Proteins
- Created by: Lois Maxwell
- Created on: 25-02-14 19:46
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- Proteins
- Function
- Structural components, e.g. of muscle and bone
- Membrane carriers and pores for active transport and facilitated diffusion
- All enzymes are proteins
- Many hormones are proteins
- Antibodies are proteins
- Amino acids
- Proteins are long chains of amino acids - monomers joined together by covalent bonds to form polymers
- Contain an amino group (NH2), a carboxyl group (COOH), and an R group
- A condensation reaction occurs between the amino group of one amino acid and the carboxyl group of another
- A covalent bond is formed between the amino acids and a water molecule is also produced
- The new bond is a peptide bond and the new molecule is called a dipeptide
- Peptide bonds can be broken through a hydrolysis reaction, which uses a water molecule
- Structure
- Primary
- The sequence of amino acids found in a protein molecule
- Secondary
- When the polypeptides coil to make an alpha helix, or fold to make a beta pleated sheet
- Hydrogen bonds hold the coils in place. Although they are quite weak, altogether they provide a strong structure
- Tertiary
- When the structure coils or folds itself even more, held in place by a number of different types of bonds
- An increase in temperature will denature the enzymes and break some of the bonds - the whole tertiary structure will unravel and the protein will no longer function properly
- Quaternary
- Where a protein consists of more than one polypeptide chain
- Examples: haemoglobin and collagen
- Primary
- Globular
- Spherical molecules
- Soluble in water
- Have metabolic roles
- Examples: enzymes, plasma proteins, antibodies
- Fibrous
- Form fibres
- Insoluble in water
- Possess structural roles
- Examples: collagen, keratin
- Haemoglobin
- Quaternary structure with 4 polypeptide sub-units (2 alpha chains and 2 beta chains)
- Function: carry oxygen from the lungs to the tissues
- Has 4 haem groups, each with an iron ion - can bind up to 4 oxygen molecules
- Collagen
- Made of 3 polypeptide chains wound around each other with hydrogen bonds in between - provide strength
- Form covalent bonds with other collagen molecules to form fibrils and fibres
- Provides mechanical strength in many areas of the body, e.g. arteries, skeletal muscle, bones, cartilage
- Function
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