Influence Of Interactions - Actin & Mosin Flashcards
Factors that influence the interactions of an R group in an amino acid.
Temp and pH
Any factor which changes the interactions of the R groups will also change structure of protein.
Some proteins are more resistant to change ( proteins on themophillic bacteria) but all have specific ranges where they maintain one confirmation and where they no longer do.
Denatured = when a protein loses its shape and so it’s function.
Effect of temp on protein/enzyme
As temp increases so does rate of reaction because there is more energy.
When the temperature gets too high , weak hydrogen bonds break and then stronger covalent bonds break. This changes the structure of the enzyme and so it’s function, meaning it has become denatured.
Enzyme pH graph
As pH increases as does rate of reaction. When pH gets too high for that particular protein it can change and alter the orientation of basic or acidic components of the R groups on certain amino acids. This will effect the structure and so the function of the protein, peptide bonds may break.
How do hydrophobic and hydrophilic interactions of R groups influence the orientation of the R groups within a protein ?
Hydrophobic - non polar
Hydrophilic - basic , polar , acidic
Hydrophilic R groups will predominate at the outside of a soluble protein found in the cytoplasm - in these proteins the hydrophobic R groups will cluster at the centre to form a globular structure.
What is the cell membrane made up of ?
Proteins and phospholipids. The proteins can either be integral or peripheral.
Describe an integral membrane protein
Embedded in the cell membrane and held there by strong hydrophobic interactions between the hydrophobic R groups and the phospholipids. Some integral proteins can be trans-membrane , meaning they span the entire membrane. (Channel, transporter and many receptors)
Describe a peripheral membrane protein
Have fewer hydrophobic R groups so interact less with the phospholipids. They are not embedded and instead form weak bonds to the surface of the membrane.
What is a ligand
Ligand is a substance which can bind to a protein through complimentary shape and chemistry e.g. Positively charged histone protein and negatively charged DNA (ligand)
Describe the ligand binding to form chromosomes
DNA ( ligand ) is negatively changed and so the positively charged histone protein binds to the sugar phosphate backbone of the DNA . This then forms a nucleosome which is then packaged in to chromosomes.
Ligand binding on control of transcription
ACTIVATOR PROTEINS have binding sites that are complimentary to particular sequences of DNA and when bound to can either inhibit or stimulate the initiation of transcription
What is the induced fit theory
Substrate binds to enzyme at active site. Enzyme then changes conformation to a more induced fit around substrate due to an increase in bonds creating an enzyme substrate complex. The bonds put a strain on the substrate and so the product is produced quicker. When product is released the enzyme returns to its original shape.
Describe activation energy
The energy required to bring about a reaction.
The addition of a catalyst provides an alternative route for the reaction to take. The catalyst reduces the activation energy required for reaction
Describe the cooperativity theory
The more oxygen present in haemoglobin, the more are attracted. Becomes easier for oxygen to bind to the haemoglobin each time one binds. At low pressure there is low saturation due to lack of affinity for oxygen to bind. As the pressure increases , the first oxygen molecule will bind, rapidly increasing the saturation of the haemoglobin until all 4 oxygen are bound…. saturation then levels off
What is an allosteric enzyme
An Enzyme which changes conformation upon binding a modulator to its secondary binding site
How does a positive modulator effect an allosteric enzyme
Binding a positive modulator to an allosteric enzyme will change the shape of its active site to better fit the substrate - decreasing activation energy
