food and diet
TRANSCRIPT
Food &
Diet
Food is needed for:1. Energy and warmth2. Growth3. Repairing and replacing tissues4. Keeping the body healthy and fight disease
The amount of energy needed by a person depends upon:-
1) age 2) sex 3) temperature4) job
A balanced diet is composed of the right amounts of:-
1. Water2. Carbohydrates3. Lipids4. Proteins5. Mineral salts6. Vitamins7. Dietary fibre or
roughage
1. Water2. Carbohydrates3. Lipids4. Proteins5. Mineral salts6. Vitamins7. Dietary fibre or roughage
The food guide pyramid
Malnutrition condition that results from taking an
unbalanced diet in which certain nutrients are:
lacking in excess (too high an intake) or in the wrong proportions
Components of a balanced diet :-
1. Water2. Carbohydrates3. Lipids4. Proteins5. Mineral salts6. Vitamins7. Dietary fibre or roughage
Uses of water in organisms:-1. as part of cytoplasm (most cells contain 75%
water)2. as a solvent in which chemical reaction occur3. to activate enzymes4. for photosynthesis in plants5. for growth and support in plants6. to transport substances round the body (blood
has a lot of water)7. brings about cooling on evaporating
Animals get water from:- 1. Drinking2. Eating3. Chemical reactions e.g.
respiration
O2
food
ATP
H2O
Components of a balanced diet :-
1. Water2. Carbohydrates3. Lipids4. Proteins5. Mineral salts6. Vitamins7. Dietary fibre or roughage
CARBOHYDRATES contain the elements:
Carbon Hydrogen Oxygen
have more oxygen than fats Glucose:
is the simplest carbohydrate (C6 H12 O6)
Easy to remember elements:
Food ElementsCarbohydrates C, H, OLipids C, H, OProteins C, H, O, N [sometimes
S and P]
Food rich in carbohydrates
Uses of carbohydrates:- a) provide energy (17kJ/g)
Sugar in energy drink equivalent to six pastries.
Question: MAY, 2004Give biological explanations for each of the following statements:
The diet of athletes is usually high in carbohydrates. (5)Athletes need a lot of energy. Carbohydrates are the body’s main energy source. Carbohydrates like starch in bread are digested into glucose. Glucose is used in respiration to release energy. If athletes take in monosaccharides, i.e. sugars e.g. glucose, they are provided with energy very quickly.
Uses of carbohydrates:-
Cell wall
c) to build cell walls in plants
b) to store energy e.g. starch in potatoes or roots
Storage organs
Uses of carbohydrates:- d) fibre is important to prevent constipation
Food sources of fibre: whole wheat, bran, fresh or dried fruit & vegetables. Constipated!!
In what form are excess carbohydrates stored?
1) in plants:
2) in animals:
Name two places in animals where glycogen is stored.
starch
glycogen
Liver & muscles
Three types of carbohydrates
1. Monosaccharidese.g. glucose, fructose
2. Disaccharidese.g. maltose, lactose, sucrose
3. Polysaccharidese.g. starch, glycogen, cellulose
Sweet &
Soluble
Monosaccharides
Disaccharides
PolysaccharidesNot sweet
& Insoluble
Name the monosaccharide which forms starch, glycogen and cellulose.
Glycogen Cellulose Starch
Glucose
How do starch, glycogen and cellulose differ?
Glycogen Cellulose Starch
The way glucose units are linked together
Question: MAY, 2008 (IIB)Where in a plant would you expect to find:
i) Cellulose (1)ii) Starch (1)
i) Cellulose – found in cell walls of plant cellii) Starch – found stored in roots /
storage organs
Why is the tired athlete choosing sugar rather than starch?
Sugars, especially monosaccharides can
be used for respiration right away.
Starch needs to be digested first.
Components of a balanced diet :-
1. Water2. Carbohydrates3. Lipids4. Proteins5. Mineral salts6. Vitamins7. Dietary fibre or roughage
LIPIDS a name for fats and oils contain the elements:- C, H, O
lard
Food rich in lipids:-
Nuts
Egg yolk
uses of lipida) provide energy (39 kJ/g)b) store energy
uses of lipidc) insulation in mammalsd) protection of delicate
organs from bumps
Fat around kidney.
Fat lines body wall of a rabbit.
Question: MAY, 2008 (IIB)Explain why one kilogram of starch crops releases less energy when burnt, compared to one kilogram of oil crops. (2)
Starch is a carbohydrate whilst oil is a lipid. Carbohydrates have a lower energy content than lipids.
building blocks of a lipid molecule: Glycerol Fatty acids
A molecule of fat
excess lipids are stored:- 1) in the ADIPOSE TISSUE under the skin2) around organs
Fat around heart.
What does this pyramid show about
intake of lipids?
Few lipids must be taken.
