Introduction to biomolecules Flashcards
What is the general formula of a monosaccharide?
(CH2O)n or CnH2nOn
What type are the majority of the monosaccharides found in the human body?
D-type
Which carbohydrate is present in DNA?
Deoxyribose
D-glucose and L-glucose are not?
Anomers
The most common site of phosphorylation of nucleotides found in cells is the hydroxyl group attached to which carbon?
Carbon 5’
What are adjacent nucleotides joined by in nucleic acids?
Phosphodiester bond
What functions does cholesterol have?
Roles in membrane structure
Adds rigidity to liquid-crystalline phospholipid bilayers
Precursor for the synthesis of the steroid hormones
Precursor for the synthesis of vitamin D
What is the mode of DNA replication?
Semiconservative and bidirectional
The synthesis of DNA in lagging strands takes place in short segments, what are these called?
Okazaki fragments
Unwinding of the double helix of DNA during replication is done by what enzyme?
DNA helicase
What reaction is required for proofreading during DNA replication by DNA polymerase III?
3’-5’ exonuclease activity
Are nucleotides added on to the 5’ end of the growing DNA strand in DNA replication?
No
What is the name of the enzyme that fills in the gap between fragments in the lagging strands?
DNA polymerase I
Which enzyme is used to join the DNA fragments of the lagging strand
DNA ligase
Which reaction in DNA replication is catalysed by DNA ligase?
Formation of phosphodiester bond between the 3’ OH of one Okazaki fragment and the 5’ phosphate of the next on the lagging strand
In which would you find telomeres?
Human chromosomes - repetitive DNA sequences on the end of human chromosomes
Do telomeres become longer or shorter as they age?
Shorter
Do somatic cells have little or lots of telomerase?
Little
Do immortal cancer cell lines have high levels of telomerase?
Yes
What is the enzyme that elongates chromosomes by adding repeated sequences to the end of existing chromosomes during replication in eukaryotes?
Telomerase
What describes the Pribnow box?
The -10 box
What is the region of DNA that leads to initiation of transcription?
Promoter
What is the role of the sigma factor in bacterial RNA polymerase?
To position RNA polymerase correctly on the DNA template
In eukaryotes the assembly of transcription factors on a promoter begins some 25 nucleotides upstream where it binds to start a … sequence?
TATA
Which is described as a sequence that can be several thousand base pairs upstream or downstream of a eukaryotic promoter and which increases gene expression as much as 200-fold?
Enhancer
What is the role of methylation of DNA?
To insure that genes that are turned off, stay off
What direction is RNA synthesis?
5’ to 3’
What is the cap modification of eukaryotic mRNA?
A modified guanine nucleotide added to the 5’ end of the transcript
At which cell cycle checkpoint is the cell cycle halted if the cells DNA is damaged?
G1 - S
Termination causes a stem-loop structure forming in the RNA transcript - is this true
Yes
What is the role of eukaryotic RNA polymerase I?
Transcription of the major RNA transcript
