© OUP: To be used solely in purchaser’s school or college 8A Food and digestion Food Balancing...

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8A Food and digestion

Balancing your diet

Digestion

What do we need food for?

Energy to do things

8A Food – who needs it?

Raw materials to grow larger

Raw materials to repair damaged body parts

Proteins

8A So what’s in food?

Food is a complicated mixture of different chemicals. We can sort these chemicals into different types. What are the main types?

Carbohydrates (starch and sugars)

Vitamins

Minerals

Can you make up a sentence with words starting with the same letters – a mnemonic?

Roughage

8A Which food contains which chemical?

Which foods belong to which food groups?

Proteins

Fats Carbohydrates Water

Proteins

Water Carbohydrates

8A What’s in food?

We can test foods to find out what chemicals they contain.

Orangey-brown iodine turns blue-black when it reacts with starch.

drop iodine solution onto the food

black = starch

Blue Benedict’s solution turns orangey-red when it is boiled with glucose.

blue turns orange/red= glucose

chopped up food

hot water

In the Biuret test the solution turns purple.

chopped up food

potassium hydroxide

coppersulphate

purple = protein

Fats go cloudy white when they are mixed with ethanol and water.

Now see if you can use these tests to identify the food chemicals on the next slides.

grind food with ethanol

add waterfilter

cloudy = fat

For each food, decide on the chemicals found in them.

Fats Protein Starch Glucose

Food sample Test Result

Iodine solution orangey-brown

Benedict’s test blue

Biuret test purple

Ethanol test cloudy white

Iodine solution blue-black

Benedict’s test blue

Biuret test blue

Ethanol test clear

Benedict’s test orangey-red

Biuret test blue

Ethanol test clear

Benedict’s test orangey-red

Biuret test blue

Ethanol test clear

8A Vitamins

Vitamin Found in Gives you

Liver, butter, green vegetables

Cheese, milk, liver, eggs, green vegetables

Citrus fruits, green vegetables, potatoes

Fish liver oil, eggs, sunlight on the skin

Healthy skin and teeth

Healthy skin

Healthy teeth and gums, without it you get scurvy

Healthy bones – without it you get rickets (soft bones)

Balancing your diet

1. A balanced diet…

a) contains the same amounts of the main food groups

b) contains healthy amounts of the main food groups

c) doesn’t fall off the table.

2. A balanced diet for most people has more…

a) fat than water

b) carbohydrate than protein

c) crisps than fruit.

8A A food test for YOU!

3. To test for protein in food you…

a) add iodine solution

b) do the Biuret test

c) poke it with a big stick.

4. Sugar and starch are both…

a) proteins

b) fats

c) carbohydrates.

5. Iodine solutions turns blue-black with…

a) starch

b) protein

c) age.

6. A food went orangey-red when it was boiled with Benedicts solution. It could be…

a) a carrot

b) a boiled sweet

c) a sausage.

7. Not enough vitamin C gives you…

a) headaches

b) scurvy

c) weak bones.

8. Riboflavin is…

a) a B vitamin

b) a fruit drink

c) an elf from The Lord of the Rings.

Digestion

8A Why digestion?

Food is a mixture of molecules.

Some of these molecules are too large to pass into the body.

Digestion breaks down food in the gut into smaller molecules.

The body uses these smaller molecules for energy or to build body parts.

8A Where it all happens

What happens where? Follow the food down through the body.

Mouth breaks large lumps of food into smaller lumps.

Stomach produces enzymes to break down proteins.

Intestines produce enzymes to break down proteins, carbohydrates and fats. Start to absorb food into body.

Colon absorbs water and stores waste until time to pass out of the body.

8A Watching the digestives

8A Absorbing stuff

1. Enzymes are made of protein.

2. Enzymes only work in acid solutions.

3. Enzymes can only break down molecules.

4. A protease is an enzyme that breaks down protein into smaller molecules.

8A Digestion - True or False?

True or False?

1. An enzyme works best at a particular temperature.

2. Most enzymes in the human body work best at about 57°C.

3. Enzymes work best in boiling water.

4. Snakes produce one enzyme that can digest everything in its victim from the skin to the bones.

5. Amylase is an enzyme that breaks down starch.

8A Digestion - True or False?

True or False?

© OUP: To be used solely in purchaser’s school or college 8A Food and digestion Food Balancing...

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