Post on 26-Dec-2015
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