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Y2B1 - GIT πŸ“• > Biochemistry πŸ§ͺ > Flashcards

Biochemistry πŸ§ͺ Flashcards

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1
Q

Introduction

A
  • Dietary CHO, fats and proteins are large complex molecules that cannot be absorbed.
  • They must be digested to small simple molecules (monosaccharides, monoglycerides and amino acids) which are easily absorbed from the intestine.
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2
Q

CHO digestion

A
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3
Q

Triglycerides digestion

A
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4
Q

Triglycerides digestion

A
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5
Q

triglycerides digestion

A
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6
Q

phospholipids digestion

A
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7
Q

cholesterol esters digestion

A
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8
Q

Protein digestion

A
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9
Q

Protein digestion

A
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10
Q

protein digestion

A
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11
Q

what is the PH of salivary secretions?

A

6.2 - 7.6

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12
Q

what are the components of salivary secretions?

A

Electrolytes: mainly Na+, K+, Ca++, Cl-.

Organic contents: Salivary enzymes (salivary amylase, lingual lipase) and mucus.

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13
Q

what are the effects of salivary secretions?

A

Starts the digestion of CHO and fat:

Salivary amylase:
- partially digests starch and glycogen to dextrin and few maltose.
- It acts on cooked starch.

Lingual lipase:
- It is secreted by the dorsal surface of the tongue (Ebner’s glands).
- It helps fat digestion in new-born infants (their pancreatic lipase is still not developed).

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14
Q

effect of salivary secretions on CHO digestion

A

Salivary amylase:
- partially digests starch and glycogen to dextrin and few maltose.
- It acts on cooked starch.

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15
Q

effect of salivary secretions on Fat digestion

A

Lingual lipase:
- It is secreted by the dorsal surface of the tongue (Ebner’s glands).
- It helps fat digestion in new-born infants (their pancreatic lipase is still not developed).

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16
Q

what is the PH of gastric secretions?

A

1 - 3

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17
Q

what are the components of gastric secretions?

A

Inorganic: mainly HCl

organic: Gastric enzymes (lipase, pepsin, gelatinase, renin), mucus, Intrinsic factor.

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18
Q

what are the effects of gastric secretions?

A

affects CHO, dietary fat (triglycerides) & proteins

19
Q

effect of gastric secretions on CHO

A
  • No carbohydrate digesting enzymes available in gastric juice.
  • Only, HCl can partially hydrolyze the disaccharides and polysaccharides.
20
Q

effect of gastric secretions on fat (triglycerides digestion)

A
  • Ingested triglycerides are emulsified then undergo enzymatic hydrolysis by lipase enzymes.
  • Gastric lipase (pH 3-6) hydrolyses triglycerides containing only the unsaturated fatty acids at the third ester bond to form FFA and Ξ±, ꞡ(1, 2)-diglycerides.
21
Q

what is emulsification?

A

Breakdown of large fat globule into small ones. In the mouth (chewing), in the stomach (peristaltic contractions) and in intestine (peristaltic movement, bile salts and by lyso-phospholipids).

22
Q

effect of gastric secretion on proteins

A

Protein digestion begins in the stomach by:
- gastric HCL
- Pepsin
- rennin
- gelatinase

23
Q

role of gastric HCL in protein digestion

A
  • It causes denaturation of proteins to the easily digested metaproteins.
  • It activates pepsinogen to pepsin.
  • It makes pH in the stomach suitable for the action of pepsin.
24
Q

PH & role of Pepsin in protein digestion

A

PH: 1.5 - 2.2

  • An endo-peptidase acting on central peptide bond in which NH2 belongs to aromatic amino acids e.g. phenyl alanine, tyrosine and/or tryptophan.
  • Secreted as inactive pepsinogen.
  • Activated by HCL then by autoactivation.
25
Q

PH and role of rennin in protein digestion

A

PH: 4

  • A milk-clotting enzyme in the stomach of infants and young animals.
  • Acts on casein converting it to soluble paracasein, which binds calcium ions forming insoluble calcium paracasinate.
  • Calcium paracaseinate is then digested by pepsin.
26
Q

role of gelatinase in protein digestion

A

liquefies gelatin.

