1. Mechanical vs. Chemical digestion
Aim: What is the differences between mechanical and chemical digestion?
Do now: You just ate a potato chip. Describe its’ journey through out your body ? Be as detailed as you can.

2. Mechanical digestion
involves the physical breakdown of food. Mechanical digestion occurs in the following locations:
Mouth
teeth and tongue
Esophagus - peristalsis
Stomach – muscular churning action of stomach
Small intestine (SI) – peristalsis

3. Chemical Digestion
During the chemical digestion of food, enzymes break down large food molecules by the process of hydrolysis .
Hydrolysis- a water molecule is added at the site where a bond is broken.
Why are enzyme very specific ?

4. Chemical Digestion
The mouth begins the process of carbohydrate digestion through the action of saliva. The enzyme found in saliva, salivary amylase , starts the chemical digestion of starch, converting it from a polysaccharide to the disaccharide maltose.

5. Mechanical digestion
Peristalsis - muscular contraction in both the esophagus and small intestine.

6. Chemical digestion Stomach gastric juices
Pepsinogen is NOT an enzyme but a forerunner of the enzyme pepsin .
The hydrochloric acid secreted increases the acidity of the stomach contents to a pH of 2 or lower. At this pH, pepsinogen is converted to pepsin, an active enzyme which begins the chemical digestion of proteins into peptides.

7. Quick Fact
Salivary amylase functions best at pH 6 or 7 (very slightly acidic or neutral).
What is the pH in the stomach?
Therefore, What stops being broken down in the stomach ?

8. Chemical Digestion Small Intestine
Final digestion of proteins and carbohydrates must occur, and fats have not yet been digested.
Villi have cells that produce intestinal enzymes which complete the digestion of peptides and sugars.

9. Affecting Enzyme ActionpH
Temperature
What happens when the pH does not correspond to the optimal pH at which the Enzyme reacts?

10. pH effects on enzymatic activity
The point where the enzyme is most active - is known as the optimum pH.
Extremely high or low pH values generally result in complete loss of activity for most enzymes.

11. Final step in Chemical digestion
-Absorption in Small Intestine through a thin-walled small blood vessels (capillaries) by passive transport. -Fat digestion do not pass into the capillaries, but instead enter a vessel called a lacteal . The absorbed fat droplets are transported to adipose (fat) tissue where they are stored.

12. Villus (Villi) role in chemical digestion

13. Simulation-Procedure
Procedure 1) Take a piece of chalk and crush it. 2) Then place the pieces of chalk in the vinegar for 20 seconds. Questions A)What did the chalk , vinegar, the device used to crush the chalk represent? B)How this represents chemical and mechanical digestion ? C)What would be the next step in digestion process. Design the next step of the simulation . D) What is the difference between Mechanical and Chemical digestion?