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BIOC192 2022 > lecture 25 - carbohydrate & protein absorption > Flashcards

lecture 25 - carbohydrate & protein absorption Flashcards

1
Q

What are the adaptions of the small intestine that give it a large surface area for absorption?

A

Villi, microvilli

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2
Q

Are sugars water or lipid soluble?

A

Highly Water soluble

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3
Q

What are the 2 types of transport of sugars across GI epithelial cell membranes?

A

Active transport and facilitative transport

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4
Q

What are the 2 glucose transporters that transport glucose across the intestinal epithelia?

A

SGLT 1 (sodium glucose linked transporter 1), GLUT 2

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5
Q

What type of transport is done by SGLT1?

A

Secondary active transport of glucose across the intestinal epithelia

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6
Q

What type of transport is done by GLUT 2?

A

Facilitative transport (down concentration gradient) of glucose across the intestinal epithelia

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7
Q

Where are SGLT 1 membrane transporters found?

A

On the apical surface (lumen side) of intestinal epithelial cells

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8
Q

Where are GLUT 2 membrane transporters found?

A

On the basolateral membrane of epithelial cells in the intestines

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9
Q

What symport is involved in SGLT 1 transport?

A

Sodium and glucose symport/cotransport

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10
Q

What membrane protein creates a concentration gradient for SGLT 1 symport?

A

Na+/K+ ATPase pumps Na+ out of the epithelial cell to maintain low intracellular [Na+] to ensure a concentration gradient so that Na+ can diffuse through SGLT 1, facilitating glucose transport

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11
Q

What creates the concentration gradient needed for GLUT 2?

A

SGLT 1 transports glucose into the epithelial cell, creating a high concentration that pushed glucose out via GLUT 2 passively.

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12
Q

What is the ratio of Na+ and K+ transported in/out of the cell by Na+/K+ ATPase?

A

For every 3 Na+ transporters out of the ell, 2 K+ are transported into the cell.

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13
Q

How does Na+/K+ ATPase work to actively transport?

A

Hydrolysis of ATP and the subsequent phosphorylation of the transport lead to conformational change that enables the transport of the Na+, followed by the K+.

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14
Q

How is glucose taken up by tissues once in the blood circulation?

A

Taken up by different glucose transporters (GLUT 1,2,3 or 4)

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15
Q

What glucose transporter is used for glucose uptake in the liver, pancreas, kidney and intestinal epithelia?

A

GLUT 2

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16
Q

What glucose transporter is used for glucose uptake in the brain?

A

GLUT 3

17
Q

What glucose transporter is used for glucose uptake in muscle and adipose tissue?

A

GLUT 4

18
Q

What is the ubiquitous (found everywhere) glucose transporter?

A

GLUT 1

19
Q

What is the size of peptides that absorbed in the GI tract?

A

di- and tri-peptides

20
Q

What membrane transporter is used to transport di- and tri - peptides into the epithelium of the small intestine?

A

PepT1 - uses cotransport with H+ ions

21
Q

At what point in protein digestion are di and tri peptides finally converted to amino acids and absorbed?

A

Di- and tri-peptides are digested into individual amino acids by cytoplasmic peptidases in epithelial cells in the small intestine

22
Q

What system is used to transport amino acids from the lumen of the small intestine into the epithelial?

A

Semi-specific Na+-dependent transport system

23
Q

What do Na+-dependent carriers transport

A

Na+ and an amino acid - via cotransport

24
Q

Why are there different types of Na+-dependent amino acid carriers?

A

Carriers are amino acid side chain specific - different for neutral, acidic, basic, etc.

25
Q

In what scenario in newborn mammals are intact proteins absorbed from the GI tract?

A

The uptake of immunoglobulins in colostrum milk to acquire passive immunity

26
Q

What is pancreatitis?

A

Disease that leads to inappropriate activation of zymogens/proenzymes resulting in ‘self-digestion’ of the pancreas

27
Q

What is the cause of peptic or stomach ulcers?

A

The breakdown of mucosa that normally protects against protease action

28
Q

What is the effect of cystic fibrosis on digestion and absorption?

A

Causes thick pancreatic secretions that block the pancreatic duct from secreting digestive enzymes preventing absorption

29
Q

What is the body’s reaction to gluten for those with coeliac disease?

A

Antibodies react with transglutaminase

30
Q

What is the result of coeliac disease on the small intestine?

A

Villi are flattened so that nutrients cannot be properly absorbed

31
Q

What is the first stage in the breakdown of dietary nucleic acid polymers?

A

DNA and RNA are subject to partial acid hydrolysis in the stomach

32
Q

What enzymes hydrolyse phopshodiester bonds in nucleic acid polymers in the small intestine?

A

Endonuclease enzymes

33
Q

What is the role of exonuclease enzymes in dietary nucleic acid polymer digestion?

A

Release individual nucleotides - nucleoside mono phosphates

BIOC192 2022 (37 decks)

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