Tuesday, June 24, 2008

Compendium Review Unit 2 Major Topic: Nutrition


Table of Contents
I. Digestive System and Nutrition
II. Converting Food into Energy

I. Digestive System and Nutrition
A. Overview of Digestion
1. Ingestion, digestion, movement, absorption, elimination
2. Wall of the digestive tract
a. mucosa (mucous membrane) - lines tract, protects wall from enzymes, contains glands in mouth, stomach, & small intestine, diverticulitis (pouches in mucosa)
b. submucosa - broad band of connective tissue, contains blood & lymphatic vessels & nerves, inflammatory bowel disease (colitis, inflammatory response)
c. muscularis - 2 layers of smooth muscle (circular & longitudinal), moves GI contents, irritable bowel syndrome (spastic colon, contractions of wall)
d. serosa (serous membrane) - secret serous fluid, part of peritoneum, appendicitis can lead to peritonitis
Figure 8.1 from the text shows an overview of the human GI tractB. First Part of the Digestive Tract
1. The mouth
a. mechanical (teeth and tongue) and chemical (saliva)
2. The pharynx and esophagus
a. swallowing - voluntary and involuntary (once food pushed back into pharynx)
b. peristalsis - rhythmic contraction that pushes food along esophagus
Figure 8.4 from the text shows the path of a bolus as it moves through the first part of the GI tract.C. The Stomach and Small Intestine
1. The stomach
a. continuous with esophagus and duadenum of small intestine
b. stores food, initiates digestion of protein, controls movement of chyme
c. muscularis contains 3 layers of smooth muscle - circular, longitudinal, oblique
d. mucosa has rugae & gastric pits -> gastric glands -> gastric juice (pepsin,HCl, mucus)
2. The small intestine
a. 18ft long
b. digestion completed here
c. duodenum receives enzymes from pancreas and bile from liver and gallbladder
d. nutrients (sugars, amino acids, fatty acids, glycerol) absorbed by sm intestine
e. villi and microvilli increase surface area for absorption
3. Lactose intolerance sufferers lack enzyme, lactase
4. Obesity: diabetes type 2 and cardiovascular disease
a. cells become resistant to insulin and can't utilize glucose
Figure 8.5 from the text illustrates the structure and function of the stomach, table 8.1 which lists the major digestive enzymes, and figure 8.6 which depidcts the anatomy of the small intestine can be found here for later reference. Figure 8.7 which shows digestion and aborption of nutrients is shown below.D. Three Accessory Organs and Regulation of Secretions
1. Three accessory organs
a. pancreas - produces pancreatic juice into duodenum, secrets insulin into blood
b. liver - cleanses blood, stores iron & vitamins, stores glucose, breaks down glycogen, converts glycerol & amino acids to glucose, urea is byproduct, makes plasma proteins
c. gallbladder - stores bile
d. liver disorders - hepatitis, cirrhosis,
2. Regulation of digestive secretions
a. controlled by nervous system and by digestive hormones
Figure 8.8 from the text illustrates the three accessory organs.E. The Large Intestine and Defecation
1. Functions of the large intestine
a. absorbs water
b. intestinal flora produce vitamins which are absorbed by the large intestine
c. forms feces
d. defecation
2. Disorders of the colon and rectum
a. diarrhea, constipation, hemorrhoids, diverticulosis, IBS, IBD, polyps, cancer
Figure 8.10 from the text shows the anatomy of the large intestine.F. Nutrition and Weight Control
1. How obesity is defined
a. body mass index - looks at height and weight
2. Classes of nutrients
a. carbohydrates - simple (eg glucose) complex (body breaks down to glucose)
b. complex carbohydrates better than refined grains
c. proteins - digested to amino acids
d. 8 essential amino acids - daily supply needed
e. lipids - best sources - oils
f. polyunsaturated (contain essential fatty acids)- corn and safflower
g. monounsaturated - olive and canola
3. Minerals
a. trace - body contains less than 5 grams, major - body contains more than 5 grams
b. calcium - construct bones & teeth, nerve conduction, muscle contraction
c. sodium - regulates body's water balance
4. Vitamins
a. 13 vitamins - 4 fat-soluble, 9 water-soluble
b. some are portions of enzymes, others precursors
c. antioxidants - vit. C, E, & A believed to defend the body against free radicals
d. vitamin D - after modification in kidneys & liver, promotes the absorption of calcium by the intestines
5. How to plan nutritious meals
a. eat a variety of foods
b. eat more fruits and vegetables
c. eat less food with saturated or trans fat, sugar, cholesterol, salt, alcohol
d. exercise
e. eat less processed foods
6. Eating disorders
a. anorexia nervosa, bulimia nervosa, binge-eating disorder, muscle dysmorphia
II. Converting Food into Energy
A. Glycolysis1. Glucose converted to pyruvate
2. NET result of single glycolysis run 2 NADH, 2 ATP
3. Lactic acid is end end product under anaerobic conditions
4. 6-Carbon sugar diphospate split into 2 3-Carbon sugar phospate molecules
5. Aerobic conditions, pyruvate is further oxidized to yield more ATP

B. Krebs Cycle1. Occurs in mitochondrion
2. Acetyl-CoA from pyruvate enters Krebs Cycle
3. Single turn of cycle yields 1 ATP, 3 NADH, 1 FADH2
4. Initial reaction involves addition of a 2-Carbon to a 4-Carbon molecule

C. Electron transport chain
1. Electrons are accepted in the following order: cytochrome c, cytochrome c oxidase, oxygen
2. Electrons transferred through the chain originally belonged to NADH and FADH2
3. Movement of protons through ATP synthase: from intermembrane space into matrix
4. Water is produced when oxygent accepts electrons
5. Oxidative phosphorylation is the production of ATP from ADP plus phosphate. The energy used is derived from the movement of proton from the intermembrane space to the matrix

D. How NAD+ Works
1. Cells obtain energy by oxidizing food molecules
2. Coenzyme NAD is reduced NAD+ + H -> NADH
3. Hydrogen atom consists of a proton and an electron
4. Reduction is the addition of an electron, oxidation is the removal of an electron
5. When one molecule is reduced another must be oxidized
6. NADH serves as an electron carrier that can donate its hydrogen

Definitions for chapter 8 can be found here.
Mader, Syliva S. Human Biology. New York, NY: McGraw-Hill (2008).

Links provided throughout the summary take you to online sources.

IMPORTANT NOTE: Any time "text" or "the text" is referenced in the above summary, I am referring to the textbook Human Biology by Sylvia Mader (cited directly above).

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