Digestive System

Question 1

List the parts of the digestive system and there features

What enzymes they produce, their function etc

Answer 1

• Mouth - saliva lubricates food + contains amylase
• Oesophagus - moves food from mouth to stomach using peristalisis (wave like muscle contractions)
• Stomach - releases protease, contains hydrochloric acid to creatae optimum pH + kill pathogens
• Liver - makes bile which helps break down fats
• Gall bladder - stores bile
• Pancreas - secretes protease, amylase, lipase that break down various food
• Small intestine - releases protease, amylase, lipase to complete digestion + absorb into blood stream
• Large intestine - absorbs excess food + water
• Rectum - stores solid waste + releases via rectum

Question 2

Why do carbohydrates, proteins and lipids need to be broken down?

Answer 2

Needed for growth, repair and metabolism.
Molecules are too large ; broken down by digestive enzymes then synthesised by other enzymes

Question 3

How are carbohydrates digested?

Provide example(s) and digestive enzyme

Answer 3

Eg. glycogen, starch, surcose and glucose.
Amylase breaks down carbohydrates into simple sugars.

Question 4

How are proteins digested?

Provide example(s) and digestive enzyme

Answer 4

Eg. haemoglobin, keratine, pepsin (in stomach)
Protease breaks down proteins into amino acids.

Question 5

How are lipids digested?

Provide example(s) and digestive enzyme

Answer 5

Eg. fats and oils
Lipease breaks down lipids into fatty acids and glycerol

Question 6

List the steps for testing for starch in a food sample.

Answer 6

Add iodine solution to 5cm^3 food sample you want to test in test tube and shake gently.
Foods containing starch turn from orange/brown to black/blue

Iodine = irritant - avoid contact with eyes. Wear goggles

Question 7

List the steps for testing for simple sugars in a food sample.

Answer 7

Add benedicts solution to 5cm^3 food sample you want to test.
Prepare water bath between 75-80
Place test tube in water bath for 5 mins
If sample contains sugars, will change from green to yellow to orange to red

Benedicts solution = irritant

Question 8

List the steps for testing for protein in a food sample.

Answer 8

Add 2cm^3 biurets solution to 2cm^3 food sample and shake gently
If food contains protein will either turn purple or a ring between layers

Biuret solution = irritant

Question 9

List the steps for testing for fats in a food sample.

Answer 9

Use pipette to add 3 drops of Sudan III solution to 5cm^3 food sample
If lipids are present, mixture will separate into 2 layers, top layer will turn red

Question 10

How do you prepare a food sample?

Answer 10

1. Break piece of food up with pestle +mortar
2. transfer to beaker filled with distilled water
3. Stir with glass rod to dissolve some food
4. Filter solution using funnel lined with filter paper to get rid of remaining solids

Question 11

Describe the function of muscle in the cell wall of the stomach.

Answer 11

They contract to churn food for digestion. Use peristalsis.