15- digestive system 3

Question 1

what is a monosaccharide?

Answer 1

a simple sugar

Question 2

how are glucose and galactose absorbed into cells?

Answer 2

glucose and galactose are absorbed into epithelial cells through active transport via sodium-glucose symporter

they move out of epithelial cells and into the bloodstream via facilitated diffusion on GLUT2 sugar transporter

Question 3

how is fructose absorbed into cells?

Answer 3

Absorbed into epithelial cells through facilitated diffusion​ and moved out of epithelial cells and into the bloodstream via facilitated diffusion on GLUT2 sugar transporter

Question 4

How are amino acids and dipeptides absorbed into the epithelial cell?

Answer 4

via active transport with the assistance of Na+ or H+ ions (symporters)​

Question 5

How do amino acids and dipeptides leave an epithelial cell into capillaries?

Answer 5

by facilitated diffusion

Question 6

How are all dietary lipids are absorbed?

Answer 6

by simple diffusion.

The process differs slightly depending on the length of the fatty acid chain

Question 7

what are micelles?

Answer 7

free fatty acids and monoglycerides that associate with bile salts (form micelles)
they ‘ferry’ them into the intestinal mucosa

Question 8

what are lipoproteins?

Answer 8

Lipoprotein is the name given to the combination of lipid and protein transporters that function to transport lipids in the blood

(Plasma lipids such as fatty acids, triglycerides, cholesterol are insoluble in water and body fluids)

Question 9

explain bile reabsorption

Answer 9

Once lipids enter epithelial cells they leave bile salts behind in the lumen. These bile salts are then reabsorbed into the blood and reformed into bile in the liver​

Question 10

what happens to fatty acids and monoglycerides once inside absorptive cells?

Answer 10

they recombine into triglycerides

Question 11

Name 9 electrolytes

Answer 11

Sodium
chloride, iodide and nitrate
Iron, magnesium, potassium and phosphate ions
Calcium

Question 12

4 ways electrolytes are absorbed?

Answer 12

Sodium: Absorbed by diffusion, secondary active transport and Na+/K+ pumps (active transport)​
Chloride, iodide and nitrate: Absorbed by active or passive transport​
Iron, magnesium, potassium and phosphate ions: Absorbed by active transport​
Calcium: Absorbed by active transport, which is stimulated by calcitriol

Question 13

how are fat-soluble vitamins absorbed?

Answer 13

Fat-soluble vitamins (A, D, E, and K) travel across the border in micelles and are absorbed by simple diffusion​.

Question 14

how are water-soluble vitamins absorbed?

Answer 14

Water-soluble vitamins (B and C) are absorbed by simple diffusion​.

Question 15

How is B12 absorbed?

Answer 15

B12 combines with intrinsic factor (IF) before it is transported into the cells​ via receptor-mediated endocytosis​.

Question 16

name the 4 sections of the large intestine

Answer 16

• caecum
• colon (ascending, transverse, descending, and sigmoid portions)
• rectum
• anal canal ( contains 2 sphincters; one voluntary and one involuntary)

Question 17

what is the only secretion of the large intestine?

Answer 17

mucous

Question 18

effects of bacterial fermentation in the large intestine?

Answer 18

Undigested carbohydrates: Turn into hydrogen, carbon dioxide and methane gas​, causing flatulence​.
Undigested proteins: Turn into indole, skatole, hydrogen sulfide, and fatty acids​, causing fecal odour and Urinary excretion​.
Excess bilirubin: Turns into simpler pigments (such as stercobilin​), and may alter the fecal colour​.

It Is also important to note that B Vitamins and Vitamin K are all produced by bacteria in the colon​.

Question 19

how much water absorption in occurs in the large intestine?

Answer 19

90%

Question 20

what do faeces consist of?

Answer 20

Water
A large number of bacteria and products of bacterial decomposition
Inorganic salts
Sloughed-off epithelial cells (from the mucosa of the gastrointestinal tract)
Unabsorbed digested materials and indigestible parts of food

Question 21

2 types of dietary fibre?

Answer 21

soluble and insoluble

Question 22

functions and dietary sources of soluble fibre?

Answer 22

Soluble fibre:
These fibres are soluble in water​. In addition to helping the passage of food through the GIT, they also assist with lowering cholesterol (by removing it from the GIT and preventing bile salt reabsorption, therefore encouraging the liver to instead use cholesterol to make more).

Dietary sources include beans, oats, barley, broccoli, prunes, apples, and citrus fruits.​

Question 23

functions and dietary sources of insoluble fibre?

Answer 23

Insoluble fibre: These fibres are insoluble in water​ and aren’t able to be fully digested. Insoluble fibre has been shown to help protect the bowel from colon cancer.

Food sources are the woody parts of plants (wheat bran, veggie skins)​, which have been shown to help protect against colon cancer. ​

Question 24

name the 3 phases of digestion

Answer 24

1. Cephalic phase​
2. Gastric phase​
3. Intestinal phase​