chapter 4 nutrition in humans

Question 1

define digestion

Answer 1

breaking down of large, complex, insoluble, food substances into small, soluble substances that can be absorbed into body cells

Question 2

how does the mouth aid in physical and chemical digestion?

Answer 2

physical:
- teeth chew and cut up food
- increases surface area to volume ratio

chemical:
salivary glands secrete saliva which contains salivary amylase that catalyses the breakdown of starch to maltose

Question 3

what is the function of the pharynx?

Answer 3

it connects the mouth to the oseophagus and the windpipe

Question 4

the oseophagus is made up of which muscles?

Answer 4

circular muscles (inner one) and longitudinal muscles (outer one) .
they are antagonistic muscles

Question 5

define peristalsis

Answer 5

the rhythmic, wave-like muscular contractions in the alimentary canal from the oseophagus to the rectum

Question 6

describe the process of peristalsis (4 steps)

Answer 6

1. The circular muscles behind the food bolus contract, while the longitudinal muscles behind the food relax.
2. This causes the lumen behind the food to constrict, and the food is pushed forward.
3. The longitudinal muscles in front of the food bolus contracts, while the circular muscles relaxes.
4. The lumen in front the food dilates (widens), and allows the food bolus to move forward.

Question 7

the stomach secretes gastric juice, which contains which enzyme and digests what?

Answer 7

the gastric juice contains pepsin, which is a protease that catalyses the breakdown of proteins into polypeptides.

Question 8

why does the gastric juice secreted by the stomach contain hydrochloride acid? (3 reasons)

Answer 8

the hydrochloride acid
1. denatures salivary amylase (& stops its action)
2. provides optimum pH for pepsin (pH 2)
3. kills harmful microorganisms

Question 9

what is the function of physical digestion?

Answer 9

to increase the surface area to volume ratio of the food, to increase efficiency of chemical digestion

Question 10

the pancreas secretes…

Answer 10

1. insulin & glucagon
2. pancreatic juice

Question 11

the pancreatic juice contains which enzymes?

Answer 11

1. pancreatic amylase: catalyses the breakdown of starch to maltose
2. pancreatic protease (trypsin): catalyses te breakdown of proteins to polypeptides
3. pancreatic lipase: catalyses the breakdown of fats to fatty acids & glycerol

Question 12

what is the function of bile?

Answer 12

bile emulsifies fat into tiny fat droplets (physical digestion) to increase surface area to volume ratio of the fat droplets, to increase efficiency of chemical digestion of fats

Question 13

bile is produced and stored at which organs?

Answer 13

bile is produced at the liver, and stored at the gall bladder before flowing into the duodenum through the bile duct.

Question 14

what is the function of the gall bladder?

Answer 14

the gall bladder receives bile from the liver & stores bile temporarily.

Question 15

how does the pancreatic juice work?

Answer 15

the pancreatic juice goes into the duodenum via pancreatic duct & breaks down all the main nutrient groups in the duodenum.

Question 16

name the 3 components of the small intestine & where digestion mainly takes place at

Answer 16

1. duodenum (digestion mainly takes place here)
2. jejunum
3. ileum

Question 17

the intestinal gland on the walls of the small intestine secretes intestinal juice that contains which enzymes?

Answer 17

1. maltase: catalyses the breakdown of maltose to glucose
2. intestinal protease (erepsin): catalyses the breakdown of polypeptides into amino acids
3. intestinal lipase: catalyses the breakdown of fats into fatty acids & glycerol

Question 18

why are pancreatic juice, bile, and intestinal juice alkaline?

Answer 18

to neutralise the acid in the food & provide an alkaline environment for digestive enzymes to work well

Question 19

define absorption

Answer 19

the taking in of small, soluble nutrients in the bloodstream

Question 20

what are the adaptations of the small intestine that allow for greater efficiency of absorption? (6 adaptations)

Answer 20

1. long & coiled tube
2. many folds & furrows
3. inner walls are lined with villi (finger-like protrusions)
4. epithelial cells have microvilli (tiny protrusions)
5. walls of each villus are thin & only one-cell thick
6. villus has a network of blood capillaries

Question 21

what is the function for the small intestine having a long & coiled tube?

Answer 21

provides sufficient time for complete digestion & absorption of food as it moves through the intestine, so more nutrients can be absorbed

Question 22

which adaptations are does the small intestine have to increase the surface area to volume ratio? (3 adaptations)

Answer 22

1. many folds & furrows
2. the inner walls are lined with villi
3. epithelial cells have microvilli