Proteins & DNA

Question 1

What are proteins in terms of their monomer?

Answer 1

A sequence of amino acids linked by peptide bonds

Question 2

Describe the primary structure of proteins.

Answer 2

A sequence of amino acids

Question 3

Describe the secondary structure of proteins

Answer 3

This is where the polypeptide chain interacts with itself, causing folding. Both caused by hydrogen bonding

• Alpha helix
• Beta pleated sheet

Question 4

Describe the tertiary structure of proteins

Answer 4

Final shape of a single polypeptide chain (further folding). Bonds form due to interactions between R groups

Question 5

What bonds can form in the tertiary structure of proteins

Answer 5

• Hydrogen bonds
• Ionic bonds
• Disulfide bridges
• Hydrophobic and Hydrophilic interactions

Question 6

What are the main features of disulfide bridges?

Answer 6

• S – S bonds
• Occur in tertiary and quarternary structures
• Oxidation of cystine residues
• Harder to break than hydrogen bonds
• Weaker than covalent bonds

Question 7

Describe the quarternary structure of proteins

Answer 7

Involves more than one polypeptide chain. E.g. haemoglobin

Question 8

Describe the hydrolysis of proteins

Answer 8

Addition of water to break apart the molecule into its monomers, amino acids.

Question 9

What method is used to separate and identify amino acids?

Answer 9

Thin layer chromatography

Question 10

What developing agents can be used when carrying out thin layer chromatography?

Answer 10

• Ninhyrdin

- Ultraviolet light

Question 11

How do you calculate Rf values in order to determine different amino acids?

Answer 11

Distance traveled by spot / Distance traveled by solvent

Question 12

Describe the link formed between two amino acids in a dipeptide?

Answer 12

amino acid-C–CO—NH–C-amino acid

- Where CO is C=O

Question 13

What is an enzyme?

Answer 13

A protein that acts as a biological catalyst

Question 14

What are breaker enzymes?

Answer 14

Enzymes that break down molecules to smaller pieces (eg polymers to monomers)

Question 15

What are builder enzymes?

Answer 15

Enzymes that join molecules together to form bigger molecules

Question 16

Describe the enzyme model of action.

Answer 16

The substrate binds to the active site of the enzyme as they are complementary to each other. The enzyme that breaks the substrate down into smaller pieces.

Question 17

What is a competitive inhibitor?

Answer 17

Binds to the active site, preventing the substrate from binding to it

Question 18

What is a non-competitive inhibitor?

Answer 18

Binds to the enzyme itself, changing the shape by distorting bonds, so the active site is no longer complementary to the substrate

Question 19

Describe the structure of a DNA nucleotide

Answer 19

Deoxyribose sugar attached to a phosphate group and a nitrogenous base

Question 20

What are the 4 nitrogenous bases and which are complementary to each other?

Answer 20

• Adenine and thymine

- Guanine and cytosine

Question 21

What is the technical name for the backbone of DNA, as a result of many nucleotides joining together?

Answer 21

Sugar-phosphate backbone

Question 22

What bonds form between base pairs?

Answer 22

Hydrogen bonds

Question 23

How many bonds form between each base pair?

Answer 23

• AT forms 2

- GC forms 3

Question 24

Describe the structure of DNA

Answer 24

Double helix

Question 25

What is the name and structure of the molecule used as an anticancer drug?

Answer 25

Cisplatin

- Central Pt with 2 Cl above and 2 NH₃ below.

Question 26

How does cisplatin prevent DNA replication in cancer cells?

Answer 26

• Ligand replacement reaction

- Bond formed between platinum in cisplatin and a nitrogen atom in guanine.

Question 27

What is the risk associated with anticancer drugs?

Answer 27

They are non-specific, so they could kill healthy human cells

Question 28

How is the risk in using anticancer drugs minimised?

Answer 28

• Targeted to the area where the tumour is

- Used in small doses