Digestion
& Reassembly
Oh, YUCK!
http://www.youtube.com/watch?v=Uzl6M1YlU3w
1
Animal Nutrition
Why do we eat?
We need matter and energy to grow, repair, and maintain
our bodies: nutrients (E.g.: carbs, proteins, lipids, water…)
Some nutrients cannot be made by our bodies from other
materials, so we must get them through our food:
Essential nutrients
• Essential amino acids
– Building the “ALABAMA” protein
• Essential fatty acids
– E.g., omega-3 and omega-6 fatty acids (found in fish and seeds)
• Vitamins
– E.g., vitamin A, B vitamins, vitamin C, Niacin, Folic acid
• Minerals
– E.g., calcium, phosphorus, sodium
2
Mammalian Digestive System
• Is the digestive tract inside or
outside of the body?
• Does digestion happen inside
or outside of our cells?
Fig. 41.10
Stages of Food Processing
3
5
The Mouth
• Mechanical digestion - chewing
• Chemical digestion - enzyme
that hydrolyzes starch &
glycogen
The Stomach
• Secretes acid and an enzyme
– HCL (hydrochloric acid)
• pH 2
• Disrupts extracellular matrix
of cells
• Kills most bacteria
• Denatures proteins
– enzyme
• breaks bond
between amino
acids
6
The Small Intestine - Digestion
•
•
•
•
Churning
Nutrient-rich broth (chyme) enters small intestine
Liver secretes bile – helps digestion of fats
Pancreas secretes enzymes & chemicals that
raise the pH
• Small intestine secretes enzymes
Food now broken down into
monosaccharides, amino
acids, glycerol, fatty acids,
nucleotides
8
The Small Intestine - Absorption
• Nutrients transported across epithelial cells to
bloodstream.
• Nutrients in bloodstream circulated to all cells in the
body and transported across plasma membrane for use
in the cell.
9
The Large Intestine
10
• Colon
– Recover water for the
body
• Rectum
– Stores feces (undigested
material such as
cellulose, and lots of
intestinal bacteria!)
http://en.wikipedia.org/wiki/Large_intestine
11
Starch to glycogen
Proteins to (different) proteins
Lipids to (different) lipids
Polynucleotides to (different)
polynucleotides
From
food
cells to
our
cells!