Proteins And Enzymes Flashcards
What are the monomers of proteins?
Amino acids
NH2CHRCOOH
How are polypeptides formed?
Via condensation reactions between amino acids
What is the primary structure of a protein?
The amino acid sequence and type of amino acids that are present
What is the secondary structure of a protein?
The coiling or folding of the amino acid chain into an alpha helix or beta pleated sheet.
Held together via hydrogen bonds
What is the tertiary structure of a protein?
The folding of the alpha helicies and beta pleated sheets into a 3D structure held together via hydrogen bonds ionic bonds or disulphide bridges between the r groups of amino acids.
What is the quaternary structure of a protein?
More than 1 polypeptide chain bonded together forms a quaternary protein.
Examples are haemoglobin or antibodies
What are fibrous proteins?
Proteins with an extended straighter structure which are insoluble in water, weak acids and bases.
What are globular proteins?
Proteins that are spherical and therefore compact in shape and are soluble in water, acids and bases
What is collagen?
A structural component found in the skin, arteries, bones, cartilage.
It provides mechanical strength.
It is a fibrous protein
What is haemoglobin?
A quaternary protein that is found in the red blood cells.
Made from 4 polypeptide chains (2x alpha and 2x beta chains)
Has a haeme group which is an Fe^3 + ion
Transports oxygen from the lungs to the respiring tissues
What are enzymes?
Biological catalysts that speed up metabolic reactions without being used up in the reactions.
What are intracellular enzymes?
Enzymes that are used in metabolic pathways
What are extracellular enzymes?
Enzymes that are secreted and often used for digestion of molecules before they are up-taken
What is the structure of an enzyme?
Enzymes are tertiary proteins which have a specific tertiary structure relating to its function.
They have an active site which is complementary to their substrates.
What are cofactors?
Substances that must be present to ensure that an enzyme catalysed reaction occurs at the correct rate.
What are co-enzymes?
Small organic non protein molecules that temporarily bind to the active site and chemically changed
(They must be recycled)
What is the lock and key hypothesis of enzyme action?
Enzymes have a specific shape and fit perfectly to their substrate
What is the induced fit hypothesis of enzyme action?
There are subtle changes to the shape of the active site in the presence of substrates in order to get an exact fit when forming an enzyme substrate complex
What are competitive inhibitors?
Have a complementary shape to the active site of an enzyme and can therefore bind in place of the substrate blocking the substrate from binding to the active site: this means that no enzyme substrate complexes can be formed.
Competitive inhibitors are not permanently bound to the active site.
What are non competitive inhibitors?
Bind to an allosteric site which changed the tertiary structure of the enzyme and therefore the active site also change shape. This means that the active site is no longer complementary to the substrate and no enzyme substrate complexes can be formed.
This is a permanent change to the enzymes
How does temperature affect enzymes?
Enzymes work at an optimum temperature where they have the highest kinetic energy and therefore have the most chances of successful collisions increasing the chances of forming ESC’s. This has the fastest rate of reaction
Below this temperature enzymes still function but at a slower rate of reaction.
Above he optimum temperature the enzymes start to denature as the hydrogen bonds between the r groups of the amino acids start to be disrupted. Therefore the tertiary structure of the enzyme changes and hence the active site changes shape and is no longer complementary to the substrate. This means no ESC’s form and the rate of reaction is reduced
How does pH affect enzymes?
At optimum pH the enzymes can work efficiently and therefore the rate of reaction is greater due to more successful collisions between enzymes and substrates.
Away from the optimum pH at the extremes, the ionic bonds between the r groups of the amino acids are changed so the tertiary structure of the enzyme changes and therefore the active site is no longer complementary to the substrate.
How does substrate concentration affect the rate of reaction with enzymes?
As the concentration of the substrate increase the rate of reaction increase until a certain point at which the limiting factor changes. This causes the rate of reaction to start to plateau.
How does enzyme concentration affect the rate of reaction with enzymes?
As the enzyme concentration increases so does the rate of reaction until the number of enzymes exceeds the number of substrates present at which point the substrate number is now the limiting factor and the rate of reaction begins to plateau.
