Proteins and Enzymes Flashcards
Amino acids, The structure of a protein, Function of proteins, Biuret test, Enzyme function, Lock and key, Induced fit,Rate of change, Limiting factors, Inhibitors
What is the monomer of a protein?
Amino Acid
What is the function of Hb?
Transports oxygen
What is the function of antibodies?
Defend the bodies against infections
What is the function of enzymes?
Increase the rate at which chemical reaction occur by lowering the activation energy
What is the function of actin and myosin?
Involved in muscle contraction
What is the structural role of keratin?
Found in nails and hooves
What is the structural role of collagen?
Found in tendons
How many different types of amino acids are there?
20
What groups are in the general structure of an amino acid?
Amine group, alpha carbon, H atom, carboxyl group, variable side chain
What type of bond forms a dipeptide?
Peptide bond
What type of reaction occurs in the joining of amino acids?
Condensation reaction
What is the primary structure of a protein?
The number and sequence of amino acids in a polypeptide chain
What is the secondary structure of a protein?
The -NH group has an overall positive charge and the -C=O has an overall negative charge. The H bond forms between the slight positive charge on the H and the slight negative charge on the O. These 2 groups form weak H bonds but because there is so many they are strong. Die to the H bonding the polypeptide chain coils into alpha helixes or beta pleated-sheets
What is the tertiary structure of a protein?
Further folding into a specific, complex 3D shape. Contains H bonds, Ionic bonds (between -N-H and -C=O bot being used in the peptide bonds) and Disulphide bridges
What is the Quaternary structure of a protein?
Contains a number of single polypeptide chains that are linked inactive number of different ways. They may also contain non-protein groups like iron in Hb
What is denaturation?
Increasing the temperature increases the kinetic energy of the molecule making them vibrate which can break the weak bonds holding the structure together, as the bonds break the tertiary shape of the molecules is lost, this is DENATURATION. Denaturation can also be caused by a change in pH which can disrupt the ionic bonds.
How do you perform a biuret test?
- Add the sample
- Add an equal volume of biuret solution to the sample
- If the colour changes to purple, protein is present
Define activation energy:
- The minimum energy required for a successful chemical reaction
How do enzymes speed up the rate of a chemical reaction?
They lower the activation energy by putting pressure on the bonds and bending the bonds on the substrate during the formation of enzyme substrate complexes
What is the specific area that is functional called?
A active site
What is the majority of the enzyme structure for?
Holding the active site in place
What is it called when the unique shape of the active site binds to a substrate?
They are complimentary
What is it called when an enzyme active site binds to a substrate?
Enzyme-substrate complex
How is the substrate held in the active site in an enzyme-substrate complex?
Temporary bonds form between the substrate and amino acids in the active site
In the lock and key theory the active site is … to it’s substrate
Complimentary
What does the lock and key model state about the enzymes active site?
It is rigid or inflexible
Why is the lock and key theory useful?
It helps to describe the specificity demonstrated by enzymes
How was the induced fit model made?
Scientists observed other molecules binding to enzymes at places other than the active site. These molecules altered the activity of the enzyme suggesting the active site can be changed
What is the induced fit model?
The substrate ‘induces’ a change in the shape of the active site making it complimentary
What are the 2 changes most commonly recorded?
- Formation of products
- Disappearance of substrate
How is the rate of reaction measured
The gradient of the graph
What effect does temperature have on enzymes?
As the temperature increases the enzymes and substrates have more kinetic energy, so are more likely to collide and form E-S complexes. So the rate of reaction increases.
The temperature causes the H and Ionic bonds to vibrate and break, resulting in the active site changing shape.
If the temperature is increased further than it’s optimum the H and Ionic bonds between the R groups that form the tertiary structure break, featuring the enzyme.
What effect does pH have on enzymes?
Effects the H and Ionic bonds between the -NH and the -C=O groups of the amino acids in the tertiary structure so the ionic bonds are broken
What effect does concentration have on enzymes?
As the concentration increases the rate of reaction increases as it is no longer the limiting factor therefore the rate if reaction levels off
What effect does concentration have on enzymes?
As the concentration increases the rate of reaction increases as it is no longer the limiting factor therefore the rate if reaction levels off
What is the role competitive inhibitors?
They compete with the substrate to bind with the active site
- They have a similar shape to the substrate and block the active site preventing E-S complexes from forming
- They are not permanent so only reduce the rate of reaction
What is the role of Non-competitive inhibitors?
These bind to the allosteric site (away from the active site), changing the shape of the active site so that the substrate can not bind meaning fewer E-S complexes are formed
What is a metabolic pathway?fron optimum
A series of reactions where each stage is catalysed by an enzyme. These enzyme controlled pathways are highly regulated. The enzymes involved in these pathways are usually attached to the cell or organelle in a precise order.
If too much product is made, this could damage the cell in some way. So it’s important to keep a relatively constant concentration of the product in the cell or organelle.
This is achieved through end product inhibition.
This means the final product of the series of metabolic reactions will inhibit the enzyme that catalyses the first reaction.
When the concentration of product decreases, there will be less of it to inhibit the first enzyme, so the pathway starts again.
This is an example of negative feedback. This is when a change away from the optimum concentration of the chemical causes a change that brings the concentration of the chemical back to normal.
