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
http://www.pcrm.org/magazine/gm07autumn/health_pork.html
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
CB 41.2
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
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.
CB 41.13
Physical digestion:
liquefying of food
Chemical digestion:
breaking large molecules
into small molecules
Cb 41.11
Chewing and adding saliva begins the
process of liquification
Amylase
in mouth
Amylase begins the chemical digestion of
carbs
CB 41.10
The primary function
of the stomach is
food storage
In the stomach
liquification continues.
Pepsin
in stomach
Pepsin begins
the chemical
digestion of
proteins.
CB 41.12
CB 41.10
The Digestive System
CB 41.15
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 41.10
The Digestive System
CB 41.11
Carb’sprovide energy
and
structural support
Most organisms cannot break
down cellulose
CB 5.8
Ruminants have multiple stomachs where
microorganisms help digest cellulose
CB 41.20
Carnivores have a
short digestive system
CB
41.19
Herbivores have a
long digestive system
CB
41.19
Bears
Both humans
and grizzly
bears are
omnivores.
Our digestive
systems can
tell us about
our ancestors.
Humans
Chimps commonly hunt small animals including
other smaller primates.
Hunting encourages cooperative behavior and may
help produce more cohesive and advanced societies.
http://wwwrcf.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. 1994. Evolutionary perspectives on human nutrition: the influence of brain and body size on diet and
metabolism. Am. J. Hum. Biol. 6:77–88
Brain size, body size, and molar (grinding)
tooth area
Table 2 Annual Review of Nutrition Vol. 27: 311-327 Effects of Brain Evolution on Human Nutrition and Metabolism
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
http://www.boingboing.net/2010/08/03/theres-more-energy-i.html
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: 10.1021/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: 10.1021/es100310d
CB
54.11
Producers and
Consumers
CB
54.11
Higher
consumers are
usually larger
and fewer in
number than
lower
consumers
CB 55.10
Energy is lost in each consumer
1000
CB 55.10
Energy is lost as it is consumed: where does it
go?
1000
only a
small
percent of
energy
from plants
enters the
food chain
only a small percent of energy is stored
in organism
CB 55.9
CB 55.10
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.
http://bicycleuniverse.info/transpo/beef.html
Next: Diets,
homework due
Mid-semester
report due