CHAPTER 3: ENZYMES Flashcards
1
Q
what are biochemical pathways
A
- biochemical reactions: chemical reactions that occur in living things
- a biochemical pathway is a series of interconnected biochemical reactions
- eg. cellular respiration and photosynthesis
- each step requires a specific enzyme
- the product formed by one step of the pathway becomes the reactant for the next step of the pathway and so on
2
Q
why are enzymes needed in living things
A
- catalyze reactions like growth, repair, cellular respiration, photosynthesis, reproduction, digestion, breathing
- enzymes increasing the rate of chemical reactions (which would otherwise occur too slowly to sustain life)
3
Q
what are enzymes
A
- are proteins made of 1 or more polypeptides
- speed up chemical reactions - are catalysts
- substrate specific
- have an active site
- works best in certain conditions
- are not used up in the reaction
- the shape (3d structure) is crucial
4
Q
types of reactions
A
-
catabolic reactions: occurs when a large substrate is broken down into smaller products
- energy is released → cellular respiration
-
anabolic reactions: occurs when smaller substrates are joined to form a larger product
- energy is used → photosynthesis
5
Q
how do enzymes speed up chemical reactions
A
- enzymes allow chemical reactions to occur at a greater rate by lowering the activation energy of the reactions
- enzymes bring molecules close together in the correct orientation and bend the substrate to allow bonds to break or form easily
- as activation energy is lower when the enzyme is used, more substrate molecules and enzymes will have sufficient energy to react when they collide
- They DO NOT change the direction of the reaction nor do thy change the amount of product produced
6
Q
what is activation energy
A
the minimum amount of energy required to initiate a chemical reaction
7
Q
induced fit model vs lock and key model
draw a diagram too
A
- induced fit model:
- the shape of the active site is not rigid and can adjust to the shape of its substrate
- lock and key model
- substrate and enzyme fit together rigidly and tightly
the substrate exactly fits into the enzyme
- substrate and enzyme fit together rigidly and tightly
8
Q
what is a coenzyme
A
- they are organic, non-protein molecules that bind loosely with an enzyme at its active site, assisting the catalytic function of the enzyme
- bound to their enzyme only when the enzyme is acting on a substrate to alter the rate of reaction
- they act with an enzyme to alter the rate of a reaction and can:
- bind to the active site to help the substrate fit
- cycle energy protons, hydrogen, and electrons around the cell
- act as shuttles → transfers atoms and energy
- exists in two inter-convertible forms
- high energy form that is loaded w/ a group that can be transferred
- a lower energy form that is unloaded
9
Q
role of ATP
A
- energy-rich and its major role is to transfer energy within cells
- this energy is made available when the last phosphate group of ATP is removed to form ADP
- transfers both energy and donates a phosphate group to substrates
10
Q
role of NADP+
A
acts as hydrogen donors and in the transfer of energy in photosynthesis
11
Q
role of FAD
A
- the unloaded form acts as a hydrogen and electron acceptor (FAD)
- the loaded form acts as a hydrogen and electron donor (FADH2)
12
Q
role of NAD+
A
- unloaded NAD+ is a receiver/acceptor of electrons and hydrogen ions from substrates
- loaded NADH transfer their hydrogens and electrons in the last stages of cellular respiration
- catalyses reactions in which substrate is reduced and needs to gain hydrogen ions and electrons
- when NADH unloads its electrons the energy released is transferred via a number of steps and is used to produce ATP
13
Q
factors affecting enzyme activity
A
- temperature
- pH
- concentration of enzyme
- concentration of substrate
- competitive and non-competitive enzyme inhibitors
14
Q
factor: temperature
A
- at low temps, there is less movement of substrate and enzyme
- less chance of molecules colliding
- lower reaction rate
- as temperature increases, the kinetic energy of the enzymes and substrate increase
- more likely to collide and reactions are more likely to occur (as there is more movement)
- above the optimum temp, the kinetic energy becomes too high
- bonds that hold the shape of the enzyme begin to break
- the enzyme starts to change shape, causing the active site to be disrupted and enzyme activity quickly starts to drop
- the change in the shape of the active site of the enzyme is called denaturation
- it is irreversible
15
Q
factor: pH
A
- if surrounding pH is too high or low from the optimal ph level, it can alter intra- and inter-molecular bonds of the active site and substrate complex
- changes the shape of the active site
- reduces or stops the function
- when the ph is above or below the optimum range for enzyme, groups between the active site of enzyme and the substrate are no longer able to form a bond, causing enzyme activity to decline and eventually stop