bio chapter 5

Question 1

physical digestion of the mouth

Answer 1

breaks large pieces of food into smaller pieces
-> increased surface area to volume ratio
-> increased efficiency of enzymes

Question 2

functions of the tongue

Answer 2

1. mixes food with saliva to soften it
2. moves food to back of mouth during swallowing by rolling food into bolus for ease of swallowing
   bolus = small, slippery, round masses [plural = boli]
   -> peristalsis pushes each bolus down oesophagus into stomach

Question 3

function of salivary glands

Answer 3

food in mouth stimulates salivary glands to:
-> secrete saliva containing salivary amylase

Question 4

function of salivary amylase

Answer 4

salivary amylase [pH7 is the optimum pH for enzyme to be most active]
-> catalyzes the break down of starch into maltose

Question 5

definition of peristalsis

Answer 5

= rhythmic, wave-like muscular contractions in wall of alimentary canal

Question 6

functions of peristalsis

Answer 6

1. enables food to be mixed with digestive juices
2. pushes/propels food along the gut

Question 7

relationship between muscles in peristalsis

Answer 7

antagonistic muscles -
longitudinal muscles + circular muscles

Question 8

what happens when the gut dilates?

Answer 8

longitudinal muscles contract
circular muscles relax
-> gut becomes narrower and shorter
-> widens lumen for food to enter

Question 9

what happens when wall of gut is constricted?

Answer 9

longitudinal muscles relax
-> shortens and widens lumen
circular muscles contract
-> constricts lumen

-> gut becomes narrower and longer
-> food is squeezed/pushed forward

Question 10

what do gastric glands in the inner surface of the stomach do?

Answer 10

presence of food in stomach stimulates gastric glands to secrete gastric juice into stomach cavity

Question 11

what does gastric juice secreted by gastric glands contain?

Answer 11

dilute hydrochloric acid (pH2), mucus, enzyme protease pepsin

Question 12

what is the purpose of dilute hydrochloric acid (pH2) in gastric juice?

Answer 12

1. stops action of salivary amylase by denaturing it
2. provides a low pH acidic environment for enzyme protease to digest proteins optimally
3. kills certain potentially harmful microogranisms in food

Question 13

what does the mucus layer on the inner surface of the stomach do?

Answer 13

1. moistens food to allow easy movement within stomach
2. protects stomach wall against being digested by the enzymes it produces

Question 14

what happens to partially digested food in the stomach?

Answer 14

partially digested food:
- remains in stomach for around 3 to 4 hrs
- is liquified into chyme that passes in small amounts into duodenum when pyloric sphincter relaxes and opens

Question 15

what is the function of peristalsis in the stomach?

Answer 15

1. churns and breaks up food
2. mixes food well with gastric juice

Question 16

gall bladder

Answer 16

greenish-yellow bag attached to liver
where bile is stored temporarily before use

Question 17

bile duct + duodenum

Answer 17

when gall bladder contracts, bile flows into duodenum via bile duct

Question 18

structure of small intestine

Answer 18

U-shaped duodenum + much-coiled ileum
*carries out most of digestive process
-> lining of walls contains glands that secrete digestive enzymes
-> water and nutrients absorbed

Question 19

what happens when chyme enters the duodenum?

Answer 19

chyme simulates:
1. pancreas to secrete pancreatic juice that passes through pancreatic duct into duodenum
2. gall bladder to release bile that passes through bile duct into duodenum
3. epithelial cells in small intestine to produce enzymes maltase, protease, lipase

food now comes in contact with pancreatic juice, bile and intestinal juice that are
all alkaline
-> neutralizes acidic chyme
-> provides suitable alkaline medium (pH8) for action of pancreatic juice and intestinal enzymes

Question 20

structure of pancreas

Answer 20

connected to duodenum by pancreatic duct

Question 21

functions of pancreas

Answer 21

1. produces pancreatic juice which contains digestive enzymes pancreatic amylase, lipase, protease
2. secretes hormones insulin and glucagon
   -> controls blood sugar level in body

Question 22

function of colon

Answer 22

absorbs about 90% of remaining water and mineral salts from undigested food material

Question 23

process of egestion in large intestine

Answer 23

1. faeces stored temporarily in rectum
2. when rectum contracts, faeces are expelled through anus and undigested matter is removed in the process called egestion

Question 24

absorption

Answer 24

= process whereby digested food substances are absorbed into body cells

Question 25

how are products of digestion absorbed by small intestine?

