GI + Metabolism ( 10% )

Question 1

The following GI peptides are all distributed distal to the gastric antrum except

• Secretin
• CCK
• GIP
• Neurotensin
• Gastrin

Answer 1

Gastrin

• Secretin - Duodenum/jejunum (ileum to a small degree)
• CCK - Duodenum/jejunum (ileum to a small degree)
  
  • ​The above two both release in response to fat/AA in intestine, and act by stimulating pancreatic enzymes/GB, and inhibiting gastric secretions
• GIP - duodenum/jejunum
• Neurotensin

Question 2

Regarding HCl secretion by the parietal cells, which is false

• H is actively pumped out by ATPase
• After a meal the blood pH can rise
• H is exchanged for Cl
• Histamine and gastrin stimulate H secretion
• Parietal cells are rich in carbonic anyhdrase

Answer 2

H is exchanged for K+

• Hydrogen is pumped out in exchange for K+ by H-K-ATPase. Chloride ions are secreted seperately.*
• Hydrogen is derived from the hydration of CO2 (H20 + CO2 -> H2CO3 -> H+ + HCO3). This is catalysed by carbonic anhydrase*
• HCO3 is produced as a byproduct of the H+ formation - this diffuses into the blood stream (alkaline tide) and can later be used to buffer the acid once it is not needed.*
• Stimulants: gastrin, histamine, ACh*
• Inhibitors: VIP, GIP*

Question 3

After complete hepatectomy, a rise would be expected in blood levels of

• Glucose
• Fibrinogen
• 25-hydroxycholecalciferol
• conjugated bilirubin
• oestrogens

Answer 3

oestrogens

All others are created by the liver

Question 4

Gastric emptying occurs

• Via sympathetic mediation
• When pressure increases in the body of the stomach
• Due to stomach contractions lasting up to 30s
• With no regurgitation of contents from the duodenum
• With the passage of mixed solid and liquid gastric contents into the duodenum

Answer 4

With no regurgitation of contents from the duodenum

• Receptive relaxation occurs - the antrum and fundus relax to allow food to enter without an increase in pressure, whilst peristalsis begins mixing food in the lower portion of the stomach. This is vagally mediated.*
• Small, semi-liquid portions enter the duodenum (not solids)*
• Systolic waves last up to 10sec, 3-4/min*
• Osmotic pressure in the duodenum influences gastric emptying - high osmotic pressures -> slower emptying*

Question 5

with respect to GI hormones (2 correct)

• gastrin stimulates insulin secretion after a carbohydrate meal
• secretin stimulates the secretion of gastric acid
• CCK is found in nerves of the distal ileum and colon
• GIP secretion is stimulated by glucose and fat in the duodenum
• VIP increases secretion of pancreatic enzymes and electrolytes

Answer 5

CCK is secreted by I cells in the upper small intestine, and also found in nerves of the distal ileum and colon, and brain.

GIP secretion is stimulated by glucose and fat in the duodenum

• gastrin stimulates glucagon secretion after a carbohydrate meal
• secretin inhibits the secretion of gastric acid
  
  • Stimulates watery pancreatic secretions, with a high bicarb content
  • CCK stimulates pancreatic enzyme release
• VIP increases secretion of intestinal electrolytes and water
  
  • ​VIP is found in nerves in the GI tract, and is thus not a hormone

Question 6

toxins that increase cAMP content of the intestinal mucosa cause diarrhea because they

• increase Cl secretion into the intestinal lumen
• increase Na absorption in the small intestine
• increase K secretion into the colon
• increase Na/K cotransport K secretion into the colon
• none of the above

Answer 6

increase Cl secretion into the intestinal lumen​

• As well as reduced NaCl reabsorbtion*
• This is what occurs in Cholera*

Question 7

Which cells secrete IF

• Chief cells
• G cells
• K cells
• S cells
• Parietal cells

Answer 7

Parietal cells

Parietal cells also produce gastric acid

• Chief cells - pepsinogen
• G cells - gastrin
• K cells - GIP
• S cells - secretin
• I cells - CCK

Question 8

secretin causes

• increased gastric motility
• increased volume of secretions
• an enzyme rich secretion

Answer 8

increased volume of pancreatic secretions

• a bicarb-rich, watery, pancreatic secretion.
  
  • CCK is enzyme rich
• increased gastric motility

Question 9

gastric emptying

• is not related to pH in the duodenum
• duodenal pressure is not important
• normally takes 1-3 hours to empty

Answer 9

normally takes 1-3 hours to empty

Carbs fastest -> proteins -> fats (slowest)

• is related to pH in the duodenum
  
  • Low pH causes reduced emptying
• duodenal pressure is not important

Question 10

the pH of pancreatic secretion is

• 5.0
• 6.0
• 7.0
• 7.5
• 6.5

Answer 10

7.5

Gangongs just states ‘alkaline’

Question 11

Upon stretching intestinal smooth muscle

• It hyperpolarizes
• The tension is due to elastic forces only
• It depolarizes
• Relaxation occurs
• It is an example of a multi-unit smooth muscle

