digestion and absorption

Question 1

What are carbohydrates broken down into?

Answer 1

Monosaccharides

and disaccharides

Question 2

What are carbohydrates broken down by?

Answer 2

Amylase

Disaccharidases

Question 3

What are lipids broken down into?

Answer 3

Fatty acids

monoglyceride (glycerol with one fatty acid)

Question 4

What are lipids broken down by?

Answer 4

Lipases

and bile salts

Question 5

What are proteins broken down into?

Answer 5

amino acids

Question 6

What are proteis broken down by?

Answer 6

• endopeptidases- e.gpepsin, trypsin- break bond in middle of polypeptide chain
• exopeptidases (membrane bound exopeptidases) break down terminal peptide bonds to break off single amino acids ( leave dipeptides)
• dipeptidases (membrane bound dipeptidases) breaks down into single amino acids

Question 7

name the main areas of the digestive tract

Answer 7

Mouth
oesophagus
stomach
Small intestine (duodenum, illium)
Large intestine
Rectum

Question 8

what is mechanical digestion

Answer 8

mechanical digestion is the physical breakdown of food by the teeth and action of the tongue

Question 9

describe the process of carbohydrate digestion in humans

Answer 9

beginning of carbohydrate digestion in the mouth: Salivary amylase
breaks starch into maltose (disaccharide)
salivary amylase denatured by stomach pH
food passes to the small intestine
mixes with pancreatic juices which contain pancreatic amylase
membrane bound disaccharidases (e.g maltase) break down the maltose into two molecules of alpha glucose
(sucrase breaks sucrose into glucose and fructose
lactase breaks down lactose to glucose and galactose)

Question 10

describe the process of protein digestion in humans

Answer 10

Protein digestion begins in the stomach
Pepsinogen is secreted cells in the stomach called chief cells. pepsinogen is activated by H+ ions to become pepsin
pepsin is an endopeptidase

Question 11

describe the process of lipid digestion in humans

Answer 11

lipids are emulsified (split into smaller droplets) into micelles (to increase SA) by bile salts

lipase from the pancreatic juices break down lipids into

Question 12

what are the contents of saliva

Answer 12

salivary amylase
salts
pH ~8

Question 13

what are the contents of pancreatic juices

Answer 13

pancreatic amylase

lipase

Question 14

what are the contents of bile

Answer 14

bile salts

Question 15

where is bile made and stored

Answer 15

made: liver
stored: gall bladder

Question 16

how are monosaccharides absorbed into epithelium of gut from lumen

Answer 16

Co transport with Na+ ions
Na+ ions move from high conc to low conc and bring a molecule of glucose with it against its concentration gradient (low to high conc). Na+/K+ pump maintains the concentration gradient of Na+ inside the epithelium.

(facilitated difusion)

Question 17

how are amino acids absorbed into epithelium of gut from lumen

Answer 17

Co transport with Na+ ions
Na+ ions move from high conc to low conc and bring an amino acid with it against its concentration gradient (low to high conc).Na+/K+ pump maintains the concentration gradient of Na+ inside the epithelium.

(facilitated diffusion)

Question 18

how are amino acids absorbed into blood from the epithelium of gut

Answer 18

facilitated diffusion

Question 19

how are monosaccharides absorbed into blood from the epithelium of gut

Answer 19

facilitated diffusion

Question 20

what are micelles

Answer 20

broken down fatty acids and monoglycerides associated with bile salts

Question 21

how are lipids absorbed into the lacteal from the lumen of the gut

Answer 21

micelles break down and release monoglycerides and fatty acids which diffuse into epithelium
monoglycerides and fatty acids turned back into triglyceride at endoplasmic reticulum and golgi body
triglycerides associate with cholesterol and lipoproteins to form chylomicrons.
exit epithelial cell by exocytosis and enter lacteal.