digestion !

Question 1

ingestion !

Answer 1

intake of food into our body via the mouth

Question 2

digestion !

Answer 2

process whereby large, complex, indiffusible, insoluble food molecules are broken down into small, simple, diffusible, soluble molecules that can be absorbed into body cells

Question 3

physical digestion

Answer 3

physical process of breaking up food into smaller molecules through chewing & peristalsis

Question 4

chemical digestion

Answer 4

process of hydrolysing (breaking down) food into simpler, soluble, diffusible molecules via enzyme action

Question 5

importance of digestion

Answer 5

food must be digested to break down the large, complex, insoluble, indiffusible into smaller, simple, soluble and diffusible molecules

• can pass through the walls of the small intestine & into the blood vessels
• blood plasma can then transport the simple food molecules (glucose, amino acids) to other parts of the body for use of various processes

Question 6

digestive tract

Answer 6

mouth & buccal cavity 
pharynx 
oesphagus 
stomach 
small intestine 
large intestine 
anus

Question 7

mouth !

Answer 7

site of ingestion

physical : teeth
- chewing action breaks up solid food into smaller pieces -> increases surface area to volume ratio for salivary amylase to act on it more efficiently

chemical : salivary glands

• secrete saliva containing salivary amylase into food
• moistens food + breakdown starch -> maltose

Question 8

tongue

Answer 8

1. rolls food particles into bolus
   - easier for food particles to be swallowed via the pharynx into the oesophagus
2. mix food with saliva

Question 9

pharynx !

Answer 9

connects buccal cavity to oesophagus & larynx

common passageway for air and food

Question 10

epiglottis

Answer 10

swallowing : food prevented from entering trachea

• larynx : moves upwards
• epiglottis covers glottis

breathing : air passes into trachea

• larynx : moves downwards
• glottis is open

if food gets into trachea : person will cough to force the food out

Question 11

oesophagus !

Answer 11

transports food from pharynx to stomach

- gravity + peristalsis

Question 12

peristalsis in oesophagus pt 1 !

Answer 12

enables food to be mixed with digestive juices
caused by the actions of antagonistic muscles
- circular & longitudinal

Question 13

peristalsis in oesophagus p2 !

Answer 13

circular contract - longitudinal relax
- wall of gut : contracts -> becomes narrower & longer -> food is pushed forward

circular relaxes - longitudinal contract
- wall of gut : dialtes -> becomes wider & shorter -> widens lumen for food to enter

Question 14

stomach !

Answer 14

secretes gastric juice : contains hydrochloric acid, pepsin, renin

distensible muscular bag with thick & well developed muscular wall
- can expand

stomach wall : has numerous pits
- secretes gastric juice into stomach cavity

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

Question 15

pyloric sphincter

Answer 15

muscular valve found at the end of stomach

contracts : entrance to small intestine (duodenum) closes

relaxes : entrance to small intestine (duodenum) opens

Question 16

peristalsis in stomach !

Answer 16

churns + breaks up food substances from big particles to small particles

• increases surface area to volume ratio for protease to act on
• mixes food substances well with gastric juice

Question 17

hydrochloric acid in gastric juice / stomach’s acidic conditions !

Answer 17

stops action of salivary amylase by denaturaing it
changes inactive form of pepsinogen to active form pepsin
provides an acidic pH condition for gastric enzymes
kills potentially harmful microorganisms in food

Question 18

renin

Answer 18

curdles milk proteins : converts soluble caseinogen in milk -> insoluble caesin
- requires Ca2+ : allows insoluble caesin to remain in the stomach long enough for digestion by pepsin

Question 19

chyme

Answer 19

partly digested food that has been liquified

enters duodenum in small amounts when pyloric sphincter relaxes & opens

Question 20

small intestine parts !

Answer 20

duodenum : (from stomach ) + digestion
jejunum : more digestion + assimilation
ileum : absorption + digestion complete

Question 21

duodenum !

