Digestion & absorption

Question 1

What is the effect of secretin, CCK and GIP?

Answer 1

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

Question 2

What is the proton pump?

Answer 2

H+/K+ ATPase

Question 3

Which phase has most effect in control of gastric secretion?

Answer 3

Gastric (roughly 60%)

Question 4

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

Answer 4

Intestinal phase (>70%)

Question 5

What secretes CCK?

Answer 5

I cells

Question 6

What is a zymogen?

Answer 6

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

Question 7

Function of trypsin, chymotrypsin and elastase

Answer 7

Cleave internal peptide bonds

Question 8

Function of carboxypeptidase

Answer 8

Attacks peptides at C-terminal end

Question 9

Function of Amylase

Answer 9

Digests starch to maltose and oligosaccharides

Question 10

Function of lipase

Answer 10

Cleaves glycerides liberating fatty acids and glycerol

Question 11

Function of phospholipase A2

Answer 11

Cleaves fatty acids from phospholipids

Question 12

Function of cholesterol esterase

Answer 12

Releases esterified cholesterol

Question 13

Function of RNAase and DNAase

Answer 13

Cleaves RNA/ DNA into short fragments

Question 14

What is achlorhydria?

Answer 14

Absence of hydrochloric acid in the gastric secretions

Question 15

What are endocrine glands?

Answer 15

Glands which secrete hormones or other products directly into the blood

Question 16

What are exocrine glands?

Answer 16

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

Question 17

Affect of cystic fibrosis on pancreas

Answer 17

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

Question 18

Which monosaccharides does the disaccharide lactose contain?

Answer 18

Glucose

Galactose

Question 19

Which monosaccharides does the disaccharide maltose contain?

Answer 19

Glucose

Glucose

Question 20

Which monosaccharides does the disaccharide sucrose contain?

Answer 20

Glucose

Fructose

Question 21

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

Answer 21

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

Question 22

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

Answer 22

Duodenum

Question 23

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

Answer 23

Ileum

Question 24

What is the main site of bile acid absorption?

Answer 24

Ileum

Question 25

How does lactulose function?

Answer 25

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

Question 26

Explain how glucose is produced by starch digestion

Answer 26

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)

Question 27

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

Answer 27

No - maltose & maltotriose are the products

Question 28

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?

Answer 28

Secondary active transport

Question 29

What are cotransporters? e.g. SGLT1

Answer 29

The transport proteins responsible for secondary active transport

Question 30

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

Answer 30

SGLT1 (sodium glucose transport protein) | GLUT 2

Question 31

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

Answer 31

SGLT1 (sodium glucose transport protein)

Question 32

How can fructose pass the apical membrane of enterocytes?

Answer 32

``` GLUT 5 (selective for fructose) GLUT2 carriers if present ```

Question 33

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

Answer 33

GLUT 2

Question 34

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

Answer 34

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

Question 35

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

Answer 35

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

Question 36

Name the enzymes involved in protein digestion

Answer 36

Gastric pepsinogen Pancreatic trypsinogen Secreted as zymogens (inactive forms)

Question 37

Where other than enterocytes can protein be taken up?

Answer 37

M (microfold) cells that line lymphoid Peyer's patches | Where protein is packaged into vesicles

Question 38

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

Answer 38

CCK

Question 39

vvv

Answer 39

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

Question 40

Functions of cholesterol

Answer 40

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

Question 41

Where is the main site of fat absorption?

Answer 41

Jejunum

Question 42

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

Answer 42

Yes

Question 43

How are water-soluble vitamins (BC) absorbed?

Answer 43

Diffusion/ carrier mediated transport

Question 44

What activates trypsinogen?

Answer 44

Enteropeptidase