Lecture 13 RNA Biology Flashcards
Compare the relative stabilities of RNA and DNA
- DNA is more stable
- RNA is more unstable
Why is RNA less stable than DNA
The ribose sugar in ribonucleic acid has an added hydroxl group
- The presence of this hydroxyl group makes the RNA more likely to undergo change and thus more labile.
Why is RNA suitable for more short term functions as opposed to an ideal storage molecule (like DNA)
as RNA is less stable than DNA and more likely to undergo change.
In a cell, would you find more DNA or more RNA
In a cell there is 10 x more RNA than DNA!
Describe the chemical structure of RNA.
- Ribose sugar
- ## Ribose sugar contains two hydroxyl groups
Describe the chemical structure of DNA
- The ribose (pentose) sugar in DNA lacks an oxygen, and thus lacks the 2nd hydoxyl group.
- DNA has a hydrodgen instead.
- This makes DNA more stable
Which bases are pyrimidine
Adenine and Guanine.
Which bases are purine bases
Cytosine and Thymine
4 bases in RNA are…
Adenine, Guanine, Cytosine and Uracil
How does Uracil differ chemically from Thymine
- Thymine has a methyl group as its R group
- Uracil lacks this methyl R group
- Uracil has a hydrogen as its R group
The R group in the Uracil base is what….
A hydrogen
The R group in the Thymine base is…
A methyl group
Describe the two key functions of small nuclear RNA
- Small nuclear RNA catalyzes the removal of introns from pre MRNA.
- Small nuclear RNA processes and modifies ribosomal RNA.
What are two features of catalytic RNA
- It has self splicing introns
- it has natural and artificial created ribozymes ??
Roughly how much RNA is present within a single cell
10pg
This is equal to 10^-11 grams of RNA.
This is 10 x more than the amount of cellular DNA.
Describe the relative compositions of the different types of RNA present in a cell
- 85 percent of total RNA is ribosomal RNA
- 10-15 percent is transfer RNA and small nuclear RNA (these are low molecular weight RNA’s)
- 1-5 percent of total RNA is messenger RNA.
Which type of RNA comprises the greatest proportion of total cellular RNA
Ribosomal RNA constitutes 85 percent of total RNA in the cell
Describe the physical features of RNA
- Single stranded polynucleotide chains typically
- tends to fold back on itself and complementary base pair with itself forming hair pin loop structures
- tend to bury themselves on the inside of water molecules,
Why does RNA tend to fold back on itself
There is an entropy price to pay, due to an exposed end.
Which type of nucleotide sequences are capable of forming a hair pin
Palindromic sequences
List reasons why secondary structure of RNA is important
- Catalysis
- Organization
- Recognition
State the ways in which the amount of RNA can be regulated within the cell
- synthesis
- Degradation of RNA via the transferrin receptor
- Proteins can control the use of certain RNA’s, eg the ferritin messenger RNA.
