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8A Food and digestion
Food
Balancing your diet
Digestion
8A Food and digestion
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Food
8A Food and digestion
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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
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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?
Fats
Carbohydrates (starch and sugars)
Vitamins
Minerals
Water
Can you make up a sentence with words starting with the same letters – a mnemonic?
Roughage
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8A Which food contains which chemical?
Which foods belong to which food groups?
Proteins
Fats Carbohydrates Water
Proteins
Water Carbohydrates
Fats
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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
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8A What’s in food?
Blue Benedict’s solution turns orangey-red when it is boiled with glucose.
blue turns orange/red= glucose
heat
chopped up food
hot water
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8A What’s in food?
In the Biuret test the solution turns purple.
chopped up food
potassium hydroxide
shake
coppersulphate
purple = protein
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8A What’s in food?
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
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8A What’s in food?
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
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8A What’s in food?
For each food, decide on the chemicals found in them.
Fats Protein Starch Glucose
Food sample Test Result
Iodine solution blue-black
Benedict’s test blue
Biuret test blue
Ethanol test clear
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8A What’s in food?
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 orangey-red
Biuret test blue
Ethanol test clear
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8A What’s in food?
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 orangey-red
Biuret test blue
Ethanol test clear
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8A Vitamins
Vitamin Found in Gives you
A
B2
C
D
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)
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Balancing your diet
8A Food and digestion
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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!
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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.
8A A food test for YOU!
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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.
8A A food test for YOU!
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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.
8A A food test for YOU!
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Digestion
8A Food and digestion
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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.
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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.
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8A Watching the digestives
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8A Absorbing stuff
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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?
TRUE
FALSE
FALSE
TRUE
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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?
TRUE
FALSE
FALSE
FALSE
TRUE
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