Chapter 29 Nutrition & Digestion

Food as a Source of Nutrients Your body needs nutrients from food to build tissue and do cellular work (energy)

Key Questions What materials do organisms need maintain homeostasis? How do they obtain these materials?

Look at the table on page 1 of your notes…

Carbohydrates…

Organic Found in bread, pasta, grains, cereals, fruit, candy

Function = ENERGY! END PRODUCTS (building blocks) monosaccharides (glucose)

Recall these molecular structures:

Lipids…

Organic Found in fatty foods (meat, oils, nuts, avacados)

Function = Store ENERGY! END PRODUCTS: fatty acids and glycerol

Proteins…

Organic Found in meat, fish, eggs, nuts, beans

Function = enzymes, hormones, muscle END PRODUCTS amino acids

Minerals…

Calcium, Copper, Iodine, Iron, Magnesium, Zinc, Phosphorus, Potassium Inorganic ions Found in all foods Calcium, Copper, Iodine, Iron, Magnesium, Zinc, Phosphorus, Potassium

Function=help life processes ex. Calcium-bones & teeth; iron-hemoglobin END PRODUCTS Minerals are NOT broken down!

Vitamins…

Vitamin C – C6H8O6 Vitamin B5 – C9H17NO5 Vitamin A – C20H30O Are vitamins organic??

Organic Found in all foods

Function = coenzymes END PRODUCTS: Vitamins are NOT broken down!

Water…

Inorganic Found in all foods

FUNCTION = needed for metabolism, 2/3 of body is water END PRODUCTS: Water is not broken down!

Minerals and water are different from other nutrients because _______________ They are inorganic

The major elements found in nutrients are _____________ H, O, N, C, P, S C HOPKINS CaFe Mg NaCl

4 Stages of Food Processing 1. Ingestion 2. Digestion 3. Absorption 4. Elimination (egestion)

1. Ingestion The act of bringing food into the body (eating or drinking) Importance: food enters internal spaces for digestion

2. Digestion Process of breaking food down into small molecules that can be absorbed 2 types of digestion…

a. Mechanical Makes food smaller by tearing, chewing, grinding Increases surface area

b. Chemical Chemically changing food (by hydrolysis) Large molecules broken down to small molecules Enzymes are used

b. Chemical i. Intracellular – inside a cell (in a vacuole) ii. Extracellular – outside a cell in a cavity (like our stomach)

3. Absorption Nutrients entering the cells of an organism Molecules must be small enough to cross cell membranes

4. Elimination (egestion) Undigested or indigestible materials leaving the organism (Feces) Not the same as excretion

Read the story on page 3

Digestion Occurs in a Tube Food typically moves in one direction through a twisting tube as food is broken down

Organs of the Digestive System…

Human Digestive System Overview Alimentary Canal (food passes through) Mouth Esophagus Stomach Small intestine Large intestine Accessory Organs Pancreas Liver Gall Bladder

1. Oral cavity ( mouth) Location of Ingestion Mechanical digestion – teeth Chemical digestion - amylase

1. Oral cavity ( mouth) Secretions – saliva contains mucous for lubrication salivary amylase – enzyme that begins the digestion of carbohydrates

2. Pharynx Also called the throat Junction of the digestive tract and the passageway of the lungs

2. Pharynx Bolus – chewed up clump of food Epiglottis – flap of cartilage that seals off the trachea when you swallow so food doesn’t enter it

Activity of the mouth and throat http://www.linkstudio.info/images/portfolio/medani/Swallow.swf

3. Esophagus 12 inch tube that carries the bolus of food from the mouth to the stomach

3. Esophagus Peristalsis - muscular contractions that pushes food to stomach No Digestion occurs in the esophagus

4. Stomach Muscular sac; holds up to ~2L of liquid Mechanical Digestion –muscles churn food by peristalsis mixing it with secretions.

4. Stomach Secretions (lining of stomach): Chemical Digestion –pepsin (enzyme) begins the digestion of proteins Hydrochloric acid (made in stomach) makes an acid environment

“Valves” (sphincter) at each end are supposed to seal contents until mixed

5. Small intestine Length = ~ 20 ft Digestive function – Digestion of carbs, protein and lipids is completed in the SI.

5. Small intestine Mechanical – peristalsis and bile (from liver) Chemical –many digestive enzymes used in the SI:

5. Small intestine Secretions – from small intestine lining, pancreas and liver all used in SI peptidases - proteins amylase & maltase - carbohydrates lipase – lipids

5. Small intestine Absorption – digested nutrients (small molecules) are absorbed from the SI into the blood.

5. Small intestine Villi – fingerlike projections from the lining that increase surface area for absorption. Villi - contain small blood vessels

Villi in the Small Intestine Capillaries

Glucose Amino Acids Glycerol Fatty Acids List the materials that would be absorbed from the fluids of the small intestine into the villi: Glucose Amino Acids Glycerol Fatty Acids

Appendix: Blind sac of tissue at the junction of the Small Intestine and Large Intestine. Vestigial Structure Function?

6. Large Intestine Length ~ 1.5 meters No digestion occurs here Water absorption from the food mass into the blood occurs in the LI

6. Large Intestine Vitamin K and some B vitamins are made in the LI (by bacteria) and absorbed into the bloodstream

6. Large Intestine Forms feces (solid waste) – that is temporarily stored in rectum and leaves body (egested) through the anus

Accessory Organs Page 6 Contribute to digestion but food does not travel through

Pancreas Secretes hydrolytic enzymes into the SI: Amylase – digests carbohydrates Proteases – digests proteins Lipase – digests lipids

Liver Makes bile which emulsifies lipids (mechanical digestion)

Gallbladder Thin sac that stores bile and delivers it to the small intestine

Pharynx Salivary Glands Teeth Mouth Tongue Salivary Glands Epiglottis Esophagus Liver Stomach Gall Bladder Pancreas Bile Duct Duodenum Sm. Intest. Lg. Intest. Appendix Rectum Anus

http://www. argosymedical http://www.argosymedical.com/Digestive/samples/animations/Digestion/index.html