Biochem Flashcards
What is the difference between a nucleotide and a nucleoside?
Nucleotide = base + sugar + phosphate Nucleoside = base + sugar
What end are new nucleotides added on to and what direction is DNA read in?
New nucleotides added to 3’ end
Read from 5’ - 3’
What type of bond is between A and T and C and G?
A=T (double bond)
C=-G (triple bond)
What enzyme catalyses DNA replication?
DNA polymerase (can only build onto an RNA primer - primase)
Where does DNA transcription start and which side does it read?
Origins or replication (there are multiple points)
Bidirectional
What are the 2 strands called in DNA replication?
Leading strand (has a free 3' end) Lagging strand (okazaki fragments)
What enzyme unwinds DNA?
Helicase
What enzyme checks the transcribed DNA strand for mutations?
DNA polymerase
Where on DNA is the initiation site for RNA transcription?
Promotors - TATA box
Where are steroid receptors active?
Only in the nucleus (inactive in the cytoplasm)
What are the 3 tRNA binding sites on a ribosome?
EPA
E = exit
P = peptidyl
A = aminoacyl
What are the types of chomosomal mutation?
Deletion,
Duplication,
Translocation,
Inversion
What are the types of DNA mutation?
Point, frameshift
What is the difference between lock-and-key enzyme binding and induced fit?
Lock and key: active site of substrate is complementary to that of the enzyme
Induced fit: partial binding of the enzyme initiates a conformational change which increases binding of the enzyme to the substrate
What enzyme phosphorylates and what dephosphorylates a molecule?
Phosphatase: dephosphorylates
Kinase: phosphorylates
What is Km?
The concentration of substrate and which the reaction is progressing at half of Vmax
On a line weaver-Burk plot which point indicates Km and which indicates Vmax?
Km: intersection with X axis (1/[S])
Vmax: intersection with y axis (1/v)
What does a low Km indicate?
Higher affinity for the substrate (needs a lower conc to progress at a high rate)
What is the difference between competitive and non-competitive inhibition and are they reversible?
Competitive: inhibitor binds to same site as substrate to stop it binding
Non-competitive: inhibitor binds to site other than substrate and changes the conformation of the active site to prevent binding
Both are reversible
In competitive and non-competitive inhibition which factor remains constant?
Competitive: Vmax remains constant (Km varies)
Non-competitive: Km remains constant (Vmax varies)
