4. Biochemical Pathways Flashcards
How do enzymes affect speed
Enzymes are capable of speeding up (catalysing) biochemical reactions within the cell. Therefore they are called biological catalysts
What are enzymes made up of
Enzymes are proteins made up of a single chain of amino acids folded to form specific 3D shape determine by the order number and type of amino acids that make up the chain.
What is an active site?
Typically a small pocket or cleft in an enzyme is an active site (substrate binding site). The substrate of an enzyme is the molecule it acts on/input to an enzyme reaction. The output of an enzyme catalysed is the product. Substrates have a complementary shape to the active site.
Lock and key model
The substrate fits into the active site of the enzyme perfectly like a lock and key. The substrate is structurally complementary to the active site. The model assumes the active site is rigid and fixed.
Induced fit model
The active site of the enzyme changes shape slightly to fit the substrate. The active site of an enzyme has a defined shape but also a degree of flexibility
Cellular metabolism
The sum of chemical reactions that occur in a living cell.
Anabolic reactions and endergonic reactions
Anabolic reactions are chemical reactions in which atoms and molecules are joined together to make more complex molecules. Energy is required to make new chemical bonds, therefore termed endergonic reactions.
Catabolic reactions or EXERGONIC reactions
Catabolic reactions break down complex molecules into simpler molecules. They release energy and are termed EXERGONIC reactions
Activation energy and enzymes
Enzymes are able to reduce the activation energy of a reaction, that is enzymes reduce the amount of energy required to begin the reaction they catalyse.
How does temperature affect enzyme activity
As temperature increases molecules become more excited, have more kinetic energy, more collisions.
Increased collisions increases opportunity for substrate to bump into the enzyme, increasing rate of reaction.
If the temperature becomes too high the structure of the protein is permanently changed and the active site changes shape disrupting its tertiary source so the substrate cannot bind to it….denaturation
Enzyme activity in low temperatures
Low temperatures means molecules have low kinetic energy, collisions between substrate and enzyme occur at slower rates.
Psychrophiles
Enzymes that function at very low temperatures because the protein has a more flexible structure and requires less energy
Effect of pH on enzyme concentration
Enzymes have an optimum ph range and are denatured by extreme pH levels
Effect of substrate concentration on enzyme activity
As substrate concentration increases the rate of reaction increases as there is more substrate to bind with the active site of the enzyme. However at saturation point all the enzymes are occupied and the rate cannot get higher no matter how much substrate is present. The rate plateaus.
Effect of enzyme concentration on enzyme activity
As enzyme concentration increases the rate of reaction increases as there are more enzymes for the substrate to bind to. However at saturation point all the available substrates are converted into products. Therefore the rate of reaction cannot get any higher no matter how much enzyme is present and the rate plateaus.
Inhibitor
An enzyme inhibitor is a molecule that binds to an enzyme reducing its activity by interfering with the enzyme in some way.
Irreversible inhibitors
Irreversible inhibition of an enzyme occurs when a compound binds covalently to one or more amino acids and alters the structure of the enzyme affecting it’s active site. This permanent inhibits the enzyme because the inhibitor to enzyme bond is so strong that the inhibition cannot be reversed by the addition of excess substrate,
Reversible inhibitors
The enzyme is not permanent inhibited in reversible inhibition. Reversible inhibitors inactivate enzymes through non covalent interactions that con be reversed
Competitive inhibitors
- have similar shape to the usual substrate for the enzyme and compete with the substrate for the active site. Competitors bind temporarily with the he active site
- the complex does not react further to form products
- it can be reversed by increasing substrate concentration so the substrate can outcompete the inhibitor
Non competitive inhibitors
Do no attack to the active site, but to the allosteric site. Causes the 3D structure of the enzyme to change shape, changing shape of the active site and therefore can no longer catalyse the usual reaction
Biochemical pathways
A biochemical process occurs when the chemical bonds of reactants are broken and atoms recombine to form new substances or products. Biochemical reactions go through a series of steps in which the product of one step becomes the reactant of the next
End product inhibition
The presence of an allosteric binding site on an enzyme enables regulation of metabolic pathways to occur through a process termed end product inhibition (allosteric effect).
In a biochemical pathway the end product may act on an enzyme in the chain to regulate its own production
The end product of a biochemical pathway can act as an inhibitor
Cofactors
Inorganic mineral ions, non proteins component that bind tightly to the enzyme. Can be considered helper molecules that are essential in biochemical transformations
Coenzymes
Non protein organic vitamins that bind loosely to the enzyme. Do not form a permanent part of the enzymes structures and assist in the transfer of molecules. Act with enzymes to alter the rate of reaction.
