C1.1 Enzymes and metabolism Flashcards
1
Q
A
2
Q
What does metabolism describe?
A
The totality of all enzyme-catalysed reactions that occur within a living cell or organism.
3
Q
How can control over metabolism be exerted?
A
Through enzymes.
4
Q
What are the two key functions of metabolic reactions?
A
- Provide a source of energy for cellular processes
- Enable the synthesis and assimilation of new materials for use within the cell.
5
Q
What do anabolic reactions do?
A
Build up complex molecules from simpler ones.
6
Q
What type of reactions occur during the synthesis of organic molecules via anabolism?
A
Condensation reactions.
7
Q
Give an example of an anabolic reaction.
A
- The production of glucose by photosynthesis
- The synthesis of polypeptide chains from amino acids
- The semi-conservative replication of DNA.
8
Q
What do catabolic reactions do?
A
Break down complex molecules into simpler ones.
9
Q
What type of reactions occur during the breakdown of organic molecules via catabolism?
A
Hydrolysis reactions.
10
Q
Give an example of a catabolic reaction.
A
- The oxidation of substrates in cell respiration
- The breakdown of macromolecules into monomers during chemical digestion.
11
Q
What is an enzyme?
A
A globular protein that acts as a biological catalyst.
12
Q
Are enzymes changed or consumed by the reactions they catalyse?
A
No, enzymes are not changed or consumed and can be reused.
13
Q
How are enzymes typically named?
A
After the molecules they react with, ending with the suffix ‘-ase’.
14
Q
What is the active site of an enzyme?
A
The region on the surface of the enzyme to which a substrate molecule binds.
15
Q
What is activation energy (EA)?
A
The amount of energy required for a chemical reaction to proceed.
16
Q
How do enzymes affect activation energy?
A
They lower the activation energy.
17
Q
What happens if the reactants contain more energy than the products?
A
Free energy is released into the system (exergonic).
18
Q
What type of reactions are usually exergonic?
A
Catabolic reactions.
19
Q
What happens if the reactants contain less energy than the products?
A
Free energy is lost to the system (endergonic).
20
Q
What type of reactions are usually endergonic?
A
Anabolic reactions.
21
Q
What is an enzyme?
A
A globular protein that acts as a biological catalyst by speeding up the rate of a chemical reaction.
Enzymes are crucial for various biochemical processes in living organisms.
22
Q
Are enzymes changed or consumed by the reactions they catalyze?
A
No, enzymes are not changed or consumed and can be reused.
This allows enzymes to work efficiently in low amounts.
23
Q
How are enzymes typically named?
A
Enzymes are named after the molecules they react with (substrates) and end with the suffix ‘-ase’.
Examples include lipase for lipids and proteases for proteins.
24
Q
What is the active site of an enzyme?
A
The region on the surface of the enzyme to which a substrate molecule binds.
The active site is crucial for the enzyme’s function.
25
What is the composition of the active site?
The active site is composed of a few amino acids only.
## Footnote
Interactions between these amino acids shape the active site to complement the substrate.
26
What is activation energy (EA)?
The energy required for a chemical reaction to proceed.
## Footnote
All chemical reactions require a certain amount of activation energy.
27
How do enzymes affect activation energy?
Enzymes lower the activation energy, allowing the reaction to proceed at a faster rate.
## Footnote
This means less energy is needed to convert the substrate into a product.
28
What happens if the reactants contain more energy than the products?
Free energy is released into the system (exergonic).
## Footnote
These reactions are usually catabolic, breaking down molecules.
29
What type of reactions are typically exergonic?
Catabolic reactions that release energy from broken bonds within a molecule.
## Footnote
These reactions are essential for energy production in cells.
30
What occurs if the reactants contain less energy than the products?
Free energy is lost to the system (endergonic).
## Footnote
These reactions are usually anabolic, requiring energy to synthesize bonds.
31
What type of reactions are typically endergonic?
Anabolic reactions that require energy to synthesize bonds between molecules.
## Footnote
These reactions are vital for growth and cell repair.
32
What is a catalyst?
A substance that allows a reaction to proceed at a faster rate or under different conditions than otherwise possible
## Footnote
Catalysts are crucial in both chemical and biological reactions.
33
What are enzymes?
Biological catalysts that are not consumed by the specific reactions they catalyse
## Footnote
Enzymes can operate in low amounts and are essential for various biological processes.
34
What role do enzymes play in chemical reactions?
