AS Biology Chapter 1.3 Food and Health

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Chapter 1.3 ­ Food and Health
We need macronutrients (carbohydrates, proteins and fats/lipids) and micronutrients (mineral salts
and vitamins) and fibre and water.
Macronutrients form the majority of the diet
Carbohydrates ­ Provide energy. They are broken down in digestion into glucose, which is
used in cellular respiration to release energy. Some glucose is converted into glycogen and
stored in the liver, muscles and brain. Excess carbohydrates are stored as fat in the body.
Lipids ­ Provide energy. Any excess is stored as fat.
Proteins ­ Growth and repair of cells. They are broken down in digestion to form amino
acids. These are then rebuilt during protein synthesis to form proteins that the body needs.
Essential amino acids are vital as the body can't make them.
Micronutrients are needed in very small quantities
Calcium (mineral salt) ­ Needed for formation of skeleton and teeth, for your muscles to
contract properly and for blood clotting to take place,
Sodium (mineral salt) ­ Needed for the nerves to work properly, for muscular contraction
and to maintain your heartbeat.
Vitamins ­ Complex organic substances which are absorbed directly into the blood stream
from the gut.
Vitamin C- Important in the formation of connective tissue in the body, such as bones, teeth,
skin and internal body cells including the endothelial lining of blood vessels. Lack of vitamin
C causes scurvy, which results in bleeding gums, easy bruising and painful joints.
Fibre can't be digested but it holds water and provides bulk for the intestinal muscles to work on.
Without fibre, food moves slowly through the gut causing problems such as constipation.
Organic compounds contain carbon, hydrogen, oxygen and less frequently nitrogen, sulphur and
Each carbon atom can make four bonds. In some carbon compounds small molecules (monomers)
bond with many other similar units to make a very large molecule called a polymer.
The best known carbohydrates are sugars such as glucose, sucrose and starches. Sucrose is the white
crystalline `sugar', glucose is the energy supplier in sports and health drinks and starch is found in
flour and potatoes.
The basic structure of all carbohydrates is made up of carbon, hydrogen and oxygen. There are three
groups of carbohydrates depending on the complexity of the molecules: monosaccharides,
disaccharides and polysaccharides.
Monosaccharides ­ the simple sugars. Their molecules contain one oxygen atom and two hydrogen
atoms for each carbon atom present. The general formula is (CHO) n
Triose (n=3) sugars have the formula CHO. They are important in the mitochondria, when
glucose is broken down to triose sugars in cellular respiration.

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Pentose (n=5) sugars have the formula CHO. These include ribose and deoxyribose which
are important in nucleic acids DNA and RNA, which make up genetic material.
Hexose (n=6) sugars have the formula CHo. They are the best known monosaccharides.
This includes glucose, galactose and fructose.
Disaccharides ­ Double sugars. Made up of two monosaccharides joined together. The two
monosaccharides join in a condensation reaction and a molecule of water (HO) is removed.…read more

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In an unsaturated fatty acid, the carbon chains have one or more double bonds in them.
A fat or oil results when A bond is formed in a A molecule of water is
glycerol combines with condensation reaction removed and the
one, two or three fatty between the carboxyl resulting bond is
acids, to form a mono-, groups (-COOH) of a fatty known as an ester
di- or triglyceride acid and one of the bond.
hydroxyl groups (-OH) of
the glycerol.…read more

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Iconic bonds ­ Formed between some strongly positive and negative amino acid side chains found
deep in the protein molecules. They are strong but not as common as the other structural bonds.
Proteins can be described by their primary, secondary, tertiary and quaternary structure.
Primary Structure ­ Linear sequence of amino acids in a peptide
Secondary Sector ­ The repeating pattern in the structure of the peptide
chains, such as a -helix or pleated sheets.…read more

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Paper chromatography and electrophoresis are used to discover the details of the molecular
structure of proteins.
The amount of energy contained in a food can be measured using a process known as calorimetry.
Calorimetry measures the amount of energy released when a known quantity of food is completely
oxidised by burning it in pure oxygen. Energy is released to the surroundings as heat, so the
temperature rise can be measured.…read more


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