcards

Flashcards in 4.5-CO-TRANSPORT AND ABSORPTION OF GLUCOSE IN THE ILEUM Deck (30)
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1

What does the epithelial cells lining the ileum possess?

microvilli

2

What are microvilli?

finger-like projections of cell-surface membrane

3

Approximately how long are microvilli?

0.6μm in length

4

What are microvilli collectively termed as?

'brush border'

5

Why are microvilli collectively termed as 'brush border'?

they look like bristles on a brush

6

What do the microvilli provide?

more surface area for insertion of carrier proteins through which diffusion, facilitated diffusion + active transport can take place

7

What is another mechanism to increase transport across membranes?

increase number of protein channels + carrier proteins in any given area of membrane

8

What is diffusion?

net movement of molecules/ions from region where they're highly concentrated to region where their concentration lower

9

As carbohydrates and proteins are being ingested continuously what does this cause?

normally a greater concentration of glucose and amino acids within the ileum than in the blood

10

As there is normally a greater concentration of glucose and amino acids within the ileum than in the blood what does this mean?

a concentration gradient down which glucose moves by facilitated diffusion from inside ileum into blood

11

How is glucose absorbed into the blood continuously being removed?

blood is continuously being circulated by the heart

12

What is the glucose being absorbed into and why?

continuously being removed by cells as they use it up during respiration

13

As the blood is continuously being circulated, what does this maintain?

concentration gradient between inside of ileum and blood

14

As the concentration gradient between the inside of the ileum and the blood is maintained what does this mean?

rate of movement by facilitated diffusion across epithelial cell-surface membrane increased

15

At best what does diffusion only result in?

concentrations either side of intestinal epithelium becoming equal

16

As diffusion only results in the concentrations becoming equal, what does this mean?

not all the available glucose + amino acids can be absorbed in this way + some may pass out of body

17

However, why does the glucose + amino acids not pass out of the body?

glucose + amino acids also being absorbed by active transport

18

As glucose + amino acids are also being absorbed by active transport, what does this mean?

all the glucose + amino acids should be absorbed into blood

19

What is the actual mechanism of how glucose + amino acids being absorbed from the small intestine an example of?

co-transport

20

Why is the term co-transport used?

as either glucose/amino acids drawn into cells along with sodium ions that have been actively transported out by sodium-potassium pump

21

How co-transport happens #1

sodium ions actively transported out of epithelial cells by sodium-potassium pump into blood
takes place in one type of protein- carrier molecule found in cell-surface membrane of epithelial cells

22

How co-transport happens #2

what is maintained as sodium ions actively transported out of epithelial cells?

maintains much higher concentration of sodium ions in lumen of intestine than inside than inside epithelial cells

23

How co-transport happens #3

sodium ions diffuse into epithelial cells down concentration gradient through different type of protein carrier (co-transport protein) in cell-surface membrane

24

As the sodium ions diffuse in through the second carrier protein, what do they carry with them?

carry an amino acid or glucose molecule with them

25

How co-transport happens #4

glucose/amino acid pass into blood plasma by facilitated diffusion using another type of carrier

26

Does sodium ions move down or against concentration gradient when moving into cell?

sodium ions move down concentration gradient

27

Does glucose molecules move down or against concentration gradient when moving into cell

glucose molecules move against their concentration gradient

28

What powers the movement of glucose + amino acids into the cells?

sodium ion concentration gradient rather than ATP directly

29

What type of active transport is it when the glucose/amino acid molecules move into the cell?

indirect

30

Why is it indirect active transport when the glucose/amino acid molecules move into the cell?

sodium ion concentration gradient rather than ATP that powers movement of the molecules