1.4 enzymes and biological reactions Flashcards
what does metabolism mean?
all reactions of the body. they occur in sequences called metabolic pathways, which are controlled by enzymes.
what does anabolic mean?
building up molecules, e.g. protein synthesis.
what does catabolic mean?
breaking down molecules, e.g. digestion.
what protein structure is an enzyme?
tertiary; 3D globular shape.
what does intracellularly mean?
can act inside the cell.
what does extracellularly mean?
can be secreted by cells.
how do enzymes work?
the enzyme and substrate collide by binding successfully to form an enzyme-substrate complex.
what is important about the active site?
they have specifically shaped active sites that are complementary to the shape of the substrate.
what is activation energy?
the minimum energy required for a reaction to take place.
what is the lock and key theory?
the active site is a fixed shape - the substrate must collide in the right way in order for them to come together. they fit together like a lock and key.
what is the induced fit hypothesis? an example?
as the substrate comes into the active site, it changes its shape around the substrate, forming stronger bonds. it has been shown to occur with lysozyme.
what is an enzyme?
a biological catalyst that speeds up the rate of reaction by lowering activation energy. it stays unchanged and does not get used up in the reaction.
how does temperature affect enzyme activity?
- as temperature increases, particles gain kinetic energy.
- as kinetic energy is increased, there is a higher chance of the substrate colliding with the active site.
- enzymes are inactive in lower temperatures.
what is the temperature in humans at which enzymes denature and what does this mean?
enzymes denature at 40°C. bonds begin to vibrate and break - weak hydrogen bonds break first.
how does pH affect enzyme activity?
- amino acids contain basic + acidic groups. changes in pH can change the bonding between amino acids + therefore changes secondary + tertiary structure of the proteins.
what does a small change in pH mean?
small changes in pH are reversible in enzyme structure, so activity is reduced (inactivated).
what does a large change in pH mean?
large changes in pH cause permanent damage to enzyme structure, which denatures them.
how does substrate concentration affect enzyme activity?
if the amount of enzyme is constant, the rate of reaction will increase as the substrate increases.
what happens at low substrate concentration?
all the enzyme’s active sites will become filled and work to full capacity and therefore stops the reaction.
how does enzyme concentration affect enzyme activity?
as the enzyme concentration increases, there are more active sites available and therefore rate of reaction increases.
what is a competitive inhibitor?
a substance that has a close structural resemblance to a substrate molecule and can bind temporarily to the active site instead of the normal substrate. this is reversible.
how do competitive inhibitors work?
it blocks the active site so the substrate cannot bind to it.
how are competitive inhibitors overcome?
adding more substrate outcompetes the competitive inhibitor.
what is a non-competitive inhibitor?
a substance that has no structural resemblance to a substrate but binds to the enzyme at a point other than the active site - the allosteric site. some are reversible, some are not.