Answer 25

products of digestion: - simple sugars - amino acids - fatty acids - glycerol nutrients are absorbed throughout small intestine (especially along ileum) and diffuse from cells of small intestine into bloodstream

Question 26

absorption of water and mineral salts

Answer 26

absorbed by small intestine (mostly) that absorbs most of water entering alimentary canal and colon

Question 27

how is the small intestine adapted for absorption?

Answer 27

inner surface of ileum is folded extensively and has numerous finger-like projections called villi [singular: villus] -> increases surface area to volume ratio for absorption

Question 28

absorption of glucose and amino acids in villi

Answer 28

glucose and amino acids enter via diffusion and active transport into blood capillaries of villi -> blood capillaries allow blood to transport absorbed glucose and amino acids to maintain a concentration gradient -> active transport happens when there is a lower concentration of digested food substances in lumen of small intestine than in blood capillaries

Question 29

absorption of fatty acids and glycerol in villi

Answer 29

fatty acids and glycerol diffuse into epithelium and recombine to form fat globules which enter lacteal

Question 30

features of epithelial cells

Answer 30

1. contain many microvilli that further increase surface area to volume ratio of small intestine 2. contain many mitochondria to provide energy for active transport of nutrients into villi

Question 31

epithelium in villus

Answer 31

only one cell thick -> short diffusion distance for nutrients to pass through

Question 32

function of lacteal in villus

Answer 32

transports absorbed fat away and maintains steep concentration gradient

Question 33

transport of bile salts for fat digestion

Answer 33

produced by liver stored by gall bladder released into duodenum

Question 34

emulsification of fats by bile salts

Answer 34

= breaking up of fats into tiny fat droplets *not chemical digestion, only physical digestion of fats as no enzymes involved -> increases surface area to volume ratio of fats -> speeds up digestion of fats/lipids by lipase

Question 35

function of bile salts in emulsification of fats

Answer 35

1. lowers surface tension of fats -> reduces attractive forces between fat molecules 2. causes fats to break into tiny fat droplets suspended in water 3. forms an emulsion

Question 36

digestion in mouth

Answer 36

saliva from salivary glands contains salivary amylase that catalyzes break down of starch into maltose

Question 37

digestion in stomach

Answer 37

protease in gastric juice secreted by gastric glands digests proteins into polypeptides

Question 38

digestion by bile in small intestine

Answer 38

bile salts secreted by liver emulsifies fats

Question 39

digestion by pancreatic juice in small intestine

Answer 39

pancreatic juice secreted by pancreas contains: 1. protease digests proteins into polypeptides 2. pancreatic amylase digests starch into maltose 3. lipase digests fats into fatty acids and glycerol

Question 40

digestion by intestinal enzymes in small intestine

Answer 40

intestinal enzymes secreted by epithelial cells contains: 1. protease digests polypeptides into amino acids 2. maltase digests maltose into glucose 3. lipase digests fats into fatty acids and glycerol

Question 41

assimilation

Answer 41

= process whereby some of the absorbed nutrients are converted into new cytoplasm or used to provide energy

Question 42

function of hepatic portal vein in liver

Answer 42

transports nutrients mainly glucose and amino acids from small intestine to liver

Question 43

how hepatic portal vein is formed

Answer 43

1. after absorption, blood in villi is rich in nutrients 2. blood capillaries unite to form larger blood vessels 3. in turn unite to form hepatic portal vein

