[HDS] human digestive system

Question 1

what are enzymes?

Answer 1

enzymes are biological catalysts that speed up chemical reactions without undergoing any chemical changes themselves

Question 2

what is the primary function of enzymes in cells?

Answer 2

enzymes build up and break down complex substances in cells

Question 3

how are enzymes different from other chemicals involved in reactions?

Answer 3

enzymes are required in minute amounts, and they remain chemically unchanged at the end of the reactions they catalyse

Question 4

are enzymes specific in their actions?

Answer 4

yes, enzymes are highly specific in action, only catalysis specific chemical reactions
(eg. amylase for starch only, lipase for lipids only)

Question 5

what happens to enzymes at extreme pH levels?

Answer 5

they lose their shape in a process known as desaturation, which is irreversible

Question 6

what is the digestive system composed of?

Answer 6

the alimentary canal, the associated organs and glands

Question 7

name the organs in the alimentary canal

Answer 7

mouth, oesophagus, stomach, small intestine, large intestine, rectum and anus

Question 8

what are the associated organs and glands?

Answer 8

liver, gall bladder and pancreas

Question 9

describe the process of digestion

Answer 9

digestion breaks down large, insoluble food substances into small, soluble simple molecules that can be absorbed by body cells

Question 10

what is the role of the mouth in digestion?
(three roles)

Answer 10

• chewing (physical digestion) breaks food into smaller pieces
• salivary glands produce saliva containing salivary amylase, which digests starch into maltose
• the tongue forms chewed food into a small ball for swallowing

Question 11

what is peristalsis?

Answer 11

it is a wave-like muscle contraction that propel food along the oesophagus

Question 12

where does peristalsis occur?

Answer 12

in the oesophagus

Question 13

what happens in the stomach during digestion?

Answer 13

• gastric glands secrete gastric juice containing hydrochloride acid and pepsin
• pepsin digests proteins into polypeptides
• churning action (physical digestion) mixes food with gastric juices, forming chyme

Question 14

what is bile?

Answer 14

bile is an alkaline, greenish-yellow liquid

Question 15

where is bile produced and stored in?

Answer 15

bile is produced in the liver and stored in the gall bladder

Question 16

what is the role of bile in digestion?

Answer 16

• neutralise acidic chyme from the stomach
• emulsifies lipids, breaking large fat droplets into tiny ones, increasing the rate of lipid digestion

Question 17

what is pancreatic juice?

Answer 17

pancreatic juice is an alkaline secretion from the pancreas

Question 18

what enzymes does pancreatic juice contain?

Answer 18

pancreatic amylase, trypsin and pancreatic lipase

Question 19

what do the walls of the small intestine contain?

Answer 19

it contains glands that secrete digestive enzymes including carbohydrates, peptidase and intestinal lipase

Question 20

what is the function of the large intestine in digestion?

Answer 20

it absorbs water and mineral salts from undigested matter, forming faeces

Question 21

where is faeces stored and expelled from?

Answer 21

faeces is stored in the rectum and expelled through the anus in egestion

Question 22

describe the overall sequence of process in the digestive system

Answer 22

ingestion>digestion>absorption>elimination

Question 23

what is the purpose of chewing in the mouth during digestion?

Answer 23

it break downs solid food into smaller pieces, increasing the surface area to volume ratio and facilitating digestion by enzymes

Question 24

how does churning in the stomach contribute to digestion?

Answer 24

it mixes food with gastric juices, which increases the surface area to volume ratio, enhancing the rate of protein digestion by pepsin. a liquid called chyme is produced

Question 25

what are the functions of enzymes found in pancreatic juice?

Answer 25

• pancreatic amylase (starch > maltose)
• trypsin (protein > polypeptides)
• pancreatic lipase (lipids > fatty acids and glycerol)

Question 26

what are the functions of the digestive enzymes secreted in the small intestine?

Answer 26

• carbohydrates (maltose > glucose)
• intestinal lipase (lipids > fatty acids and glycerol)
• peptidase (polypeptides > amino acids)