Biological Molecules 2 Flashcards
Structure of proteins
Primary - sequence of amino acids in polypeptide chain
Secondary - folding/coiling of polypeptide due to hydrogen bonds between amino acids - A helix and B pleated sheet
Tertiary - further folding/coiling of secondary structure due to hydrogen bonds, ionic bonds and disulphide bridges, specific and unique, determines shape of active site
Quaternary - complex proteins consisting of more than one polypeptide chain - held together by ionic, hydrogen and sometimes disulphide bridges
Denaturation of proteins
Alteration in tertiary structure
Often irreversible and protein no longer functions
Caused by breaking of hydrogen and ionic bonds due to high temp, changes in pH and heavy metals
Disulphide bridges not broken at same temp which hydrogen and ionic bonds are broken
Biuret test for proteins
Add biuret reagent
Purple lilac mauve = protein is present
If solution remains blue no protein is present
Enzyme specificity
Lock and Key model - molecules complementary to active site will bind to it to form an enzyme substrate complex - active site fixed
Induced fit model - active site is flexible - presence of correct substrate induces the change in shape so it moulds itself around the substrate - enzyme remains unchanged
Effect of substrate conc on enzyme reactions
Increase in substrate increase rate of reaction to a particulate point
Collisions more likely
Active sites all occupied so rate levels out
Rate is limited by conc of enzyme
Effect of enzyme conc on enzyme reactions
Increase of enzyme increases rate
More active sites
More enzyme substrate complexes
Effect of temperature on enzyme reactions
Increase in temp increases kinetic energy more collisions more enzyme substrate complexes
Increasing temp above optimum denatures enzyme so rate decreases as substrate cannot bind to altered active site
Effect of pH on enzyme reactions
Different pHs from optimum can cause denaturation
Change in pH alters ionic charges
Hydrogen and ionic bonds broken altering tertiary structure so substrate cannot bind
Competitive inhibitor
Similar in structure to normal substrate and competes for active site
Rate of reaction reduced as substrate cannot bind when inhibitor is occupying active site
Can be reduced by the addition of more substrate as substrate outcompetes inhibitor
Non competitive inhibitors
Not similar in structure to substrate
Combines at position other than active site to form enzyme inhibitor complex and alters the tertiary structure and shape of active site
Substrate cannot attach to altered active site
Degree of inhibition completely dependent on amount of inhibitor
High conc of substrate will not reduce non competitive inhibition
Dna
Holds genetic information
Ran
Transfers genetic information from Dna to ribosomes
What is a nucleotide formed from?
Pentose (5 carbon sugar)
Nitrogen containing organic base
Phosphate group
Structure of DNA
Pentose sugar deoxyribose
Phosphate group
One of 4 nitrogen containing bases (cytosine, guanine, adenine or thymine)
Nucleotides joined together by phosphodiester bonds
Semi conservative DNA replication
- DNA helicase unwinds double helix& breaks hydrogen bonds
- each strand acts as a template
- DNA nucleotides align next to expose bases according to complementary base pairing (AT CG)
- joined by phosphodiester bonds by DNA polymerase to form complementary strands
- 2 new strands of DNA are joined by hydrogen bonds
- identical to each other and original DNA
