Lecture Notes for General Biology BI 101 - Digestive Systems

I Digestive Systems

	A) Function
		1) breakdown food into smaller molecules
		2) absorption of food molecules
			Summary of digestive process
	B) Components
 		1) Vary in different organisms
			a) Range from Simple ------ Complex
	C) Simple
		1) diffusion of unicellular organisms
		2) active intake of food by phagocytosis (form food vacuoles)
	D) Complex - Animal digestive systems
		1) Primitive example - simple tube, one opening (Hydra 
			and Flatworms)
		2) Segmented tube - some division along the tube, gizzard 
			and intestines, two openings (Earthworms)
		3) Vertebrate digestive systems - highly differentiated, 
			complete division of labor + accessory glands
			a) different functions - digestion, absorption, 
	E) Basic layout of vertebrate digestive system - human
		1) mouth - teeth for physical breakdown of food, 
			some chemical digestion of starches
		2) Esophagus (+ pharynx) connect mouth with stomach, 
			can be enlarged as in birds for temporary storage
		3) Stomach - storage  and chemical breakdown of foods
			a) acids - break down all types of foods
			b) enzymes for digestion of proteins
		4) Small intestine - absorption and digestion
			cells and cell parts
		5) Large intestine - absorption of water
		6) Rectum - storage of feces
		7) Accessory glands - deliver enzymes to small intestine 
				for digestion
			a) pancreas - enzymes for digesting proteins and 
			b) liver - provides bile through gall bladder to 
				break down fats

II Diet and Nutrition

	A) Diet - what an animal eats
		1) Diet studies document what prey species an organism 
			feeds on
	B) Nutrition - assessment of the quality of the diet
		1) Amount of energy in food 
			a) use of the bomb calorimeter
		2) Measure the % composition of proteins, fats, 
			carbohydrates in diet
		3) number of calories per day in the diet
	C) 4-9-4 rule - used to calculate composition of food
		1) proteins - 1g burns 4 cal (multiply the number of 
			grams by 4)
		2) fats - 1g burns 9 cal (multiply the number of grams 
			by 9)
		3) carbohydrates - 1g burns 4 cal (multiply the number 
			of grams by 4)
		4) Hyothetical Example - BLT
Molecule # of grams Calories/g Total calories % of Diet
Proteins 25g (25%) 4 100 15.3% (100/650)
Fats 50g (50%) 9 450 69.4% (450/650)
Carbohydrates 25g (25%) 4 100 15.3% (100/650)

	D) RDA standards for a healthy diet
		1) Protein - 10%, Fat - 30%, Carboh. - 60%
		2) Caloric intake
			a) influenced by gender, age and activity level
			b) males - 15-25 yrs should be 2800 cal/day
			c) females - 15-25 yrs should be 2200 cal/day
			d) balance between intake (eating)  and expenditure (exercise)
	E) Goal of RDA standards
		1) Reduce proteins - excess is turned into fat
		2) Reduce fat content associated with heart disease
		3) Carbohydrates are OK if they are complex sugars
			found in vegetables and fruits
	F) Nutritiondata.com - online food analyzer

III Other considerations - Rounding out the diet

	A) Minerals - inorganic (needed in small amounts)
		1) Ca - bone and muscle, found in dairy products, 
		2) Na - nerve and muscle cells, found in salts, 
			most foods
		3) K - nerve and muscle cells, found in most foods
		4) Fe - blood cells (hemoglobin), found in whole 
			grains, vegetables
		5) Summary from Campbell - see symptoms associated with deficiencies 
				for minerals above
	B) Vitamins
		1) A - vision, found in milk, eggs, yellow fruits, 
			fish liver
		2) B (B6) - metabolism, found in whole grains, vegetables 
		3) C - fight infection, cartilage and bone, found in 
			fruits and vegetables
		4) K - blood coagulation, found in vegetables, bacteria 
			in large intestine
		5) Summary from Campbell - - see symptoms associated with deficiencies 
				for vitamins above

IV Well balanced diet and the Food Pyrmaid

	A) Diet composition (1 = eat the least of, least healthy - 5 = 
		eat the most of, most nutritious)
		1) refined sugars, fats and oils
		2) milk - meat 
		3) fruit & vegetables
		4) grains, pasta
	B) Goals of the pyramid
		1) reduce intake of fats (reduce risk of heart 
	C) New views on the Food Pyramid
		1) Rearranging the food pyramid
		2) Dr. Willet's new food pyramid
			Top - foods to use sparingly 
				red meats,animal fats, white rice and bread, potatoes, some pasta and sweets
				margarine, vegetable shortening and trans-fatty acids, coconut and palm oils
				deep-fried foods
			Middle - moderate amounts
				fish, poultry, eggs
				Nuts and legumes
			Bottom - larger amounts
				vegetables (crunchy vegetables), fruits
			Bottom - largest amounts
				whole grain foods (wheat and high fiber, etc.), plant oils

V History of Food

	A) For fun - check out these web sites
		1) The food timeline
		2) History of food and agriculture

BI 01 Homepage

Saint Anselm College Homepage

Blackboard at Saint Anselm College

Dr. Jay's Homepage


Trademark and Disclaimers

Copyright © 2001 Jay Pitocchelli. All rights reserved. The contents of this page are the intellectual property of Dr. Jay Pitocchelli for distribution to students enrolled in General Biology BI 01 at Saint Anselm College. These pages may not be copied, photocopied, reproduced, translated, or published in any electronic or machine-readable form in whole or in part without prior written approval of Jay Pitocchelli. Students enrolled in General Biology BI 01 at Saint Anselm College have permission to print this material for their lecture notes. The images linked to this web page are the sole property of Addison Wesley/ Benjamin Cummings Publishers™.