Allow chemical reactions to proceed within a biologically relevant passage of time
## Footnote
This is crucial for processes such as DNA replication and nutrient absorption.
35
What would happen without enzymes in DNA replication?
DNA replication would be unable to occur within the lifetime of a cell
## Footnote
This would prevent organismal growth and repair.
36
What is the consequence of lacking enzymes for food digestion?
Food would be unable to be chemically digested within the period of transit through the digestive tract
## Footnote
This would lead to insufficient nutrient absorption.
37
How do enzymes contribute to maintaining temperature homeostasis?
Allow for chemical reactions to proceed at biologically appropriate temperatures
## Footnote
Without enzymes, reactions would require higher temperatures that could denature cell components.
38
What is required for enzyme catalysis to occur?
The substrate must be brought into close physical proximity with the active site
## Footnote
This is essential for the formation of the enzyme-substrate complex.
39
What is formed when a substrate binds to an enzyme's active site?
An enzyme-substrate complex is formed
## Footnote
This complex is crucial for the catalysis of the substrate into product.
40
What happens after the enzyme catalyses the conversion of the substrate?
An enzyme-product complex is created, and the enzyme and product then dissociate
## Footnote
The enzyme can continue to catalyse further reactions since it is not consumed.
41
What does the induced fit model describe?
The enzyme’s active site undergoes a conformational change when exposed to a substrate
## Footnote
This improves binding and explains broad specificity of enzymes.
42
What is an example of an enzyme with broad specificity?
Lipase can bind to a variety of lipids
## Footnote
This demonstrates how enzymes can act on different substrates.
43
How does the conformational change in enzymes affect substrate reactivity?
It stresses bonds in the substrate, increasing reactivity
## Footnote
This is a key mechanism in enzyme catalysis.
44
Where do enzyme reactions typically occur?
In aqueous solutions such as cytoplasm or interstitial fluid
## Footnote
The random movement of substrate and enzyme (Brownian motion) facilitates reactions.
45
What is a situation where an enzyme may be fixed in position?
When it is membrane-bound
## Footnote
This localization serves to concentrate reactions at specific sites.
46
What must happen for an enzymatic reaction to occur?
The substrate and enzyme must physically collide in the correct orientation
## Footnote
This facilitates binding to the active site.
47
How can the rate of enzyme catalysis be increased?
By improving the frequency of collisions through:
* Increasing molecular motion of particles
* Increasing concentration of particles
## Footnote
Thermal energy can enhance kinetic energy, promoting collisions.
48
What is the site where the substrate binds to an enzyme?
Active site
## Footnote
The active site has high specificity for the substrate.
49
What determines the shape and chemical properties of the active site?
The three dimensional shape of the enzyme
## Footnote
The active site's properties are highly dependent on the enzyme's overall structure.
50
What can modify enzyme structure?
External factors such as high temperatures and extreme pH
## Footnote
These factors can disrupt essential chemical bonds.
51
What negative effect does denaturation have on enzymes?
It affects the enzyme’s capacity to bind the substrate
## Footnote
Denaturation changes the structure of the active site.
52
What are molecules that can reduce enzyme-substrate interactions called?
Inhibitors
## Footnote
Inhibitors can occlude the active site or alter its shape.
53
Fill in the blank: The active site of an enzyme is a _______ or cavity.
indentation
## Footnote
This indentation allows for specific binding of the substrate.
54
True or False: The active site is not affected by changes in temperature or pH.
False
## Footnote
High temperatures and extreme pH can disrupt the enzyme's structure.
55
What happens to the chemical bonds of an enzyme when it is exposed to high temperatures?
They are disrupted
## Footnote
Disruption of chemical bonds can lead to loss of enzyme function.
56
What factors may affect the activity of enzymes?
Frequency of enzyme-substrate collisions and the capacity for interaction
## Footnote
This includes factors like temperature, pH, and substrate concentration.
57
How does temperature influence enzyme activity?
Low temperatures lead to insufficient thermal energy, while increasing temperature raises enzyme and substrate motion
## Footnote
Higher kinetic energy results in more frequent collisions.
58
What happens to enzyme activity at optimal temperature?
The rate of enzyme activity is at its peak
## Footnote
Optimal temperature may vary for different enzymes.
59
What occurs at higher temperatures regarding enzyme stability?
Enzyme stability decreases, leading to denaturation due to disrupted hydrogen bonds
## Footnote
This affects the enzyme's active site and its shape.
60
How does pH affect enzyme function?
Alters the charge of the enzyme, affecting protein solubility and shape
## Footnote
Changes in shape or charge of the active site diminish substrate binding.