What happens to a person’s weight when:
Weight remains constant
What happens to a person’s weight when:
Weight increases
Obese person
What happens to a person’s weight when:
Weight decreases
Components of a balanced diet :-
1. Water2. Carbohydrates3. Lipids4. Proteins5. Mineral salts6. Vitamins7. Dietary fibre or roughage
PROTEINS contain the elements:-
C, H, O, N (sometimes S and P)
food rich in proteins:- Meat Fish Egg white Cheese
Uses of proteins:-1. for growth2. for cell repair and replacement3. to make enzymes4. to make antibodies
What are the building blocks of proteins called?
Amino acids
Two amino acids are linked by a:
dipeptide:2 amino acids linked together
Peptide bond
Polypeptide: many amino acids are linked
A protein: many polypeptides joined up
different amino acids occur in proteins
Two types of amino acids:
1. Essential [8 amino acids]must be eaten as they
cannot be made by the body
2. non-essentialcan be made by the
body
contain significant amounts of all the essential amino acids
Source: animals : eggs, meat, fish, cheese
deficient in one or more essential amino acid Source: plants
For example, corn is deficient in one amino acid
Individuals who eat only corn would show symptoms of protein deficiency.• This is true from any diet limited to a
single plant source, including: Rice Wheat or potatoes
are an exception:
Soya bean protein is a good source of protein,
for vegetarians and vegans or for people who cannot afford
meat. Explain.
Have you ever tasted: Soya bean milk Tofu
Tofu is made by coagulating soya milk and then pressing the resulting
curds into soft white blocks.
• is referred to as:
Artificial meat is manufactured from : soya beans bacteria and fungi
Artificial meat is flavoured and textured to taste like
chicken or ham.
How can protein deficiency from a vegetarian diet be avoided?
By eating a combination of plant
foods that complement each other to supply all essential amino acids.
– For example, beans supply the lysine that is missing in corn, and corn provides the methionine which is deficient in beans.
Excess proteins: cannot be stored in the body are broken down in the liver by a process
called DEAMINATION the waste product produced is called UREA
liver
Components of a balanced diet :-1. Water2. Carbohydrates3. Lipids4. Proteins5. Mineral salts6. Vitamins7. Dietary fibre or roughage
MINERAL SALTS contain certain elements that help cells to
function properly
CALCIUM is needed for:-
a) hard bones and teeth b) muscles to contractc) to clot blood
is found in: milk cheese fish
Rickets: deformed bones
deficiency of calcium
IRON is needed to build the red pigment in blood
called haemoglobin
IRON is found in:
red meat like liver & kidneys
green vegetables: spinach, broccoli
Normal amount of red blood cells
Anaemic amount of red blood cells
A lack of iron results in: ANAEMIA
Question: MAY, 2004Give biological explanations for each of the following statements:
a) A dietician suggested to an anaemic person to include liver in the diet. (5)Person lacks iron. Red meat like liver is rich in iron. Iron is needed to form haemoglobin in red blood cells.
b) Nutritionists often recommend a low intake of fried foods. (5)
Fats provide a lot of energy. May lead to obesity.
Fried foods are rich in cholesterol that may block arteries = higher risk for a heart attack.
MAGNESIUM forms the centre of the chlorophyll molecule
in green plants
No magnesium: yellow leaves
Components of a balanced diet :-
1. Water2. Carbohydrates3. Lipids4. Proteins5. Mineral salts6. Vitamins7. Dietary fibre or roughage
VITAMINS needed in small quantities for the normal
chemical activities of the body
cannot be used as: a source of energy
OR to build cell structures
A disease develops if a vitamin is missing. How can the person be cured?
By taking the missing vitamin.
vitamins can be :- a) Water soluble – vitamins B and Cb) Fat soluble – vitamins A, D, E, K
Water-soluble vitamins are lost from the vegetables when they are boiled but
not when steamed.
Why is it better to steam vegetables
rather than boil them?
Vitamin Food source Deficiency disease
A Milk, liver Night blindness
C Citrus fruit, potatoes
Scurvy
D Milk, liver Rickets
Carrots are a rich source of vitamin A
Vitamin A prevents night blindness.
QUESTION: MAY 2010 Explain why the student used this picture when mentioning night blindness. (2)Night blindness is caused by a lack of Vitamin A in the diet. 1 markCarrots are a good source of Vitamin A that can help to prevent night blindness. 1 mark
Found in Citrus fruit
Deficiency of Vitamin C:
Which vitamin prevents colds?
Vitamin D is made by the action of sunlight on the
skin.
