SPM Biology 4 Chemical Composition of the Cell Part 5 Organic Compounds in the Cell - Nucleic Acids

1. Macromolecules containing carbon, hydrogen, oxygen, nitrogen, and phosphorus.

2. The building blocks (monomers) of nucleic acids are called nucleotides.

3. Each nucleotide consists of three parts:

• A 5-carbon sugar or pentose
• A phosphate group
• A nitrogenous base

Structure of nucleotide

4. 2 types of pentose sugars

• ribose
• deoxyribose

5. Nitrogenous base

• adenine (A)
• guanine (G)
• cytosine (C)
• thymine (T)
• uracil (U)

6. Importance: store & transmit hereditary (genetic) information.

7. There are 2 types of nucleic acids:

• Deoxyribonucleic acid (DNA)
• Ribonucleic acid (RNA)

Deoxyribonucleic acid (DNA)

1. DNA contains deoxyribose sugar. 

2. Nitrogenous base groups for DNA - A, T, G, C

3. Consists of 2 polynucleotide strands twisted around each other in the form of a double helix.

4. DNA is found in the nucleus, mitochondrion & chloroplast.

5. Importance: carries the genetic code; to store genetic information

Ribonucleic acid (RNA)

1. RNA contains ribose sugar.

2. Nitrogenous bas groups for RNA - A, U, G, C

3. Consists of single-stranded polynucleotide chain, shorter than DNA.

4. RNA is found in nucleus & cytoplasm.

5. 3 types of RNA:

• messenger RNA (mRNA)
• ribosomal RNA (rRNA)
• transfer RNA (tRNA)

6. Importance: involve in protein synthesis

RNA and DNA structures

Formation of chromosomes

Formation of chromosomes