Enzymes & Biochemical Pathways (4.1) Flashcards
State the two major characteristics of enzymes
- Specificity
2. Catalytic Power
Describe enzyme specificity
Different enzymes act as catalysts for specific biochemical reactions by binding to specific substrate.
Some enzymes are able to act on multiple substrates. State whether this is true/false.
True. Enzymes can act on multiple substrates and catalyse multiple reactions.
Define substrate
Molecule which an enzyme acts upon
State whether or not enzymes are consumed when they catalyse reactions
No. Enzymes are not consumed when catalysing reactions.
Define catalytic power
Potential of an enzyme to increase the rate of a biochemical reaction
Describe what forms the enzyme active site
Tertiary protein folding
Describe the active site
Complex 3D shape that interacts with a specific substrate to catalyse specific reaction/s.
State what forms when the active site binds to the substrate
Enzyme-substrate complex
State the 2 enzyme-substrate interaction models
- Lock and key
2. Induced fit
State what stabilises the presence of the substrate in the active site
- hydrogen bonds
- hydrophobic interactions
Describe the lock and key model
The active site and substrate fit as a lock and key
State the real-life object represented by the ‘lock’ in the lock and key model
The active site
State the real-life object represented by the ‘key’ in the lock and key model
The substrate
Describe the induced fit model
When a substrate binds to the active site of an enzyme, a conformational change occurs.
Describe conformational change
A change in the 3D arrangement of atoms in a macromolecule (e.g. protein or nucleic acid).
State whether or not some reactions can be catalysed in both directions
True. Some reactions can be catalysed in both directions
Describe activation energy
The energy that is required to start a biochemical reaction
Describe where the catalytic power of enzymes comes from
Ability to reduce activation energy
Describe 3 ways that enzymes reduce activation energy
- proximity and orientiation
- micro-environment
- ion exchange
Describe the effect of enzymes on proximity and orientiation
Enzymes bring reactants closer to one another to increase collision potential.
Describe the effect of enzymes on the micro-environment
Reaction environment becomes non-polar to allow stabilising interactions to occur
Provide 3 examples of stabilising interactions which occur in non-polar environment
- hydrogen bonding
- hydrophobic interactions
- van der Waals interactions
Describe the effect of enzymes on ion exchange
Amino acids in the active site can often exchange H+ ions with the substrate.
State the 3 major types of biochemical pathways
- linear
- branched
- cycles
Describe metabolism
Collection of all of the biochemical reactions that occur in living cells.
State the 2 major types of metabolic reactions
- catabolic
2. anabolic
Describe catabolic reactions
Reactions in which the substrates are broken down and energy is released
State whether catabolic reactions are exergonic or endergonic
Exergonic, because they release energy to break bonds between molecules.
Describe anabolic reactions
Reactions that require an input of energy in order to produce larger molecules from smaller substrates.
State whether anabolic reactions are exergonic or endergonic
Endergonic, because they require energy to form bonds between molecules.
Describe reaction coupling
A reaction that releases energy will be coupled with a reaction that requires an input of energy
State the 2 directions of biochemical reactions
substrate -> product
product -> substrate
Describe the structure of most enzymes
Globular
Tertiary or quaternary folding
Describe enzyme catalysis
Reactions are reversible and can be catalysed in both directions
Provide an example of an anabolic reaction
Building glucose in photosynthesis
Provide an example of a catabolic reaction
Breakdown of glucose in cellular respiration
Describe what activation energy is abbreviated as
E,A
Describe transition state
High-energy state which peaks after the desired activation energy has been added. Bonds must be broken in a reaction. For them to be broken molecules must be contorted to an unstable state
State the common form of activation energy
Heat
Describe the effect of heat on the behaviour of enzymes and substrates within a reaction
Thermal energy speeds up motion of reactants, increasing force and frequency of collisions allowing for bond breakage.
Describe the general trend between activation energy and reaction rate
The higher the activation energy the slower the reaction rate
Describe what the process of speeding up a reaction by reducing reaction rate is known as
catalysis
Describe what the factor that is added to reduce activation energy is known as
catalyst
Describe biological catalysts
enzymes
