Nucleic acids (WIP)

educas alevel

Describe DNA

-deoxyribonucleotides. The sugar is deoxyribose

Describe RNA

ribonucleotides and ATP (adenosine triphosphate). The sugar is ribose

ATP

Adenosine Triphosphate

The energy currency of the cell. Made of three phosphate groups, ribose, and adenine. Its highest energy bond releases 30.6 kJmol^-1

Phosphorylation

ADP + Pi (inorganic phosphate) = ATP

ENDERGONIC- requires energy (opposite to chem)

nucleotides

Makes up DNA and RNA (nucleic acids). Made of pentose sugar, one phosphate group and one organic base containing nitrogen

Pyrimidines

Single ring structure bases.

Cytosine, Thymine (DNA only) and Uracil (RNA only)

Purines

Double ring structures. Adenine and Guanine

How do nucleotides join together?

form long chains by condensation reaction and forms phosphodiester bonds between the phosphoate groups on C5 of one sugar and the hydroxyl group on C3

How does DNA double helix arrange itself?

Anti-parallel- 5’ to 3’ on one and the other is 3’ to 5’

What is RNA

Polymer made of sub-units called ribonucleotides

each ribonucleotide has one ribose, one phosphate, one organic base containing nitorgen

3 types of RNA

rRNA- structural, forms an important part of both subunits of ribosomes

mRNA- codes for a protein

tRNA- carries an amino acid

details of tRNA

-clover leaf shape

-one side is anticodon and one side is amino acid. The anticodon aligns with the bases at the end of the chain which codes for the amino acid attatchment

What are the 2 major functions of DNA

1. Replication- accurate copying of DNA is required for cell division

2. Protein synthesis- Genetic code, each gene codes for a protein

What does DNA helicase do?

break the hydrogen bonds between the bases, unwinding the DNA

What does DNA polymerase

read the conserved strand of DNA and attached free complementary nucleotides to it forming a new strand

What is the non-coding region of DNA called?

intron

what is the coding region of DNA called?

exon

Describe Transcriptions

DNA helicase binds to the DNA double helix and unwinds it with the H bonds breaking

RNA polymerse moves along the strand and binds free complementary RNA nucleotides on the the exposed DNA bases forming a molecule of mRNA

mRNA is processed, introns are removed and the exons form the code

How many hydrogen b9nds between each base pairs?

Adenine and Thymine= 2

Guanine and cytosine= 3

How does Translation happen?

-large subunit and small subunit attatch and form ribosomes

-mRNA attaches to the ribosomes and codons enter the information processing region. A tRNA binds to the first codon

Keeps going

one gene one polypeptide hypothesis

Each gene is responsible for a single polypeptide chain (not just a single enzyme)

Modifications in polypeptides?

Can have carbs, lipids or phosphates added or be combined like haemoglobin.

Happens in Golgi Body

DNA helicase

Unwinds th DNA into two strands

The hydrogen bonds holding the base pairs break

DNA polymerase

catalyses the addition of complementary free nucleotides to the exposed bases. The result is two DNA molecules each made up of one newly synthesised strand and one conserved Strand from the origional molecules

Watson and Crick

Franklin and Maurice Wilkins studied DNA using X-rays.

Franklin produced an X-ray photograph. In 1953, this allowed two other researchers - James Watson and Francis Crick - to work out the 3D structure of DNA. The structure of DNA was found to be a double helix

Meselson and Stahl

semi conservation- proposed by watson and crick, proved by meselson stahl

Why is Meselson and Stahl right and not the other

conservative replication- WRONG because if this were the case then 50% would be heavy and 50% light in gen 1 when really 100% was intermediate.

dispersive replication- WRONG gen1 would all be intermediate which is true but gen2 would all be light when in reality 50% is light at 50% is intermediate

semi-conservative- RIGHT gen1 all intermediate which is correct and gen2 50% light and 50% intermediate which is right

What is the structure of ATP?

Adenine (organic base)

Ribose

Sequence of 3 phosphate groups

Why is ATP important?

The uncontrolled release of energy from glucose could increase the temperature and destroy cells.

Instead gradual release of energy in small steps to produce ATP

How is ATP formed?

ADP is converted to ATP by the addition of a phosphate molecule. This is an endoganic reaction as 30.6kJmol-1 is used to add each

How does ATP release energy?

Hydrolysed to release energy as a phosphate molecule is removed

Short term energy store.

Oxidative Phosphorylation

Happens on the membrane of mitochondria during aerobic respiration

Photophosphorylation

Membranes of chloroplasts during photosynthesis

Advantages of ATP

Only one Enzyme is needed to release energy from ATP

In small amounts where and when needed

Common source of energy for many chemical reactions

Not stored it has to be synthesised

DNA extraction core practical

-put the strawberry in a plastic bag and crush it, making sure it’s completely crushed

-mix together 10cm3 of detergent, 1g of salt, and 100cm3 of water

-add 10cm3 of this into the bag and mix , avoiding making any soap bubbles

-filter the liquid

-pour slowly down the side of the beaker cold 90% alcohol without mixing or stirring

-watch for the development of a cloudy white substance (DNA)

-tilt the beaker and pick up the DNA with a wooden stick. Test it with acetic-orcein, a red colour will show, showing it contains nucleic acids.