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1.1 Histology, Anatomy and Physiology > Gastrointestinal Tract - Digestion of Biomolecules > Flashcards

Gastrointestinal Tract - Digestion of Biomolecules Flashcards

1
Q

Where does the digestion of carbohydrates start?

A

In the mouth

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2
Q

What enzyme is found in the mouth that begins the digestion of carbohydrates?

A

Salivary amylase

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3
Q

What happens to salivary amylase in the stomach?

A

Its action is diminished

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4
Q

Why does salivary amylase not work in the stomach?

A

The pH of the stomach is too low

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5
Q

Other than the mouth where does amylase work?

A

The small intestine

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6
Q

What form is amylase in the small intestine?

A

Pancreatic amylase

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7
Q

Why does amylase work in the small intestine but not the stomach?

A

Because the pH of the small intestine rises

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8
Q

Where does pancreatic amylase enter the small intestine?

A

The duodenum

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9
Q

What breaks down maltose?

A

Maltase

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10
Q

Where is maltase found?

A

The brush border

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11
Q

In general what happens to disaccharides in the GIT?

A

Disaccharides are broken down into simple sugars

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12
Q

Where in the GIT are disaccharides broken down into simple sugars?

A

The small intestine

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13
Q

What must simple sugars pass through in order to enter the bloodstream?

A

The apical membrane

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14
Q

How do glucose and sodium enter enterocytes?

A

They must bind to protein in order to enter the enterocyte

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15
Q

Explain the process of sodium and glucose entering an enterocyte.

A

Sodium must be pumped out of one cell and into another to set up the concentration gradient across the basal lateral membrane

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16
Q

How does glucose move from an enterocyte to the bloodstream?

A

By diffusion

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17
Q

What happens when glucose enters the bloodstream?

A

It passes through to the liver

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18
Q

What happens to glucose in the liver?

A

It is either stored in the liver or used by the body

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19
Q

Whether or not glucose is stored in the liver depends on what?

A

It depends on the levels of insulin in the body

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20
Q

Explain how insulin controls how much glucose is stored by the liver.
(2)

A

Increased insulin causes glucose to be stored as glycogen in the liver

Low insulin causes glycogen to be used

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21
Q

What is the name of the protein that carried glucose across membranes?

A

Transport proteins

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22
Q

What is another name for simple sugars?

A

Monosaccharides

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23
Q

Where exactly in the bloodstream do monosaccharides enter?

A

They enter the portal circulation

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24
Q

What are proteins also called?

A

Polypeptides

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25
Q

What happens to proteins in the gastric phase?

A

In the gastric phase hydrochloric acid and pepsin breaks down polypeptides into peptide fragments

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26
Q

What enzyme is used to break down polypeptides?

A

Pepsin

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27
Q

What are proteins broken into in the gastric phases?

A

Peptide fragments

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28
Q

How long does it take for proteins to be broken down into peptide fragments?

A

This process takes hours

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29
Q

What is the brush border?

A

Microvilli of the small intestine

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30
Q

What part of the intestine receives the chyme?

A

The duodenum

31
Q

What is present in pancreatic juices that helps break down peptide fragments?

A

Sodium carbonate (alkaline)

Enzymes - pancreatic amylase and zymogens

32
Q

What enzymes are present in pancreatic juices?

2

A

Pancreatic amylase

Zymogens

33
Q

What are zymogens?

A

Inactive enzymes responsible for breaking down proteins

34
Q

Why are zymogens used to break down proteins?

A

Zymogens are inactive in the pancreas but become active in the duodenum so as to not damage the pancreas

35
Q

What is cystic fibrosis?

A

Blockage of pancreatic juice which leads to inflammation due to incomplete breakdown of proteins

36
Q

What does the chyme in the small intestine containing broken down peptide fragments trigger?

A

It triggers the enterogastro reflex

37
Q

What is the enterogastric reflex?

2

A

This is releases enterogasterones

This relaxes the hepatopancreatic sphincter which causes it to open

38
Q

What happens when the hepatopancreatic sphincter opens?

