Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

GI part 2 > Carb digestion > Flashcards

Carb digestion Flashcards

1
Q

Carbohydrate classification

A

Monosaccharides-Monomers
Oligosaccharides-Short polymers
Polysaccharides-Long polymers

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Polysaccharides- 2 classifications and some examples

A

Non-digestible polysaccharides
(Fiber, Pectin and cellulose)

Digestible polysaccharides

  • Starch (45-60% of dietary carbohydrates in western society, Primarily from plants)
  • Glycogen (Primarily from animals)
  • Amylose (Straight polymer)
  • Amylopectin (Branched polymer)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Dietary Oligosaccharides

A

sucrose, lactose

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Dietary monosaccharides

A

glucose, fructose

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What can the intestine absorb in terms of carbs?

A

Intestine can only absorb monosaccharides

Therefore, all carbohydrates must by digested to monosaccharides

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Digestive Process

A
  1. Intraluminal hydrolysis

2. Membrane digestion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Intraluminal Hydrolysis

A 
Enzymatic digestion within the lumen
a-Amylases
Secreted in the enzymatically active form
Salivary amylase
Initiates starch digestion
Inactivated by gastric acid
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

pancreatic alpha amylase

A

Completes starch digestion in lumen of small intestine
Secretion stimulated by Cholecystokinin (CCK)
Cannot digest all linkages and the resultant products are oligosaccharides
Cannot digest terminal linkages and branch points

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Membrane digestion

A

Occurs through the action of brush border oligosaccharidases

Mostly in proximal jejunum, none in large intestine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Integral membrane proteins

A

Lactase
Digests lactose into glucose and galactose
Expression decreases after weaning in the infant
Glucoamylase (Maltase)
Sucrase-isomaltase (Two enzymes, Cleaves sucrose and splits branch points)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Lactase Deficiency or Lactose Intolerance

A

Lactase downregulation determined hereditarily (Occurs after weaning)

Symptoms include:
cramps
diarrhea
flatus

(osmotic diarrhea, hydrogen gas)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Lactase deficiency symptoms are determined by…

A

Rate of peristalsis and gastric emptying
Colonic bacteria (Metabolize undigested lactose into:
- Short chain fatty acids: Induce osmotic diarrhea
- CO2: Contributes to flatulence
- H2: Released in breathe (Hydrogen breath test, Similar to glucose tolerance test)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Three monosaccharides are readily absorbed by small intestine:

A

Glucose
Galactose
Fructose

synthetic sugar: lactulose not digested–> diarrhea

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

2 apical membrane transporters

A 
SGLT 1 (na/ glucose transporter)
GLUT 5
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Na/glucose transporter (SGLT1)

A

Responsible for glucose and galactose uptake
Secondary Active transcellular
Driven by intracellular [Na+] via Na,K-ATPase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

GLUT5

A

Responsible for fructose uptake
In jejunum
Facilitated diffusion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

basolateral membrane transport

A

GLUT2
Responsible for the transport of all three monosaccharides into interstitium
At basolateral membrane
Facilitated diffusion

18
Q

Glucose-Galactose Malabsorption

A

Single aa substitutions in SGLT1
Inhibits uptake of glucose and galactose via SGLT1
Results in diarrhea
Consequence of reduced Na+ absorption via SGLT1
Subsequent osmotic diarrhea
Treatment
Eliminate glucose, galactose and lactose from diet

19
Q

Protein Digestion (brief overview)

A

Proteins must first be digested into oligopeptides and amino acids to be absorbed

20
Q

Four pathways of protein digestion

A

Luminal proteases
brush border proteases
luminal proteases- 2 types

21
Q

Protein digestion Path 1: Luminal proteases

A

Secreted by stomach and pancreas

Hydrolyze into peptides and amino acids

22
Q

Protein digestion Path 2: Brush Border proteases

A

Hydrolyze peptides to amino acids

23
Q

Protein digestion Path 3: Luminal proteases

A

Hydrolyze peptide into oligopeptides
Oligopeptides taken up by enterocyte
Hydrolyzed intracellularly to amino acids

