nutrition in man

Question 1

function of physical digestion

Answer 1

physically breaks food up into smaller pieces: increases SA to vol ratio of food so enzymes can hydrolyse food molecules faster

Question 2

salivary glands

Answer 2

secrete salivary amylase that hydrolyses amylose (starch) to maltose

Question 3

tongue

Answer 3

mixes food with saliva and shapes into boli

Question 4

oesophagus (structure)

Answer 4

muscular tube that connects the pharynx to the stomach

Question 5

peristalsis

Answer 5

rythmic wave-like contractions of the muscles to mix (stomach) and propel the contents of the ailmentary canal

Question 6

food pushed forward

Answer 6

circular muscles contract and longitudinal muscles relax so the wall of the gut constricts

Question 7

lumen widens for food to enter

Answer 7

longitudinal muscles contract and circular muscles relax so wall of the gut dilates

Question 8

stomach physical digestion

Answer 8

churning mixes food with gastric juice and breaks food up into even smaller pieces

Question 9

stomach chemical digestion

Answer 9

secretes gastric juice – contains HCl and inactive pepsinogen

Question 10

pepsinogen

Answer 10

inactive form of pepsin to prevent protease from digesting cells that secrete it

Question 11

pepsin

Answer 11

protease enzyme that catalyses the hydrolysis of proteins into polypeptides

Question 12

HCl functions (4)

Answer 12

1. activates inactive pepsinogen into active pepsin
2. creates optimal acidic environ for pepsin
3. kills bacteria ingested with food
4. denatures proteins, exposes peptide bonds for protein hydrolysis

Question 13

parts of the small intestine

Answer 13

duodenum, jejunum, ileum

Question 14

chemical secretions in duodenum

Answer 14

1. pancreatic juice (amylase, trypsin, lipase)
2. intestinal juice (maltase, peptidase, lipase)
3. bile produced by liver and stored and released by gall bladder

Question 15

trypsin (similar to pepsin)

Answer 15

proteins into polypeptides

Question 16

peptidase

Answer 16

polypeptides into amino acids

Question 17

maltase

Answer 17

maltose to glucose

Question 18

lipase

Answer 18

fats to glycerol and fatty acids

Question 19

chemical secretions are alkaline

what contributes & why?

Answer 19

bicarbonate ions
1. neutralise acidic chyme from stomach
2. optimal pH for maximum activity of enzymes

Question 20

small intestine physical digestion

Answer 20

fat emulsification by bile
– large droplets of fats are emulsified into small droplets of fats – increases SA to vol ratio

Question 21

absorption of glucose and amino acids in small intestine (villi)

Answer 21

enter epithelial cells via active transport, transported away by blood capillaries (via facilitated diffusion)

Question 22

absorption of glycerol and fatty acids in small intestine

Answer 22

glycerol and fatty acids enter epithelial cells via diffusion, transported away as fat globules via lacteals

Question 23

structural adaptations of small intestine

(4)

Answer 23

1. very long
2. many folds, presence of villi, individual epithelial cells have microvilli
3. epithelium of villi is one cell thick
4. rich network of capillaries + lacteals in villi

Question 24

long

Answer 24

large total surface area, and sufficient time for absorption of nutrients

Question 25

many folds, villi, microvilli

Answer 25

large SA to vol ratio, increases rate of absorption of digested substances

Question 26

epithelium one cell thick

Answer 26

short distance, increases rate of absorption of digested food subs

Question 27

rich network of capillaries + lacteals in villi

Answer 27

absorbed nutrients quickly transported away from SI –> maintains steep conc gradient between lumen of SI and its blood supply –> increases rate of absorption

Question 28

hepatic portal vein

Answer 28

blood capillaries in the villi combine to form HPV
– transports blood rich in nutrients from SI towards liver

Question 29

hepatic portal vein function

Answer 29

transports blood rich in glucose and amino acids from small intestine towards liver

Question 30

hepatic vein

Answer 30

deoxygenated blood that is rich in nutrients leaves liver via hepatic vein

Question 31

functions of liver

(6)

Answer 31

1. regulation of blood gluc conc
2. deamination of amino acids & formation of urea
3. fat digestion
4. detoxification of toxic/harmful subs
5. breakdown of hormones
6. break down of old RBCs

Question 32

deamination of excess amino acids & formation of urea

Answer 32

amino groups of amino acids are removed and converted into urea (excreted in urine by kidneys) during deamination
– rest of molecule converted into glucose in liver

Question 33

detoxification of harmful substances

Answer 33

convert them into more soluble, harmless subs to be removed from the body
eg. alcohol broken down by alcohol dehydrogenase into acetaldehyde, converted into compounds that can be broken down in respiration

Question 34

break down of old RBCs

Answer 34

broken done in spleen
haemoglobin transported then broken down in liver – iron is stored in liver + bile pigments formed from remaining molecule

Question 35

effect of alcohol

Answer 35

1. cirrhosis of liver – liver cells are destroyed and replaced with fibrous tissue – liver is less able to function – liver failure
2. ethanol – carcinogen (liver cancer)

Question 36

large intestine absorption

Answer 36

absorption of water and mineral ions

Question 37

absorption

Answer 37

small and soluble molecules move from lumen of SI into bloodstream of SI

Question 38

assimilation

Answer 38

absorbed food molecules are use to create new protoplasm or to release energy

Question 39

egestion

Answer 39

faeces removed from body (temporarily stored in rectum, egested at anus)