Answer 11

It depolarizes

Multiunit smooth muscle is foud

Question 12

concerning pancreatic secretion

• the pancreas secretes gastrin
• pH is 6.0
• it contains anti-trypsin molecules
• it contains an enzyme converting polysaccharides to monosaccharides

Answer 12

it contains anti-trypsin molecules

• Trypsin is produced as trypsinogen and then converted into trypsin in the intestine, to stop auto-digestion of the pancreas itself. Pancreas also secretes anti-trypsin molecules to help in this regard.*
• pH is 7.5*
• Gastrin is secreted by the gastric antrum (G-cells)*
• Pancreatic amylase converts polysaccharides to disaccharides. Conversion to monosaccharides occurs via intestinal enzymes.*

Question 13

With regard to the parasympathetic nerve supply to the gut, it is

• Essential
• Non-essential
• Modulatory
• Passive

Answer 13

Modulatory

parasympathetic increases activity of intestinal smooth muscle, whilst sympathetic relaxes it whilst causing sphincters to contract

Question 14

Which is true of faeces

• 50mL is produced daily on average.
• it is chiefly formed from protein breakdown products
• solids form 75% of its composition
• the solid portion contains 30% bacteria
• the brown colour is due to melanin

Answer 14

the solid portion contains 30% bacteria

• 200mL is produced daily on average.
• it is chiefly formed from water, bacteria, and inorganic material
• solids form 25% of its composition (Water 75%)
• the brown colour is due to bile salts or bacteria (unsure which)

Question 15

The majority of the water ingested or secreted into the bowel is usually absorbed in the

• Stomach/duodenum
• Jejunum
• Ileum
• Ascending and transverse colon
• Descending and sigmoid colon

Answer 15

Jejunum

Question 16

regarding absorption, which is false

• glucose absorption is an example of secondary active transport
• galactose is absorbed by the same mechanism as glucose
• fructose is absorbed by facilitated diffusion
• insulin regulates glucose absorption in the intestine

Answer 16

insulin regulates glucose absorption in the intestine

Insulin plays little if any role in glucose absorption (same as the PCT). Glucose and galactose are absorbed by SGLT and fructose by GLUT

• glucose + galactose absorption is an example of secondary active transport via SGLT-1 (sodium co-transporter), gradient set-up by Na-K-ATPase
• fructose is absorbed by facilitated diffusion through GLUT

Question 17

The majority of ingested iron is absorbed from the

• Duodenum
• Proximal jejunum
• Distal jejunum
• Proximal ileum
• Distal ileum

Answer 17

Duodenum

Question 18

Ca absorption is increased by

• Hypercalcaemia
• Oxalates in the diet
• 1,25 dihydroxycholecalciferol
• increased Na absorption
• iron overload

Answer 18

1,25 dihydroxycholecalciferol

• Proteins increase absorption*
• Oxalates and phosphates reduce it*

Question 19

With respect to the absorption of vitamins and minerals

• Folate absorption is Na dependent
• All vitamins are absorbed in the upper small intestine
• Vitamin A can still be absorbed in pancreatic insufficiency
• Ca absorption is mostly by passive diffusion along concentration gradients
• Iron is more readily absorbed in the Ferric state

Answer 19

Ca absorption is mostly by passive diffusion along concentration gradients

Taken up across the brush border of epithelial cells via channels

• Folate absorption is Na independent (as is B12)
• All vitamins except B12 (ilium) are absorbed in the upper small intestine
• Vitamin A cannot be absorbed in pancreatic insufficiency
• Iron is more readily absorbed in the ferrous (Fe2+) state

Question 20

Where are Vit A, D and K absorbed

• Stomach
• Proximal small bowel
• Terminal ileum
• Duodenum
• Ascending colon

Answer 20

Proximal small bowel

• All vitamins except B12 (terminal ileum) are absorbed in the proximal small bowel*
• All water-soluble except B12/Folate are via sodium co-transport*

Question 21

iron absorption

• is increased by Vit C
• is constant regardless of need
• occurs in the proximal small bowel
• requires intrinsic factor

Answer 21

occurs in the proximal small bowel

• Primarily duodenum*
• Uptake is dependent on need, and only enough to replace losses*
• Requires vitamin C but levels of it do not see, to change uptake, as this is regulated by three factors:*
• • recent dietary iron intake*
• -state of the bodies iron stores*
• • state of erythropoiesis in the bone marrow*

Question 22

Regarding iron

• It is absorbed in the duodenum
• 70% is present in myoglobin
• a deficiency can cause diabetes
• the amount absorbed ranges between 10-20%
• mobilferin binds less iron in iron deficiency

Answer 22

It is absorbed in the duodenum

• 70% is present in haem
• a deficiency can cause anaemia
• the amount absorbed ranges between 3-6%
• mobilferin binds less iron in iron deficiency - not mentioned in Ganongs

