Proteins Flashcards
What is the pH range for human blood?
7.35-7.45
What are the 3 mechanisms that maintain pH in humans?
The renal system
The respiratory system
Chemical buffering system
What are the 3 types of chemical buffers?
Bicarbonate, phosphate and protein
Describe the bicarbonate reaction:
The dissolution of carbon dioxide in water, catalysed by the enzyme carbonic anhydrase produces carbonic acid (a weak acid). This can then dissociate in an equilibrium to produce bicarbonate and hydrogen ions.
CO2 + H2O <> H2CO3 <> HCO3- + H+
Describe what the Bohr effect is:
The pH of blood in the lungs has a higher pH than that of the tissues which have a lower pH which promotes the release of oxygen at the tissues. Deoxyhaemoglobin has no o2 and is called the T state. The R state is the oxygemoglobin. If the T state is stabilised then the oxygen is released into the tissues
What are fibrous proteins?
Secondary structures with highly regular, repetitive amino acid sequences. They have both mechanical and structural strength
What are 3 examples of fibrous proteins?
- Keratin (wool)
- Fibroin (silk)
- Collagen (skin)
Describe the properties of a fibrous proteins (alpha helix)
They are helical proteins with cross linking S-S bonds. They are tough insoluble protective structures of varying hardness and flexibility. They are right handed and have 3.6 amino acids per turn. Every H does H bonding and the C=O of residue 1 H-bonds with the H-N of residue 5. They are rigid, coiled and compact.
Describe the properties of a fibrous proteins (B sheet)
They are sheet forming proteins that form soft and flexible filaments.
Describe the B sheet structure of fibroin (silk):
It is a repetitive sequence with alternating alanine and serine layers. There is variable spacing and interdigitation
Describe the alpha helix structure of keratin (wool/hair)
It contains a long alpha helix with a globular head where every 4th residue is hydrophobic. 2 molecules coil up so that the hydrophobic is in the middle and hydrophilic on the outside. Filaments are held together by hydrogen, ionic or disulfide bonds
Describe wet hair:
When the hair is wet, the water molecules break the H bonding so the alpha helices filaments can slide back and fourth and then when they are dry the hydrogen bonds form again so the hair is set in place.
What is the protein associated with curly hair?
Cystine - it forms disulfide bonds which disrupt the shape
Describe non polar side chains:
They have lots of carbons and are found on the inside of protein molecules
Describe polar side chains:
They have electronegative atoms like OH, S, NH2 etc. Acidic charged side chains are -ve i.e they have lost a proton and basic side chains are +ve because they have gained a proton
What is the definition of toughness?
The ability to absorb energy without breaking
Describe the structure of spindroin (spider silk):
Sticky, stretchy and tougher than steel and tevlon because of the mixture of beta sheet nano-crystalline regions and amphorus regions
What makes up a salt bridge?
A positive and negative charge i.e a electrostatic interaction
What happens when protein folding goes wrong, what diseases can you get?
Amyloid diseases:
- alzeimers
- huntingtons
- prion disease
What are prions?
They are infectious proteins which cannot replicate themselves. They are misshapen versions of normal brain proteins which interact with normal proteins which then also becomes mis folded and exposes pieces of polypeptide chains. These molecules then aggregate into large beta sheets and accumulate deposits in the body.
