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Medicine phase 1 exams > GI Digestion and absorbtion. > Flashcards

GI Digestion and absorbtion. Flashcards

1
Q

What confirmation of amino acids are found in proteins in the human body?

A

L

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2
Q

What are the two phases of protein digestion?

A

Gastric and Intestinal.

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3
Q

Which enzymes causes the breakdown of proteins in the stomach and how?

A

Pepsin which causes the breakdown of proteins into smaller peptides by breaking the collagen links.

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4
Q

What are the precursors to pepsin and where are they produced?

A

Pepsinogen I= In HCl secreating regions of the stomach only.

Pepsinogen II= Only in the pyloric region.

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5
Q

What occurs in the intestinal phase of protein digestion.

A

Pancreatic juices and intestinal juices mix and completely break down peptides to amino acids.

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6
Q

What protease enzyme is found in the pancreatic juices?

A

Chymotrypsinogen and trypsinogen (inactive form)

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7
Q

What causes the activation of the pancreatic proteases in the small intestine?

A

Enteropeptidase activates tripsinogen to trypsin and trypsin activaes chymotrypsinogen to chymotrypsin.

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8
Q

What does the digestion in the intestinal lumen produce?

A

Oligopeptides.

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9
Q

What is the first stage of protein absorption?

A

Olgiopeptides are further broken down by membrane amino-oligopeptidase enzymes.To single, di or tri peptides.

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10
Q

What is the second stage of protein absorption?

A

Transport of single di/tri peptides to cytoplasmic space via transport pumps. Amino acids enter via a sodium pump. Di and Tri enter together by a transport protien.

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11
Q

What is the third stage of protein absorption?

A

Cytoplasmic digestion to amino acids via di and tri peptidases.

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12
Q

What is the final stage of protein absorption?

A

Passive diffusion out of the cell into local capillaries.

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13
Q

What are the two forms of carbohydrates?

A

Free sugars which cause a rapid shift in blood glucose as are quickly absorbed.
Slow digesting.

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14
Q

What is the first stage of carbohydrate digestion?

A

Alpha amylase in the saliva starts digestion.

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15
Q

How does alpha amylase work?

A

It hydrolyses alpha amylase bonds in large polysaccharides to make glucose and maltose.

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16
Q

Where does alpha amylase function?

A

From the mouth to the stomach where it is deactivated by low pH.

17
Q

What is the second stage of carbohydrate digestion?

A

Pancreatic amylase continues digestion to maltose, maltriose and larger polysaccharides.

18
Q

What is the final stage of carbohydrate breakdown?

A

Microvilli in small intestine have oligosacharidases e.g. maltase, lactase, sucrase and dextrinase.

19
Q

What are the oligosaccharidases in the SI?

A

Maltase, lactase, sucrase and dextrinase.

20
Q

What causes lactose intolerance?

A

Amount of lactase produced decreases with age. If lactose is not broken down it continues to the colon causing more water to be excreted .

21
Q

How are hexoses and pentoses absorbed?

A

Passes easily across intestinal mucosa to the portal vein.

22
Q

How is glucose absorbed?

A

Via na+/glucose co-transporter into cells. THen via GLUT2 pump into the blood.

23
Q

How is galatose absorbed?

A

It follows glucose.

24
Q

How is fructose absorbed?

A

An independent fructose carrier.

25
Q

How and where are dietary lipids digested?

A

In the duodenum by pancreatic lipase.

26
Q

What is the first stage of lipid absorption?

A

FA’s + bile salts= Micelles, soluablalise FA’s to allow them to diffuse into the cell.

27
Q

What is the second stage of lipid absorption?

A

Once in the cell the micelles are esterified to chylomicrons to maintain concentration gradient.

28
Q

What is the third stage of lipid absorption?

A

Chlyomicrons exit the basolateral membrane by exocytosis and are absorbed into the lymph.

29
Q

What is an amino acid zwitterion?

A

An amino acid with no overall charge but +ve and -ve regions.

30
Q

What do chylomicrons do?

A

They carry lipids from the gut to either muscles to the used or adipose tissue to be stored.

31
Q

What enzyme breaks down starch?

A

Alpha amylase.

Medicine phase 1 exams (15 decks)

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