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PCS 2 > Digestion & absorption > Flashcards

Digestion & absorption Flashcards

1
Q

What is the effect of secretin, CCK and GIP?

A

They inhibit secretion of gastrin from G cells and HCl from parietal cells

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2
Q

What is the proton pump?

A

H+/K+ ATPase

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3
Q

Which phase has most effect in control of gastric secretion?

A

Gastric (roughly 60%)

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4
Q

Which phase has most effect in control of pancreatic exocrine secretion?

A

Intestinal phase (>70%)

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5
Q

What secretes CCK?

A

I cells

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6
Q

What is a zymogen?

A

An inactive substance which is converted into an enzyme when activated by another enzyme

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7
Q

Function of trypsin, chymotrypsin and elastase

A

Cleave internal peptide bonds

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8
Q

Function of carboxypeptidase

A

Attacks peptides at C-terminal end

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9
Q

Function of Amylase

A

Digests starch to maltose and oligosaccharides

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10
Q

Function of lipase

A

Cleaves glycerides liberating fatty acids and glycerol

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11
Q

Function of phospholipase A2

A

Cleaves fatty acids from phospholipids

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12
Q

Function of cholesterol esterase

A

Releases esterified cholesterol

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13
Q

Function of RNAase and DNAase

A

Cleaves RNA/ DNA into short fragments

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14
Q

What is achlorhydria?

A

Absence of hydrochloric acid in the gastric secretions

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15
Q

What are endocrine glands?

A

Glands which secrete hormones or other products directly into the blood

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16
Q

What are exocrine glands?

A

Glands which secrete their products through ducts opening on to an epithelium rather than directly into the blood

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17
Q

Affect of cystic fibrosis on pancreas

A

Loss of apical cAMP-activated Cl- channels on duct cells
Causes a reduced secretion of HCO3- and H2O
Protein-rich primary secretion thickens, leading to blockage of ducts

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18
Q

Which monosaccharides does the disaccharide lactose contain?

A

Glucose

Galactose

19
Q

Which monosaccharides does the disaccharide maltose contain?

A

Glucose

Glucose

20
Q

Which monosaccharides does the disaccharide sucrose contain?

A

Glucose

Fructose

21
Q 
Glucose 
Galactose 
Fructose 
Sucrose
Maltose 
Lactose 
Maltotriose 
Which are monosaccharides, disaccharides and trisaccharides?
A

Monosaccharides - Glucose Galactose Fructose
Disaccharides - Sucrose Maltose Lactose
Trisaccharides - Maltotriose

22
Q

What is the main site of carbohydrate, protein and lipid absorption?

A

Duodenum

23
Q

What is the main site of cobalamin (vit B12) absorption?

A

Ileum

24
Q

What is the main site of bile acid absorption?

A

Ileum

25
Q

How does lactulose function?

A

It is unable to be digested so remains in lumen of intestine
It’s osmotic effect pulls fluid out of tissues into lumen
Relieving constipation

26
Q

Explain how glucose is produced by starch digestion

A

Salivary/ pancreatic a-amylase secreted in active form cleaves a-1,4-glycosidic bonds to release maltose & maltotriose
Which are then converted to glucose by enzymes on the brush border of enterocytes (cell of the intestinal lining)

27
Q

Is glucose a product of starch digestion by a-amylse?

A

No - maltose & maltotriose are the products

28
Q

What is the form of active transport where a transporter protein couples the movement of an ion (typically Na+/ H+) down its electrochemical gradient to the uphill movement of another molecule/ ion against a concentration/ electrochemical gradient?

A

Secondary active transport

29
Q

What are cotransporters? e.g. SGLT1

A

The transport proteins responsible for secondary active transport

30
Q

In high glucose/ galactose concentrations how can they pass the apical membrane of enterocytes?

A

SGLT1 (sodium glucose transport protein)

GLUT 2

31
Q

In low glucose/ galactose concentrations how can they pass the apical membrane of enterocytes?

A

SGLT1 (sodium glucose transport protein)

32
Q

How can fructose pass the apical membrane of enterocytes?

A 
GLUT 5 (selective for fructose)
GLUT2 carriers if present
33
Q

How can fructose/ glucose/ galactose pass the basolateral membrane of enterocytes?

A

GLUT 2

34
Q

What maintains the high Na+ conc in intestinal lumen compared with inside enterocytes essential for glucose/ galactose transport across apical membrane?

A

Na+/K+-ATPase on basolateral membrane
Pumps:
Na+ into extracellular space between enterocyte and capillary
K+ into enterocyte

35
Q

What is the difference between glucose/ galactose transport out of intestine compared with fructose?

A

Glucose/ galactose - Na dependent secondary active transport when low conc of sugar in lumen
Fructose - Na independent facilitated diffusion

36
Q

Name the enzymes involved in protein digestion

A

Gastric pepsinogen
Pancreatic trypsinogen
Secreted as zymogens (inactive forms)

37
Q

Where other than enterocytes can protein be taken up?

A

M (microfold) cells that line lymphoid Peyer’s patches

Where protein is packaged into vesicles

38
Q

What is the main cause of gall bladder contraction/ emptying?

A

CCK

39
Q

vvv

A

lipids emulsified by bile salts so they are more accessible to digestion by pancreatic lipase
pancreas secretes colipase, cholesterol esterase and phopholipase A2 as zymogens activated by trypsin in duodenal lumen
pancreatic lipase alos secreted but in its active form, it hydrolyses ester linkages of 1 and 3 positions = each triglyceride is broken down into 2 fatty acids and one monoglyceride (no free glycerol)
lipase binds with colipase to form a lipase-colipase complex to prevent lipase inhibition by bile salts/ phospholipids/ proteins

40
Q

Functions of cholesterol

A

Essential component of plasma membrane
Synthesis of bile acids
Synthesis of steroid hormones
Synthesis of vitamin D

41
Q

Where is the main site of fat absorption?

A

Jejunum

42
Q

Do fat-soluble vitamins (KADE) use same pathway as fat absorption?

A

Yes

43
Q

How are water-soluble vitamins (BC) absorbed?

A

Diffusion/ carrier mediated transport

44
Q

What activates trypsinogen?

A

Enteropeptidase

PCS 2 (8 decks)

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