2 Exam Qs

Question 1

describe the differences and similarities between starch and glycogen 6

Answer 1

all

• use a glucose
• are energy stores
• are insoluble
• are compact
• easily hydrolysed when needed for respiration
• have 1,4 glycodisic bonds
• amylose has no branching
• glycogen is highly branched
• glycogen is found in the liver and muscle cells
• amylose and amylopectin are found in starch grains in plants
• amylopectin and glycogen are branched and have 1,4 and 1,6 bonds

Question 2

explain how the chemical bonding between water molecules makes water a valuable coolant in living organisms 2

Answer 2

• hydrogen bonds betwen water molecules
• breaking H bonds requires + removes a lot of energy
• H bonds break when water evaporates

Question 3

water has important solvent properties. explain these properties using an example to illustrate your answer

[3]

Answer 3

water molecule is polar

water forms hydrogen bonds with polar substances;

positive/hydrogen side/pole of water attracted to negative ions

glucose/other example dissolves because it is polar

OR

sodium chloride/other example dissolves because ions are attracted to water

Question 4

explain the base pairing rule [3]

Answer 4

• purines with pyrimidines
• A and T and U have 2 h bonds
• C and G have 3 h bonds
• hydrogen bonds are always teh same length

Question 5

explain how the structure of DNA is ideally suited to its role [3]

Answer 5

• double stranded to make it stable
• polymer so lots of information
• base sequence used for code for protein syntheiss
• double stranded helps with the accuracy of replication

Question 6

the primary structure of a protien consists of chain of amino acdis.

describe how a second amino acid would bond to cysteine in forming the primary structure of a protein [3]

Answer 6

hydroxyl group of one and amine group of the other

condensation reaction

peptide bond