Answer 21

pancreatic juice

• inactive trypsinogen -> active trypsin by enterokinase
• pancreatic lipase
• pancreatic amylase : starch -> maltose

intestinal juice
- erepsin : hydrplyses polypeptides -> amino acids
proteins -> polypeptides by trypsin
polypeptides -> peptidases by erepsin -> amino acids

• intestinal lipase

fat digestion : bile
emulsifies fat into minute fat globules : increase surface area to volume ratio for digestion by lipase

Question 22

jejunum !

Answer 22

lactose : lactose -> galactose + glucose

sucrose : sucrose -> glucose + fructose

Question 23

absorption !

Answer 23

process whereby digested food substances are taken in by the body cells

1. diffusion
   - glucose + amino acids into blood capillaries of villi
   - glycerol + fatty acids into epithelium -> combine to form minute fat globules -> enter lymphatic capillary
2. active transport
   - glucose + amino acids : when there is a low conc of digested food substances in lumen of small intestine than blood capillaries

Question 24

small intestine features !

Answer 24

inner walls : extensively folded
- provides a large surface area to volume ratio -> increased efficiency for absorption

bears numerous villi : providing a large surface area for absorption

long & coiled : provide sufficient time for absorption

Question 25

villi features !

Answer 25

walls : one cell thick - shorter diffusion distance -> faster rate of absorption microvilli in epithelium of villi : increases surface area to volume ratio -> faster rate of absorption lacteal / lymphatic capillary + rich network of blood capillaries - help transport amino acids & glucose away quickly -> maintain diffusion gradient -> maintain high rate of absorption

Question 26

hepatic portal vein !

Answer 26

transports blood rich in glucose & amino acids absorbed from small intestine -> liver

Question 27

assimilation !

Answer 27

process whereby absorbed food substances are converted into new protoplasm or used to provide energy

Question 28

assimilation : glucose !

Answer 28

used by cells in respiration to release energy - most glucose : converted to glycogen for storage in liver - some glucose : transported by hepatic vein to diff parts of body

Question 29

assimilation : amino acids !

Answer 29

used by cells to make proteins, enzymes, hormones & new protoplasm excess amino acids : converted to urea by deamination - remains of deaminated amino acids : converted back to glucose

Question 30

assimilation : fats !

Answer 30

used to build protoplasm stored in adipose tissues : protect vital organs from shock broken down : to release energy when there is a lack of glucose used as an insulating material against heat loss

Question 31

liver : carbohydrate metabolism !

Answer 31

regulates concentration of blood glucose after meals : too much glucose in blood - insulin secreted (pancreas) - excess glucose -> glycogen for storage in liver - blood glucose level decreases fasting / in between meals : too little glucose in blood - glucagon secreted (pancreas) - glycogen -> glucose to replenish glucose used in respiration by cells - blood glucose increases

Question 32

liver : fat digestion !

Answer 32

produces bile : stored in gall bladder + discharged into duodenum by bile duct - emulsification of fats...

Question 33

liver : iron storage !

Answer 33

worn out RBC : destroyed in spleen - haemoglobin from RBC : transported to liver to be broken down - iron released from haemoglobin : stored in liver for synthesis of new RBC

Question 34

liver : deamination of amino acids !

Answer 34

excess amino acids deaminated in liver : amino groups removed converts amino groups -> urea - removed from body as an excretory product converts remains of amino acids -> glucose - excess glucose -> glycogen

Question 35

liver : detoxification !

Answer 35

converts toxins & harmful substances into harmless substances - alcohol - hydrogen peroxide

Question 36

liver : heat production !

Answer 36

numerous metabolic activities take place in the liver : large amt of heat produced - heat generated : distributed to rest of body -> maintain body temperature -> opt temp for enzymes

Question 37

effects of alcohol !

Answer 37

slower reaction time reduces self control increases risk of liver failure, gastric ulcers, cirrhosis (formation of fibrous tissue in liver), haemorrhage (bleeding in liver) & death