ENZYMES
ENZYMES AND BIOLOGICAL CATALYSTS
what are catalysts?
a substance which can alter or speed up chemical reaction, without being chemically changed at the end of the reaction
what are enzymes?
proteins that function as biological catalysts
can alter or speed up chemical reactions and remain unchanged at the end of the reaction
enzymes lower activation energy
the energy needed to start a chemical reaction is called activation energy
what reactions do enzymes catalyse?
digestion is an enzyme-catalysed process
some food molecules are large and insoluble in water, these molecules can't diffuse through the cell surface membrane
food is digested by digestive enzymes
amylase: digests starch to maltose
maltase: digests maltose to glucose
protease: digests protein to amino acids
lipase: digests fats to fatty acids and glycerol
build up/break down complex substances
reactions that build up complex substances (anabolic reactions)
reactions that break down complex substances (catabolic reactions)
how are enzymes named?
digestive enzymes are hydrolases
types of hydrolases:
ones that catalyse hydrolytic reactions are knoasydrolases
proteases
lipases
carbohydrases
digest carbs
digest proteins
digest fats (lipids)
CHARACTERISTICS OF ENZYMES
enzymes are required in minute amounts
enzymes are specific in action
enzymes speed up chemical reactions
they alter the rates of chemical reactions that occur in a cell
they speed it up by lowering the activation energy needed to start the reaction
they are very efficient molecules
a small amount can catalyse a large number of chemical reactions
each chemical reaction inside a cell is catalysed by a unique enzyme
enzymes are affected by temperature
has optimum temperature of 40-45 degrees
are inactive at low temperatures as the kinetic energy is low
enzymes are affected by pH
it is affected by the acidity or alkalinity of the solutions in which they act
enzymes catalyse reversible reactions
some reactions in living cells can proceed in the forward or backward direction