Biochemistry Flashcards
bond strengths strongest to weakest
covalent > ionic > hydrogen > hydrophobic > van der waals
major classes of biomolecules
peptides and proteins, lipids, nucleic acids, carbohydrates
monosaccharide, disaccharide and polysaccharide examples
monosaccharide = glucose disaccharide = lactose polysaccharide = cellulose and glycogen
1st law and 2nd law of thermodynamics
1st = energy cannot be created or destroyed 2nd = when energy converted from one form into another, some becomes useless (eg lost as heat)
Change in free energy = ?
Delta G = (energy of products) - (energy of reactants)
exergonic reactions
have negative deltaG, can occur spontaneously
endergonic reactions
have positive deltaG, cannot occur spontaneously as require energy
how is free energy related to equilibrium
DeltaG near zero characteristic of readily reversible reactions
structure of proteins
primary = sequence of amino acids secondary = result of hydrogen bonding along backbone tertiary = 3d structure quaternary = arrangement of multiple subunits
secondary structures and quaternary structures
Alpha = NO and COOH of amino acids 4 apart bond together
Beta sheets = can be parallel or antiparallel
Triple helix = tropocollagen, abundant in connective tissues
smooth ER and Rough ER
smooth ER = synthesis of steroid hormones, cholesterol, lipid synthesis
Rough ER = studded with ribosomes. synthesis of polypeptides/proteins
golgi apparatus
comprised of flattened, membrane-bound cisternae.
- receives material from ER and distributes
- modify proteins
nucleoside and nucleotide
nucleoside = base + sugar nucleotide = nucleoside + phosphate
DNA structure
- purines = A and G (2 carbon-nitrogen ring)
- pyrimidine = U, T,C
- phosphodiester bonds between 3’ OH and 5’ triphosphate
- CG is a triple bond
how does DNA replication happen
- helicase unwinds
- primase adds RNA primers
- DNA polymerase makes strand
- Leading strand = continuous as has free 3’ end
- Lagging strand = Okazaki fragments sealed with ligase
Types of RNA
rRNA = combines with protein to form ribosome tRNA = carries amino acids for protein synthesis mRNA = carries genetic information
how many types of RNA in eukaryotes and prokaryotes and what synthesises all mRNA
prokaryotes = 1 type
eukaryotes = 3 types
- pol || synthesises all mRNA
transcription requires transcription factors. what is the general one used for all pol || transcribed genes
TFIID
how many amino acids and combinations are there
64 amino acids and 20 combinations
how does translation occur
- requires energy from GTP
- ribosome moves along mRNA until start codon found.
- tRNA with anticodon binds
- Elongation: elongation factor brings aminoacyl-tRNA to A site. GTP hydrolysed and factor released.
- 2nd elongation factor resynthesises 1st one to pick up next aminoacyl-tRNA
- Peptidyl transferase catalyses bonds between amino acids in P and A sites.
- ‘empty’ tRNA moves to E site and growing peptide moves from A to P site
what are the 3 tRNA binding sites
Exit, Peptidyl, Aminoacyl
what do free ribosomes and bound ribosomes make proteins for
free: cytosol, mitochondria, nucleus
bound: Golgi, ER, plasma membrane
what’s the difference between degenerate and unambiguous in genetic code
degenerate: amino acid has more than one codon
unambiguous: one codon for one amino acid
what do enzymes do
they speed up rate reaction reaches equilibrium but don’t change its position. Also lower Ea.
