NUCLEIC ACIDS

                                  

FUNCTION• The main functions of nucleic acids are:

– information storage (DNA)– protein synthesis (RNA)– energy transfers (ATP and NAD).

Nucleotides

• Nucleotides consist of three parts:

– A 5-carbon sugar (pentose).

– A nitrogen-containing ring structure called a base.

– phosphate groups ( the number of these varies)

DNA• Deoxyribose sugar: has a hydrogen atom attached to its #2 carbon

atom

                                                                                            

• Four different bases are found:

adenine (A) thymine (T) and

cytosine (C) guanine (G)

DNA• DNA is double-stranded, so there are

two stands alongside each other. The strands are antiparallel, i.e. they run in opposite directions (5' 3’ and 3’5’)

• The two strands are wound round each other to form a double helix.

• The two strands are joined together by hydrogen bonds between the bases. The bases form base pairs, which are like rungs of a ladder.

• The base pairs are specific. A only binds to T and C only binds to G. These are called complementary base pairs. This means that whatever the sequence of bases along one strand, the sequence of bases on the other strand must be complementary to it.

• In man, the DNA molecule in a diploid cell, if fully extended, would have a total length of 1.7 metres.

• If you unwrap all the DNA you have in all your cells, you could reach the moon 6000 times!

RNA• RNA :

– Has a hydroxyl (-OH) on carbon 2 on the ribose sugar

– Bases: instead of thymine, it uses uracil (U). adenine (A) and uracil (U). cytosine (C) and guanine (G).

– Is usually linear and shorter– Are named by function/location: messenger

RNA, transfer RNA, ribosomal RNA, small nuclear RNA

ATP ADENOSINE TRIPHOSPHATE

• All living cells require energy, and this energy is provided by respiration.

glucose + oxygen carbon dioxide + water (+ energy)

• What form is this energy in? It’s in the form of chemical energy stored in a compound called ATP

• Respiration converts chemical energy stored in glucose into chemical energy stored in ATP.

• ATP is a nucleotide that functions as an energy storage molecule.

• ATP is built up from ADP and phosphate (PO4

3-) (abbreviated to Pi)

ADP + P + Energy ---> ATP

ATP --> ADP + P + Energy

• All the processes in a cell that require energy (such as muscle contraction, active transport and biosynthesis) use ATP to provide that energy.

• So the ATP molecules in a cell are constantly being cycled between ATP and ADP + Pi.