Digestion and Absorption

Question 1

Digestion can be

Answer 1

mechanical or chemical

Question 2

?: chewing, swallowing, peristaltic mixing and propulsion. continues in small intestine

Answer 2

mechanical digestion

Question 3

?: breaks down macromolecules into smaller molecules by use of enzymes

Answer 3

chemical digestion

Question 4

Mouth:

Answer 4

• mechanical via chewing and swallowing
• chemical of amylose (CHO) in saliva
• intact from of protein and lipids enter, while CHO (polysaccharides) have been degraded (into oligo and disacch)

Question 5

Stomach:

Answer 5

• mechanical: peristalsis
• Chemical digestion of proteins:
  G cells in stomach release gastrin, stimulates gastric acid and IF from parietal cells, as well as pepsinogen and gastric lipase from chief cells (HCL in stomach), this activates pepsinogen to pepsin, turns food into chyme
• Gastric acid denatures pepsin giving pepsin better access to break proteins into polypeptides
• Gastric lipase breaks fat droplets into smaller ones
• No digestion of CHO in stomach because pepsin acts on protein and lipase acts on lipids

Question 6

Small intestine

Answer 6

• mechanical digestion: some segmentation and peristalsis
• MAINLY Chemical
• semi-liquid chyme enters duodenum via pyloric sphincter, stimulates release of pancreatic juice containing pancreatic enzymes and bicarbonate, as well as release of bile
• Digestive hormones: CCK, VIP, Secretin

Question 7

Bile

Answer 7

produced by liver and stored in gallbladder for lipid digestion. IMPORTANT FOR LIPID DIGESTION

Question 8

Fat droplet form in:

Answer 8

stomach (mechanical spraying from pyloric sphincter combined with bile secretion from gallbladder separate fat into smaller droplets

Question 9

Pancreas releases: (upon entering small intestine)

Answer 9

pancreatic juice containing lipase. Bile salts attach to lipid droplets making the smaller (emulsification), so pancreatic lipase then cleaves triglycerides into free fatty acids and monoglycerides

Question 10

Emulsifies fat droplets with lipase then:

Answer 10

move into enterocytes via micelles encasing free fatty acids and monoglycerides where fatty acids relink into triglycerides, combined into chylomicrons and secreted into lymph transporter to liver repackaged into different lipoproteins (HDL, LDL, IDL, VLDL)

Question 11

CHO in small intestine broken down:

Answer 11

glycosidic bonds of oligosaccharides and disaccharides in small intestine broken down by pancreatic amylase and brush border enzyme (maltase, lactase, sucrase) further breaking down to monosaccharide, final into enterocyte

Question 12

Gastrointestinal hormones:

Answer 12

• Stomach: Ghrelin (stimulates hunger), Gastrin (gastric acid, IF, and pepsinogen secretion), enterostatin (increase satiety)
• Small intestine: Secretin (pancreatic juice), CCK (release bile and pancreatic juice), PPYY (satiety), GLP-1 (insulin secretion)
• Large intestin: GLP-1 (insulin secretion)

Question 13

Absorption via:

Answer 13

• Active transport
• Facilitated diffusion
• Passive diffusion

Question 14

?: process of moving ions across cellular membrane against concentration gradient, uses enzymes and energy (ATP)

Answer 14

Active transport (eg: SGLT-1 transport and Na-K-ATPase)

Question 15

?: uses carrier protein to transport faster than passive diffusion

Answer 15

Faciliated diffusion (eg: GLUT-2 and GLUT-5)

Question 16

?: moving ions along a concentration gradient, molecule must be able to pass via phospholipid membrane

Answer 16

Passive Diffusion (gas via alveolar surface, lipid absorption into enterocytes)

Question 17

Stomach absorbs:

Answer 17

Cu, Iodide, Fl, molybdenum, water, alcohol

Question 18

Duodenum absorbs:

Answer 18

Thiamin, riboflavin, niacin, biotin, folate, fat soluble vitamins, Ca, Phos, Mg, Fe, Cu, Selenium

Question 19

Jejunum absorbs:

Answer 19

• lipid absorption starte here
• water and fat soluble vitamins
• Ca, Mg, Fe, Phos, Zn, Chromium, Manganese, molybdenum

Question 20

Peyers patches found where?

Answer 20

Ileum

Question 21

Ileum absorbs:

Answer 21

Vit C, Folate, Vit D, Vit K, Mg, B12 (b12 bound to R protein and will connect to IF)
bile salts and acids absorbed and recycled

Question 22

Colon absorbs:

Answer 22

Vit K, vit B, Na+, Cl, K, H2o

Question 23

Carbohydrate aboorption:

Answer 23

• glucose and galactose absorbed at brush border via active transport (SGLT-1) and facilitated transport (GLUT 2)
• fructose via facilitated diffusion (GLUT 5)
• Glucose through enterocyte, then liver

Question 24

Protein absorption:

Answer 24

• protein into polypeptides via pepsin and gastric acid
• Polypeptides into free amino acids (40%) and oligopeptides (60%)
• oligopeptides into tripeptides and dipeptides, go into enterocyte via PepT1
• Free AA into enterocyte by Na-K-ATPase pump

Question 25

Lipid absorption:

Answer 25

• free fatty acids and monolycerides in micelles repackages in golgi and then into chylomicrons, taken into enterocyte via passive diffusion