Digestion Lab

Question 1

What role does pancreas play in the digestion of carbohydrates, protein and fats?

Answer 1

Carbohydrates- pancrease secretes a-amylase which breaks down a1-4 bonds in carbs
Fats- pancreas secretes lipase and colipase which works with bile acids to digest lipids.
Proteins- pancrease secretes trypsin, chymotrypsin, carboxypeptidase and elastase which breaks down peptide bonds in proteins

Question 2

what is the end product of the action of pancreatic amylase on carbohydrate?

Answer 2

• maltose
• maltotriose
• a-dextrins

Question 3

What happens to the end products of amylase before absorption can occur?

Answer 3

They are disaccharides.
they are further broken down by brush border enzymes like sucrase, maltase, lactase and a-detrinase to monosaccharides (glucose) and then absorbed into the blood stream via GLUT 2 channels

Question 4

What carbs are digested by amylase and why?

Answer 4

cooked potato starch and raw potato starch

they were digested because amylase only breaks down a1-4 glycosidic bonds which these carbs have

Question 5

What carbs are not digested by amylase and why?

Answer 5

Raftilose (made of fructose) and Cellulose

they do not have a1-4 glycosidic bond. they had a1-6 glycosidic bonds or B1-4 glycosidic bonds

Question 6

what happens to carbs not digested by amylase?

Answer 6

digested by brush border enzymes in small intestines

digested through fermentation by colonic bacteria in the large intestine

Question 7

what are the main enzymes involved in protein digestion?

Answer 7

trypsin
chymotrypsin
carboxypeptidase
elastase

Question 8

why are protein enzymes released as zymogens.

Answer 8

to prevent digestion of human tissue

Question 9

what are the final products of protein digestion and how are they absorbed?

Answer 9

Amino acids and peptides absorbed by active transport via 7 Na+ linked carriers.

Question 10

What are the main pancreatic secretions required for fat digestion

Answer 10

Pancreatic Lipase:
acts on water insoluble triglycerides
- releases fatty acids and 2-monoglycerides
- co-lipase inhibits adsorption onto lipid: water interphase which would denature lipase
- lipase has isoelectric pH of 6.8. Therefore, has + charge on proximal small intestine.

Phospholipase:
acts on lipid containing phosphate

Question 11

Outline the process of fat digestion in the gut.

Answer 11

Tongue- Lingual Lipase
Duodenum- CCK causes release of bile salts and pancreatic lipase. PL breaks down insoluble triglycerides into FFA and 2-monoglyerides. FFA and 2-monoglycerides interact with bile salts to form micelles. Micelles release their contents into the cytoplasm.

Monogylcerides and FFA are resynthesises into chylomicron.

Question 12

What are the main causes of acute pancreatitis in the UK

Answer 12

• Gall stones

- Alcohol

Question 13

What are the tests available for pancreatic DAMAGE

Answer 13

– Serum amylase
– Urine amylase
– Serum lipase

Question 14

What are the tests available for pancreatic FUNCTION

Answer 14

– Direct and Indirect (not available in UK) function tests
– Faecal chymotrypsin
– Faecal elastase

Question 15

Describe serum amylase test

Answer 15

normal: <100 U/L
acute pancreatitis:
– Rises within 5-8 hrs of onset of symptoms, normalises
by day 4.
macroamylase- not biologically active so does not cause problems but can count towards patient’s amylase levels- confusing results.

Question 16

What are some other causes of hyperamalysaemia

Answer 16

• Pancreatic disease
• Other intra-abdominal disease
• Ruptured ectopic pregnancy
• Salivary gland lesion
• Renal insufficiency
• DKA
• Tumours
• Drugs
Cystic fibrosis

Question 17

Describe urine amylase test

Answer 17

Normal: 30-600 U/L
Can help exclude macroamylasaemia: ↑serum
amylase, ↓urine amylase.

Question 18

Describe serum lipase test

Answer 18

normal 30-210 U/L
acute pancreatitis:
– Rises within 4-8 hrs of onset of symptoms, peaks at 24
hrs and normalises within 8-14 days.
Higher clinical sensitivity and specificity than
amylase.

Question 19

describe direct pancreatic function tests

Answer 19

• Gold standard: secretin-pancreozymin test
  • Measures pancreatic enzymes i.e. trypsin in duodenum
  aspirate over 2 hrs
  – Lundh test:
  • Measures [bicarb], amylase or trypsin activity following a meal
  • Historical

Question 20

describe faecal chymotrypsin test

Answer 20

Low values indicate pancreatic insufficiency.

Question 21

Describe faecal elastase test

Answer 21

• Useful marker of pancreatic insufficiency (gold standard)
  • < 200 μg/g of stool indicates an exocrine
  insufficiency.
  • May be useful in determining the amount of
  pancreatic enzyme replacement therapy required
  in patients with cystic fibrosis or chronic
  pancreatic insufficiency.
  • ELISA kit
• high levels indicate pancreatic insufficiency