Dipeptide
- two amino acids joined together by peptide bond
Peptide bond (3)
- bond between two amino acids
- between amino group and carboxyl group
- formed through condensation/ dehydration reaction
Describe primary structure of protein
- sequence showing a linear chain of amino acids
- maintained through peptide bonds
Secondary structure of protein
- partially 3D structure maintained by hydrogen bonds
- alpha helix
- beta pleated
Tertiary structure
- interactions between the R groups to create a 3D shape
- hydrophobic interactions
- disulphide bonds
- iconic bonds
Quaternary structure and example
- more than one tertiary structures fitted together
- weak R group interactions
- Van de Waal forces between sub units
- eg Haemoglobin
Describe Haemoglobin
- globular
- 4 subunits
- 2 beta chains, 2 alpha chains
- 4 haem groups
- transports oxygen in the blood; haem group contain iron binds to oxygen
Describe collagen
- fibrous
- connective tissues; skin, tendons, ligaments
- mainly glycerin
What is the amino acid generalised structure?
- central CH
- Amino group- NH2
- carboxyl group; COOH
- R group
Insulin
Hormone that controls blood glucose concentration
Globular
How are proteins used in signalling
Hormones
Act as chemical messengers at receptors of cells
Enzymes
Change receptors
Keratin
Fibrous
Structural protein
Found in; hooves, hair, scales, nails
Pepsin and lipase
Hydrolytic digestive enzymes of the gut
Prosthetic groups
In conjugated proteins
Not an amino acid
Eg Haem group
Tripsin
Globular Protease
Breaks down proteins first in alimentary canal
Fibrinogen
Protective protein
Essential for blood clotting
Prothrombin
Blood clotting
Elastin
Structural component
Skin and coverings
Describe fibrous proteins and examples
Insoluble in water
Usually structural components; rope like strong shape
Parallel polypeptide chains held with cross links
Eg Collagen, silk, Heratin, fibrinogen
Describe globular proteins and examples
Hydrophilic outside with hydrophobic inside
Eg Tripsin, Haemoglobin, DNA polymerase
Biological functions of proteins. (6)
- Enzymes: eg hydrolysed like amylase, protease and lipase in digestion.
- Hormones: eg insulin which regulates blood glucose concentration
- Contractile proteins: contract/ lengthen to enable movement eg actin and myosin in muscles.
- Transport: Bind to and release substances. Eg haemoglobin for oxygen transport in blood.
- Protective/ immune defence: Primary defends such as blood clotting factors with fibrinogen and thrombin. Antibodies which neutralise antigens.
- Buffers: Amino acids and proteins are able to reduce pH. Haemoglobin can be reduced.