Question 44

function of hepatic artery in liver

Answer 44

brings oxygenated blood from heart

Question 45

function of hepatic vein in liver

Answer 45

remaining glucose and amino acids leave liver via hepatic vein to by distributed round the body by deoxygenated blood leaving liver

Question 46

function of liver - production of bile

Answer 46

aids in fat digestion by secreting bile = an alkaline greenish-yellow liquid containing bile salts bile stored temporarily in gall bladder before use

Question 47

function of liver - deamination of excess amino acids

Answer 47

= process by which amino groups are removed ad converted into urea -> removed from body in urine -> remains of deaminated amino acids converted into glucose in liver -> any excess glucose found in this way is converted into glycogen carboxyl group is converted into glucose that is either: 1. used immediately or 2. converted to glycogen and stored

Question 48

assimilation of amino acids in liver

Answer 48

amino acids - that enter cells are converted into new cytoplasm used for growth and repair of worn-out parts of body - also used to form enzymes and hormones

Question 49

function of liver - regulation of blood glucose concentration

Answer 49

most absorbed sugars/excess glucose converted to glycogen and stored liver plays key role in carbohydrate metabolism by keeping amount of glucose in blood constant pancreas secretes hormones: insulin 1. when blood glucose concentration rises above normal (after heavy meal) 2. insulin stimulates liver cells to convert excess glucose into glycogen 3. when body needs energy, liver converts stored glycogen back to glucose 4. glucose is then transported by blood to cells 5. blood glucose concentration decreases back to normal -> all cells use glucose as a source of energy -> glucose is assimilated and then broken down during tissue respiration to release energy for vital activities of cells glucagon 1. when blood glucose concentration falls below normal (during fasting) 2. glucagon simulates liver to convert glycogen into glucose to be released into bloodstream 3. blood glucose concentration increases back to normal

Question 50

function of liver - breakdown of hormones

Answer 50

hormones are broken down in liver after they have served their purpose

Question 51

function of liver - detoxification

Answer 51

= process of converting harmful substances into harmless ones these harmful substances may be absorbed into blood from gut e.g. alchohol -> can cause damage to digestive system -> can slow down brain functions liver cells contain an enzyme which breaks down these harmful substances into compounds that can be used in respiration, providing energy for cell activites

Question 52

impacts of alchohol on - digestive system

Answer 52

1. stimulates acid secretion in stomach 2. excess stomach acid increases risk of gastric ulcers 3. too much alcohol may lead to cirrhosis of liver = disease in which liver cells are destroyed and replaced with fibrous tissue, making liver less able to function 4. alcohol cirrhosis may lead to haemorrhage in liver, liver failure and subsequent death

Question 53

impacts of alchohol on - nervous system

Answer 53

depressant: - alcohol is a depressant which slows down some brain functions reduced self-control: - becomes carefree and may do things they may regret later on effect on reaction time: - slurred speech - blurred vision - poor muscular coordination (clumsy, unable to walk steadily) effect on judgement: - judgement deteriorates - tends to underestimate speed -> may drive faster with less caution and slower reaction time -> drink driving -> traffic accidents

Question 54

impacts of alchohol on - brain

Answer 54

-> heavy drinking of alcohol over a long period can have long-term effects on the brain 'wet brain': = type of dementia caused by brain damage - alcohol interferes with the absorption of vitamin B1 (thiamine) in the small intestine vitamin B1 = part of an enzyme needed to break down sugar to release energy for brain activities, e.g. in the conduction of nerve impulses shrinkage of brain volume: - brain becomes smaller than normal, especially the region associated with memory and reasoning alcohol during pregnancy: - heavy consumption of alcohol during pregnancy may interfere with the development of the fetus' brain -> may lead to lifelong physical, mental and behavioral problems

Question 55

impacts of alchohol on - social implications

Answer 55

can easily get addicted to alcohol when drunk frequently -> body becomes dependent on alcohol -> becomes an alcoholic may: - neglect work and families - exhibit violent behavior, especially towards family members - tend to commit crimes under the influence of alcohol