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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’
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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
Energy ‘barrier’ • Molecules must overcome this barrier in order to take part in the reaction
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
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
Organic, non-protein molecule • (Often) carry chemical groups between enzymes • So enzyme controlled reactions can link together in sequence
What is it called when an enzyme and substrate fit together? [1]
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
A substance or molecule which slows down the rate of an enzyme controlled reaction.
Polynucleotide • Contains bases adenine, guanine, cytosine and thymine • Double stranded
RNA contains: • Ribose sugar • Has uracil instead of thymine • Single stranded • Exist in 3 forms: Mrna, tRNA and rRNA
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
The strands lie opposite each other, parallel, but run in opposite directions (the 3’ end goes with the 5’ end)
Complementary base pairs pair up • C-G • A-T or U in RNA • Hydrogen bonds link base pairs
DNA provides the template strand for mRNA and determines the sequence of amino acids and therefore the structure of proteins
Messenger RNA • Complementary to the DNA Strand • Contains Uracil instead of Thymine • Passes through the nuclear pore and attaches to a ribosome
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