amino acids, proteins & DNA

Question 1

How many bonds does a and t form

Answer 1

2 hydrogen bonds

Question 2

How many bonds does c and g form

Answer 2

3 hydrogen bonds

Question 3

What is the monomer, nucleotide of DNA made from

Answer 3

A phosphate
A sugar
A base

Question 4

What is an example of an anti-cancer drug

Answer 4

cis-platin.

This has the formula [PtCl2(NH3)2]

Question 5

How does cis platin prevent DNA replication

Answer 5

The CIS isomer has 2 Cl ligands adjacent to each other, and 2 NH3 ligands. It works by binding to the DNA in cancerous cells.

This prevents the DNA from unwinding and so the cancer cell cannot replicate.

This prevents the growth and spreading of cancerous cells.

Question 6

What are the considerations of cis platin

Answer 6

-Cis-platin will also bind to the DNA in healthy cells.
- This can cause unwanted side effects.
- The cis-platin drug can be targeted straight to the cancer cells to reduce the effect on healthy tissue.
- It can also be used in minimal amounts.

Question 7

How is a zwitterion formed in acidic conditions

Answer 7

If the ‘R’ group contains an amine group, this can also get protonated.

Question 8

How is a zwitterion formed in acidic conditions

Answer 8

If the ‘R’ group contains a COOH group, this can also get deprotonated.

Question 9

What are proteins

Answer 9

Proteins are sequences of amino acids joined by peptide links

Question 10

What is the primary structure of proteins

Answer 10

The sequence of amino acids in a protein is called the primary structure

Question 11

What is the secondary structure of proteins

Answer 11

The secondary structure is only held in place by H-bonds. These are approximately 1/10th the strength of a covalent bond, and so can be broken by gentle heating or changes in pH.

Question 12

What is the tertiary structure and what is it held in place by

Answer 12

The α-helix or β-pleated sheet can itself be folded into a 3D shape called a tertiary structure.

The tertiary structure can be held in place by:
- Hydrogen bonds
- Some ionic interactions (i.e. the COO- on one amino acid, and the NH3+ on another)
- Disulfide bonds

Question 13

What can two cysteine amino acids can form

Answer 13

a disulphide bond

Question 14

What are enzymes

Answer 14

Proteins

Question 15

What is stereo specific

Answer 15

The shape of the active site is so specific to the substrate that in many cases one optical isomer may fit whereas another optical isomer may not fit

Question 16

Describe enzyme inhibition - how drugs work

Answer 16

(1) An undesirable biological process occurs which is catalysed by an enzyme.

(2) A computer is used to determine the shape of the active site, and design another molecule which will fit into the active site. This must be the correct enantiomer.

(3) The new molecule is called the inhibitor. This fits into the active site and prevents the substrate from reacting in the active site.