Question 23

Which of the following is a nutritionally essential amino acid

• Glycine
• Cysteine
• Tyrosine
• Tryptophan
• Histidine

Answer 23

Histidine

Question 24

Under basal conditions the percentage of the heart’s caloric needs met by fat is

• 70%
• 60%
• 50%
• 40%
• 30%

Answer 24

60%

Question 25

The following is an essential fatty acid * Linoleic * Palmitic * Stearic * Oleic * Meralonic

Answer 25

Linoleic

Question 26

All of the following statements about lipid transportation are correct except * HDL transport TG and cholesterol * FFA are transported by albumin * LDL provides cholesterol to the tissues. * Chylomicron receptor is recycled by the cell membrane * Apo B100 transports endogenous lipids from the liver

Answer 26

**Apo B100 transports endogenous lipids from the liver** * APO B100 appears to be a component of chylomicrons, LDL, IDL and VLDL, not a transporter itself. I cant find it mentioned in lipid metabolism in Gangongs.* * Nick thought '*Chylomicron receptor is recycled by the cell membrane' *but I dont see this referenced anywhere either.* * Who knows, who cares.*

Question 27

Amino acids are derived from * Creatinine * Neurotransmitters * Deanimation * Ammonia * Transamination

Answer 27

**Transamination**

Question 28

deficiency of β oxidation fatty acids causes * pulmonary hypersecretion * Cardiomyopathy * Cirrhosis * Glomerulonephritis * Asthma

Answer 28

Cardiomyopathy *Occurs in Carnitine deficiency, and can also causes hypoketonemic hypoglycaemia due to glucose depletion due to lack of fatty acids for energy*

Question 29

Protein digestion * Begins in the mouth * The actions of pepsins are terminated by pancreatic juice * HCl activates trypsinogen * Approximately 5% of dietary proteins appears in the stool * Mucin protects desquamated intestinal cells from being digested

Answer 29

**The actions of pepsins are terminated by pancreatic juice** * Protein digestion begins in the stomach, where HCl activates pepsins* * Presumably desquamated cells want to be digested - it is the healthy intact ones the mucous protects* * Cant find it, but I would assume almost all protein is absorbed or digested*

Question 30

All of the following will increase BMR except * Exercise * Hyperthyroidism * Younger age * Anxiety * Dieting

Answer 30

Dieting

Question 31

In carbohydrate metabolism * Breakdown of glucose to lactate is called glycogenolysis * The end products of the citric acid cycle is acetyl CoA and CO2 * Aerobic metabolism produces 36 mol of ATP per mol of glucose metabolized. * 2 mol ATP is produced by the Embden-Meyerhof pathway of glucose metabolism * the amount of ATP produced via the hexose monophophate shunt is dependent on the amount of NADH supplied

Answer 31

**2 mol ATP is produced by the Embden-Meyerhof pathway of glucose metabolism** * Glycogenolysis is breakdown of glycogen to glucose* * End product of citric acid cycle is CO2 and reformation of acetyl-CoA - it also produces 3 NADH and 1 ATP or GTP* * Aerobic metabolism produces 32 mol of ATP per mol of glucose*

Question 32

With regard to fat metabolism * Fatty acids can enter the Embden-Meyerhof pathway * acetate and β hydroxylate are referred to as ketone bodies * brown fat has extensive sympathetic innervation * chylomicrons are converted to LDL by lipoprotein lipase * cholesterol is delivered to the tissues by HDL

Answer 32

**brown fat has extensive sympathetic innervation** * *Only glucose* can enter the Embden-Meyerhof pathway * acetate and β hydroxylate are referred to as ketone bodies * chylomicrons are converted to LDL by lipoprotein lipase * cholesterol is delivered to the tissues by *LDL* * *​HDL delivers cholesterol to the liver*

Question 33

The contents of chylomicrons include * Apoprotein E and apoprotein A * Cholesterol 30%, protein 20%, TG 50% * Lecithin 10%, cholesterol 25%, TG 65% * Protein 2%, cholesterol 5%, TG 90% * The enzyme protein phosphorylase

Answer 33

Protein 2%, cholesterol 5%, TG 90%

Question 34

With respect to protein digestion * It begins in the duodenum. * Pancreatic enzymes are most important * Is largely completed in the small intestine * Commences upon the action of saliva

Answer 34

**Is largely completed in the small intestine** * It begins in the *Stomach* * Pancreatic enzymes are most important * *Carbohydrate digestion* commences upon the action of saliva

Question 35

regarding fat digestion * it begins in the duodenum * co-lipase is required for digestion * bile salts on their own are the most important to emulsify fats

Answer 35

**it begins in the duodenum** *Lipase is required for digestion - colipase helps stabilise lipase only*

Question 36

regarding cholesterol which is false * essential in cell wall synthesis * plants have cholesterol but it is not absorbed by humans * only found in animal cells

Answer 36

**only found in animal cells** *plants have cholesterol but it is not absorbed by humans - this is true*

Question 37

with regard to fat metabolism * micelles are formed in the brush border * co-lipase is required for metabolism * none of the above

Answer 37

**none of the above** * micelles are formed in the *lumen and diffuse down their concentration gradients to the* brush border * co-lipase *speeds up but is not* required for metabolism