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  • Created on: 21-11-12 22:32

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2.1.1 Biological Molecules
1. Name four functions of water.
As a reactant: in photosynthesis and hydrolysis
As a solvent
For transport of substances, eg. glucose and oxygen
For temperature control ­ carries heat energy away and evaporates
2. Explain why there is polarity in water molecules
Because the shared hydrogen electrons are pulled towards the oxygen atom, leaving the other side with a
positive charge. The unshared oxygen electrons give the oxygen atom a negative charge
3. Explain why the hydrogen bonds in water give it a high specific heat capacity
The hydrogen bonds between the water molecules need a large amount of energy to break them, and thus
a high specific heat capacity. (Specific heat capacity is the amount of energy required to raised 1 gram of
water by 1 C
4. Why is water cohesive?
Because water molecules are polar, they "stick" together, making them very cohesive and good at
transporting substances.
5. Explain how ions dissolve in water
The positive end of water will attract the negative ion (and vice versa). The ion will then get totally
surrounded by water molecules ­ it dissolves
6. Describe the general structure of an amino acid
A carboxyl group (-COOH) and an amine group (-NH2) attached to the carbon atom. There is also a varying
"R" group which determines the amino acid
7. Describe how amino acids join
In a condensation reaction, the amino acids join by peptide bonds to form dipeptides and polypeptides. A
water molecule is released. (The reverse is hydrolysis where a molecule of water is needed to break
the peptide bond.
8. What is the primary structure of a protein?
The sequence of amino acids in the polypeptide chain
9. What happens to the primary structure of a protein to turn it into the secondary structure?
Hydrogen bonds form between the amino acids which makes it coil into an alpha helix or fold into a beta
pleated sheet
10. Describe the tertiary structure of amino acid
The secondary structure is coiled and folded further and more bonds form
11. Explain, with an example, the quaternary structure of a protein
The quaternary structure is the way the polypeptide chains are assembled together. Haemoglobin is made
of four polypeptide chains bonded together

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Describe the bonding in the primary and secondary structure of proteins
In the primary structure, the amino acids are held together by peptide bonds. In the secondary structure,
hydrogen bonds form (which create the alpha helix or beta pleated sheets)
13. Describe the four different types of bonding in tertiary structure
Ionic interactions are weak attractions between negative and positive charges on different parts of the
molecule. Disulfide bonds form when two amino acids containing sulphur come close together.…read more

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One molecule of glucose with two fatty acids and one phosphate group. The phosphate group is ionised
and so it attracts water molecules
23. Describe the structure of cholesterol (found in cell membranes)
It has a hydrocarbon ring structure attached to a hydrocarbon tail. The hydrocarbon ring has a polar
hydroxyl group attached to it, making the cholesterol soluble
24.…read more

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What is the function of DNA?
It contains all the genetic information and instructions to grow and develop from a fertilised egg to a fully
grown adult.
2. Describe the structure of DNA
It is a polynucleotide. Each nucleotide contains a deoxyribose sugar, a phosphate group and a varying
base. The four possible bases are adenine (A), thymine (T), cytosine (C) and guanine (G).
3.…read more

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1. Enzymes are globular proteins. True or false?
2. Describe how enzymes speed up a reaction, and thus act as biological catalysts
Enzymes reduce the amount of energy required to start the reaction ­ the activation energy. This speeds up
the reaction. The formation of an enzyme-substrate complex lowers the activation energy as repulsion is
lowered and so bonding can occur more easily. In a breakdown reaction, the substrate's bonds are
weakened and so the molecule breaks up more easily
3.…read more

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Give two ways in which the rate of an enzyme-controlled reaction can be measured
You can measure how fast the reaction appears or you can measure the disappearance of the substrate
12. Explain how cofactors work
They work by helping the enzyme and substrate bind together. They are not changed or used up
13. Explain how coenzymes work
They participate in the reaction and are changed by it. They often act as carriers, moving chemical groups
between different enzymes.…read more

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Which nutrient is required for growth and repair?
4. Give an example of a vitamin and state its function
Vitamin K is needed for blood clotting. Vitamin D is needed for calcium absorption
5. Give an example of mineral and state its function
Iron is needed to make haemoglobin the blood and calcium is needed for bone formation
6. What does fibre do?
Aids movement of food through the gut
7.…read more

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They are at the start of food chains which are then eaten and the energy is used by humans
17. How do fertilisers increase crop production?
They provide minerals that the plants need to grow so that lack of minerals doesn't limit growth of the next
18. How do pesticides increase crop production?
They kill pests that feed on the crops meaning that fewer plants are damaged or destroyed
19.…read more

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The low pH of the acidic vinegar reduces enzyme activity so they cannot function properly and their growth
is limited
29. How does heat treatment kill microorganisms?
The food is heated to a high temperature which kills any microorganisms present (eg. pasteurisation)
30. How does irradiation prevent food spoilage?
The food is exposed to radiation (eg. X-rays or gamma rays), which kills any microorganisms
2.2.2 Heath and Disease
1.…read more

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Through droplet infection ­ when an infected person coughs or sneezes, the tiny droplets of saliva and
mucus containing bacteria are breathed in by other people
11. Why is malaria, HIV and TB more common in developing countries?
Limited access to good healthcare (drugs not always available and surgical equipment may not always be
sterile, etc.), limited health education, limited equipment to reduce spread of infections (eg. lack of
mosquito nets) and overcrowded conditions increases the risk of TB infection
12.…read more


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