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Class 3 > Lecture 26: Chemical Digestion > Flashcards

Lecture 26: Chemical Digestion Flashcards

1
Q

What is chemical digestion?

A

when we release the nutrients necessary for our own growth and energy needs

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2
Q

Motility carries out mechanical digestion which is essential for chemical digestion. How?

A

Mechanical digestion breaks up the food into small pieces which is needed for chemical digestion

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3
Q

How does motility aid in chemical digestion?

A

mechanical digestion mixes the food with digestive enzymes

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4
Q

How does motility aid absorption?

A

by moving the food through the GI tract at a rate that allows for maximum absorption

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5
Q

How does secretion aid mechanical digestion?

A

the mucous coats the food and stops abrasion of epithelium

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6
Q

Why is secretion essential for chemical digesiton?

A

secretions contain digestive enzymes and electrolytes which ensure optimal pH for the enzymes

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7
Q

How does secretion aid in absorption?

A

By suspending food molecules in solution so they can be exposed to absorptive surfaces

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8
Q

What are the three main nutrients that undergo chemical digestion?

A
  • carbohydrates (sugars)
  • proteins
  • lipids (fats)
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9
Q

What is the main form of carbohydrates that we ingest?

A

storage polysaccharides

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10
Q

Give an example of a storage polysaccharide in grains and meat

A

starch in grains and glycogen in meat

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11
Q

What are storage polysaccharides?

A

very large complex chains of monosaccharides such as glucose

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12
Q

A large number of ________ molecules are bound together in long chains which is bound together in further chains to form _______ _______

A

glucose

storage polysaccharides

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13
Q

Starch and glycogen are storage carbohydrates that are joined by what type of bonds?

A

α 1-4 glycosidic bonds

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14
Q

As well as ingesting storage carbohydrates, we can also ingest _______

A

disaccharides

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15
Q

Give three examples of disaccharides and what monosaccharides they are made of

A
  1. sucrose made from glucose and fructose
  2. lactose made from glucose and galactose
  3. maltose made from two glucose molecules
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16
Q

We also ingest a small number of monosaccharides. What monosaccharide do we ingest?

A

glucose

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17
Q

Proteins are required to be ingested for us to have ______ ______

A

amino acids

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18
Q

According to the lecture slide, how many amino acids are there and how many can we synthesise?

A

21 amino acids

12 can be synthesised

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19
Q

What is an essential amino acid?

A

amino acids that we need to access from our diet

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20
Q

Where are our two sources of protein?

A
  • diet

- endogenous proteins

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21
Q

What are endogenous proteins?

A

proteins secreted into our intestine such as enzymes and immunoglobins which we digest and reabsorb

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22
Q

Ingested proteins are long chains of ______ ______ linked by ______ bonds

A

amino acids

peptide

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23
Q

The lipids that we ingest are mainly

A

triglycerides

24
Q

What does a triglyceride consist of?

A

a glycerol back bone with 3 fatty acids attached

25
Q

Fatty acids can be variable in chain length. How many carbons make up short chain fatty acids, medium chain fatty acids, long chain fatty acids respectively?

A
  • short: less than 6 carbons
  • medium: 6 - 12 carbons
  • long: 12 - 24 carbons
26
Q

Why do we need chemical digestion?

A

because we ingest nutrients in the form of large complex molecules (carbs, proteins, lipids) but we can absorb nutrients as small molecules

27
Q

What is the purpose of chemical digestion?

A

to reduce the size of nutrients to allow them to be absorbed

28
Q

Where does chemical digestion occur?

A

At the surface of food particles

29
Q

During chemical digestion, we break up molecules into its constituent parts. What are the constituent parts of sugars, proteins and fats?

A
  • sugars: monosaccharides
  • proteins: amino acids
  • fats: monoglycerides and free fatty acids
30
Q

Chemical digestion utilises ________ enzymes

A

chemical

31
Q

What are digestive enzymes?

A

Extracellular, organic catalysts

32
Q

Are digestive enzymes specific?

A

yes

they need different enzymes for different substrates

33
Q

Give the different substrates for amylase, protease and lipase

A

Amylase: carbohydrates
Proteases: proteins
Lipases: fats

34
Q

Enzymes have an optimal pH. Give the optimal pH for salivary, gastric and small intestinal enzymes

A

Salivary: alkaline
Gastric: acidic
Small intestinal: alkaline

35
Q

What are the two stages of chemical digestion?

A

luminal digestion

contact digesiton

36
Q

What is luminal digestion?

A

the initial digestion involving enzymes secreted into the lumen

37
Q

Give examples of enzymes involved in luminal digestion in the mouth, stomach and small intestine

A

salivary amylase
pepsin
pancreatic enzymes

38
Q

What is contact digestion?

A

involved enzymes produces by enterocytes and attached to brush border of the enterocytes

39
Q

Where does contact digestion only occur?

A

in the small intestine

40
Q

What are enterocytes?

A

epithelium of the small intestine

41
Q

Describe the luminal digestion of carbohydrates

A

salivary amylase in the mouth converts polysaccharides to oligosaccharides and pancreatic amylase converts oligosaccharides to disaccharides in the small intestine

42
Q

Describe contact digestion of carbohydrates

A

Disaccharides are converted to monosaccharides by different enzymes attached to the brush border

43
Q

What are three enzymes involved in the contact digestion of carbohydrates and what do they break down?

A
  • Sucrase breaking down sucrose to glucose and fructose
  • lactase breaking down lactose to glucose and galactose
  • maltase breaking down maltose into two glucose molecules
44
Q

Describe the luminal digestion of proteins

A

Pepsin in the stomach and trypsin, chymotrypsin, carboxypeptidase in the small intestine convert proteins to polypeptides

45
Q

Describe the contact digestion of proteins in the small intestine

A

peptidases attached to the brush border convert polypeptides into individual amino acids

46
Q

What is different about the chemical digestion of fats compared to the digestion of proteins and carbohydrates?

A

there is no contact digestion

47
Q

What is the main digestive enzyme involved in digestion of lipids?

A

pancreatic lipase

48
Q

What are the four phases of the chemical digestion of fat?

A
  1. emulsification
  2. stabilisation
  3. digestion
  4. formation of micelles
49
Q

Describe the emulsification stage of fat digestion

A
  • motility breaks up fat droplets into small droplets which forms an emulsion
50
Q

Where does the emulsification phase of fat digestion occur and what are the processes occurring here that allow that to happen?

A

stomach - retropulsion

small intestine - segmentation

51
Q

Where does the stabilisation phase of fat digestion occur?

A

in the small intestine

52
Q

What is involved in emulsification?

A

breaking up large fat droplets into smaller droplets

53
Q

What is the role of bile salts in the stabilisation phase of fat digestion?

A

Bile salts secreted by the liver and concentrated in the gallbladder are released into the small intestine with the arrival of food. They have both a hydrophobic side and a hydrophilic side. They stabilise the emulsion in the small intestine by preventing the droplets from coalescing due to like charges repelling

54
Q

Describe the hydrolysis stage of lipid digestion

A

colipase binds to the bile salt around the small droplets and anchors pancreatic lipase at the surface of the droplet to convert the triglycerides to monoglycerides and free fatty acids

55
Q

What is the purpose of micelle formation around free fatty acids and monoglycerides?

A

FFA and MAGs are insoluble in water so they need to be kept in solution through the formation of the micelles.

56
Q

What are micelles?

A

small droplets made from bile salts surrounding the FFA and MAGs

Class 3 (41 decks)

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