1. Digestive System
Obtaining nutrients

2. Nutrition

3. 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.

4. Many lipids are made up of fatty acids and glycerine.
Lipids are fats, oils, and waxes.
Lipids are energy dense, containing 9 calories per gram.
Lipids are used for storing energy, making cell membranes, and synthesizing steroid hormones.
Many lipids are made up of fatty acids and glycerine.

5. 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. Nerve cells must have glucose to operate.
Starch is made up of glucose.

6. 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.
Proteins are made up of amino acids.

7. 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)
Fatty acid chains, glycerine (except steroids)
Used for cellular energy and energy storage; used to make cell membranes, steroid hormones.

8. Minerals
Sodium, potassium, zinc, iron, calcium, copper, and selenium are among the minerals that humans need.
Most minerals can be found in whole grains, fruits, vegetables, nuts, and meats. Highly processed foods may be deficient.

9. Major Minerals Mineral Major roles Natural sources Calcium
Bone and tooth formation; muscle and nerve function.
Dairy products, leafy greens, dry beans.
Iron
Used to make hemoglobin and myoglobin.
Red meats, eggs, nuts, whole grains, leafy greens.
Zinc
Component of certain enzymes, required for growth.
Meats, whole grains, nuts, legumes.
Phosphorous
Bone and tooth formation; pH of body fluids, phospholipids.
Dairy products, grains.
Potassium
Maintains pH of body fluids; used in action potentials.
Many fruits and vegetables, meats, milk.
Sodium
Table salt, meats.
Selenium
Used by the immune system.
Nuts, esp. Brazil nuts; many fruits and vegetables.

10. Major Vitamins Vitamins Major roles Natural sources
Vitamin A (fat soluble
Used to make visual pigments; maintains epithelial tissues; needed for normal growth.
Orange and yellow fruits and vegetables, egg yolk, dairy products.
B complex vitamins (water soluble)
Used in cellular respiration to metabolize sugars and other carbon compounds.
Whole grains, legumes, many fruits and vegetables. B12 comes from animal sources.
Vitamin C (water soluble)
Used in collagen synthesis, possible role in immune function.
Fresh fruits and vegetables.
Vitamin D (fat soluble)
Bone growth, calcium absorption, possible role in immune function.
Eggs, dairy products. Sunlight on skin oils creates Vitamin D.
Vitamin E (fat soluble)
Antioxidant, reduces cellular damage.
Nuts, whole grains, leafy vegetables.
Vitamin K
Plays a role in blood clotting.
Produced by intestinal bacteria.

11. Antioxidants
Free-radicals are released by cell damage and many cell processes.
Anti-oxidants, such as Vitamins C and E, and many plant pigments, combine with free radicals and reduce their effects, which slows cell aging.
Moral of the story: eat colorful food
No, Skittles don’t count as “colorful food!”

12. Digestion

13. Incomplete 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.

14. Complete 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.

15. 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.

16. 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.

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

18. 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.

19. 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.

20. Villi and microvilli

21. 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.

22. 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.

23. Hormones and digestion
Many hormones produced by the digestive system itself are responsible for appetite and digestion.
Gastrin in the stomach, produced when food is present, signals release of acid.
Secretin signals the release of sodium bicarbonate by the pancreas.
Ghrelin and Leptin, recently discovered, control appetite. Changes in these hormones cause overeating, because people with too little of these hormones don’t realize they’re full.

24. Hormones
NOVA Science Now video: Hormones and Obesity