Exam Questions 1
Differences between the structure of glycogen and collagen
Carbohydrate (made of monosaccharide’s) Protein ( made of amino acids)
Branched molecule Unbranched molecule
Glycosidic bond Peptide bond
No cross links Cross links between chains
Identical units Different amino acid units
One chain per molecule Three chains per molecule
Exam Questions 2
Properties of collagen (in ligaments) that make it suitable for holfing the bones together at joints:
- Does not stretch
State what the term glycoprotein means
- protein/polypeptide with a carbohydrate chain
Name a shape formed by the coiling of the primary structure of a protein
- alpha helix
Name a shape formed by the folding of the primary structure of a protein
- beta pleated sheets
Exam Questions 3
Explain why cholesterol must be carried by the blood by proteins while glucose does not need any transport protein.
- Cholesterol is insoluble in water
- Cholesterol has a hydrophobic nature
- However, glucose is soluble
State what a gene codes for
- a sequence of amino acids
State the role of RNA (mRNA)
- they take RNA (transcribed gene codes) to ribosomes and allow the assembly of proteins (protein synthesis).
- they transfer gene codes for ribosomes where amino acids are assembled to create proteins.
Exam Questions 4
Suggest how changing the sequence of DNA nucleotides could affect the final product the DNA codes for.
- Each sequence of DNA nucleotides consists of amino acids,
- this would affect the final product as the amino acids assemble in different orders.
- different sequences of amino acids can affect the final product, e.g. protein, enzyme.
DNA is found in the nucleus. The molecule is twisted into a double helix in which each of the strands are anti-parallel. It has two sugar-phosphate backbones attached to one another by complementary bases. These bases pair in the centre of the molecule by means of hydrogen bonds.
Exam Questions 5
Three ways in which the structure of DNA differs from RNA.
Feature DNA RNA
Number of strands 2 1
Bases present GCAT GCAU
Sugar present deoxyribose ribose
Exam Questions 6
Substance heat biuret reagent benedicts reagent dilute acid result is blu/blac
lipid x x x x yes
protein x yes x x x
starch x x x x x
reducing sugar yes x yes x x
non- reducing s yes x yes yes x
To test for a non-reducing sugar you boil with dilute acid and then carry out the same test for a reducing sugar.
Exam Questions 7
Amino acids contain carboxyl, R group and amine group. In cysteine
- Carboxyl = C=0, C-OH
- R group = CH2-SH
- Amine group = N-H, N-H
Describe how a second amino acid would bond to cysteine in forming the primary structure of a protein.
- A H from one amine group of an amino acid would combine with OH from a Carboxyl group of another amino acid.
- A peptide bond is formed between these amino acids. This continues with many amino acids on the surface of the ribosome.
- Water is lost in the reaction and covalent bond formed, the primary structure is formed.
Exam Questions 8
Describe how R groups can interact to determine the tertiary structure of a protein.
- Some R groups can attract/ repel (ionic bonds form between oppositely charged R groups)
- Disulfide bridges form between the amino acids,
- Hydrogen bonds form
Name the bond that joins the two molecules to form a disaccharide.
- glycosidic bond
What is marker assisted selection?
- A section of DNA is used as a marker to recognise the desired characteristics.
- Once offspring have been produced from selective parents, DNA is checked.
- allows selection at a very early stage.
- e.g. tomatoes bred with improved disease resistance.
Exam Questions 9
A balanced diet is one which provides an adequate intake of energy and nutrients for the maintenance of our body. If energy intake exceeds energy usage over a period of time, an individual can become obese. The deficiancy disease anaemia can be caused by a lack of the mineral iron in the diet. As a result of this deficiency, the body is unable to produce sufficient amounts of the protein haemoglobin in red blood cells.
BMI = mass in kg/(height in m)2
Factors that may prevent the BMI from being completely correct.
- Doesn't account for pregnancy
- Doesn't distinguish between men and women
- Does not measure actual fat (doesn't take into account muscle)
Two diseases associated with obesity
Type 2 diseases and CHD
Exam Questions 10
Explain what is meant by the term activation energy
- Energy required for a reaction to take place. Enzymes reduce energy required
Describe how the lock and key model can be used to explain how an enzyme breaks down a substrate molecule.
- the substrate, or 'key' fits into the enzyme 'lock' creating an enzyme-substrate complex.
- the enzyme has a specifcally shaped active site.
- this induces a reaction when the substrate fits into the enzyme
Describe how the induced fit model differs from the lock and key model of enzyme action
- that the changes in shape of enzyme occur as the substrate binds to the active site.