Enzymes as biological catalysts Flashcards
What two methods can you use to help a reaction reach the activation energy?
Heat (gives reactants more energy) or use an enzyme ( lowers the activation energy)
What is the activation energy?
The energy required by reactants to reach the unstable transition state which allowed them to convert to the products.
What do enzymes do?
Speed up the rate at which a reaction reaches equilibrium.
An enzyme affects the position of the equilibrium in a reaction. True or false?
False.
The transition state of a reaction is the point of highest free energy. True or false?
True.
What is glycogen storage disease/ Von Gierke’s disease?
An enzyme deficiency that results in failure of glycogen to enter the transition state to be phosphorylated (not broken down properly). Normally occurs in the liver, muscles and kidney.
Symptoms include:
• Hypoglycaemia
• Hepatomegaly (liver swelling)
• Skin & mouth ulcers
• Bacterial and fungal infections
• Bowel inflammation
Treatment:
• Slow release glucose meal (e.g. corn starch)
Feed little and often to mimic glycogen conversion to glucose
What two main conditions can affect enzyme activity?
pH and Temperature.
What does the catalytic activity of enzymes depend on?
the presence of small molecules called co-factors or co-enzymes
Describe co-factors.
Inorganic, metal ions which form a metal co-ordination centre in the enzyme, making the enzyme a metalloprotein. Commonly involved in redox reactions. Examples include Zinc, copper and iron.
What is an enzyme called that doesn’t have a cofactor?
Apoenzyme.
What is an enzyme called that has a cofactor?
Holoenzyme.
Describe coenzymes.
Organic molecules derived from vitamins which change their charge or structure during the reaction but are regenerated. Normally only associated temporarily with enzymes and are involved in redox reactions. Example is NAD+. (prosthetic groups)
What are isoenzymes?
Isoforms of enzymes which catalyse the same reaction but may have different optimum conditions, properties, structure and sequence.
What is the advantage of isoenzymes?
allows you to regulate the transcription of them separately to ensure you have the right amount of protein. Also useful for diagnostic purposes.
What reaction is a type of reversible regulation of enzyme activity?
Phosphorylation- converts enzyme to active or inactive form carried out be kinases
