what is the full definition of enzymes? (+ what is a catalyst?)
enzymes are biological catalysts. they are biological substances because they are made by living cells and are mostly proteins in nature (except ribosomes). a catalyst is a substance which speeds up a chemical reaction without itself being chemically changed at the end of the reaction.
what does every chemical reaction between molecules involve?
bond breaking and bond forming
what is activation energy?
it is the energy required to make the substances react
what is the relationship between the activation energy and reaction?
the greater the activation energy, the slower the reaction at any particular temperature.if activation energy of a reaction decreased, the rate of reaction would be increased.
what do enzymes do to activation energy?
enzymes provide an alternative pathway with lower activation energy required to start a chemical reaction --> in our bodies, enzymes speed up the breakdown of glucose and fats to CO2 and water at body temperature. no strong heat is required to start a reaction
what is the amount of enzymes required for a reaction?
enzymes are very efficient molecules that are required in minute amounts. since they remain chemically unchanged in the reactions they catalyse, the same amount of enzyme can catalyse a large number of chemical reactions
what are the three steps that all enzyme-catalysed reactions include?
1. the binding of a substrate to an enzyme to form a short-lived enzyme-substrate complex2. the conversion of enzyme-substrate complex to the enzyme-product complex3. the release of the product from the enzyme-product complex, to yield free the product and free the enzyme
what is enzyme-substrate complex?
enzyme substrate complex is a short-lived complex
what is the process of an enzyme in a chemical reaction?
- while enzyme and substrate are joined, the catalytic action of the enzyme converts the substrate to the product(s) of the reaction- this proximity of the enzyme with the substrate in the complex greatly increases the chances of a reaction occurring- once a reaction has occurred, the complex breaks up into products and enzyme
what happens to an enzyme at the end of the experiment?
the enzyme remains unchanged at the end of the reaction and is free to interact again with more substrate
what is the relationship between the speed of reaction and the products formed?
the faster the speed of reaction, the more enzyme-substrate complexes are formed per unit time
what is a metabolic pathway?
a metabolic pathway is a series of enzyme-catalysed reactions in which the product from one reaction is the substrate for the next --> each enzyme catalyses a specific chemical reaction, leaving the enzyme unchanged
what are the two sets of opposing reactions that is involved in metabolism?
catabolic pathways and anabolic pathways
what is the function of catabolic pathways?
catabolic pathways hydrolyse complex molecules into smaller molecules, thereby generating both a useful form of energy for the cell and some of the small molecules that the cell needs as building blocks.
what is the function of anabolic pathways?
anabolic pathways use the energy harnessed by catabolism to drive the synthesis of the any other molecules that form the cell.
when are digestive enzymes produced?
digestive enzymes are only produced when there is food to digest in the gut
explain how digestive enzymes help with digestion
- some food molecules (carbohydrates, fats, protiens) are large and insoluble in water --> cannot diffuse through the cell surface membrane - the large insoluble molecules must first be converted into simpler smaller molecules which are soluble in water and small enough to diffuse through cell surface membranes.
what are some examples of digestive enzymes?
- amylase --> digest starch to maltose- maltase --> digest maltose to glucose- protease --> digest proteins to amino acids-lipase --> digests fats to fatty acids and glycerol
what are enzymes that catalyse hydrolytic reactions known as?
hydrolasesw
what are the different types of hydrolases?
carbohydrases, proteases and lipases
are enzymes specific in their action?
enzymes are highly specific in their action --> chemical reaction inside a cell is catalysed by a unique enzyme
why is an enzyme specific?
an enzyme is specific due to its 3D conformation and active site --> an enzyme's active site is complementary in conformation to its substrate
what is the 'lock and key' hypothesis?
the substrate is imagined to be like a key whose conformation is complementary to the enzyme (lock)w
what is the explanation of the 'lock and key' hypothesis?
- the active site has the specific conformation- once the products are formed, the products no longer fit into the active site and move into the surrounding medium, leaving the active site free to receive other substrates
what does the 'induced fit' hypothesis suggest?
- it suggest that the initial conformation of the active site of an enzyme may not be complementary to the conformation of the substrate molecule
what happens during the 'induced fit' hypothesis?
- the binding of the substrate to the active site induces a conformational changed in the active site which enables the substrate to fit more tightly into the active site- the amino acids side chains which make up the active site are molded into a precise conformation which enables the enzyme to perform its catalytic function --> the active site has a conformation complementary to that of the substrate only after the substrate is bound - this enables the enzyme to perform its catalytic function more effectively
what are the factors affecting rate of enzyme-catalysed reaction?
- enzyme concentration- substrate concentration- temp- pH
how are enzymes affected by enzyme/substrate concentration?
- as enzyme/ substrate concentration increases, rate of enzyme-catalysed reaction increases linearly --> frequency of effective collisions between enzymes and substrate molecules increase since there are more active sites available- more enzyme-substrate complexes are formed per unit time resulting in more products formed per unit time --> thus rate of enzyme-catalysed reaction increases
what happens at high enzyme/substrate concentration?
any increase in enzyme/substrate concentration will not increase rate of reaction --> enzyme/substrate is no longer a limiting factor
what is the rate of reaction at or near 0 degrees?
the rate of reaction is zero or very low this is because:- the kinetic energy of the enzyme and substrate molecules is very low --> thus rate of effective collision between enzyme and substrate molecules is very low - enzymes are said to be inactive, but NOT denatured- inactivation of enzyme is reversible and enzyme resumes their activity with increase in temperature
what happens to the rate of reaction between 0 degrees to optimum temperature?
the rate of reaction doubles for every 10 degrees increase in tempthis is because:- as the temp increases, the KE of enzymes and substrate increase --> frequency of successful collisions between enzymes and substrate molecules increases - more enzyme-substrate complexes are formed per unit time resulting in more products formed per uni time
what is the rate of reaction at the optimum temp?
- enzymes have the highest rate of reaction at the optimum temp --> the rate of successful collisions between enzymes and substrate molecules to form enzyme-substrate complexes is at the highest- thus the largest amounts of product molecules formed per unit time
what happens to the rate of reaction beyond the optimum temp?
the rate of reaction decreasesthis is because:- the KE of the enzyme and substrate molecules continue to increase with temp, leading to higher frequency of collision - this disrupts the bond maintaining the 3D conformation of enzymes - this leads to a loss of 3D conformation of the enzyme's active site- enzyme is denatured --> denaturation is irreversible- the rate of reaction drops to zero when all the enzymes are completely denatured
how are enzymes affected by pH?
enzymes are affected by the acidity or alkalinity of the solutions in which they act
what are the optimum pH values for amylase, pepsin and trypsin
amylase in saliva: pH 7pepsin in stomach: pH 2trypsin in small intestine: pH 8
what happens when there are extreme changes in the acidity or alkalinity of the solutions?
it will denature the enzymes