61
What is the effect of changing pH on enzyme activity?
Diminishes enzyme activity when moving outside the optimal pH range
## Footnote
Optimal pH may differ between enzymes.
62
What is the relationship between substrate concentration and enzyme activity?
Increasing substrate concentration increases enzyme activity
## Footnote
More substrates lead to more collisions and reactions.
63
What happens to enzyme activity after a certain substrate concentration is reached?
The rate of activity ceases to rise, even with further increases in substrate levels
## Footnote
Environment becomes saturated with substrate, and all enzymes are bound and reacting (Vmax).
64
Fill in the blank: Insufficient thermal energy at low temperatures prevents the activation of an enzyme-catalysed reaction to _______.
proceed
65
True or False: Higher temperatures always increase enzyme activity.
False
## Footnote
Higher temperatures can lead to denaturation and loss of activity.
66
What are the three key decisions to be made when designing an experiment to test enzyme activity?
1. Which specific enzyme/substrate reaction to investigate
2. Which experimental factor to manipulate (independent variable)
3. How to measure the enzyme activity (dependent variable)
## Footnote
These decisions are crucial for the experimental design and outcomes.
67
How can the rate of an enzyme-catalysed reaction be calculated?
By plotting according to the time taken for the reaction to proceed
## Footnote
This involves measuring either the amount of product formed or the amount of substrate consumed.
68
What is the relationship between reaction rate and time taken?
Reaction rate is the inverse of time taken
## Footnote
This means that a higher reaction rate corresponds to less time taken.
69
What is the formula for calculating the rate of reaction?
Rate of reaction (s–1) = 1 ÷ time taken (s)
## Footnote
This formula allows for quantifying enzyme activity based on time measurements.
70
Fill in the blank: The rate of reaction can be calculated as _______.
Rate of reaction (s–1) = 1 ÷ time taken (s)
## Footnote
This formula is essential for determining the efficiency of enzyme activity.
71
True or False: The time taken for a reaction is directly proportional to the reaction rate.
False
## Footnote
Reaction rate is inversely related to time taken.
72
What two measurements can be used to determine the time taken for an enzyme-catalysed reaction?
1. Amount of product formed
2. Amount of substrate consumed
## Footnote
Both measurements provide insights into enzyme activity and reaction kinetics.
73
What does metabolism describe?
The sum total of all enzyme-catalysed reactions that occur within an organism in order to maintain life.
74
What do most chemical changes in a cell result from?
A series of reactions (pathways), with each step controlled by a specific enzyme.
75
Where can metabolic pathways be found?
Both within the cytoplasm (intracellular) and outside of the cell (extracellular).
76
Give two examples of intracellular reactions.
* Glycolysis
* Krebs cycle
77
What is an example of an extracellular reaction?
The breakdown of nutrients within the gut (chemical digestion).
78
What is required for the production of extracellular enzymes (exoenzymes)?
A well developed secretory pathway within the cell.
79
List components of the secretory pathway involved in producing exoenzymes.
* Rough ER
* Golgi complex
* Vesicles
80
What are metabolic pathways typically organised into?
Chains or cycles of enzyme-catalysed reactions
81
What type of pathway is glycolysis an example of?
Linear pathway
82
What type of pathway is blood clotting an example of?
Linear pathway
83
What type of pathway is the Krebs cycle an example of?
Cyclical pathway
84
What type of pathway is the Calvin cycle an example of?
Cyclical pathway
85
Why do metabolic pathways allow for greater regulation?
The chemical change is controlled by numerous intermediates
86
Fill in the blank: Linear pathways are present in processes such as _______.
glycolysis and blood clotting
87
Fill in the blank: Cyclical pathways are present in processes such as the _______ cycle and the _______ cycle.
Krebs; Calvin
88
True or False: Metabolic pathways can only be linear.
False
89
What is the efficiency of metabolic reactions in energy transfers?
Metabolic reactions are not 100% efficient; a proportion of energy is always lost as heat.
## Footnote
This inefficiency is a common characteristic of biological systems.
90
What type of animals are classified as endotherms?
Mammals and birds.
## Footnote
Endotherms generate heat to maintain a constant body temperature.
91
What type of animals are classified as ectotherms?
Reptiles, amphibians, and most fish.
## Footnote
Ectotherms rely on the environment to regulate their body temperature.
92
What affects the level of heat production by an animal?
The level of metabolic activity.
## Footnote
Higher metabolic activity typically results in greater heat production.
