lecture 26

Question 1

what are the main nutrients that undergo chemical digestion?

Answer 1

Carbohydrates (sugars)
Proteins
Lipids (fats)

Question 2

How many carbs do we consume per day?

Answer 2

250-800gm per day

Question 3

What is the most common source of starch?

Answer 3

Carbohydrates

Question 4

What is the most common source of glycogen?

Answer 4

Carbohydrates

Question 5

What kind of saccharide is glucose?

Answer 5

Monosaccharide

Question 6

Starch and glycogen are long chains of glucose joined by?

Answer 6

alpha 1-4 glycosidic bond

Question 7

Sucrose breaks into?

Answer 7

Glucose and fructose

Question 8

Lactose is a combination of?

Answer 8

Glucose and galactose

Question 9

Maltose is a combination of?

Answer 9

Glucose and glucose

Question 10

Key disaccharides in our diet?

Answer 10

Sucrose
Lactose
Maltose

Question 11

Are proteins are source of energy?

Answer 11

No

Question 12

Proteins are required for what?

Answer 12

Source of amino acids (building blocks)

Question 13

how many amino acids can be synthesised by our bodies?

Answer 13

12

Question 14

How much of our protein comes from our diet?

Answer 14

50%, the rest come from endogenous proteins

Question 15

What are endogenous proteins?

Answer 15

Proteins secreted into intestine from enzymes and immunoglobulins

Question 16

Are lipids essential for our diet?

Answer 16

no

Question 17

Lipids are important source of what?

Answer 17

Energy

Question 18

Lipids are an important source of what type of vitamins?

Answer 18

Fat soluble vitamins A,D,E,K

Question 19

Lipids have slow what?

Answer 19

Gastric emptying

Question 20

Lipids are mainly made up of what?

Answer 20

Tyglycerides, a glycerol back bone with 3 fatty acids attached

Question 21

What is a short chain fatty acid?

Answer 21

<6 carbons

Question 22

What is a medium chain fatty acid?

Answer 22

6-12 carbons

Question 23

What is a long chain fatty acid?

Answer 23

12-24 carbons

Question 24

Why do we need chemical digestion?

Answer 24

ingest nutrients in form of large complex molecules

can only absorb nutrients as small molecules

Question 25

Where does chemical digestion occur?

Answer 25

at the surface of food particles

Question 26

Are digestive enzymes intra or extracellular?

Answer 26

Extracellular

Question 27

Do enzymes and substrates require specificity?

Answer 27

Yes they have to be specific

Question 28

what does amylase break down?

Answer 28

Carbohydrates

Question 29

Why can't we digest cellulose?

Answer 29

They have beta 1-4 glycosidic bonds and amylase can't break it down

Question 30

Optimal pH for salivary enzymes?

Answer 30

Alkaline

Question 31

Optimal pH for gastric enzymes?

Answer 31

acidic

Question 32

Optimal pH for small intestine?

Answer 32

alkaline

Question 33

Stage one of chemical digestion?

Answer 33

luminal digestion

Question 34

Initial chemical digestion involves enzymes being secreted into where?

Answer 34

lumen

Question 35

What do salivary glands secrete for chemical digestion?

Answer 35

Salivary amylase

Question 36

What does the stomach secrete?

Answer 36

pepsin

Question 37

what does the small intestine secrete?

Answer 37

pancreatic enzymes

Question 38

what are pancreatic enzymes?

Answer 38

``` pancreatic amylase trypsin chymotrypsin carboxypeptidase lipase ```

Question 39

stage two of chemical digestion?

Answer 39

Contact digestion

Question 40

Where does contact digestion occur?

Answer 40

small intestine

Question 41

Contact digestion involves enzymes produced by?

Answer 41

enterocytes and attached to brush border of enterocytes

Question 42

Key enzymes for carbohydrate breakdown?

Answer 42

salivary and pancreatic amylase

Question 43

polysaccharides are converted into what?

Answer 43

oligosaccharides and disaccharides

Question 44

During contact digestion disaccharides are converted to?

Answer 44

monosaccharides

Question 45

Contact digestion involves the enzymes?

Answer 45

sucrase lactase maltase

Question 46

where are the enzymes that are involved in contact digestion?

Answer 46

bound to brush border

Question 47

Cleaving of pepsinogen only occurs when?

Answer 47

at low pH

Question 48

What converts proteins into polypeptides?

Answer 48

pepsin trypsin chymotrypsin carboxypeptidase

Question 49

Contact digestion converts polypeptides into?

Answer 49

individual amino acids

Question 50

site of action where proteins are turned into large polypeptides?

Answer 50

stomach

Question 51

site of action where large polypeptides are turned into small poly/peptides?

Answer 51

small intestine

Question 52

Chemical digestion of lipids only occurs where?

Answer 52

in lumen of small intestine

Question 53

Chemical digestion of lipids doesn't involve what type of digestion?

Answer 53

Contact digestion

Question 54

what is the main digestive enzyme for lipids?

Answer 54

pancreatic lipase

Question 55

Which enzymes have a minor role is chemical digestion of lipids?

Answer 55

lingual lipase and gastric lipase

Question 56

What is the problem with lipid digestion?

Answer 56

digestive enzymes are dissolved in luminal fluid

Question 57

why do lipids require a more complex digestion process?

Answer 57

lipids (fats) are insoluble in water

Question 58

Stages of chemical digestion of fats?

Answer 58

emulsification stabilisation digestion formation of micelles

Question 59

What stabilises formation of small droplets?

Answer 59

bile salts

Question 60

What breaks up liquid lipid droplets?

Answer 60

motility, retropulsion in stomach and segmentation in small intestine

Question 61

where does stabilisation occur?

Answer 61

small intestine

Question 62

What does stabilisation involve?

Answer 62

bile salts that are secreted by liver

Question 63

when are bile salts released into small intestine?

Answer 63

with arrival of food

Question 64

how do bile salts stabilise emulsified drops?

Answer 64

by having a hydrophobic and hydrophilic side

Question 65

what does hydrolysis involve?

Answer 65

lipase and cofactor colipase

Question 66

where are lipase and cofactor colipase secrete from?

Answer 66

pancreas

Question 67

what does colipase do?

Answer 67

anchors lipase to surface of droplet

Question 68

what does lipase do?

Answer 68

convert triglycerides to monoglycerides and free fatty acids

Question 69

Are monoglycerides and long chain fatty acids soluble?

Answer 69

no they are insoluble

Question 70

what do micelles do?

Answer 70

keep insoluble lipid products in solution

Question 71

what are micelles?

Answer 71

small droplets consisting of 20-30 molecules of: bile salts fatty acids monoglycerides