Cell and Its Molecules
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What does a nucleotide have that a nucleoside does not?
Name the purines and how many rings do they have?
Name the pyrimidines and how many rings do they have?
Uracil pairs with?
How is the direction of DNA strands described?
What 2 groups go along the backbone of DNA and what overall charge does this have and from what group?
Phosphate and deoxyribose sugar, negative from phosphate
How many hydrogen bonds present between A-T?
How many hydrogen bonds present between G-C?
Name 3 differences between DNA and RNA
- 1. RNA has ribose sugar, DNA has deoxyribose. (RNA has -OH instead of -H on C2)
- 2. RNA uses the base uracyl -CH3 replaced with -H on C5 of thymine
- 3. DNA is always double, RNA is single (mRNA can double back)
What post transcriptional modifications improve the stability of mRNA?
- 5' cap - guanine bound 5'-5'
- poly adenylation tail, lots of adenines on 3' end
tRNA can be described as a _______ structure.
The anticodon matches the 'sticky end' for amino acid binding. True or false?
rRNA is present in what organelle?
How many proteins bind to DNA to make chromatin?
What charge do histones carry and why?
Which histone sits outside the main nucleosome structure?
How many beads of histone are present in the nucleosome strucure?
Nucleosomes come together to make what structure?
What does the 30nm fibre benefit to the fibre of DNA?
30 nm fibres come together to make what structure in DNA?
Loops may be specific to what information carried by DNA?
What happens to the strucutre of chromatin in dividing cells?
What happens to the H1 proteins in the dividing cell and what does this do and why?
They are phosphorylated, changes charge on histones ->packs tighter together.
What feature of histones allows chromosomes to be seen in the dividing cell?
Change charge, pack closer together, takes up stain
What happens in interphase in regards to histones?
H1 dephosphorylated, DNA unwinds slightly
What is the structure hierarchy of a chromosome?
DNA strand -> nuclesome (histones) ->30nm fibre -> loops -> chromosome
Explain the need for DNA packaging which condenses the DNA for cell division, but which allows expression of the DNA between divisions.
Packaging must be dynamic so that between divisions DNA is unwound enough to allow transcription but during division must be condensed enough to avoid tangling.
What is the general principles of diagnostic enzymology?
When a cell is damaged it releases its contents into blood. This will include enzymes, some of which are tissue specific and not normally present in blood so if a particular enzyme can be tested for, a knowledge of which tissue is damaged can be gained.
List factors that may cause release of intracellular enzymes.
Explain what information may be gained by assaying enzymes.
- Tissues affected
- Extent of damage, more enzymatic activity=more cells affected
Describe those features of an enzyme that make it suitable for diagnostic use.
- 1. Can be specific to tissues.
- 2. If you present with its substrate then a reaction will occur
- 3. Do not need natural substrate- can use an artificial one that will give some sort of detectable change such as a change of colour
- 4. Rate of reaction proportionate to amount of damage
- 5. Kits readily available that allow diagnosis to be made in practice away from the lab.
Explain why enzyme activity is measured, not enzyme concentration.
Enzyme quantity may be far too small to be measured outright, measuring rate allows for a noticible reaction to occur and is proportional to the quantity of enzyme.
Name 2 enzymes that can be measured for to diagnose liver pathologies.
- Alkaline phsophatase
- Amino transferases
Describe alkaline phosphatase enzymology.
- Para-nitrophenyl phosphate -> para-nitrophenolate
- colourless --> yellow.
What are the advantages and disadvantages of alkaline phosphatase analysis?
- AdvantagesObvious colour change
- Cheap test
- DisadvantagesAlkaline phosphatase present in re-modelling bone so can not be used in young animals
Descibe briefly aminotransferase analysis.
- Transfers amino group
- -present serum with alanine and a-oxoglutarate
- 2 stage reaction with an enzyme in kit - Lactate dehydrogenase
What reaction does lactate dehydrogenase catalyse?
NADH + H+ +pyruvate <-> NAD+ +lacate
What makes the reaction 'NADH + H+ +pyruvate <-> NAD+ +lacate' detectable?
NADH->NAD+, absorption in spectrophotometer drops
What is a disadvantage of aminotransferase analysis?
Kit requires enzyme so is expensive
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