6.2 Digestion In Humans

Question 1

What is Digestion

Answer 1

Digestion is the process whereby large food molecules are broken down into smaller, soluble
molecules that can be absorbed into the body cells.

Question 2

Digestive processes in the mouth,
Food in the mouth stimulates the salivary glands to secrete __?

Answer 2

• Food in the mouth stimulates the salivary glands to secrete saliva

Question 3

Digestive processes in the mouth, Saliva is mixed with food. ____ in saliva helps to soften the food.
- Saliva contains an enzyme called ______ which digests starch

Answer 3

Saliva is mixed with food. Mucus in saliva helps to soften the food.
- Saliva contains an enzyme called salivary amylase which digests starch to maltose.

Question 4

Digestive processes in the mouth, pH of the saliva, effect on enzyme?

Answer 4

The pH of the saliva is neutral. Salivary amylase is most active at this pH.

Question 5

Digestive processes in the mouth, What does Chewing do?

Answer 5

Chewing breaks the food up into smaller pieces. This increases the surface area to volume
ratio for salivary amylase to work on.

Question 6

Digestive processes in the mouth, The tongue rolls the food into small, slippery, round masses or ___.

Answer 6

boli (bollus)

Question 7

Digestive processes in the mouth, boli are swallowed and passed down into the ___ via the ____
- _____ in the walls of the oesophagus pushes each bolus of food down into the _____ .

Answer 7

boli are swallowed and passed down into the oesophagus via the pharynx.
- Peristalsis in the walls of the oesophagus pushes each bolus of food down into the stomach.

Question 8

Digestive processes in the stomach, The presence of food in the stomach stimulates what?

Answer 8

The presence of food in the stomach stimulates the gastric glands to secrete gastric juices
into the stomach cavity

Question 9

Digestive processes in the stomach, Peristalsis in the stomach purpose?

Answer 9

Peristalsis in the stomach wall churns and breaks up the food. Peristalsis also mixes the food
well with gastric juices

Question 10

Digestive processes in the stomach, Gastric juice is a dilute solution of ?

Answer 10

Gastric juice is a dilute solution of hydrochloric acid and pepsin

Question 11

Digestive processes in the stomach, Purpose of the dilute hydrochloric acid:

Answer 11

• stops the action of salivary amylase by denaturing it.
• changes the inactive form of the enzyme pepsinogen, in the gastric juice to the
  active pepsin.
• provides a slightly acidic medium suitable for the actions of pepsin
• kills certain potentially harmful microorganisms in food.

Question 12

Protease (pepsin) digests proteins to __?

Answer 12

polypeptides

Question 13

Food normally remains in the stomach for how long?

Answer 13

three to four hours.

Question 14

what is chyme

Answer 14

liquefied partly digested
food

Question 15

Chyme passes in small amounts into the ___ when the ___ relaxes and
opens.

Answer 15

Chyme passes in small amounts into the duodenum when the pyloric sphincter relaxes and
opens.

Question 16

Digestive processes in the small intestine, When Chyme enters the small intestine, what does it stimulate ?

Answer 16

• the pancreas to secrete pancreatic juice. Pancreatic juice contains the enzymes
  pancreatic amylase, pancreatic protease (trypsin), and pancreatic lipase. The
  pancreatic juice passes through the pancreatic duct into the duodenum.
• the gall bladder to release bile. Bile does not contain enzymes so it cannot digest
  good, but bilt salts sped up the digestion of fats. Bile passes through the bile duct
  into the duodenum.
• the epithelial cells in the small intestine to produce the enzymes maltase, peptidases
  and lipase.

Question 17

Digestive processes in the small intestine,
pancreatic juice, bile and intestinal juice are all alkaline, what do they do when they come into contact w chyme

Answer 17

• neutralise the acidic chyme
• provide a suitable alkaline medium for the action of the pancreatic and intestinal
  enzymes.

Question 18

what enzyme digests Carbohydrates

Answer 18

Starch is digested by amylases.

Question 19

carbs to simple sugar, enzymes present and process?

Answer 19

-Starch is digested by pancreatic amylase to form maltose.
- Maltose is digested by maltase to form glucose.
- Lactose is digested by lactase to form glucose and galactose.
- Sucrose is digested by sucrase to form glucose and fructose

Question 20

what are proteins digested by

Answer 20

Proteins are digested by proteases

Question 20

protiens to amino acids process?

Answer 20

-Some protein digestion begins in the stomach, where pepsin digests proteins to
polypeptides.
- The undigested proteins which enter the small intestine are digested by trypsin to
polypeptides.
- The polypeptides produced are further digested to amino acids by peptidases.
- The end-products of protein digestion are amino acids.

Question 21

Fats are digested by?

Answer 21

Fats are digested by lipases.