6.9- ENZYMES AND DIGESTION

Question 1

What is the human digestive system made up of?

Answer 1

long muscular tube + its associated with glands

Question 2

What do the glands associated with the digestive system produce?

Answer 2

enzymes that hydrolyse large molecules into small ones ready for absorption

Question 3

What is the digestive system used for?

Answer 3

exchange surface through which food substances absorbed

Question 4

What are the main parts of the digestive system? (7)

Answer 4

oesophagus 
stomach
ileum 
large intestine 
rectum 
salivary glands 
pancreas

Question 5

What does the oesophagus do?

Answer 5

carries food from mouth to stomach

Question 6

What is the stomach?

Answer 6

muscular sac with inner layer that produces enzymes

Question 7

What is the role of the stomach?

Answer 7

store + digest food, especially proteins

Question 8

What does the stomach have which digest protein?

Answer 8

glands that produce enzymes which digest proteins

Question 9

What is the ileum?

Answer 9

long muscular tube

Question 10

What is done to food in the ileum?

Answer 10

food further digested in ileum by enzymes produced but its walls + glands that pour their secretions into it

Question 11

What are the inner walls of the ileum folded into?

Answer 11

villi

Question 12

What does the inner walls of the ileum being folded into villi give them?

Answer 12

large surface area

Question 13

What is the surface are of the villi of the ileum further increased by?

Answer 13

millions of tiny projections, called microvilli, on epithelial cells of each villus

Question 14

What does the increased surface of the ileum from the villi and microvilli adapt the ileum for?

Answer 14

its purpose of absorbing products of digestion into bloodstream

Question 15

What do the large intestines do?

Answer 15

absorbs water

Question 16

What is most of the water absorbed by the large intestines from?

Answer 16

water from secretions of many digestive glands

Question 17

What is the final section of the intestines?

Answer 17

rectum

Question 18

What is stored in the rectum?

Answer 18

faeces

Question 19

How is the faeces removed from the rectum?

Answer 19

via anus in process called egestion

Question 20

Where are the salivary glands situated?

Answer 20

near the mouth

Question 21

How do the salivary glands pass their secretions?

Answer 21

via duct into mouth

Question 22

What does the secretion of the salivary glands contain?

Answer 22

enzyme amylase, which hydrolyses starch into maltose

Question 23

What is the pancreas?

Answer 23

large gland situated below stomach

Question 24

What is the secretion of the pancreas called?

Answer 24

pancreatic juice

Question 25

What does the pancreatic juice contain?

Answer 25

proteases to hydrolyse proteins, lipase to hydrolyse lipids + amylase to hydrolyse starch

Question 26

What are the two stages of digestion in humans?

Answer 26

1 physical breakdown | 2 chemical digestion

Question 27

If the food is large, how is it broken down into smaller pieces in physical breakdown?

Answer 27

by means of structures i.e. teeth

Question 28

What does food being broken down into smaller pieces by the teeth make possible?

Answer 28

ingest food + provides large SA for chemical digestion

Question 29

How is food physically broken down in the stomach?

Answer 29

food churned by muscles in stomach

Question 30

What does chemical digestion do?

Answer 30

hydrolyses large. insoluble molecules into smaller, soluble ones

Question 31

What is chemical digestion carried out by?

Answer 31

enzymes

Question 32

What do all digestive enzymes function by?

Answer 32

hydrolysis

Question 33

What is hydrolysis?

Answer 33

splitting up of molecules by adding water to chemical bonds that hold them together

Question 34

How many enzymes is needed to hydrolyse a large molecule?

Answer 34

more than one

Question 35

How does hydrolyses of a large molecule usually happen?

Answer 35

one enzyme hydrolyses large molecules into sections + these sections then hydrolysed into smaller molecules by one/more additional enzymes

Question 36

What are 3 particularly important digestive enzymes?

Answer 36

carbohydrases lipases proteases

Question 37

What do carbohydrases hydrolyse and into what?

Answer 37

carbohydrates to ultimately monosaccharides

Question 38

What do lipases hydrolyse and into what?

Answer 38

lipids (fats + oils) into glycerol + fatty acids

Question 39

What do proteases hydrolyse and into what?

Answer 39

proteins, ultimately into amino acids

Question 40

Where is amylase produced?

Answer 40

mouth + pancreas

Question 41

What does amylase hydrolyse?

Answer 41

alternate glycosidic bonds of starch molecules to produce disaccharide maltose

Question 42

What is the maltose produced from amylose hydrolyses, hydrolysed by?

Answer 42

by maltase into monosaccharide α-glucose

Question 43

What is maltase produced by?

