1. Digestive System
Obtaining nutrients

2. Energy Body cells need energy to run cell processes.
Animals obtain chemical energy from food. Energy is derived from breaking chemical bonds.
Food energy is measured in units called calories.

3. Many lipids are made up of fatty acids and glycerine.
Lipids are fats, oils, and waxes.
Lipids are used for storing energy, making cell membranes, and synthesizing steroid hormones.
No Monomer
Many lipids are made up of fatty acids and glycerine.

4. Starch is made up of glucose.
Carbohydrates
Sugars and starch are the carbohydrates that humans can digest. “Fiber” is indigestible carbohydrates, such as cellulose and inulin.
Glucose is needed by all body cells as energy.
Monomer = monosaccharide
Starch is made up of glucose.

5. Proteins are made up of amino acids.
Amino acids from digested proteins are used by cells to build all the proteins that our body needs.
Humans need a balance of the 20 amino acids, which can be obtained from animal proteins, or by blending plant protein sources.
Monomer = amino acids
Proteins are made up of amino acids.

6. Macromolecule summary
Polymers
Monomers
Roles
Complex Carbohydrates (i.e. starch)
Glucose and other simple sugars
Broken apart to get energy to make ATP.
Proteins
Amino acids
Used to make our own enzymes and other body proteins.
Lipids (Fats, waxes, oils, and steroids)
None
Used for cellular energy and energy storage; used to make cell membranes, steroid hormones.
Nucleic Acids
Nucleotides
Store and transmit hereditary information

7. Digestion

8. Two-way digestion
Simple animals have a single digestive pouch with a single opening.
Food enters through the opening, waste leaves through the same opening.
These organisms must finish digesting before eating again.

9. One-way digestion More complex animals have one-way digestion.
Food enters one opening and waste leaves from another.
Animals with one-way systems can eat any time, which is an advantage.

10. Mechanical digestion
In humans, mechanical digestion takes place in the mouth.
Human incisors and canines are adapted for tearing food, while molars are adapted for grinding food.
Saliva, which contains enzymes, mixes with food.

11. Stomach Acid digestion occurs in the stomach.
Gastrin, a hormone, stimulates acid release.
Pepsin, an enzyme that breaks up proteins, requires an acidic environment to become active.

12. Duodenum
Alkaline digestion takes place in the upper small intestine, the duodenum.
Enzymes from the pancreas require an alkaline environment to be active.

13. Pancreas and Liver
Pancreas releases pancreatic juice, containing bicarbonate, lipases, proteases, and amylase.
The liver makes bile, which emulsifies fats. Bile is made from cholesterol, which is made in the liver.

14. Small intestine
The walls of the small intestine are lined with millions of microvilli. This is the site of nutrient absorption.
Small intestines also produce many digestive enzymes to break large polymers completely down into monomers.

15. Digestion and pH Location pH Enzymes Molecules digested Mouth neutral
Amylase
Starch
Stomach
acidic
Pepsin (a peptidase)
Initial protein digestion
Small intestine
Basic to neutral
Mixture of amylase, peptidases, lipases
Digestion of starches, final breakdown of proteins, digestion of lipids.

16. Large intestine
Water from digested food is absorbed in the large intestine.
Bacteria present in the large intestine feed on unabsorbed nutrients, and produce several vitamins.
Fecal material is formed from fiber and other undigested material.

17. Digestion Diagram

18. Digestion