Download Elementary Biochemistry To grow, respire and allow cells to function

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Elementary Biochemistry
To grow, respire and allow cells to function properly, we need a number of substances in
our diet. These can be divided into organic (contain carbon) and inorganic (no carbon)
substances.
Organic
Carbohydrates (fibres/roughage)
Lipids
Proteins
Nucleic acids
Carbohydrates
-
Inorganic
Vitamins
Minerals
Water
general formula is CH20
Glucose
C6H12O6
Provides energy for the body when they are respired.
17KJ/g
This energy is often supplied quickly and easily as they are easy to break down.
Contain: Carbon, Hydrogen and Oxygen
Proteins
-
made of amino acids
used for growth, repair and replacement of cells and tissues
also make enzymes and some hormones
can be used to provide energy when carbohydrate and lipids are unavailable.
However, this causes muscle wastage – person is probably starving
composed of Carbon, Hydrogen, Oxygen and Nitrogen or Sulphur or Phosphate
building blocks of proteins are called amino acids.
There are 20 common amino acids, which can be joined in many different ways
and make different length chains.
These chains can be joined together in different ways.
Consequently, there are thousands of different ways.
This gives a huge variety of structural diversity in the body.
AA
dipeptide
AA
AA AA
AA
AA
AA
AA
Polypeptide – join to make proteins
Foods rich in protein are:
Meat, fish, milk, cheese and eggs
-
animal sources
Peanuts, Soya beans
-
plant sources
-
most rich
Lipids
-
made of Glycerol
-
composed of fats and oils
-
plant sources are usually liquid at room temperature(e.g. olive oil, sunflower oil)
-
animal sources are usually solid at room temperature(e.g. lard, butter)
-
All lipids are composed of 2 substrates (building blocks)
-
Provide 39KJ/g of energy
-
Provide insulation by fat under skin
-
Provides waterproofing by oil on skin/feathers.
Fatty acids
Glycerol
Triglyceride
Water
Most cells contain about 75% of water and will die if their water content falls much below
this. Water is a good solvent and many substances move around the cell in a watery
solutions. Water molecules take part in many vital chemical reactions (e.g. photosynthesis).
In plants, it is the water pressure in the vacuoles, which keep the cells turgid.
The physical and chemical properties of water differ from other liquids but make it
uniquely effective in supporting living activities. For example, water has a high capacity
for heat which means that it can absorb a lot of heat without its temperature rising to high
levels. However, because water freezes at 0oC, most cells are damaged if their temperature
falls below this and ice forms in the protoplasm. Oddly, quick-freezing of cells in liquid
nitrogen (-196oC) does not harm them.
Nucleic Acids
These are the building blocks of DNA in the nucleus and of another compound called
RNA. There are four types. All are similar but one component alters – the base.
P
S
B
B
P
S
Base
Phosphate
Carbon sugar (pentose)
There are 4 possible bases:
Ademine
(A)
Thymine
(T)
Cytosine
(C)
Guonine
(G)
Minerals/Salts
Iron
Where they are
found
Eggs,
Red meat,
Vegetables,
Red blood cells
(haemoglobin)
Calcium
Blood plasma,
Milk,
Cheese,
Hard water,
Bread
Iodine
Sea fish,
Vegetables,
Salt
Phosphorous
Cheese,
Meat,
Fish,
Milk
What they are used
for
Deficiency disease
Needed in muscles,
Carry oxygen round
the body in
haemoglobin.
Anaemia
Make muscles
contract.
Transmit nerve
impulses.
Healthy blood, and
teeth.
Help blood clot.
Essential part of
thyroxine which
speed up respiration
in cells.
Calcium phosphate
for bones and teeth.
ATP and DNA
production.
Important in
membranes
Bones and teeth will
be brittle.
Nerves will be slow.
Neck swelling
Lower respiration
speed
Brittle bones and
teeth.
Cells begin to
breakdown.
Reduction in growth.
Vitamins
Vitamins are only needed in small quantities, but are essential.
Vitamin
Found in
Used for
Keeps cells lining
butter
cheese
A (retinol)
carrots
egg yolk
cod liver oil
liver
the breathing system
healthy.
Needed to make red
cells in the eye.
Allows vision in dim
light.
Ascorbic Acid
Vitamin C
Vitamin B
e.g. riboflavin,
niacin
Ascorbic Acid
Healthy immune
Citrus foods:-
system
oranges
Deficiency disease
Infections of
breathing system,
Night blindness,
Long term
deficiency can lead
to total blindness.
Scurvy
Bleeding gums and
joints
vegetables
Keeps cells and
potatoes
tissues healthy
wholemeal bread
Involved in many
liver
chemical reactions in
brown rice
the body
Muscular weakness
yeast extract
e.g. respiration
and paralysis
Can be fatal
Beri Beri
butter
Vitamin D
Calciferol
egg yolk
Helps calcium and
phosphate to make
made by body in
sunlight
healthy bones
Rickets: bones do
not develop properly
Food Tests
Benedicts test for reducing sugars (e.g. glucose)
Set up a water bath by half-filling the 250cm3 beaker with tap water. Bring the water to the
boil and turn down the Bunsen flame to maintain a steady boil.
