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Nutrition Biochemisty > Digestion and Absorption > Flashcards

Digestion and Absorption Flashcards

1
Q

What are the four basic types of tissue layers surrounding the lumen of the GI tract?

A
  1. Mucosa
  2. Submucosa
  3. Muscular Externa
  4. Serosa or Adventitia
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2
Q

What 4 areas make up the large intestine?

A
  1. Cecum
  2. Colon
  3. Rectum
  4. Anal Canal
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3
Q

What is neutral pH?

A

7.0

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4
Q

What is an exocrine gland?

A

a functional unit of cells that together secrete substances into a ductal system to an epithelial surface.

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5
Q

What is an endocrine gland?

A

a functional unit of cells that work together to secrete products directly into the blood stream (circulatory system).

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6
Q

What are the three parts of the mucosal layer of the GI tract?

A
  1. Epithelium (directly contacts food particles).
  2. Lamina propria (connective tissue layer that contains small blood and lymphatic vessels, nerve fibers and exocrine and endocrine glands).
  3. Muscular mucosal (smooth muscle layer).
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7
Q

What is the pH of a basic solution?

A

greater than 7.0 (also known as alkaline).

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8
Q

What is acidosis?

A

a condition in which the pH of the blood is significantly lower than 7.4.

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9
Q

What is alkalosis?

A

a condition in which the pH of the blood is significantly higher than 7.4.

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10
Q

What is the pH of the stomach?

A

1-3

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11
Q

Salivary Gland:

  1. Secretes what enzyme?
  2. What is the substrate for the enzyme?
A
  1. Salivary alpha-amylase

2. Startch

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12
Q

Stomach

  1. Secretes what 2 enzymes?
  2. What are the substrates for the enzyme?
A
  1. Pepsins (pepsinogens) and Gastric Lipase

2. Proteins and TAGs

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13
Q

Pancreas: what are the enzymes secreted by the pancreas that work on proteins and what products?

A

Trypsin, Chymotrypsin, Elastase, Carboxypeptidase A, Carboxypeptidase B.
Products: peptides and amino acids.

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14
Q

Pancreas: what are the enzymes secreted by the pancreas that work on carbohydrate?

A

Pancreatic alpha-amylase digests starch, products are limit dextrins, maltose, maltitriose.

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15
Q

Pancreas: what are the enzymes secreted by the pancreas that work on TAGs?

A

Pancreatic lipase related protein, Carboxyl ester lipase. Products are monoacylglycerols and fatty acids.

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16
Q

Small Intestinal Mucosa: what are the enzymes bound to the small intestinal mucosa that digest CHO, and what are the specific substrates?

A
  1. Maltase-glucoamylase: substrate is products of starch digestion, product is glucose.
  2. Lactase-phlorizin hydrolase: substrate is lactose and monoglycosylceramides, products are galactose, glucose and ceramides.
  3. Sucrase-isomaltase: substrate is products of starch digestion, sucrose, maltose, products are glucose and fructose.
  4. Trehalase: substrate is Trehalose, product is glucose.
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17
Q

Small Intestinal Mucosa: what are the enzymes bound to the small intestinal mucosa that digest peptides, and what are the specific substrates and products?

A
  1. Aminopeptidases: substrate is peptides, products are amino acids.
  2. Carboxypeptidase: substrate is dipeptides, products are amino acids.
18
Q

Small Intestinal Mucosa: what are the enzymes bound to the small intestinal mucosa that digest nucleotides, and what are the specific substrates and products?

A

Alkaline phosphatase/nucleotide phosphatase: substrate is nucleotides and products are nucleosides, inorganic phosphate.

19
Q

Small Intestinal Mucosa: what are the enzymes bound to the small intestinal mucosa that digest nucleosides, and what are the specific substrates and products?

A

Nucleosidase, substrate is nucleosides and products are nitrogenous bases, ribose, deoxyribose.

20
Q

What is the purpose of bile?

A

Bile contains bile acids that facilitate the digestion and absorption of lipids.

21
Q

What are the primary bile acids?

A

Cholic acid and chenodeoxycholic acid.

22
Q

What are bile acids synthesized from?

A

cholesterol in the liver.

23
Q

What is the role of the small intestine in digestion and absorption?

