Metabolism and Enzymes Flashcards
what is a chemical reaction
a chemical reaction is a process that a substrate undergo chemical change in which one or more new substances are formed
like glucose + oxygen –> carbon dioxide + water + (energy)
collision theory
matters exist as particles and particles are constantly moving
in order for a chemical reaction to occur, particles of reactant must first collide with each other
only a small proportion of collision can lead to chemical reactions. this kind of collision is called effective collision
energy carried by the reactant particles and the orientation of the particles in the collision determines whether an effective collision can occur
Metabolism
Metabolism refers to all the chemical reactions which keep the cell alive
The molecules involved in metabolism are called metabolites
the overall speed of the metabolism of an organism is called metabolic rate
metabolism can be divided into catabolism and anabolism
catabolism
breaking down of complex molecules into simple molecules
energy is released (a decrease in energy level)
breaking down of glucose into water and carbon dioxide during respiration
breaking down of excess amino acids into urea in liver
anabolism
building up of complex molecules from simple molecules
energy is absorbed (an increase in energy level)
building up of glucose from water and carbon dioxide during photosynthesis
building up of cell wall from glucose
roles of enzyme in metabolism
enzyme speeds up chemical reactions in organisms
enzyme increases the metabolic rate by lowering the activation energy so that metabolism in living organisms occurs rapidly enough to sustain life, even at the relatively low temperatures ( the body temperatures of human is just 37 degrees)
without enzyme, metabolism would be too slow to sustain life or even would not occur at all
properties of enzymes (1)
all enzymes are protein
since all enzymes are protein, any properties of protein are also properties of enzymes
for example, protein structure is easily affected by temperature and pH. Thus, enzyme activity is also affected by temperature and pH
properties of enzyme (2)
enzyme action is highly specific
usually an enzyme can only catalyse one type of reaction
The shapes of enzymes and substrate molecules are complementary
properties of enzymes (3)
enzymes are biological catalysts
enzymes lower the energy barrier/activation energy required for chemical reactions to take place
Enzymes speed up metabolism in living organisms
properties of enzymes (4)
enzymes are reusable and efficient in action
enzymes temporarily combine with substrates
they remain unchanged after the reaction and can catalyse the reaction again
only a small amount of enzyme is enough
action of enzyme
each enzyme has an active site where the substrate and enzyme can combine
a reaction begins when the active site of an enzyme combines with the suitable substrate to form a temporary enzyme-substrate complex
the activation energy of the chemical reaction is reduced by forming this complex
catabolic reaction
the active site of an enzyme combines with the substrate
the enzyme then speeds up the breaking down of the substrate into product
anabolic reaction
the active site of an enzyme combines with two or more substrates
the enzyme then speeds up the building up of substrates into product
lock and key hypothesis
the specific action of enzyme can be explained by the lock-and-key hypothesis
a key of a specific shape opens only one lock
the shape of the substrate is complementary to the active site of the enzyme molecules so that the substrate can insert into the active site of the enzyme
each enzyme acts on only one or a few substrate that fits into its active site, and it therefore catalyzes only one kind of reaction
at low temperature like 10 degrees
rate of enzymatic reaction
low
enzymes are inactive in low temperatures
increasing temperature like 10 to 39 degrees
rate of enzymatic reaction
increase
the inactivation of enzymes by low temperature is reversible
as temperature increases, the kinetic energy of the substrates of enzymes increase
the substrate and enzyme vibrate faster and lead to increased collision between enzymes and substrates
more enzyme-substrate complexes can be formed
optimum temperature like 40 degrees
rate of enzymatic reaction
highest
enzymes work best at optimum temperature
different enzymes have different optimum temperatures
high temperatures like over 40 degrees
rate of enzymatic reaction
decrease
as temperature increases beyond the optimum temperature, the active sites of the enzymes are destroyed.
the enzymes are said to be denatured
the denaturation of enzymes is irreversible (the activities of enzymes cannot be resumed even after cooling down the enzymes which have been exposed to high temperature previously)
how are enzymes affected by pH
enzymes work within a narrow range of pH
enzymes work best at optimum pH
pH other than the optimum pH changes the shape of the active sites of enzymes
the substrates can no longer fit into the active sites to form the enzyme-substrate complexes
the rate of enzymatic reaction thus decreases
enzymes are said to be denatured by extreme pH
what is hydrogen peroxide
it is continuously produced as a by-product in the metabolism of living things
it is toxic and would cause harm to organisms if it is allowed to accumulate at a high level
catalase
it is found in almost any kind of living tissue. it is abundant in liver tissue as liver is for breaking down toxic substances
it breaks down hydrogen peroxide into oxygen and water
the production of oxygen can be used to indicate the breaking down action of catalase on hydrogen peroxide
how is the time taken for the reaction of starch to maltose
the time taken for the appearance of all maltose
the time taken for the disappearance of all starch (easier)
