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Chapter 8



8-1 The Process of Nutrition

Nutrients are substances that provide energy and materials for metabolic activities



Maintenance of cells


Nutrition = process by which organisms get food and break it down so it can be used for metabolism

Proteins: Organic

Carbohydrates: Organic

Fats: Organic

Vitamins: coenzymes or converted into coenzymes

Minerals: from environment, chemical elements needed for normal functioning, Fe, Ca, P, I from soil, eat plants and animals

Water: fluid

Organisms get food in two basic ways

Autotrophs – organisms that can photosynthesize food

Phototrophs – make their own food

Chemotrophs – make food from chemical reactions

Heterotrophs - takes in food, ingest organic nutrients

Energy Content of Food

For any given quantity of food, the total energy released by cellular respiration is the same as would be released by burning the food.

Amount of heat given off

Instrument: calorimeter


Joule - SI unit

Calorie – commonly used unit

One calorie equals 4.2 joules. Also, defined – the amount of heat that is needed to raise the temperature of 1 gram of water 1 degree Celsius.

Kilocalorie is 100 calories, or 1 Calorie

1 gram of carbohydrate or 1 gram of protein is about 4 Calories

1 gram of fat releases 9 Calories

Human Nutritional Needs

Energy from food

Daily calories needed affected by

Age, sex, lifestyle, weight, body condition

Younger more than old

Males more than females

Active people more than inactive

Gains weight = more calories than needed

Lose weight = less calories than needed

Figure 8-3, page 151

Healthy Diets

Need basic nutrients

Different kinds of food

Figure 8-4, page 152

Food Pyramid, figure 8-5, page 153

Six groups

grains; vegetables; fruits; milk products; meat, poultry, fish, eggs, beans, nuts; fats, oils, sweets


Guidelines for a healthy plan

Variety of foods

Maintain a healthy weight

Low in fat and cholesterol, limit fried foods

Include vegetables, fruits, grain products in diet

Moderate sugar use, limit sweets and soft drinks

Moderate use of salt and sodium

Don’t add salt to foods you eat

Linked to high blood pressure

8 - 1 Section Reviews

1. The way organisms obtain food and change it into forms usable for metabolism.

2. Proteins, carbohydrates, fats, vitamins, minerals, water.

3. Grain foods; vegetables; fruits; milk products; meat, poultry, fish, eggs, beans, and nuts; fats, oils, and sweets.

4. Humans are heterotrophs because they are classified as animals.

8 – 2
Adaptations for Nutrition and Digestion

Absorption – in order for nutrients to be used by the cell it must pass through the cell membranes.

Digestion – process by which food molecules are broken down.

Takes place in stages

Chemical breakdown into simpler compounds

Enzymes – act on surface of food particles

Mechanical breakdown of food – cut into small pieces

Exposes more food surface area to enzymes


The teeth of vertebrates are specialized to accommodate the type of food eaten.

Carnivores, eat-eaters, have pointed teeth but no flat grinding surfaces.

Herbivores, plan-eaters, have large and flat teeth.

Omnivores, such as humans, eat both plant and animal food and have both flat and sharp teeth.

Nutrition in Protists

Intracellular - happens inside the cell

Different ways

Ameba, paramecium

Attracted to food by chemical stimuli


Crawl with false feet

Projections called " pseudopods "

Cytoplasm flow in and out

Surrounds food

Membrane separates from other cell parts

Food vacuole forms

Moves about within cytoplasm

Fuses with lysosome, enzymes breakdown food into usable form

Diffusion across vacuole membrane into cytoplasm

Indigestible material is expelled from cell



Paramecium structures





Nutrition in the Earthworm

Muticellular animal


Inner tube – digestive system

Alimentary canal

Two openings

Mouth – food enters

Food travels in one direction

Broken down mechanically and chemically

Usable absorbed

Anus – waste leaves

Unusable excreted

Outer tube – body wall



Nutrition in the grasshopper

Tubular digestive system

Mouthparts breakdown food mechanically

Chews leafy vegetation

Food mixes with saliva

Salivary glands

Contains enzymes

Passes through esophagus into crop

Crop to gizzard

Ground into chitin

Passes to stomach

Chemical digestion and absorption occurs

Enzymes outside stomach act on food

Absorbs into blood stream through stomach walls

Transported to all cells

Undigested materials pass through the intestines

Stored in rectum where water is absorbed

Dried waste eliminated through anus

8 – 2 Section Review

1. In Food vacuoles within the cell

2. Hydra

3. Increase the surface area of the intestine for absorption of nutrients

4. Mouth, esophagus, crop, gizzard, stomach, intestine, rectum, anus

5. Both are chemical breakdown of large molecules; extracellular digestion is outside cells, intracellular digestion is in cells

8 – 3 Human Digestive System

Parts of the Human Digestive System

Background Information

Many adult humans cannot digest milk because they are deficient in lactase, the enzyme that hydrolyzes lactose, or milk sugar. A person who is lactose intolerant experiences abdominal bloating, cramps, flatulence, and diarrhea soon after ingesting milk or unfermented milk byproducts. Lactase deficiency is genetically determined.

The Mouth and Pharynx

The Esophagus

The Stomach

The Small Intestines

The Large Intestines

8 – 3 Section Reviews

1. The salivary glands, liver, and pancreas aid digestion by secreting digestive fluids.

2. Wet food, cause it to form a bolus, break down starch into maltose.

3. Peristalsis

4. Bile, pancreatic juice, intestinal juice.

5. Reabsorption of water, absorption of vitamins from bacteria, elimination.

6. Starch, maltose, proteins, fats, peptides.


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