24
Q

Protein digestion Path 4: Luminal proteases

A

oligopeptides
Oligopeptides taken up by enterocyte
Oligopeptides moved directly to interstitium

25
Q

Proteins: endogenous

A

enzymes, hormones, secretions
sloughed cells
About 50% of protein entering small intestine

26
Q

Proteins: digestion

A

Endopeptidase

  • Affinity for bonds adjacent to specific amino acids (sequences)
  • Products are oligopeptides (cutting in the middle)

Exopeptidase

  • Hydrolyze bonds adjacent to amino or carboxy terminus
  • Releases single amino acids (cutting from the end)
27
Q

Gastric proteases

A 
Secreted as proenzymes
Pepsinogen
- Secreted by chief cells
- pH-dependent activation at 1.8-3.5 to
                   - Pepsin (irreversible, inactivated at pH7, endopeptidase)
28
Q

Pancreatic proteases: Trypsinogen

A

Trypsinogen

– Activated by jejunal brush border enzyme to Trypsin (Autoactivates trypsinogen and other pancreatic proteases)

29
Q

Pancreatic proteases: Chymotrypsinogen

A

Activated by trypsin to
Chymotrypsin
Endopeptidase

30
Q

Pancreatic proteases: Proelastase

A

Activated by trypsin to
Elastase
Endopeptidase

31
Q

Pancreatic proteases: Procarboxypeptidase A and B

A

Activated by trypsin to
Carboxypeptidase A and B
Exopeptidase

32
Q

Brush Border peptidases

A

Small intestine
Large numbers of them because each peptidase recognizes only some peptide bonds
Larger oligopeptides

33
Q

Cytoplasmic peptidases

A

Smaller dipeptides and tripeptides

Less numerous

34
Q

PepT1 Transporter transports what?

A

Oligopeptides

35
Q

Protein Absorption: Whole protein absorption

A

In neonate
First 6 months
Mechanism of passive immunity from mother to child
Closure hormonally mediated
Corticosteroid administration induces closure

36
Q

Whole protein absorption in adults

A

Finite amounts of whole protein absorbed
Mechanism not well defined
Enterocytes:
- Whole protein endocytosed is degraded in lysosome
- Small amount transferred to interstitium

M cells:
- Found in Peyers patches (lymphoid tissue in lamina propria)
- Specialized for protein uptake
limited lysosomes
- Package proteins as antigens in clathrin coated vesicles
- Present to immunocompotent cells at basolateral membrane (Processed and transferred to lymphocytes, Important for mucosal immunity)

37
Q

Oligopeptide absorption

A
  • Greater than 90% of absorbed protein enters blood as single aa
  • Some enter the enterocyte as di-, tri-, or tetrapeptides
  • PepT1- H+/oligopeptide cotransporter
    (Active, driven by a H+ and Na+ gradient)
38
Q

Single AA Absorption: apical membrane

A

Multiple identified,
at least 7 with overlapping affinities apically
Divided into those driven by Na/K pump and Na+ independent
- Na+ dependent neutral aa
- Na+ independent basic aa and cysteine

39
Q

Single AA absorption: basolateral membrane

A

At least 5 present
- Bidirectional
3 for exit (Na+ independent)
2 for entrance (Na+ dependent, For enterocyte nutrition and growth)

40
Q

Hartnup Disease

A

Autosomal recessive hereditary disorder
Defect in apical transport of neutral aa

Symptoms:
- Pellagra
- Cerebellar ataxia
- Psychiatric abnormalities
No treatment because normal oligopeptide absorption
41
Q

Cystinuria

A

Autosomal recessive hereditary disorder
Defect in apical transport of basic aa and cysteine
Symptoms
Kidney stones
No treatment because normal oligopeptide absorption

GI part 2 (16 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions