Digestive system

Question 1

What is digestion?

Answer 1

Large insoluble molecules hydrolyzed into smaller soluble molecules that can be absorbed across cell membranes

Question 2

Enzymes involved in carbohydrate digestion

Answer 2

• Amylase: Produced in pancreas + salivary glands hydrolyzes polysaccharides to disaccharides by hydrolyzing glycosidic bonds
• Membrane-bound disaccharidase: In the duodenum + ileum will hydrolyze disaccharides to monosaccharides

Question 3

Path of carbohydrate digestion

Answer 3

Mouth-Duodenum-Ileum

Question 4

Enzymes involved in protein digestion

Answer 4

• Endopeptidase: Hydrolyzes peptide bonds between amino acids in the middle of a polymer chain
• Exopeptidase: Hydrolyzes peptide bonds between amino acids at the end of a polymer chain
• Membrane-bound dipeptidase: Hydrolyzes peptide bonds between 2 amino acids

Question 5

Path of protein digestion

Answer 5

Stomach-Duodenum-Ileum

Question 6

Explain absorption of glucose/protein in the ileum

Answer 6

CO-TRANSPORT:
- Na+ are AT out of epithelial cell-blood = reduced Na+ concentration in epithelial cell
- Na+ can diffuse from ileum to epithelial via facilitated diffusion down a concentration gradient through co-transporter protein
- Na+ attaches to protein + glucose/amino attaches = Na+ releases then glucose/amino releases into epithelial cell
- High concentration of glucose/amino in epithelial = facilitated diffusion down the concentration gradient to blood

Question 7

Enzymes involved in lipid digestion

Answer 7

• Lipase: produced in the pancreas hydrolyzes ester bonds in triglycerides = monoglycerides + fatty acids
• Bile salts: Produced in liver emulsify lipids = micelles

Question 8

Describe physical digestion of lipids

Answer 8

• Lipids are coated in bile salts = emulsion
• Small droplets of lipid = micelles = larger SA = more enzymes can attach = more enzyme-substrate complexes = faster hydrolysis by lipase

Question 9

What is a micelle?

Answer 9

• Water-soluble vesicles formed by fatty acid + monoglyceride + bile salt
• Deliver monoglyceride + fatty acid to the epithelium of ileum

Question 10

Describe chemical digestion of lipids

Answer 10

• Lipase hydrolyzes ester bonds lipids into monoglyceride + fatty acid

Question 11

Ileum adaptation to large SA:V

Answer 11

Ileum walls are covered in villi and the epithelium has smaller microvilli

Question 12

Ileum adaptation to short diffusion distance

Answer 12

Thin walls + walls have network of capillaries

Question 13

Ileum adaptation to steep concentration gradient

Answer 13

Walls of villi have a capillary network

Question 14

Explain absorption of lipids in the ileum

Answer 14

• Micelle come in contact with epithelial cell of ileum
• Micelle breakdown into monoglyceride + fatty acid
• Non-polar = diffuse across into epithelial cell
• Transport to ER and recombine = triglyceride
• Transport to Golgi apparatus = add cholesterol + protein = chylomicrons
• Move out epithelial cells via exocytosis into lymphatic system which transports into blood system
• Triglyceride in chylomicron hydrolyzed by enzyme in epithelial call of blood vessel