Biochemistry Flashcards
what is the purpose of the smooth endoplasmic reticulum?
synthesis of steroid hormones and lipids
what is the function of the rough endoplasmic reticulum?
synthesis of polypeptides
What is the purpose of the mitochondria?
the powerhouse of the cell via respiration (breaks down nutrients into energy)
what is the function of the golgi apparatus?
to recieve materials from the ER and distribute and modify proteins
function of ribosome?
to translate RNA into protein
what are the purines?
adenine and guanin
what are the pyrimidines?
Uracil, thymine and cytosine
in which direction does DNA replicate in?
5’ to 3’ direction
which end of the leading strand is always free?
3’ end
what does helicase do?
unwinds DNA
what are the three types of RNA?
rRNA = ribosomal tRNA = transfer mRNA = messenger
what does rRNA do?
combine with proteins to form ribosomes where protein synthesis takes place
what does tRNA do?
carries amino acids to be turned into proteins
what does mRNA do?
carries genetic information for protein synthesis
what are RNA polymerases?
multi-subunit complexes
What are the three types of RNA polymerases?
Pol I, II, III
what does Pol II do?
synthesises all mRNA
what are the steps of transcription?
RNA polymerase binding by detecting initiation sites on the DNA (promoters), this requires transcription factors.
DNA chain separation.
Transcription initiation, requiring additional general transcription factors.
Elongation
Termination (release of finished RNA)
what is TFIID?
a general transcription factor required for all Pol II transcribed genes
what are exons and introns?
exons = coding introns = non-coding
what are the steps of translation?
anticodons of tRNA pairs with codons of mRNA.
Initiation
Elongation
Termination
what are the components of translation?
amino acids, tRNAs, aminoacyl-tRNA synthetases, protein factors, ATP/GTP, ribosomes and mRNA
describe what happens in initiation of translation?
GTP provides energy
robosomal subunit binds to 5’ end of mRNA, moves along until start codon found.
initiator tRNA pairs to start codon.
large subunit joins assembly and initiator tRNA is found in P site.
where is initiator tRNA located?
P site
describe what happens in elongation.
elongation factor brings aminoacyl-tRNA to A site.
GTP input
Second elongation factor regenerates the first to pick up the next aminoacyl-tRNA
what does peptidyl transferase do?
catalyses peptide bond formation between amino acids in P and A sites
describe what happens in termination in translation.
occurs when A site of ribosome encounters a stop codon.
finished proteins cleave off tRNA
what are the 3 tRNA binding sites?
exit
peptidyl
aminoacyl
where is the TATA box located?
about 25 nucleotides before the transcriptional start
what is TBP and what does it do?
TBP = TATA box binding protein.
It recognises the TATA box
what does TFIID do?
determines the transcriptional start and direction and provides a landing platform for further transcription factors and for RNA polymerase
what does aminoacyl-tRNA synthase do?
binds amino acids to their corresponding tRNA molecule
what order do the tRNA binding complexes occur in?
P then A then E
free ribosomes in the cytosol are translocated____?
post translationally
bound ribosomes on the rough endoplasmic reticulum are translocated ___?
co-translationally
free ribosomes in cytosol make proteins for?
cytosol
nucleus
mitochondria
bound ribosomes on the rough ER make proteins for?
plasma membrane
ER
golgi apparatus
secretion
what is Vmax?
maximal rate of reaction at unlimited substrate concentration
what is Km?
Michaelis constant (50% of Vmax)
Vmax is the intersection of a straight line with the __ axis.
Y
Km is the intersection of the straight line with the __ axis
X
What effect does a competitive enzyme have on Vmax and Km?
Vmax is the same
Km varies
what effect does a non-competitive enzyme have on Vmax and Km?
Vmax varies
Km stays the same
What is a primary protein characterised by?
a sequence of amino acids
what is a secondary protein characterised by?
the formation of a backbone (polypeptide)
what is a tertiary protein characterised by?
3d structure
what is a quaternary protein characterised by?
spatial arrangement of multiple subunits
which bond holds proteins together in quaternary structures?
disulphide bonds
name the purines.
adenine and guanine
name the pyrimidines
uracil, thymine and cytosine
in which direction does DNA replicate?
5’-3’
what is DNA replication catalysed by?
DNA polymerases
which end is always free in the leading strand of DNA replication?
3’ end
what unwinds the DNA?
helicase
What does RNA polymerase Pol II do?
synthesises all mRNA
