Digestion Revision Notes

1. 2.19
Digestion prepares useful food molecules for absorption

2. Digestion
The process of breaking down food into nutrients that can be absorbed
by blood or lymph.
There are two different types of digestion that occur in the digestive
system: mechanical digestion and chemical digestion.

4. Digestive Enzymes
Enzymes are proteins that catalyze, or speed up, biochemical
reactions.
Foods are broken down by hydrolysis reactions (breaking down with
water)

10. • Mucus
• Pepsin, protease (protein-
digestive enzyme)
• Hydrochloric acid

13. Digestion of food molecules is completed in
the small intestine
 Enzymes from pancreas; amylase
starch maltose
trypsin (another protease) and lipase
protein amino acids
fats fatty acids
Bile from the liver
bile emulsifies large fat globules to smaller droplets
Enzymes from intestine wall; maltase
maltose glucose

14. Egestion removes undigested food
Dietary fibre; cellulose in cell walls are expelled
Egestion; the process of expelling food
Ring muscle, sphincter at the anus prevent defecation.

15. Absorption
Most absorption – ileum
Special adaptation of ileum
Very long about 6 m; enough time for absorption
 highly folded surface; larger surface
Lining has thousands of villi absorb liquid food

18. The liver and assimilation
• Digested food is absorbed into the blood stream.
• Liver sorts out digested food molecules.
Function
Manufacture of bile
Storage of glucose as glycogen
Interconversion of glucose and glycogen
Interconversion of amino acids to others that body might require
called transamination.
Excretion of excess amino acids
Remove old blood cells
Breakdown toxic substances

19. Vocabulary
• Fibrinogen
• Deamination
• Transamination
• detoxification

21. 1. Define digestion. Where does it occur?
2. Glucose can be absorbed by the body without being further broken
down. (True or False?)
3. Bile is produced in the gallbladder. (True or False?)
4. The pH of the stomach is (acidic or alkaline).

22. 5. Bile helps break down
oLipids
oCarbohydrates
oNucleic acid
oProtein

23. 6. Identify two organ systems that control the process of digestion by
the digestive system.
7. What is mechanical digestion? Where does it occur?
8. Describe chemical digestion.

24. 9. What is the role of enzymes in chemical digestion?
10. What is absorption? When does it occur?
11. Where does most absorption occur in the digestive system?
12. Why does most of the absorption occur in this organ, and not
earlier in the GI tract?