Human A&PBIO 304 · American River College ← Week 07 pre-work

BIO 304 · Week 07 · Interactive Workbook

Digestion & Absorption

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Part 1 of 4 · Recall

Fill in the blanks

Type the term that completes each statement, using the word bank. Pull it from memory first.

Word bank

Diffuse into enterocyteIronMicellesChylomicronStarch (mouth)Vitamin B12Absorbable unitCCKK+Brush border enzymesPancreatic nucleasesWater-soluble vitaminsFructoseSmall intestineAmino acids

  1. salivary amylase begins breakdown
  2. maltase, sucrase, lactase → monosaccharides (glucose, fructose, galactose)
  3. pancreatic trypsin, chymotrypsin, carboxypeptidase → small peptides + amino acids
  4. amino acids (some di- and tri-peptides absorbed too)
  5. bile salt-coated droplets that ferry products to brush border
  6. cleave DNA/RNA to nucleotides
  7. facilitated diffusion (GLUT5)
  8. multiple carriers; Na+-dependent and independent
  9. monoglycerides + free fatty acids from micelle
  10. TG + cholesterol + phospholipid + protein shell
  11. absorbed in small intestine with their cofactor systems
  12. binds intrinsic factor (from stomach parietal cells); absorbed in terminal ileum
  13. mostly absorbed in small intestine
  14. duodenum (heme & non-heme paths)
  15. duodenum response to fat & protein; signals gallbladder + pancreas

Define it: high-yield vocabulary

Write a clear definition in your own words for each term.

  1. Mechanical digestion
  2. Chemical digestion
  3. Brush border enzymes
  4. Amylase
  5. Protease (pepsin)
  6. Lipase
  7. Micelle
  8. Chylomicron
  9. Enterocyte
  10. Gastrin
  11. Secretin
  12. Cholecystokinin (CCK)

Part 2 of 4 · Anatomy lab

Draw and label

Box A. Intestinal villus close-up

Directions

  1. Draw a single intestinal villus: a finger-like projection into the lumen.
  2. Label the lumen at the top.
  3. Show the villus surface lined by absorptive epithelial cells (enterocytes), each with microvilli (brush border) facing the lumen. Label both.
  4. Inside the villus, draw a network of blood capillaries (label) and one central lac#0B1530 (a lymphatic capillary running up the center). Label.
  5. Add a goblet cell (mucus-secreting) in the epithelium. Label.
  6. Note the principle: water-soluble nutrients (amino acids, monosaccharides) enter the blood capillaries; fat-soluble nutrients (chylomicrons, fatty acids in lipid form) enter the lac#0B1530s and travel via lymph.
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Box B. Macronutrient digestion pathways

Directions

  1. Draw three parallel pathways: Carbohydrates, Proteins, Fats. Each pathway shows where digestion begins, where it continues, and what the final absorbed product is.
  2. Carbohydrates: starch (mouth, salivary amylase begins) > starch (stomach, no digestion) > maltose (small intestine, pancreatic amylase) > glucose (small intestine, brush-border enzymes like maltase). Absorbed: monosaccharides into blood.
  3. Proteins: protein (mouth, no digestion) > peptides (stomach, pepsin) > shorter peptides (small intestine, pancreatic proteases) > amino acids (small intestine, brush-border peptidases). Absorbed: amino acids into blood.
  4. Fats: triglycerides (mouth, no digestion) > triglycerides (stomach, minor lingual lipase) > emulsified fat droplets (small intestine, bile salts from gallbladder) > monoglycerides + fatty acids (small intestine, pancreatic lipase). Absorbed: re-formed triglycerides as chylomicrons into lac#0B1530.
  5. Label each enzyme, its source (which organ), and the products at each step.
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Structures to label

Label each on your drawing.

  1. Villus
  2. Microvilli (brush border)
  3. Enterocyte
  4. Goblet cell
  5. Lumen
  6. Blood capillary
  7. Lac#0B1530
  8. Salivary amylase
  9. Pepsin
  10. Pancreatic amylase
  11. Pancreatic protease (trypsin)
  12. Pancreatic lipase
  13. Brush-border enzymes
  14. Bile salts
  15. Glucose
  16. Amino acid
  17. Fatty acid + monoglyceride
  18. Chylomicron

Part 3 of 4 · Physiology lab

Reason it through

A. Enzyme, source, substrate, product

Lactose intolerance is caused by deficiency of the brush-border enzyme lactase. Predict the patient's symptoms after consuming dairy, and explain why undigested lactose causes osmotic diarrhea and bacterial gas production.
Bile salts are NOT enzymes, yet they are essential for fat digestion. Explain mechanistically how bile salts contribute to fat digestion without breaking any chemical bonds themselves (think: emulsification).

B. Synthesis

1. Celiac disease is an autoimmune reaction to gluten that damages and flattens intestinal villi. Predict the consequences for nutrient absorption and the patient's symptoms (weight loss, anemia, fatigue, diarrhea).
2. A patient has their gallbladder removed (cholecystectomy). Predict the effect on fat digestion immediately after surgery and over the long term. Why can the patient still digest fats, just less efficiently?
3. Pancreatic insufficiency (e.g., from cystic fibrosis or chronic pancreatitis) leads to malabsorption of all three macronutrients, but fat malabsorption is most pronounced. Explain mechanistically why fat absorption is hit hardest.

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