1B - More Biological Molecules

Question 1

What are DNA and RNA? What do they carry?

Answer 1

DNA (deoxyribonucleic acid)
- stores genetic information
—> all the instructions an organism needs to grow and develop from a fertilised egg to a fully grown adult

RNA (ribonucleic acid)
- similar in structure to DNA
- one main function is to transfer genetic info from DNA to ribosomes
Ribosomes synthesise the body’s proteins
Reading RNA to make polypeptides in translation
Ribosomes are made of RNA and proteins

Question 2

What are nucleotides

Answer 2

A type of biological molecule. Are made from
- a pentose sugar (5 C atoms)
- a nitrogenous organic (containing carbon) base
- a phosphate group

They’re monomers that make up DNA and RNA
(diagram no.1)

Question 3

What’s unique about DNA and RNA nucleotides

Answer 3

DNA
Each DNA nucleotide has same sugar and phosphate group
Base varies though.
- Pentose sugar in DNA nucleotide is called deoxyribose
- four possible bases are adenine, thymine, cytosine, guanine

.

RNA
these nucleotides also have a phosphate group
And one of four bases (uracil replaces thymine)
- nucleotides have ribose sugars

Question 4

What do both types of nucleotides form when joining

Answer 4

Form polynucleotides, a polymer of nucleotides.
- nucleotides join by condensation reactions
- between phosphate group of one nucleotide
- and sugar of the other

• Forms a phosphodiester bond
  (consisting of the phosphate group and two ester bonds - one already there)
• chain of sugars and phosphates is the sugar-phosphate backbone

Question 5

How to describe DNA’s structure

Answer 5

Made up of two polynucleotide chains
In a double helix

— two dna polynucleotide strands join
By hydrogen bonding between bases
— each base can only join with one particular base
This is complimentary base pairing (AT, CG)

Two anti parallel (running opposite directions)
polynucleotide strands twist to form double helix

.

DNA was first observed in the 1800s
Many scientists doubted it could carry genetic code
As it has relatively simple chemical composition
—> some argued genetic info was carried by proteins (more chemically varied)

By 1953, experiments showed DNA carried genetic code
This was the year double helix structure (helps DNA with function)
Was determined by Watson and Crick

Question 6

How is RNA structure described

Answer 6

It’s a relatively short nucleotide chain
It’s made from a single polynucleotide chain (not double)
And much shorter than most DNA polynucleotides