Deficiency of Vitamin D:
Normal Rickets
NOTE: Lack of calcium Lack of vitamin D
Reason:
Vitamin D helps the body to absorb calcium from the foods we eat. The more calcium the body can absorb, the stronger the bones will become
Question: Sep, 2004What special provisions should be made in the diet of young children and pregnant mothers? Explain why each provision you mention is important. (6, 4)Young children:1. High protein content food – e.g. meat for growth2. Drink a lot of milk – supplies proteins, calcium,
Vitamin A & D.3. Include carbohydrate-rich foods – for energy
Pregnant women:1. Folic acid (a vitamin B) – in citrus
fruit, legumes: to form the nervous system of the embryo
2. Food rich in iron – e.g. liver, green vegetables: to have enough blood in placenta to nourish embryo
3. Calcium-rich food – e.g. dairy products to supply embryo with calcium to form its skeleton
Question: Sep, 2004
Give a biological explanation for each of the following statements.a) Daily inclusion of too much Vitamin C in the
diet is a waste. (2)Vitamin C cannot be stored in the body as it is water-soluble. Lost in urine.
Give a biological explanation for each of the following statements.a) Small doses of Vitamin D (5-10mg per day)
are recommended for housebound people spending a lot of time indoors. (2)Vitamin D cannot be made by the action of sunlight on the skin. To have enough
Vitamin D, supplements are needed.
Question: MAY, 2004Give biological explanations for each of the following statements:
a) School canteens are encouraged to sell unsweetened cereals rather than sweets. (5)Sweets are carbohydrates that provide energy. Too much sweets may lead to obesity. Obesity leads to higher risk of diseases.Sweets increase chance for tooth decay.
b) Young children are encouraged to eat dairy products regularly. (5)
Milk is rich in: calcium – needed to form
strong bones and teeth. proteins – needed for
growth. Vitamins – for healthy growth; e.g. vitamin A to
prevent night blindness and vitamin D to help in the absorption of calcium and to prevent rickets.
Components of a balanced diet :-
1. Water2. Carbohydrates3. Lipids4. Proteins5. Mineral salts6. Vitamins7. Dietary fibre or roughage
DIETARY FIBRE or ROUGHAGE sources of fibre:-
vegetables fresh fruit bran cereals wholemeal bread
Cellulose : is the main source of dietary fibre
Explain why although humans cannot digest dietary fibre, it is still important.
Functions of roughage:-1. adds bulk to the contents of the intestine
and keeps food moving along the gut
Gut
Functions of roughage:-2. prevents constipation as fibre retains water
so that the faeces are soft3. prevents cancer of the colon (part of the
intestine)
faeces
Food Test Colour change
Starch
+ iodine solution Yellow to blue black
Iodine solution
Starch
Look at this picture. Is starch present in potato? Yes.
Food Test Colour change
Protein(Biuret test)
+ sodium hydroxide solution + 1-2 drops of copper sulfate solution
Blue to purple
Egg white [protein]
1. Sodium hydroxide solution2. Copper
sulfate solution
A positive test for protein was obtained for………………albumin
Food Test Colour change
Oil+ ethanol + shake + water + shake
A white emulsion forms
Food Test Colour change
Oil rub food onto a dry piece of filter paper
A greasy spot forms
Food Test Colour change
Glucose + Benedict’s solution or Fehling’s solution + heat
Blue to brick red
or orange
Food Test Colour change
Glucose + Benedict’s solution or Fehling’s solution + heat
Blue to brick red
or orange
Food Test Colour change
Starch
+ iodine solution Yellow to blue black
Protein(Biuret test)
+ sodium hydroxide solution + 1-2 drops of copper sulfate solution
Blue to purple
Oil
1) + ethanol + shake + water + shake
2) rub food onto a dry piece of
filter paper
A white emulsion forms
A greasy spot
forms
Glucose + Benedict’s solution or Fehling’s solution + heat
Blue to brick red
or orange
When the food to be tested is a solid:
1. Crush the food with some water using a pestle and a mortar.
2. Filter.3. Add the reagents to the filtrate.
pestle
mortar
How do you find how much energy is present in
a peanut?
Burn a peanut Record rise in
temperature of a known volume of water.
Why is it better to have a larger volume of water?
To absorb more heat.
Q = mc
4.2 kJ kg-1 C-1 1000: to work mass in kg
Heat energy = mass x specific heat capacity x temperature rise
Energy in peanut = mass of water x 4.2 x temperature rise in C
1000
Question: MAY, 2011 [IIB]A group of biology students would like to
compare the energy stored in two types of nuts: a peanut and an almond.
Describe an experiment to show how this is carried out. In your report include:i) The apparatus required; (You can present
this in the form of a diagram.) (2)
ii) The method; (3)Known quantity of the nut (kept constant for both nuts) ignited and held under test tube with known amount of water (kept constant for both nuts). The temperature of water before lighting the nut and after burning will be recorded.
iii) The measurements that need to be taken; Initial temperature and final temperature Mass of peanut/almond Volume of water (2)
iv) The factors that need to be kept constant throughout the experiment; (2)Same mass of nut and same quantity of water.
v) ONE possible source of error. (1) Heat loss to surroundings Heat reaching water not evenly spread
out Burning of nut is not complete
Burning food in a bomb calorimeter.
How is the energy content of food found out?
Bomb CalorimeterThe apparatus which is used to find the energy content of food.
Better than previous setup:1. No heat loss to air.2. Even heat spread.
The End