Structure of DNA and RNA Summary Notes - AQA A Level Biology

3.1.5 Nucleic acids – AQA A Level Biology Summary Notes

3.1.5.1 Structure of DNA and RNA

Deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) are important information carrying
molecules

In all living cells
- DNA holds genetic information
- RNA transfers genetic information from DNA to the ribosomes

Proteins are made in cells by protein synthesis. A cell must know which proteins to make and when.
^ This is the role of DNA and RNA, two different types of nucleic acids

Simplified way of looking at protein synthesis:
- DNA holds the genetic information which contains the instruction about how to make
different types of protein. DNA is located in the nucleus
- Ribosomes are where amino acids are joined together in specific orders to make proteins
- mRNA is a molecule that can carry genetic information from DNA in the nucleus to
ribosomes in the cytoplasm, so that ribosomes “know” the correct order to join the amino
acids to make a certain protein




Ribosomes are formed from RNA and proteins

Both DNA and RNA are polymers of nucleotides. Each nucleotide is formed form a pentose, a
nitrogen containing organic base and a phosphate group

(Nucleotides = monomers)

Each nucleotide is composed of 3 parts:
- Pentose sugar
- Nitrogen containing organic base (organic as it contains carbon)
- Phosphate group

There are 5 different types of A DNA nucleotide consists
nucleotide as they differ in their of:
base. The 5 different bases are - Deoxyribose
calles: adenine, thymine, guanine, (pentose sugar)
cytosine and uracil - Phosphate group