10 Ass 5 pt 2 Nucleotides & Genetic Control

Question 1

Describe how a polypeptide is produced through the process of translation? 6

Answer 1

The mRNA attaches to a ribosome,

then the tRNA molecule’s anticodon binds to the mRNA’s codon, holding the amino acid in place.

A second tRNA molecule enters the ribosome & holds the second amino acid in place, so both amino acids are side-by-side

this allows a polypeptide bind to form

and for the first tRNA to leave the ribosome

and the mRNA strand then moves onto the next codon

Question 2

Describe the structure of a peptide bond formed during translation 3

Answer 2

It’s formed between the carboxyl group of 1 amino acid and the amine group of another

It’s strong

it’s covalent

Question 3

What types of bonds are made during tertiary structure formation?

Answer 3

Hydrogen, Disulfide, ionic, and weak hydrophobic interactions

Question 4

Describe hydrogen bonds 3

Answer 4

They’re formed between strongly polar R-groups

They’re very weak on their own

Can form a strong structure in large numbers

Question 5

Describe disulfide bonds 3

Answer 5

Formed between cysteine R-groups

Strong and covalent

Broken by reducing agents

Question 6

Describe Ionic bonds 2

Answer 6

Broken by changes in pH

Form between ionised amino groups and ionised carboxylic groups

Question 7

Describe weak hydrophobic interactions 4

Answer 7

occur between non-polar R-groups, so hydrophobic

usually found in centre of protein, shielded by other amino acids

very weak

stay together bc they’re repelled by watery environment around them

Question 8

Q 21 c) i) (read context) with reference to Fig 3.1, suggest & explain how the mechanism of action of HIV protease can be described as an induced fit 3

Answer 8

The enzyme is flexible, and so is able to change it’s shape

so the substrate can fit into the active site better

Flap region can open to let substrate enter and leave active site

Question 9

Indinavir is one of the therapeutic drugs used in HIV anti-retroviral therapy (ART). It’s similar to the polyprotein substrate of HIV protease.
Suggest and explain how indinavir acts as a therapeutic drug. 3

Answer 9

It is a competitive inhibitor

that binds to the active site and prevents the substrate from binding

leading to less polyprotein products formed

Question 10

Q22 Look at Fig 1.1 Name the stage of protein synthesis that is shown in Fig. 1.1.

Answer 10

translation

Question 11

Q22 Look at Fig 1.1 identify A

Answer 11

mRNA

Question 12

Q22 Look at Fig 1.1 identify B

Answer 12

tRNA

Question 13

Q22 Look at Fig 1.1 identify C

Answer 13

polypeptide chain

Question 14

Q22 Look at Fig 1.1 state the base sequences at D and E

Answer 14

AAA
GUG

Question 15

Mutagenesis is a process that leads to a change in the amino acid sequences of proteins. Scientists
carry out mutagenesis to investigate the importance of particular amino acids in protein structure
and function.
Outline how changing one amino acid in the β-globin polypeptide of haemoglobin may change the
structure and function of a molecule of haemoglobin. 4

Answer 15

Changing one amino acid can prevent bonds forming between R-groups

because the R-group o the new amino acid will be different

this can also change the protein from polar to non-polar

this will lead to a change in the secondary, tertiary or quaternary structure

Question 16

Q23 Fig. 6.1 shows the formation of a polypeptide during translation in a eukaryotic cell. Name the pyrimidine bases

Answer 16

Uracil and Cytosine

Question 17

Fig. 6.1 shows the formation of a polypeptide during translation in a eukaryotic cell. Name the purine bases shown in Fig. 6.1

Answer 17

Adenine and guanine

Question 18

Fig. 6.1 shows the formation of a polypeptide during translation in a eukaryotic cell. State the name given to the group of three bases found at J on the tRNA molecule

Answer 18

Anticodon

Question 19

Fig. 6.1 shows the formation of a polypeptide during translation in a eukaryotic cell. Identify the three bases at J

Answer 19

CAG

Question 20

Fig. 6.1 shows the formation of a polypeptide during translation in a eukaryotic cell. State how the three bases at J on tRNA interact with the bases on mRNA.

Answer 20

Complementary bases are held together by hydrogen bonds

Question 21

Name the type of chemical reaction that occurs when two amino acids form a dipeptide

Answer 21

condensation

Question 22

Q 24 b) Fig. 3.1 shows two amino acids, glycine and valine.
Use the space below to make a drawing to show what happens when these two molecules join together to form a dipeptide.

Answer 22

See memo or written qp (i did corrections in written qp)