Answer 43

lining of ileum

Question 44

Amylase working in humans: saliva (1)

Answer 44

saliva enters mouth from salivary glands +t thoroughly mixed with food during chewing

Question 45

Amylase working in humans: what does saliva contain?

Answer 45

salivary amylase

Question 46

Amylase working in humans: what does the salivary amylase in the saliva do? (2)

Answer 46

starts hydrolysing any starch in food to maltose

Question 47

Amylase working in humans: what else does the saliva contain? (2)

Answer 47

mineral salts that help maintain pH at around neutral | this is optimum pH for salivary amylase to work

Question 48

Amylase working in humans: where does the food go from the mouth? (3)

Answer 48

swallowed + enters stomach, where conditions are acidic

Question 49

Amylase working in humans: what happens to the amylase in the stomach? (3)

Answer 49

acid denatures amylase + prevents further hydrolysis of starch

Question 50

Amylase working in humans: where does the food go from the stomach? (4)

Answer 50

after time food passed into small intestine, where it mixes with secretion from pancreas called pancreatic juice

Question 51

Amylase working in humans: what does the pancreatic juice contains?

Answer 51

pancreatic amylase

Question 52

Amylase working in humans: what does the pancreatic amylase in the pancreatic juice do? (5)

Answer 52

continues hydrolysis of any remaining starch to maltose

Question 53

Amylase working in humans: what does the pancreas + intestinal wall produce and why? (5)

Answer 53

alkaline salts produced by pancreas + intestinal walls to maintain pH at around neutral so amylase can function

Question 54

Amylase working in humans: what do the muscles in the intestines do? (6)

Answer 54

muscles in intestine walls push food along ileum

Question 55

Amylase working in humans: what does the epithelial lining of the intestine produce? (6)

Answer 55

produces disaccharidase maltase

Question 56

Is maltase release into the lumen of the ileum?

Answer 56

no

Question 57

Amylase working in humans: what is the disaccharidase maltase part of? (6)

Answer 57

cell-surface membranes of epithelial cells that line the ileum

Question 58

As the maltase is a part of the cell-surface membranes of epithelial cells that line the ileum, what is it called?

Answer 58

membrane-bound disaccharidase

Question 59

Amylase working in humans: what does the maltase do to the maltose? (6)

Answer 59

maltase hydrolyse maltose from starch breakdown into α-glucose

Question 60

What are two other common disaccharides other than maltose in the diet that are hydrolysed?

Answer 60

sucrose and lactose

Question 61

Where can sucrose be found in food?

Answer 61

sucrose found in many natural foods, especially fruits

Question 62

Where can lactose be found in food?

Answer 62

in milk, + hence milk products such as yoghurt + cheese

Question 63

What does sucrase do?

Answer 63

hydrolyses single glycosidic bonds in sucrose molecules

Question 64

What does the sucrase hydrolysing sucrose produce?

Answer 64

hydrolysis produces two monosaccharides glucose + fructose

Question 65

What does lactase do?

Answer 65

hydrolyses single glycosidic bond in lactose molecule

Question 66

What does the lactase hydrolysing lactose produce?

Answer 66

hydrolysis produces two monosaccharides glucose + galactose

Question 67

What are lipids hydrolysed by?

Answer 67

enzymes called lipases

Question 68

Where are lipases produced?

Answer 68

pancreas

Question 69

What do lipases do?

Answer 69

hydrolyse ester bonds found in triglycerides to form fatty acids + monoglycerides

Question 70

What is a monoglyceride?

Answer 70

glycerol molecules with single fatty acid molecule attached

Question 71

What happens to the lipids first in lipid digestion?

Answer 71

split into tiny droplets called micelles by bile salts

Question 72

What are bile salts produced by?

Answer 72

liver

Question 73

What is the process of fats being split into tiny droplets called micelles by bile salts called?

Answer 73

emulsification

Question 74

What does emulsification do?

Answer 74

increases SA of lipids so action of lipases speeded up

Question 75

What are proteins?

Answer 75

large, complex molecules

Question 76

What are proteins hydrolysed by?

Answer 76

group of enzymes called peptidases (proteases)

Question 77

What are the different types of peptidases? (3)

Answer 77

endopeptidases exopeptidases dipeptidases

Question 78

What do endopeptidases do?

Answer 78

hydrolyse peptide bonds between amino acids in central region of protein molecule forming series of peptide molecules

Question 79

What do exopeptidases do?

Answer 79

hydrolyse peptide bonds on terminal amino acids of peptide molecules formed by endopeptidases in this way they progressively release dipeptides + single amino acids

Question 80

What do dipeptidases do?

Answer 80

hydrolyse bond between two amino acids of dipeptide

Question 81

What type of enzymes are dipeptidases?

Answer 81

membrane-bound, being part of cell-surface membrane of epithelial cells lining the ileum