Physical Digestion

Reducing food without changing them chemically

• Chewing/Grinding (PHYSICAL) – Decreases particle size, while increasing surface

area – Speeds reaction rate – reduces nutrient loss

Ruminants - able to acquire nutrients from fermenting plants it in a specialized stomachs prior to digestion, principally through bacterial actions.

The process typically requires regurgitating cud and chewing it again. (repeating)

Emulsification (PHYSICAL) -see demo

Fats have the tendency to form globs in solutions. Emulsifiers- are compounds (salts) that keep fats in

smaller droplets or particles.

5

Enzymes

Enzyme - protein that acts as a biological catalyst (speeds up a chemical reaction without being used up)

- they require specific conditions (pH) to function & are temperature sensitive

Chemical Digestion Again

A Brief Summary of the digestive process:

Mouth (pH-7 neutral) - salivary glands produce amylase which breaks

starch to maltose (disaccharide)

A Brief Summary of the digestive process:

Stomach - acidic condition (pH 2) - amylase is inactivated (since pH change) - pepsin is activated---> breaks protein down to

peptides

A Brief Summary of the digestive process:

Small Intestine - alkaline condition (pH 8) - pepsin inactivated - other enzymes continue to break peptides down to

simpler peptides (proteases) - additionally, enzymes break down disaccharides to

simple sugars (maltase, sucrase, lactase)

The Pancreas

• secrete enzymes into the small intestines. • act on carbohydrates (amylase), fats (lipase),

and peptides (proteases) • secretes a basic solution (bicarbonate) to

neutralize chyme (---> making it slightly basic)

The Liver & Gall Bladder

Liver

The Liver & Gall Bladder

Liver • continuously makes bile - speeds up fat digestion

- bile emulsifies fat = physical digestion - smaller droplets of fat chemically broken down by

lipases

The Liver & Gall Bladder

Other important functions of the liver include: - breaks down old RBC - storage of excess chemicals from blood

sugar, vitamins A, D, E, K - breaks down amino acids for storage of

- detoxifies poisons and drugs (including alcohol)

gall bladder - stores bile