Today: Nutrition and Digestion

During digestion complex molecules are broken down and then used to build needed molecules and to produce energy

Food Pyramid based on 2,000 calories/day

Federal Food Subsidies vs Food Pyramid

Protein needed per day = 0.8g/kg of body weight So a 150 lb person needs 54 g or 2 oz of protein/day

20 amino acids

8 Essential Amino Acids CB 41.2

Many cultures combine these foods in their traditional diets: beans and rice, beans and corn, peanut butter on bread, soy and rice, lentils and bread or rice CB 41.2

Complex molecules are broken down and then used to build needed molecules and to produce energy

Animals take in complex molecules from the environment for energy production

Animal digestion occurs outside of our cells.

animal and fungal digestion occurs outside of our cells.

Physical digestion: liquefying of food Chemical digestion: breaking large molecules into small molecules CB 41.13

Amylase in mouth Chewing and adding saliva begins the process of liquification Amylase begins the chemical digestion of carbs Cb 41.11

The primary function of the stomach is food storage CB 41.10

Pepsin in stomach Pepsin begins the chemical digestion of proteins. In the stomach liquification continues. CB 41.12

The Digestive System CB 41.10

Most chemical digestion occurs in the first part of the small intestine CB 41.15

The small intestine has a large surface area to aid in absorbption of nutrients CB 41.15

Absorption in the Small Intestine CB 41.15

The Digestive System CB 41.10

CB 41.11

Carb’s- provide energy and structural support CB 5.8 Most organisms cannot break down cellulose

Ruminants have multiple stomachs where microorganisms help digest cellulose CB 41.20

Carnivores have a short digestive system Herbivores have a long digestive system CB 41.19

HumansBears Both humans and grizzly bears are omnivores. Our digestive systems can tell us about our ancestors. CB 41.19

Chimps commonly hunt small animals including other smaller primates. Hunting encourages cooperative behavior and may help produce more cohesive and advanced societies. rcf.usc.edu/~stanfor d/chimphunt.html

Percent of resting metabolic rate needed for brain (adults): Human = 20-25% Other primates = 8-10% Nonprimate mammals = 3-5% Leonard WR, Robertson ML Evolutionary perspectives on human nutrition: the influence of brain and body size on diet and metabolism. Am. J. Hum. Biol. 6:77–88

Table 2 Annual Review of Nutrition Vol. 27: Effects of Brain Evolution on Human Nutrition and Metabolism Brain size, body size, and molar (grinding) tooth area

Food Web

Ecological Interconnections

In the U.S. we eat an avg. of ~2800 Cal/day We produce ~3774 Cal/person/day So we waste over 25% of the food we produce

In the U.S. we eat an avg. of ~2800 Cal/day We produce ~3774 Cal/person/day So we waste over 25% of the food we produce 8,080,000,000,000,000 btu to produce our food 2,030,000,000,000,000 btu of this energy is wasted Wasted Food, Wasted Energy: The Embedded Energy in Food Waste in the United States. Amanda D. Cullar, Michael E. Webber (2010) Environmental Science & Technology DOI: /es100310d

In the U.S. we eat an avg. of ~2800 Cal/day We produce ~3774 Cal/person/day So we waste over 25% of the food we produce 8,080,000,000,000,000 btu to produce our food 2,030,000,000,000,000 btu of this energy is wasted = ~2% of total U.S. energy production Wasted Food, Wasted Energy: The Embedded Energy in Food Waste in the United States. Amanda D. Cullar, Michael E. Webber (2010) Environmental Science & Technology DOI: /es100310d

CB Producers and Consumers

CB Higher consumers are usually larger and fewer in number than lower consumers

CB Energy is lost in each consumer 1000

CB Energy is lost as it is consumed: where does it go?

only a small percent of energy from plants enters the food chain

CB 55.9 only a small percent of energy is stored in organism

CB Energy is lost in each consumer: the 10% rule

Human impact: As consumers

Use of agriculture in the U.S. About 1/2 of water and ~80% of agricultural land is used for raising animals.

Fossil Fuels: Producing beef consumes over 100 times more fossil fuel than producing potatoes. The typical American could save almost as much gas by going vegetarian as by not driving.

Next: Diets, homework due Mid-semester report due