B3

Cell

Basic unit of life

Tissue

Groups of cells with a similar structure and function

Organ

An organ is an aggregate (or group) of tissues working together to perform a specific function.

Organ System

Groups of organs working together to perform a specific function

Epithelial Tissue

Covers the inside and outside of an organ

Glandular Tissue

Produces and releases digestive chemicals that breaks down food

Muscular Tissue

It contracts to churn food with digestive juices to help break it down.

Digestion

Breaking up large insoluble molecules into smaller, soluble molecules

Why do the nutrients in our food need to be digested

The nutrients in food need to be digested into smaller molecules so that they are small enough to be absorbed by our blood stream

what do digestive enzymes do during digestion

break the bonds between nutrient molecules so they are small enough to be absorbed

digestive enzyme

biological catalysts that speed up the breakdown of large food molecules into smaller, soluble ones that can be absorbed by the body.

mouth

breaks up food

Salivary Gland

Moistens food to make it easier to swallow and releases digestive enzymes

Oesophagus

Transports food to the stomach

Stomach

Releases hydrochloric acid, kills micro organisms and releases digestive enzymes which chemically digests food and also churns food

Pancreas

Releases digestive enzymes into the small intestine

Liver

Makes bile which helps enzymes digest lipids into smaller droplets

Gall Bladder

Stores bile

Small Intestine

Digestion and absorption of nutrients

Large Intestine

Absorbs water

Rectum

Undigested food is stored here

Anus

Where undigested food exits the body

Bile

1. Neutralizes stomach acid, creates alkaline conditions for enzyme in the small intestine

2. breaks large fat droplets into smaller ones, increasing the surface area for lipase to act

What happens to food molecules after digestion in the small intestine?

They are small and soluble enough to pass through the cell membranes of epithelial cells lining the small intestine.

After entering epithelial cells, how do nutrients enter the bloodstream?

Nutrients move from the epithelial cells into the blood capillaries.

Why is it important for digested nutrients to enter the blood?

So the blood can transport nutrients around the body to the cells for use.

Adaptions of small intestine:

1. folds the inner lining of small intestine has folds that increase the surface area of absorption

2. good blood supply which maintains a higher concentration gradient so more diffusion

3. Villi are one cell thick which means diffusion distance is short

Protein

Growth and repairs tissue; needs to be digested - molecules are large and insoluble

Carbohydrate

Main source of energy; needs to be digested - molecules are large and insoluble

Fats

Energy and insulation

Vitamins and Minerals

Helps chemical reactions in the body; do not need to be digested - molecules are small and soluble

water

hydration; needs to be digested - molecules are large and insoluble

Fibre

Helps food move through the digestive system

How are carbohydrates (starch) digested?

Amylase (a carbohydrase) breaks starch into glucose. It’s made in the salivary glands, pancreas, and small intestine.

How are proteins digested?

Proteases break proteins into amino acids. They are made in the stomach and pancreas.

How are lipids digested?

Lipase breaks lipids into 1 glycerol and 3 fatty acids. It’s made in the pancreas and small intestine.

How do you test for starch and what are the colour changes?

Add iodine solution directly.

• Before: Orange-brown

• After (positive): Blue-black if starch is present

How do you test for sugar and what are the colour changes?

Add Benedict’s solution and heat in a boiling water bath.

• Before: Blue

• After (positive):

  • Green = low sugar

  • Orange = medium sugar

  • Red = high sugar

How do you test for protein and what are the colour changes?

Add Biuret solution and look for a colour change.

• Before: Blue

• After (positive): Purple/lilac if protein is present

How do you test for lipids and what are the colour changes?

Add ethanol, shake, then add water.

• Before: Colourless

• After (positive): Milky/cloudy white emulsion if lipids are present

Catalysts

Speed up reactions without being used up

Enzymes

Lower the activation energy required for a reaction and are biological catalysts made up of proteins

High temperature

enzyme and active site denatured

High and Low PH

enzyme denatured