1. DIGESTION & ABSORPTION 6.1

2. The Process Ingestion Digestion Absorption Transport
Eating!
Digestion
The series of chemical reactions to break down the food into smaller molecules.
Absorption
Small molecules are absorbed through the cells in the walls of digestive tissue into blood and lymph (circulatory system).
Transport
The circulatory system delivers the small molecules to cells around your body.

3. The problem to solve…
Most food molecules (macromolecules) are too large to pass through your cell membrane

4. Macromolecules Monomers = the smallest building blocks of the molecule
Polymer = a large molecule made up of many monomers

5. Macromolecules Macromolecule: Too big for absorption
Monomer: Good size for absorption
Carbohydrates
 polysaccharides, disaccharides, monosaccharides
monosaccharides
Lipids
 triglycerides
glycerol and fatty acids
Proteins
amino acids
Nucleic Acids
 DNA, RNA
nucleotides

6. Digestion is like… Playing LEGOS Take Apart
Put together
(protein in steak)
Take Apart (into amino acids)
Put back together (into your OWN protein)
Take Apart

7. Enzymes
Catalysts: A substance that speeds up the rate of a chemical reaction.
How? By lowering the activation energy
Enzymes: Proteins that act as biological catalysts.

8. Essential Enzymes
Remember, enzymes don’t MAKE the reaction happen, they just hold the macromolecule in its active site to help the reaction move more quickly.

9. Enzymes 1. Substrates bind to enzyme
Active Site
1. Substrates bind to enzyme
2. Substrates are converted into products
3. Products are released 2
Enzyme -substrate complex

10. Enzymes – 1st level of breakdown
Source
Substrate
Products
Optimum pH
Amylase
ex. Salivary amylase
Salivary glands
Starch (amylose)
Maltose
7 (neutral)
Protease
ex. Pepsin
Stomach cells
Proteins (polypeptides)
Amino acids, shorter peptides
3 (acidic)
Lipase
ex. Pancreatic lipase
Pancreas cells
Lipids
Glycerol & fatty acids
Phospholipase
Many diff tissues
Phospholipids
Fatty acids, glycerol, phosphate
variable

11. Enzymes Further breakdown Substrate Products Nuclease Maltase Lactase
DNA & RNA
nucleotides
Maltase
Maltose
Glucose
Lactase
Lactose
Glucose & galactose
Sucrase
Sucrose
Glucose &
Fructose
Exopeptidase & Dipeptidase
Peptides & dipeptides
Amino acids
Further breakdown

12. Digestive Tract Food has two options:
1. Get digested and used by the body
2. Be eliminated as feces

13. 6.1.4 Diagram

15. Science Museum Proposal ~40 min
You have been asked to create a new exhibit for the Seoul Science Museum. The exhibit should be a walk-through giant digestive tract with interactive features along the way. Your exhibit will be permanently built in the science museum and has a generous budget from an anonymous donor.

16. Overview of the Functions of Stomach, SI, LI
Food is churned with the gastric juices for a period of time.
Small Intestine
1. In the duodenum, the food mixes with new secretions from the liver, gall bladder, and pancreas.
2. Digested nutrients (monomers) pass through the villi into the circulatory system.
Large Intestine
1. Reabsorb the water from the food, concentrating the undigested (& unabsorbed) food into feces.
2. Home to mutualistic bacteria (eg. E. coli )that keep us healthy and produce Vitamin K.

22. Villus: Designed for absorption & transport
Digested Nutrients IN
Villus: Designed for absorption & transport
Digested nutrients pass through the 1-cell thick epithelium tissue to get to the circulatory system.
Most molecules go to the capillary bed and then are transported through the blood.
Fatty acids are absorbed into the lacteal and then are transported through the lymph.
Blood + Nutrients OUT
Blood In

23. Starch digestion in the small intestine
Illustrates many processes that we have learned about
Membrane permeability
Catalysis
Without a catalyst the reactions to digest starch would happen at very slow rates
Enzyme specificity

24. Starch digestion in the small intestine
Illustrates many processes that we have learned about
Membrane permeability
Catalysis
Enzyme specificity
Three enzymes in villi membranes break the 1,6 bonds and the 1,4 products; dextrinase, maltase, glucosidase
Salivary amylase begins the digestion.
Most starch digestion happens in the small intestine with enzyme secretions from the pancreas.
1,4 bonds broken by pancreatic amylase
These small sections are now broken down into maltose and maltotriose
Glucose

25. Starch digestion in the small intestine
Illustrates many processes that we have learned about
Membrane permeability
Catalysis
Glucose is absorbed via:
co-transport with sodium ions
into the interstitial fluid via facilitated diffusion
through large membrane pores into capillaries.
Enzyme specificity

26. Food not absorbed…
Is eliminated as feces.

27. Predict whether the bag will gain or lose mass during the experiment.
Cola drinks contain a mixture of substances with different particle sizes. This cola contains glucose, phosphoric acid, and caramel (a complex carbohydrate added to produce a brown color).
Predict which substances will diffuse out of the bag, with reasons for your prediction.
Predict whether the bag will gain or lose mass during the experiment.
Cola, left to go flat before being put in a tube
Bags made of dialysis tubing
Water