9.3 Digestive Enzymes Flashcards

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1
Q

What are digestive enzymes?

A

proteins that speed up specific chemical reactions

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2
Q

What is starch?

A

a carbohydrate that’s digestion begins in the mouth

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3
Q

What is salivary amylase?

A

an enzyme in saliva that digests starch to maltose

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4
Q

What is maltose?

A

disaccharide molecule that cannot be absorbed by the intestine

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5
Q

What is glucose?

A

a monosaccharide that can be absorbed, digestive action in the small intestine converts maltose to glucose

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6
Q

Where does protein digestion begin?

A

in the stomach

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7
Q

Why are gastric juices secreted by gastric glands very acidic?

A

(pH 2) because it contains hydrochloric acid

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8
Q

What is pepsinogen?

A

a precursor that is converted to the enzyme pepsin when exposed to HCl that is present in gastric juice

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9
Q

What is pepsin?

A

an enzyme that acts on proteins (polymers of amino acids) to produce peptides

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10
Q

Describe peptides from the stomach.

A

usually too large to be absorbed by the intestinal lining, but later in the small intestine they are broken down to amino acids

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11
Q

What is pancreatic juice?

A

enters the duodenum and has a basic pH because it contains NaHCO3 (sodium bicarbonate)

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12
Q

What does NaHCO3 do?

A

neutralizes the acid in chyme, producing the slightly basic pH that is optimum for pancreatic enzymes including pancreatic amylase and trypsin

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13
Q

What is pancreatic amylase?

A

a pancreatic enzyme that digests starch

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14
Q

What is trypsin?

A

a pancreatic enzyme that digests protein

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15
Q

What is trypsin secreted as?

A

trypsinogen, which is converted to trypsin in the duodenum

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16
Q

What is lipase?

A

a pancreatic enzyme that digests fat molecules in the fat droplets after they have been emulsified by bile salts

17
Q

What are fats?

A

triglycerides, composed of glycerol and three fatty acids

18
Q

What are the end products of lipase digestion?

A

glycerol and fatty acid molecules that are small enough to cross the cells of the intestinal villi where absoprtion takes place

glycerol and fatty acids enter the cells of the villi, and within these cells, they are rejoined and packaged as lipoprotein droplets before entering the lacteals

19
Q

What is peptidases?

A

enzyme secreted by the surface cells of the small intestine villi and completes the digestion of proteins to amino acids

20
Q

What is maltase?

A

enzyme secreted by the surface cells of the small intestine villi and completes the digestion of starch to glucose

21
Q

What is lactose intolerance caused by?

A

fermentation of of non-digested lactose by intestinal bacteria

22
Q

When do enzymes function best?

A

at an optimum temperature and pH, which helps maintain the proper shape to fit their substrate

23
Q

What does the compartmentalization of the digestive system do?

A

assists in the regulation of enzymatic activity

24
Q

Why is enzymatic activity largely controlled by pH?

A

because the entire digestive system of humans is maintained at a constant temperature of 37 C

25
Q

What is the pH of the stomach?

A

between 1 and 2, allowing the activation of pepsinogen enzyme

26
Q

When does the pH of the stomach change?

A

shortly after chyme proceeds into the duodenum, the sodium bicarbonate released from the pancreas returns the pH to around 7.4-7.8

27
Q

What does the change in pH of the stomach do?

A

serves the activate digestive enzymes released by the pancreas, thus allowing the digestion of carbohydrates, fats, and proteins