Take a test tube and add about 2 cm3 of the food solution. Add about 1 cm3 of Benedicts
solution. Heat the test tube in the water bath for 2-3 minutes. The appearance of an orange
coloured precipitate indicates that a reducing sugar is present.
The presence of glucose may be also tested by use of the Clinistix.
Iodine test for starch
At room temperature add several drops of iodine solution (I2 in KI) to a sample of the food
solution to be tested. A blue/black colour indicates the presence of starch.
Biuret test for proteins
At room temperature, put about 2 cm3 of the food solution into a test tube. Add an equal
volume of Biuret 1 (10% Sodium Hydroxide - with care!) then add Biuret 2 solution drop
by drop, mixing the solutions by gently shaking the tube. A purple colour confirms the
presence of protein.
The presence of proteins may be detected by use of the Albustix.
Emulsion test for fats
Mix equal quantities of the solution to be tested and absolute ethanol in a test tube and
shake together vigorously. Add an equal volume of cold water. A cloudy white suspension
indicates the presence of fats.
Place one drop of the solution to be tested onto greaseproof and/or brown paper. The
presence of fat is indicated by the paper appearing more transparent.
A Balanced Diet
A balanced diet contains the following components in the right proportions:
1.
Carbohydrates
2.
Proteins
3.
Lipids
4.
Vitamins
5.
Minerals
6.
Water
7.
Roughage or Fibre
The relative proportions of the components in a balanced diet varies with age, gender and
amount of activity.
Description
Energy Requirements (KJ)
0-1 years
3,200
Childhood
7,500
Adolescence
Boys: 12,000
Girls: 9,600
Adult Female
9,000
Pregnancy
10,000
Lactation
11,500
Adult male: Deskbound
office worker
Adult male: Building site
worker
Notes
Extra calcium needed for
growth of bone
Extra calcium, iron and
protein needed for growth
Extra calcium, iron and
protein needed for growth
and development of foetus
Extra calcium, iron and
protein needed for growth
and development of baby
10,000
14,000
Extra protein needed for
muscle development
Food additives
Food additives have been used in increasing numbers and volumes over the last few
decades and in the UK their use is now regulated by the European Community.
Additives are used for four main reasons:
a)
b)
c)
d)
to enhance the flavour of food
to colour food
as a preservative
to improve the texture of food
In the EEC, food additives are given a designated ‘E’ number, which enables lists of
additives to be given on food packets without the need to write out all the names of
ingredients in full.
Food additives can be of benefit to the consumer – longer shelf life for food and the
availability of convenience foods – but some additives have an undesirable side – effects
on some individuals.
Additive
Advantages
Disadvantages
Sugar
Sweetens food
Preservative
Good energy source
Can lead to obesity (and
therefore high blood
pressure)
Can lead to tooth decay
Salt
Improves flavour
Preservative
Too much can lead to high
blood pressure
E102 – Tartrazine (yellow dye)
Gives colour to orange
squash, and crisps etc.
Hyperactivity in children
Can make asthma worse
E621 – Monosodium glutamate
Provides ‘meaty’
flavour in crisps, stock
cubes meat pies etc.
E250 – Sodium nitrite
Helps preserve bacon,
ham, corned beef etc.
E122 – Carmosine
Colours food red (e.g.
jelly, sweets and packed
soups)
Can cause ‘Chinese
Restaurant Syndrome’ –
headaches, dizziness,
vomiting, muscle tightening
and heart palpitations
May cause cancer (from
nitrosamine in gut).
Also causes dizziness and
vomiting in some cases
Can cause skin rashes and
produce adverse reactions
with asthmatics.
Starvation and Malnutrition
General lack of food or not enough food leads to starvation. Body uses up all stored
reserves:
1.
2.
3.
Glycogen stores
Fat reserves respired
Protein respired
glucose
respired
muscle wastage
energy
death
Protein energy malnutrition – Kwashiorkor
Diet contains plenty or enough carbohydrates but not enough proteins.
Seen in children and causes bloated abdomen.
Also means that cells are not repaired or replaced.
Growth is limited.
Immune system fails.
Western Diets
Too much sugar
-
causes tooth decay
obesity
Too much fat
-
blockage of arteries
coronary heart attack
the more cholesterol, the more chance of getting heart
attack.
saturated fatty acids cause fatty deposits in artery
Too little fibre
-
constipation
disorders and diseases of the intestine – possibly cancer.
fibre stops you eating – may lead to obesity
Too much of everything
-
surplus fat – obesity
high blood pressure
diabetes
coronary heart disease