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]
Active site and substrate are complimentary shapes 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]
All active sites are occupied at all times 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
Contains bases adenine, guanine, cytosine and thymine Polynucleotide Contains bases adenine, guanine, cytosine and thymine Double stranded
Name some differences between DNA and RNA
Has uracil instead of thymine Single stranded RNA contains: Ribose sugar Has uracil instead of thymine Single stranded Exist in 3 forms: Mrna, tRNA and rRNA
Explain how DNA replicates
Double helix untwisted Hydrogen bonds broken DNA unzips 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