27
Q

what does the digested food passing from the stomach to duodenum contain?

A

1) Products of protein digestion: proteoses, peptones and large polypeptides.

2) Products of fat digestion: FFA, 1,2 diglycerides and emulsified undigested fat.

3) Products of CHO digestion: some dextrin, maltose, uncooked partially hydrolyzed starch.

28
Q

what is the PH of bile secretions?

A

7.5 - 8.8

29
Q

what are the contents of bile secretions?

A

Inorganic: includes Na +, K +, Cl-, HCO3-, Ca ++ and Mg++

Organic:
- Bile salts
- bile pigments
- Cholesterol
- Phospholipid as lecithin
- Fatty acids

30
Q

what are the effects of bile secretions?

A
  • Bile salts assist emulsification of fat by lowering surface tension and exposing large area of triglycerides to the action of pancreatic lipase.
  • Bile salts are required for the activity of pancreatic phospholipase A2 & cholesterol esterase.
31
Q

what is the PH of pancreatic secretions?

A

7.1 - 8.2

32
Q

what is the composition of pancreatic secretions?

A

Inorganic constituents: mainly NaHCO3

Organic constituents:
- pancreatic enzymes (amylase, lipase, colipase trypsin & other protein digesting enzymes)
- Trypsin inhibitor

33
Q

what do pancreatic secretions affect?

A

they affect the digestion of CHO, Triglycerides, phospholipids, cholesterol esters & proteins

34
Q

effect of pancreatic secretions on CHO

A

Pancreatic amylase:

  • completely digests starch, glycogen, and dextrin into the disaccharide maltose and few glucose.
  • It acts on cooked and uncooked starch.
35
Q

effect of pancreatic secretions on dietary fat (digestion of triglycerides)

A

Pancreatic lipase and colipase:

  • Pancreatic lipase (the most active lipase) hydrolyzes the 1st and 3rd ester bonds with the production of 2 FFA and Ξ² (2ry) monoglyceride (The major digestion products of TG).
  • Ξ² (2ry) monoglyceride may be converted to Ξ± (1ry) mono-glyceride by isomerase (slow ineffective process)
36
Q

effect of pancreatic secretions on digestion of fat (phospholipids)

A

Phospholipase A2:

  • It is activated by trypsin & requires bile salts and Ca++ for activity.
  • It hydrolyzes glycero-phospholipids by removing FA in position 2 (ꞡ) to form lyso-phospholipids.
37
Q

effect of pancreatic secretions on fat (digestion of cholesterol esters)

A

Pancreatic cholesterol esterase (cholesterol ester hydrolase):
- It hydrolyzes cholesterol ester into FA and free cholesterol.
- It requires bile salts for its activity

38
Q

pancreatic secretions affecting on protein digestion

A
39
Q

what is the PH of intestinal secretions?

A

7 - 8

40
Q

what are the contents of intestinal secretions?

A

Alkaline fluid containing Na+, K+, CL-, HCO3, Mucus and Enzymes

41
Q

what are the effects of intestinal secretions?

A

affects CHO, fat & proteins

42
Q

effect of intestinal secretions on CHO

A

Maltase, lactase and sucrase hydrolyze the corresponding disaccharides to produce glucose, fructose, and galactose.

43
Q

effect of intestinal secretions on fat

A

Intestinal lipase: Act within intestinal mucosal cells where it hydrolyze the absorbed primary monoglyceride forming glycerol and FFA.

Intestinal phospholipase: complete the hydrolysis of lysophospholipids to glycerol, FA, phosphoric acid and nitrogenous base.

44
Q

effect of intestinal secretions on protein

A

Y2B1 - GIT πŸ“• (9 decks)

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