Food Flashcards
What does a balanced diet consist of?
Should include appropriate proportions of:
- Carbohydrates
- Lipids
- Proteins
- Minerals
- Vitamins
- Water
- Dietary Fibre
What are Carbohydrates?
- They contain carbon, hydrogen and oxygen
- Provide substances for respiration, and so provide energy and may reduce cholesterol
- Makes up 5% of body mass
- E.G potato, rice and wheat, pasta, sugar
What are sugars?
- They are a type of carbohydrate
- They are soluble in water
- Simple sugar is a monosaccharide e.g. glucose and fructose
- disaccharide e.g. maltose, sucrose and lactose
- If you have too much sugar you may have diabetes or tooth decay
What is the test for sugar (glucose)?
Add 5cm cubed of Benedict’s solution, place in a water baths and the light blue will turn to brick red if sugar is present
What is starch?
- Starch is a large complex carbohydrate
- They are insoluble in water
- Made up of hundreds of glucose molecules and so it is a polymer of glucose
- It is a polysaccharide (made up of simple sugars bonded together)
- Has to be broken down into simple sugars during digestion, so that they can be absorbed into the blood
What is glycogen?
- Glycogen is a large complex carbohydrate
- Polymer of glucose
- Found in liver and muscles, where it acts as a store of energy for these organs
- Has to be broken down into simple sugars during digestion, so that they can be absorbed into the blood
What is cellulose?
- Polymer of glucose
- Makes up plant cell walls
- Human cannot digest, however it form dietary fibre or roughage
What is the test for starch?
Place a sample in a spotting tile, add iodine and if turns from brown to bluey/black starch is present
What are lipids (fats and oils)?
- There are two forms solid (butter) and liquid (oil)
- They contain carbon, hydrogen and oxygen
- Makes up 10% of body mass
- Provide energy, act as an energy store and they provide, insulation, protection, buoyancy and release energy
- E.G butter, milk, cheese, eggs, nuts, oily fish
What are lipids made up of?
A triglyceride
One glycerol and 3 fatty acid
What happens when lipids are digested?
Glycerol and fatty acids are absorbed into the bloodstream
What happens if you have too much lipids?
Can lead to heart disease
What is the test for lipids?
Add ethanol, shake and if lipids are present ethanol will turn cloudy
What are proteins?
- They make up 18% of body mass
- They are made up of long chains of amino acids, there are 20 different types of amino acids all containing, hydrogen, oxygen, carbon and nitrogen and 2 contain sulphur, there are lots of different combinations for different purposes
- They help for growth and cell repair (repair of tissue) and help to provide energy in emergencies
- E.G. meat, fish, eggs and proteins
What happens if you have too little protein?
Kwashiorkor
What is the test for protein?
5cm cubed of protein and 5cm cubed of Biuret solution, blue to purple if protein is present
Describe Calcium
- Source: milk, cheese, eggs
- Role: Teeth and bone development
- Deficiency: hypocalcemia and rickets
Describe Iron
- Source: liver, eggs, spinach, red meat
- Role: needed to make haemoglobin in RBC for healthy blood to help carry oxygen
- Deficiency: anemia
Describe Water
- Source: food and drink
- Role: almost every bodily function relies of water, need a constant supply to replace the water lost through urinating, breathing and sweating
Describe Dietary Fibre
- Source: wholemeal bread
2. Role: aids the movement of food through the gut
Describe Vitamin A
- Source: liver, butter, carrots
- Role: keeps the cells in the eye healthy and protects the surface of the eye and connective tissue, helps to improve vision and keep your skin and hair healthy, makes chemicals in the retina
- Deficiency: night blindness and damaged cornea
Describe Vitamin B
- Source: cereals, eggs, fish
- Role: helps will cell respiration
- Deficiency: dry skin, mouth sores, anaemia
Describe Vitamin C
- Source: fresh fruit and vegetables e.g. orange
- Role: helps heal, sticks together cells lining surfaces in the body such as the mouth, prevent scurvy
- Deficiency: scurvy
Describe Vitamin D
- Source: fish liver oils, eggs
- Role: helps bones absorb calcium and phosphate, Vitamin D is also made by your body when your skin is exposed to sunlight
- Deficiency: rickets, poor teeth
How do the energy requirements vary in different people?
- Activity level: active people need more energy
- Age: children and teenagers need more energy than older people as they need to grow and they are generally more active
- Pregnancy: pregnant woman need more energy than other woman, and they need to provide the energy that their babies need to develop
How do you test for the energy in food?
- Food can be burnt to see how much energy it contains (calorimetry)
1. You need a dry food that will burn well for example a peanut or pasta
2. Then weigh a small amount of the food and then skewer it on a mounted needle
3. Next add 25 cm cubed of water to a boiling tube which is held with a clamp (to measure the amount of heat energy that is released when the food is burnt)
4. Measure the temperature of the water
5. Then set fire to the food by placing it over a bunsen burner (make sure that the water isn’t near as may affect results)
6. Immediately hold the burning food under the boiling tube until it goes out. Then relight the food and hold it under the tube, keep doing this until the food won’t catch fire again
7. Then measure the temperature of the water
8. Finally calculate the amount of energy in the food
How would you calculate the amount of energy in the food?
energy of food (J) = mass of water (g) x temperature change of water (℃) x 4.2
(1 cm cubed of water is the same as 1g of water)
How would you calculate the amount of energy in Joules per gram?
energy per gram of food (J/g) = energy of food (J) / mass of food (g)
-You need to do this calculation so that you can compare the energy values of different foods fairly
How can the accuracy of this experiment be increasing?
- Quite a lot of energy released from burning is lost to the surroundings, hence why energy value on packet would be much higher than your own
- No constant distant, did not account for sut building up (use new test tube each time?), time the different chips were under fire i.e more time to heat up??
- Insulate the boiling tube e.g. with foil would minimise heat loss and keep more energy in the water, making your results more accurate.
- Room at constant temperature
How is the energy in food measured? How do you work out BMI?
In Kilojoules
Mass (Kg) / Height (m) sqaured
Body Mass Index works better over 18-20 as doesn’t take into account age (i.e. may still be growing), sex, body size, level of physical activity (muscle weighs more than fat)
What is the structure of carbohydrates, proteins and lipids?
- Large molecules made up from smaller basic units
- Starch and glycogen from simple sugar
- Protein from amino acids
- Lipids from fatty acids and glycerol
