1. 6.1 - Digestion

2. Digestion and Absorption
Essential Idea: The structure of the wall of the small intestine allows it to move, digest and absorb food.
6.1
Digestion and Absorption
Understandings:
The contraction of circular and longitudinal muscle of the small intestine mixes the food with enzymes and moves it along the gut
The pancreas secretes enzymes into the lumen of the small intestine
Enzymes digest most macromolecules in food into monomers in the small intestine
Villi increase the surface area of epithelium over which absorption is carried out
Villi absorb monomers formed by digestion as well as mineral ions and vitamins
Different methods of membrane transport are required to absorb different nutrients
Applications:
Processes occurring in the small intestine that result in the digestion of starch and transport of the products of digestion to the liver
Use of dialysis tubing to model absorption of digested food in the intestine
Skills:
Produce an annotated diagram of the digestive system
Identify tissue layers in transverse sections of the small intestine viewed with a microscope or in a micrograph

3. Purpose of digestion
A. Food is made of cells, and therefore macromolecules (carbs, lipids, proteins, nucleic acids) that your body needs to function
B. Macromolecules are too big to cross cell membranes
C. Your digestive system breaks polymers down into monomers so that they can get into your cells
D. Your cells use the monomers to build macromolecules

4. 4 steps
Ingestion – eat
Digestion – break down into smaller molecules
Absorption – molecules move from digestive tract into blood and lymph
Transport – circulatory system delivers molecules to cells

6. Digestion is an enzyme-driven process
A. Digestive enzymes catalyze hydrolysis reactions – hold macromolecules in place and stress bonds until body heat causes them to break

7. glycerol and fatty acids
Salivary Amylase
Pepsin
Trypsin
Pancreatic Lipase
Pancreatic Amylase
Source
Salivary Glands
Stomach cells
Pancreas
Location of action
Mouth
stomach
Small intestine
Small Intestine
Substrate
Amylose (starch)
proteins
lipids
Product
maltose, glucose
amino acids
glycerol and fatty acids pH 7
2-3 8

8. Absorption
Villi – finger-like projections that line the small intestine – increase surface area!
1. Contain a capillary network for nutrients to pass into the blood (carbs and proteins) and a lacteal for the lymph system (lipids)

9. Passive Transport
1. Simple diffusion - fatty acids
2. Facilitated diffusion – glucose, amino acids
Active Transport
Pumps – glucose, amino acids
Endocytosis – not fully digested macromolecules

10. Importance of smooth muscle
A. Longitudinal – moves food through
B. Circular – mechanical digestion