Proteins and DNA

Chapter 3

Proteins

• Proteins are polymers constructed from 20 amino acids

• Amino acids are linked by dehydration

• Covalent bonds between amino acids are called peptide bonds

Amino acid structure

• Each amino acid contains– A central carbon

– An amino group

– A carboxylic acid group

– A lone Hydrogen

– An R group which varies and makes each AA different

Levels of protein organization

1. Primary structure- DNA directions determine the sequence of 20 amino acids in a long chain. Each protein has a different sequence

2. Secondary structure – Hydrogen bonds form two folding patterns

• Alpha helix- coil• Beta pleated sheet- accordion

Or no pattern • Random coil- no shape

Levels of protein structure

3. Tertiary structure- R groups of different Amino acids bond and create distorted shapes. Protein is called a globular protein.

Most proteins are now ready to work

4. Quaternary structure- some proteins require several globular units to do their job

collagen is made of three strands

hemoglobin is made of four globs

Denaturing Proteins

• When proteins are exposed to high temperatures or extreme pH the secondary, tertiary and quaternary bonds unravel

• Protein loses its shape and cannot do its function

Nucleic Acids

• DNA- deoxyribonucleic acid• RNA- ribonucleic acid

• Made of nucleotides (monomers)

• Nucleotides are made of – A phosphate – One of two different five carbon sugars – One of five different nitrogen bases

DNA

• Nucleotide structure– Phosphate – Deoxyribose – sugar– Possible Nitrogenous bases

• Adenine (A)• Thymine (T)• Guanine (G)• Cytosine (C)

RNA

• Nucleotide structure– Phosphate – Ribose – sugar– Nitrogen bases

• Adenine • Uracil• Guanine • Cytosine