Biochemistry Flashcards
What are exergonic reactions
Reactions in which total free energy of the product is less than total free energy of reactant, Delta G is -ve
What are endergonic reactions
Reactions in which total free energy of products is more than the reactants, Delta G is + ve
What do Delta G values towards zero signify?
These are characteristic of readily reversible reactions
How do we determine Delta G for a reaction?
Delta G = - R T ln K (eq) kJ/mol
R = Universal gas constant
T = Absolute temperature (Kelvin)
K (eq) = Product/Substrate concentration
How does the body compensate for the many unfavourable reactions necessary for life
By coupling an exergonic reaction (favourable) with an endergonic reaction (unfavourable)
What are amphipathic molecules?
Molecules that are hydrophobic and hydrophilic
Differentiate acids and bases based on proton donation
Acids donate protons, bases accept protons
Most abundant protein in vertebrates
Collagen
Deficiency of what vitamin can cause weak collagen
Ascorbic Acid - Vitamin C
Types of tertiary structure
Fibrous protein - Collagen, Kerain
Globular protein - Myoglobin, Haemoglobin
What are salt bridges in proteins
Electrostatic interaction between unlike charges
What catalyzes DNA replication
DNA dependant - DNA polymerase, requires RNA primers
Limitation of DNA polymerase
Can only add to 3’ end, called leading strand. Other strand is replicated in short fragments called Okazaki fragments.
Central dogma?
DNA - Transcription - mRNA - Translation - Protein
Nucleoside vs nucleotide
Nucleoside = Base + Sugar Nucleotide = Nucleoside + Phosphate group
What is DNA polymerisation
Formation of a phosphodiester bond between the 3’ OH group and 5’ Triphosphate group
Name a HIV drug that is a nucleotide analogues
Zidovudine or Azidothymidine. Lack a 3’ OH group and hence terminate chain elongation
What direction is DNA polymerase exonuclease activity?
3’ to 5’
What are the stable RNAs
tRNA, mRNA and rRNA
Types of RNA Polymerase
Pol I, Pol II and Pol III. Pol II synthesizes all mRNA
Transcription steps
RNA polymerase detects initiation sites and binds to to these. Requires transcription factors
DNA chain separation
Initiation - Selection of first nucleotide
Elongation - Addition of further nucleotide
Termination - Release of finished RNA
What is the TATA box
Sequence of TATAT around 25 nucleotides before transcriptional start. RNA Pol II specific promoter. This is recognised by TATA box Binding Protein (TBP), part of TFIID - General transcription factor
What is the direction of newly synthesized RNA strand
5’ to 3’
What are transcription factors
DNA binding proteins that regulate transcription positively or negatively