Enzymes Flashcards
What are features of enzymes?
Globular proteins, specific tertiary structure, may be intracellular or extracellular, can only catalyse very specific reactions.
What do biological catalysts do?
Lowers the activation energy of metabolic reactions to increase the rate of reaction without being used up in the process.
What happens in an enzyme-catalysed reaction?
The enzyme binds to the substrate to form an E-S complex.
What are the stages of the Lock and Key Model?
Enzyme molecule and substrate have own kinetic energy, they collide, substrate fits into complimentary shape of enzyme active site, enzyme-substrate complex formed, reaction occurs, enzyme-product complex formed, products diffuse away from active site.
What does the Lock and Key Model propose?
The substrate binds to the active site which fits it exactly, an enzyme will only catalyse a reaction if the substrate has a complimentary shape to its active site.
What does the Induce Fit Model take into account?
That proteins have some 3-D flexibility.
What are the stages of the Induced Fit Model?
Substrate binds to enzyme at active site, this induces the enzyme to change shape such that there is an exact fit once the substrate has bound.
What does the Induced Fit model state?
Reactions can only occur after induced fit has occurred and that the shape of active sites are not exactly complimentary, but change shape in the presence of a specific substrate to become complimentary.
Why might an enzyme have to catalyse a reaction in a particular location?
Their substrates are very specific.
What are the two types of enzymes?
Intracellular and extracellular.
What are intracellular enzymes?
Enzymes that catalyse reactions inside the cell (in cytoplasm or organelles).
What are examples of intracellular enzymes?
Enzymes involved in aerobic respiration in mitochondria and enzymes that modify and process lipids in the SER.
What is oxygen essential for?
Cell function.
What might oxygen form in a cell that could damage it?
Reactive compounds like hydrogen peroxide, a potentially harmful byproduct of many metabolic reactions.
Which enzyme do the cells of most living things contain?
Catalase.
What are features of catalase?
Breaks down hydrogen peroxide, fast acting, found in small vesicles called peroxisomes, used to help kill pathogens when white blood cells ingest them, quarternary protein with a prosthetic group.
What are features of extracellular enzymes?
Enzymes which are secreted from cells and perform their function outside of cells.
What are examples of extracellular enzymes?
Amylase produced by salivary glands and in the pancreas to break down starch into maltose, trypsin made in the pancreas to break down proteins into smaller polypeptides by hydrolysis.
What is metabolism?
The sum of all the reactions that take place in an organism.
What are anabolic reactions?
Metabolic reactions that build larger molecules from smaller ones.
What are catabolic reactions?
Metabolic reactions that break down larger molecules into smaller ones.
What are metabolic pathways?
A series of chemical reactions that start with a substrate and finish with an end product.
What is a co-factor?
A non-protein substance that must be present for enzyme controlled reactions to occur, .
What are the two types of co-factors?
Co-enzymes and prosthetic groups.
What is a co-enzyme?
An organic molecule that binds either just before or at the same time as the substrate to help reactions take place in sequence.
What is a prosthetic group?
An inorganic ion that is a permanent part of the enzyme, contributing to its 3D shape and function.
What are examples of prosthetic groups?
The haem group (iron) in haemoglobin, a zinc ion in carbonic anhydrase (enzyme found in red blood cells).
What may the presence of co-factors aid?
The formation of the E-S complexes.
What are co-substrates?
Free moving co-factors which join the substrate to make the correct, complimentary shape required.
What must be present for amylase to digest starch?
Chloride ions.
What happens when co-enzymes participate in a reaction?
The are changed by it.
What do many vitamins act as?
Co-enzymes, vitamin C is a very important one.
What happens to molecules at lower temperatures?
They are constantly in motion and colliding with one another.
What happens to molecules at lower temperatures?
More E-S complexes and hence more product molecules are formed.
What is affected by temperature?
The speed of motion and number of collisions is affected by temperature.
What do a higher temperature increase?
Kinetic energy of molecules, so more frequent collisions between active sites and substrates, so more E-S complexes form, so more E-P complexes form per unit time.
What causes an enzyme to denature?
The temperature of the reactant mixture rises above the optimum temperature so the enzymes vibrate too much.
What happens when an enzyme denatures?
The weak hydrogen and ionic bonds in its structure break, changing its tertiary structure and causing its active site to change shape.
What is the consequence of an enzyme denaturing?
Shape of the active site and substrate are no longer complimentary so less E-S complexes form.
What is not affected when an enzyme is denatured?
Its primary structure as heat doesn’t break the peptide bonds.
