PIG - enzymes

What are enzymes? [3]

3 of the following:

• Biological catalysts

• Globular proteins

• Increase the rate of (chemical) reaction

• Complimentary substrate shape to its active site

• Have an active site

What is activation energy? [2]

• Energy ‘barrier’

• Molecules must overcome this barrier in order to take part in the reaction

Name the 2 enzyme theories & explain them. [4]

Lock & Key theory [1]

Active site and substrate are complimentary shapes

Induced fit theory [1]

Arrival of the substrate causes a change in the shape of the active site

Which inhibitor fits the enzyme’s active site? [1]

Competitive inhibitor

Explain how a non-competitive inhibitor affects the rate of an enzyme related

reaction. [3]

• Reduces rate of reaction

• Fits into site on enzyme away from the active site

• Attaches to tertiary structure of enzyme

• Changes shape of the active site

• Substrate can no longer bind with active site

• Permanent

Why does increasing substrate concentration eventually have no effect on the rate of reaction? [2]

• V max

• All active sites are occupied at all times

What are coenzymes? [2]

• Organic, non-protein molecule

• (Often) carry chemical groups between enzymes

• So enzyme controlled reactions can link together in sequence

What is a prosthetic group? [1]

A coenzyme that is a permanent part of an enzyme molecule.

What is it called when an enzyme and substrate fit together? [1]

Enzyme-substrate complex

How does lowering the pH of a solution affect an enzyme’s tertiary structure?

[3]

• Increased concentration of H+ ions means lower pH

• Hydrogen ions are positive so are attracted to negatively charged molecules

• Hydrogen bonds hold tertiary structure in place

• Hydrogen ions react with hydrogen bonds which alters the tertiary structure

What is an enzyme inhibitor? [1]

A substance or molecule which slows down the rate of an enzyme

controlled reaction.

Nucleic Acid PIG

Describe the structure of DNA

Polynucleotide

Contains bases adenine, guanine, cytosine and thymine

Double stranded

Name some differences between DNA and RNA

RNA contains:

Ribose sugar

Has uracil instead of thymine

Single stranded

Exist in 3 forms: Mrna, tRNA and rRNA

Explain how DNA replicates

During interphase

Double helix untwisted

Hydrogen bonds broken

DNA unzips

Free DNA nucleotides hydrogen bonded onto exposed bases

Covalent bonds between phosphates and sugars forming backbone

Explain the term anti-parallel

The strands lie opposite each other, parallel, but run in opposite directions

(the 3’ end goes with the 5’ end)

What is complementary base pairing

Complementary base pairs pair up

C-G

A-T or U in RNA

Hydrogen bonds link base pairs

What is a gene

A sequence of DNA nucleotides that codes for a polypeptide

Outline the role of DNA in protein synthesis

DNA provides the template strand for mRNA and determines the sequence

of amino acids and therefore the structure of proteins

What is mRNA for?

Messenger RNA

Complementary to the DNA Strand

Contains Uracil instead of Thymine

Passes through the nuclear pore and attaches to a ribosome

What happens at the ribosome and what is the role of tRNA

tRNA brings amino acids to the ribosome in the right order according to the base sequence on the mRNA

Amino acids then joined together by peptide bonds to give a protein