Biological Molecules exam questions

Question 1

What is poly peptide

Answer 1

It is a sequence of amino acids joined through condensation reaction

Question 2

Describe how a peptide bond is formed between two amino acids to form a dipeptide

Answer 2

Through condensation reaction between an amine group and carboxyl group

Question 3

Describe how the secondary structure of a poly peptide is produced by bonds between amino acids

Answer 3

By hydrogen bonds which form between amine group from one amino acid group and a carboxyl group from another amino acid

Bend to form b pleated sheets and a helix shape

Question 4

Explain why two proteins have the same number and type of amino acids but different tertiary structures

Answer 4

-different primary structure
-forms ionic hydrogen bonds in different places

Question 5

What is the induced fit model enzyme action ?

Answer 5

1.) active site forms as the enzyme and substrate interact
2.) proximity of substance leads to change in enzyme so the active site becomes functional
3.)The enzyme is flexible and can mould itself around the substrate
4.)glove moulding to shape of hand
5.) active site changes the shape and puts strain on the substrate molecule which distorts chemical bonds in substrate and lowers activation energy to break it.

Question 6

Describe what a condensation reaction is?

Answer 6

When a chemical bond is formed ,and water molecule is removed

Question 7

What is a polysaccharide?

Answer 7

When many monosaccharides are joined by glycosidic bonds in a condensation reaction.

Question 8

What is a semi conservative replication

Answer 8

In the daughter DNA one strand is from the parental DNA and one strand is newly synthesised.

Question 9

Describe the chemical reactions involved in the conversion of polymers to
monomers and monomers to polymers.

Answer 9

A condensation reaction joins monomers together and forms a
(chemical) bond and releases water;
A hydrolysis reaction breaks a (chemical) bond between
monomers and uses water

amino acid and polypeptide

peptide

Question 10

Describe a biochemical test to show that raffinose solution contains a
non-reducing sugar

Answer 10

Heat with acid and neutralise;
Heat with Benedict’s (solution);
Red precipitate/colour;

Question 11

give one similarity and one difference
between the structures of lactulose and lactose.

Answer 11

similarity-both include galactose
difference- one has fructose and he other don’t

Question 12

Describe two differences between the structure of a cellulose molecule
and a glycogen molecule.

Answer 12

Cellulose is made up of β-glucose (monomers) and glycogen is
made up of α-glucose (monomers);

Cellulose molecule has straight chain and glycogen is
branched;

Question 13

Suggest how glycogen acts as a source of energy.

Answer 13

glycogen hydrolyses into glucose which i used in respiration

Question 14

describe the structure of glycogen

Answer 14

polysachharide of a glucose

joined by glycosidic bonds

branched structure

Question 15

descirb how a starch molecule is adapted for their function in a cell

Answer 15

1.Insoluble;
2. Don’t affect water potential;

Question 16

Explain how cellulose molecules are adapted for their function in plant
cells.

Answer 16

1. Long and straight chains;
2. Become linked together by many hydrogen bonds to form
   fibrils;
3. Provide strength (to cell wall).

Question 17

Describe the structure of DNA.
______________________________

Answer 17

1.Polymer of nucleotides;
2. Each nucleotide formed from deoxyribose, a phosphate (group) and
an organic/nitrogenous base;
3. Phosphodiester bonds (between nucleotides);
4. Double helix/2 strands held by hydrogen bonds;
5. (Hydrogen bonds/pairing) between adenine, thymine and
cytosine, guanine;

Question 18

Describe the role of DNA polymerase in the semi-conservative replication
of DNA.

Answer 18

Joins (adjacent DNA) nucleotides;
Joins (adjacent DNA) nucleotides;

Question 19

Describe how the separation of strands occurs.

Answer 19

1.DNA helicase;
2. Breaks hydrogen bonds between base pairs/ AT and
GC/complementary bases

Question 20

what are the roles of the single stranded dna fragments

Answer 20

1.Template;
2. Determines order of nucleotides/bases;

Question 21

Give two features of DNA and explain how each one is important in the
semi-conservative replication of DNA.

Answer 21

Complementary base pairing allows accurate replication;
Weak / easily broken hydrogen bonds between bases allow two
strands to separate

Question 22

Contrast the structures of ATP and a nucleotide found in DNA to give two
differences.

Answer 22

1.ATP has ribose and DNA nucleotide has
deoxyribose
2. ATP has 3 phosphate (groups) and DNA
nucleotide has 1 phosphate (group)
3. ATP – base always adenine and in DNA
nucleotide base can be different / varies;

Question 23

Describe how an ATP molecule is formed from its component molecules.

Answer 23

adenine,
ribose/pentose, three phosphates;;
Condensation (reaction);
ATP synthase;

Question 24

Name the two products of ATP hydrolysis

Answer 24

Adenosine diphosphate

(inorganic) phosphate;

Question 25

ATP is an energy source used in many cell processes. Give two ways in
which ATP is a suitable energy source for cells to use.

Answer 25

Releases relatively small amount of energy
Can be rapidly re-synthesised;

Question 26

Describe how ATP is resynthesised in cells

Answer 26

1 From ADP and phosphate;
2 By ATP synthase;
3. During respiration/photosynthesis;

Question 27

what i the role of the hydrolysis of ATP in cells

Answer 27

To provide energy for other reactions/named process;
To add phosphate to other substances and make them more
reactive/