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Biochem Test 2 > Lecture 22 > Flashcards

Lecture 22 Flashcards

1
Q

Beta-Glycosidase Complex (AKA Lactase):

  1. What kind of enzyme is it?
  2. What is its function?
  3. Products?
  4. Structure?
  5. Highest activity in?
A
  1. Beta-galactosidase
  2. Hydrolyzes Beta-1,4 bonds and Beta bonds in glycolipids
  3. Glucose and Galactose
  4. GPI anchor
  5. Highest activity in jejunum
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2
Q

Define Glycemix Index

A

How well carbohydrates are absorbed in the body

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3
Q

Describe four causes of lactose intolerance

A
  • Lost/lacks lactase at older age (>7)
  • Injury to intestinal mucosal cells
  • Gastroenteritis
  • Excess alcohol consumption
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4
Q

Describe how disaccharides and oligosaccharides are converted to monosaccharides.
Enzymes?
Location?

A 
Glycosidases located on membranes of absorptive cells of the brush border located in the small intestine.
Glycosidases include:
1. Glucoamylase
2. Sucrase-isomaltase
3. Trehalase
4. Lactase-glucosylceramidase
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5
Q

Describe the Following about Lactose Intolerance

  1. Cause
  2. Symptoms
  3. Diagnosis
  4. Treatment
A
  1. Cause: due to lack of lactase in body, bacteria in colon ferment lactose to lactic acid, methane and hydrogen
  2. Symptoms: bloating, flatulence, diarrhea
  3. Diagnosis: hydrogen breath test
  4. Treatment: Decrease consumption of milk products, substitute acidophilus (contains lactase) treated milk for whole milk, take lactase pills
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6
Q

Describe the role and different ways Blood-Brain Barrier functions to limit glucose from enter the brain

A

Role: a separation of the circulating blood from the brain extracellular fluid (BECF) in the central nervous system

Methods:

  1. Tight junctions between endothelial cells
  2. Narrow intercellular space
  3. Lack of pinocytosis
  4. Continuous basement membrane
  5. Glucose transporters in both membranes
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7
Q

Describe trehalase substrate and trehalase deficiency

A

Trehalase cleaves alpha-1,1 bond found in mushrooms, honey, and shrimp.

Trehalase deficiency has symptoms similar to alpha-amanitin poisoning.

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8
Q

Digestion of Carbohydrates begins in the ___ and is completed in the ___

A

Begins in the mouth and is completed in the small intestine

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9
Q

Glucoamylase:

  1. What kind of enzyme is it?
  2. What is its function?
  3. Products?
  4. Structure?
  5. Highest activity in?
A
  1. Exoglucosidase
  2. Specifically cleaves (via hydrolysis) alpha-1,4 glycosidic bond from nonreducing end
  3. Monosaccharides (glucose)
  4. Structure has 2 extracellular domains and 2 catalytic sites. It is also heavily glycosylated to protect from digestion
  5. Found in highest activity in ileum
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10
Q

How are Glucose taken up by different tissues?

A

Glucose is taken up by different tissues by different tissue-specific facilitative transporters (ex. GLUT 1-5)

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11
Q

How are monosaccharides absorbed?

A

Monosaccharides are taken up by the cells of the small intestine via facilitative and Na+- dependent transporter

Facilitative transporters are on the serosal/basal side and absorbed monosaccharides are transported into the capillaries

Na+-dependent facilitated transports are co-transporter that carry glucose against concentration gradient by being coupled with Na+ in symport.

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12
Q

How are Oligosaccharides found in dietary carbohydrates

A

Oligosaccharides are found attached to glycoproteins, lipoproteins, proteoglycans (from bacteria), glycosaminoglycans (found in extracellular conn. tissues and joints)

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13
Q

Name and describe the digestive enzyme present in the mouth

A

Alpha-amylase from saliva
Function: an endoglucosidase that cleaves random alpha-1,4 glycosidic bonds in starch and other complex carbohydrates to make dextrins

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14
Q

Name Five Benefits of Dietary Fiber

A
  1. Normalize bowel movements
  2. Help maintain bowel integrity and health
  3. May lower blood cholesterol levels
  4. Help control blood sugar levels
  5. May aid in weight loss
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15
Q

Name the complex carbohydrates found in dietary carbohydrates

A

Starch and Amylopectin

Glycogen

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16
Q

Name the four examples of Glycosidases located on membranes of absorptive cells of the brush border located in the small intestine.

A

Glycosidases include:

  1. Glucoamylase
  2. Sucrase-isomaltase
  3. Trehalase
  4. Lactase-glucosylceramidase
17
Q 
Name the GLUT trasport protein used by following tissues 
RBCs:
Liver:
Muscle:
Adipose Tissue:
Brain:
Kidney:
A

RBCs: GLUT 1
Liver: GLUT 2
Muscle: GLUT 4
Adipose Tissue: GLUT 4
Brain: GLUT 1 in endothelial cells and GLUT 3 in neural cells
Kidney: uses Na+-dependent transporter to remove glucose from urine

18
Q

Name the three disaccharides found in dietary carbohydrates

A

Lactose
Sucrose
Maltose

19
Q

Name the three monosaccharides found in dietary carbohydrates

A

Fructose
Ribose
Glycerol

20
Q

Name three indigestible fiber found in dietary carbohydrates

Why are they considered indigestible?

A

Cellulose
Hemicellulose
Lignins

Body doesn’t have the correct enzyme to absorb

21
Q

Sucrase-Isomaltase:

  1. What kind of enzyme is it?
  2. What is its function?
  3. Products?
  4. Structure?
  5. Highest activity in?
A
  1. 2 subunits: Sucrase and maltase
  2. Cleaves nearly all of alpha-1,6 bonds by isomaltase-maltase subunit
  3. Monosacharrides (glucose)
  4. Synthesized as single chain that gets cleaved to 2 subunit by intestinal protease hence has 2 catalytic sites: sucrase and maltase
  5. Highest activity in jejunum
22
Q

Trehalase:

  1. What kind of enzyme is it?
  2. What is its function?
  3. Products?
  4. Structure?
  5. Highest activity in?
A
  1. Hydrolase
  2. Cleaves alpha-1,1 bond
  3. Monosaccharides (glucose)
  4. One catalytic site
  5. Active in duodenum
23
Q

What are dextrins?

A

Dextrins are carbohydrates produced by hydrolysis of starch/glycogen or other carbohydrates with random alpha-1,4 and alpha-1,6 glycosidic bonds.

24
Q

What are the three soluble dietary fiber and how are they absorbed?

A
  1. Pectins
  2. Mucilages
  3. Gums
    Digested by colonic bacteria
25
Q

What inhibits alpha-amylase from saliva?

A

stomach acid inhibits alpha-amylase to prevent carbohydrate digestion in stomach

26
Q

What neutralizes stomach acid in intestines and why is this important?

A

Bicarbonate neutralizes stomach acid and it’s important to do so because acid inhibit amylase activity

27
Q

Which Facilitative Glucose Transporter is insulin-sensitive and is present in skeletal and heart muscle and adipose tissue?

A

GLUT 4

Biochem Test 2 (2 decks)

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