T9.2 Human Digestive System

Year 9 Topic 2 @ SGS

Digestive System

Organ system that works together to digest and absorb food

Enzymes

Biological catalyst, speeding up chemical reactions in living organisms

Properties of Enzymes

• Large protein

• Catalyse a specific reaction due to its shape

• Has an optimum temperature & pH

• Denatured by extreme pH or temperatures

Lock & Key Theory

• The active site of the enzyme specifically matches the unique shape of the substrate.

• Enzymes tend to catalyse only one reaction

Digestive Enzymes

Converts food into small soluble molecules that can be absorbed into the bloodstream

Amylase

• Salivary Glands, Pancreas

• Breaks down starch into simple sugars

Protease

• Pancreas, Stomach, Small Intestine

• Breaks down proteins into amino acids

Lipase

• Pancreas, Small Intestine

• Breaks down lipids (fats) into glycerol and fatty acids

Bile

• Stored in the Gallbladder

• Neutralises stomach acid for optimum pH for lipase

• Emulsifies fats to increase surface area

Test for Carbohydrates

Iodine Test - Changes from brown-orange to blue-black

Test for Simple Sugars

• Benedict’s Test -

  • Water bath @ 75°C

  • Changes from blue to green to yellow to brick-red

Test for Proteins

Biuret Test - Changes from blue to purple

Test for Lipids (Fats)

Ethanol and Water - Changes from clear to cloudy