93
What is a state of torpor in animals?
A state that reduces heat production.
## Footnote
Examples include hibernation in winter and estivation in summer.
94
What is competitive inhibition?
Involves a molecule, other than the substrate, binding to the enzyme’s active site
95
What is a competitive inhibitor?
A molecule that is structurally and chemically similar to the substrate and binds to the active site
96
How does a competitive inhibitor affect substrate binding?
It blocks the active site and thus prevents substrate binding
97
How can the effects of a competitive inhibitor be reduced?
By increasing substrate concentration
98
What are statins?
Common cholesterol lowering drugs that function via competitive enzyme inhibition
99
Which enzyme do statins inhibit?
HMG-CoA reductase
100
What is the effect of statins on cholesterol production?
Reduces cholesterol production, minimizing health consequences associated with high cholesterol
101
What is non-competitive inhibition?
Involves a molecule binding to a site other than the active site (an allosteric site)
102
What happens when a non-competitive inhibitor binds to the allosteric site?
Causes a conformational change to the enzyme’s active site
103
What is the effect of a conformational change on substrate binding?
The active site and substrate no longer share specificity, meaning the substrate cannot bind
104
Can increasing substrate levels mitigate the effects of a non-competitive inhibitor?
No, increasing substrate levels cannot mitigate the inhibitor’s effect
105
What is cyanide?
A poison that prevents aerobic respiration, leading to death by non-competitive inhibition
106
To which enzyme does cyanide bind?
Cytochrome oxidase
107
What is the consequence of cyanide binding to cytochrome oxidase?
The electron transport chain cannot continue to function and ATP is not produced via aerobic respiration
108
What is end-product inhibition?
A form of negative feedback by which metabolic pathways can be controlled
109
How does end-product inhibition occur?
The final product inhibits an enzyme from an earlier step in the sequence
110
What type of inhibition is involved in end-product inhibition?
Non-competitive inhibition
111
What happens when the product binds to an allosteric site?
The enzyme is temporarily inactivated
112
What is the result of enzyme inactivation in end-product inhibition?
The reaction sequence is halted and the rate of product formation is decreased
113
What is the purpose of end-product inhibition?
To ensure levels of an essential product are tightly regulated
114
What happens if product levels build up in end-product inhibition?
The product inhibits the reaction pathway and decreases the rate of further product formation
115
What occurs if product levels drop in end-product inhibition?
The reaction pathway proceeds unhindered and the rate of product formation increases
116
What is an example of feedback inhibition?
Isoleucine feedback
117
Is isoleucine an essential amino acid?
Yes, it is not synthesized by the body in humans
118
What are some food sources rich in isoleucine?
* Eggs
* Seaweed
* Fish
* Cheese
* Chicken
* Lamb
119
How is isoleucine synthesized in plants and bacteria?
From threonine in a five-step reaction pathway
120
What is the first step in the synthesis of isoleucine?
Threonine is converted into an intermediate compound by threonine deaminase
121
How does isoleucine act in the synthesis pathway?
It binds to an allosteric site on threonine deaminase and acts as a non-competitive inhibitor
122
What does excess production of isoleucine inhibit?
Further synthesis of isoleucine
123
What does feedback inhibition ensure in the context of isoleucine production?
It prevents cannibalization of available stocks of threonine
124
What is mechanism-based inhibition also called?
Suicide inhibition
125
What occurs when an enzyme binds to a competitive inhibitor in mechanism-based inhibition?
Forms an irreversible complex
126
What type of bonds are formed during the normal catalysis reaction in mechanism-based inhibition?
Covalent bonds
127
What is required to restore enzyme activity after mechanism-based inhibition?
Synthesize new enzymes
128
What is an example of a mechanism-based inhibitor?
Penicillin
129
What does penicillin inhibit?
Specific transpeptidases
130
What is the consequence of penicillin inhibiting transpeptidases?
Destruction of the bacterial cell
131
Why is penicillin a highly effective antibiotic?
Targets a feature unique to prokaryotic cells
132
What unique feature of prokaryotic cells does penicillin target?
Peptidoglycan cell wall
133
What is a consequence of bacteria evolving modified versions of transpeptidase?
Increased resistance to penicillin
134
How can resistant strains of bacteria transfer their resistance?
Via bacterial conjugation
135
Fill in the blank: The only way to restore enzyme activity after mechanism-based inhibition is to _______.
synthesize new enzymes
136
True or False: Penicillin is effective against eukaryotic cells.
False