A

This allows pancreatic juice to enter the small intestine

39
Q

What enters the small intestine when the hepatopancreatic sphincter opens?
(3)

A

Trypsinogen

Chymotrypsinogen

Procarboxy-peptidase

40
Q

What is trypsinogen converted into in the SI?

A

Trypsin

41
Q

What converts trypsinogen into trypsin?

A

enteropeptidase

42
Q

Where is enteropeptidase found?

A

Mucosa

43
Q

What does trypsin do?

2

A

Converts chymotrypsinogen into chymotrypsin

Converts procarboxypeptidase into carboxypeptidase

44
Q

What is chymotrypsinogen converted into?

A

Chymotrypsin

45
Q

What is procarboxypeptidase converted into?

A

It is converted into carboxypeptidase

46
Q

How do proteins enter the blood stream?

A

Co-transport with sodium

47
Q

How do proteins enter cells using co-transport with sodium?

2

A

A concentration gradient on the basal membrane side needs to be set up for sodium

Need to decrease sodium concentration levels in enterocyte to create gradient

48
Q

What do proteins use to enter the blood stream?

A

Protein carriers

49
Q

Where in the blood stream do proteins enter?

A

The portal circulation

50
Q

Where does the digestion of lipids begin?

A

The mouth

51
Q

What is found in the mouth that digests lipids?

A

Lingual lipase in saliva

52
Q

What percentage of lipids are digested in the mouth?

A

10% of a lipid is digested

53
Q

What happens to lingual lipase in the stomach?

A

It becomes ineffective

54
Q

Why do lipids become ineffective in the stomach?

A

Low pH

55
Q

What form are lipids in the stomach?

A

Fat globules

56
Q

Are lipids polar or non-polar?

A

They are non-polar

57
Q

Lipids are non-polar what does this mean?

A

They are hydrophobic

58
Q

What happens to lipids in the small intestine?

A

They form clumps

59
Q

How are lipids broken down in the SI?

A

Lipases (enzymes) from the pancreas enter the SI and have an affect on lipids

60
Q

What needs to be done to lipids before lipases can work efficiently?

A

The lipids need to be emulsified

61
Q

How are lipids emulsified?

A

Using bile salts

62
Q

What happens to bile salts when there not needed?

2

A

They are stored in the gall bladder

They are dehydrated first then stored

63
Q

What are bile salts said to be?

A

amphipathic

64
Q

Bile salts are amphipathic, what does this mean?

A

They have a hydrophilic/polar side and a hydrophobic/non-polar side

65
Q

How do bile salts emulsify lipids?

2

A

Bile salts bind to outside of fat droplet

Chyme binds to inside of fat droplet

66
Q

Explain the effects of pancreatic juice on lipids.

3

A

Pancreatic juice contains pancreatic lipase

Lipase acts on the fat droplet

Lipase breaks down into free fatty acids, monoglyceride, monolipids

67
Q

What does pancreatic lipase break lipids into to?

3

A

Free fatty acids

Monoglycerides

Monolipids

68
Q

What is formed after the pancreatic lipase has worked on the lipids?

A

Micelles

69
Q

How do micelles enter enterocytes?

A

They diffuse through the apical membrane

70
Q

Describe the process of lipids entering circulation.

4

A

They are packaged into chylomicrons by the smooth endoplasmic reticulum and the golgi apparatus

Enter lacteals containing lymph fluid

Lymph brought to the thoracic duct

Lymph drains into general circulation

71
Q

Why do chylomicrons enter the lacteals?

2

A

Chylomicrons are too big to enter capillaries

Therefore, they bypass them by entering the lacteals in the lamina propria

72
Q

Where in the tissue are lacteals present?

A

The lamina propria

73
Q

What do lacteals contain?

A

Lymph fluid

74
Q

Where are lipids brought in the lymph fluid?

A

The thoracic duct

1.1 Histology, Anatomy and Physiology (40 decks)

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