A

Most digestion and uptake of nutrients takes place in the small intestine (jejunum and ileum). Except for iron and calcium which are absorbed in the duodenum.

24
Q

What are the functions of saliva?

A
  1. Partial digestion of starch by salivary amylase.
  2. Antibacterial activity (due to the presence of thiocyanate, lactoferrin, and lysozyme).
  3. moistening of the mouth to facilitate speech, chewing and swallowing.
  4. Neutralization of acids (due mainly to presence of Bicarbonate and carbonic anhydrase in the saliva).
  5. moistening and lubricating the bolus of food to facilitate swallowing.
  6. maintaining oroesophageal tissue integrity.
25
Q

Where does digestion by salivary amylase occurring?

A

Though salivary amylase is mixed with food in the mouth, most of the digestion by this enzyme is accomplished in the stomach rather than in the oral cavity.

26
Q

What is the purpose of the stomach?

A
  1. temporarily stores swallowed food and liquid until it is passed to the intestines.
  2. secretes HCl, enzymes (or zymogens, an inactive enzyme precursor), needed for initiating digestion, endocrine hormones that regulate the process of food assimilation, and IF that is essential for Vitamin B12 absorption in the sm. intestine.
  3. mixes up food, liquid and digestive juices and then macerates this mixture into a semiliquid state.
27
Q

What are the 4 main parts of the stomach?

A
  1. Cardia
  2. Fundus
  3. Body
  4. pyloric antrum
28
Q

What is the purpose/action of HCl?

A

Acidifies the gastric contents, which facilitates digestion by:

  1. denaturing food proteins,
  2. activating the pepsinogens secreted by chief cells, and
  3. promoting the activity of the resulting pepsins.
29
Q

What is the role of pancreatic secretions in digestion?

A

The enzymes and zymogens secreted by the pancreas are required for digestion of macromolecules in the lumen on the small intestine.
Pancreatic juice also provides a rich source of bicarbonate to neutralize the HCl in the chyme entering the duodenum from the stomach.

30
Q

What are the enzymes and zymogens in the pancreatic juice?

A
  1. Pancreatic alpha-amylase
  2. lipases (pancreatic lipase and other lipase)
  3. prophospholipase A2
  4. nucleolytic enzymes (ribonuclease and deoxyribonuclease)
  5. proenzymes for proteolytic enzymes (trypsinogens, chymotrypsinogens, proelastases, and procarboxypeptidases).
  6. procolipase (nonenzyme protein).
31
Q

What is the source, substrate and product for Retinyl Ester Hydrolase?

A

Secreted by the pancreas
Substrate is retinyl esters
Products are Retinol and Fatty Acids

32
Q

What is the source, substrate and product for maltase-glucoamylase?

A

Source: the small intestine mucosa.
Substrate: products of starch digestion
Products: Glucose

33
Q

What is the source, substrate and product for Lactase-Phlorizin Hydrolase?

A

Source: the small intestine mucosa.
Substrate: Lactose and Monoglycosylceramides
Products: Galactose and Glucose; Galactose, Glucose and ceramides.

34
Q

What is the source, substrate and product for Sucrase-Isomaltase?

A

Source: the small intestinal mucosa.
Substrate: Products of starch digestion, sucrose, maltose.
Products: Glucose, fructose.

35
Q

What is the source, substrate and product for Trehalase?

A

Source: the small intestinal mucosa.
Substrate: Trehalose
Products: Glucose

36
Q

What is trehalose?

A

A disaccharide (two glucose residues) present in small amounts in bacteria, fungi, plants and invertebrates

37
Q

What are the fermentation products of CHO by anaerobic intestinal bacteria?

A

Gases (Hydrogen, carbon dioxide, methane) and SCFAs.

38
Q

What are the most abundant SCFAs produced in the gut?

A

Acetate, propionate, butyrate. (ration of 3:1:1 in the colon and stool).

39
Q

What are the ways to lower cholesterol via bile acid excretion?

A

bind bile acids in the intestine and promote their excretion via :

  1. the intake of viscous fibers (eg psyllium husk fiber)
  2. bile acid sequestrants (drugs).
40
Q

What are the two main causes of gas?

A
  1. Swallowing air

2. Bacterial fermentation of CHO that reach the large intestine.

Nutrition Biochemisty (7 decks)

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