Unit No. 3: Enzymes. Enzymes, often referred to as the molecular catalysts of life, are the driving force behind countless biological processes that sustain living organisms. As we embark on this journey, we will unravel the fundamental principles governing enzymes, exploring their structure, functions, regulation, and their pivotal role in maintaining the delicate balance of life.
From the intricacies of enzyme-substrate interactions to the intricately choreographed biochemical reactions, these notes will serve as a comprehensive guide to understanding the remarkable world of enzymes, shedding light on the science that underpins the functioning of all living things. So, let’s embark on this enlightening exploration into the realm of enzymes and deepen our understanding of the biochemical foundation of life itself.
Unit 3 Biology of 1st Year Short Answers Questions
What is the role of enzymes in biochemical reactions?
Answer: Enzymes tremendously increase the efficiency of biochemical reactions and are specific for each type of reaction. They make reactions proceed at a reasonable speed, essential for life.
How are enzymes structured?
Answer: Enzymes are composed of hundreds of amino acids that form a globular structure, with the catalytic activity occurring at the active site. The rest of the amino acids maintain the enzyme’s globular structure.
What is the active site of an enzyme?
Answer: The active site is a small portion of the enzyme’s structure where the catalytic activity takes place. It binds to the reactant (substrate) and facilitates the reaction.
- 1st Year Biology Unit No.1 Introduction Notes
- 1st Year Biology Unit No. 2 Biological Molecules Notes
- 1st Year Biology Unit No. 4 The Cell Notes
- 1st Year Biology Unit No. 5 Variety of Life Notes
- 1st Year Biology Unit No. 6 Kingdom Prokaryotae Notes
What are cofactors and how do they contribute to enzyme function?
Answer: Cofactors are non-protein parts that can be essential for enzyme functioning. They often act as bridges between the enzyme and substrate, and sometimes contribute directly to the catalytic reaction, including providing chemical energy.
Give examples of inorganic ions used as cofactors in enzymes.
Answer: Examples of inorganic ions used as cofactors in enzymes include Mg2+, Fe2+, Cu2+, Zn2+, etc.
What is the difference between a prosthetic group and a coenzyme?
Answer: A prosthetic group is a non-protein part covalently bonded to the enzyme, while a coenzyme is loosely attached. Coenzymes are often related to vitamins and are essential for enzyme function.
What happens when a coenzyme is removed from an enzyme?
Answer: An enzyme with its coenzyme or prosthetic group removed is called an apoenzyme, which lacks activity. Adding the correct concentrated coenzyme can restore enzyme activity.
What is the term for an enzyme with its cofactor?
Answer: An activated enzyme with both the polypeptide chain and the cofactor is known as a holoenzyme.
Where are enzymes important in photosynthesis and cellular respiration located?
Answer: Enzymes important in photosynthesis are found in chloroplasts, while those involved in cellular respiration are located in mitochondria.
What role do enzymes play in protein synthesis?
Answer: Enzymes integral to ribosomes are involved in the synthesis of proteins.
How are vitamins related to coenzymes?
Answer: Vitamins are essential raw materials from which coenzymes are made. Coenzymes, like enzymes, can be reused and are required in small quantities.
What are enzymes primarily composed of?
Answer: Globular proteins.
How do enzymes affect the rate of chemical reactions?
Answer: Enzymes increase the rate of reaction without being consumed themselves.
Do enzymes influence the nature of end products in a reaction?
Answer: No, the presence of enzymes does not affect the nature or properties of end products.
In terms of quantity, how much of an enzyme is needed to accelerate a reaction?
Answer: Small amounts of an enzyme can accelerate chemical reactions.
What is the specificity of enzymes referring to?
Answer: Enzymes are very specific in their action, catalyzing only a single chemical reaction or a group of related reactions.
Name some factors that can affect enzyme activity.
Answer: pH, temperature, and substrate concentration.
What are co-factors in relation to enzyme function?
Answer: Some enzymes require co-factors for proper functioning.
How do enzymes lower the energy barrier for reactions?
Answer: Enzymes lower the activation energy of reactions.
What is the role of enzymes in a metabolic pathway?
Answer: Enzymes act sequentially in a series of chemical reactions to complete a metabolic pathway.
Why are certain enzymes produced in an inactive form?
Answer: Some enzymes are potentially damaging if active, so they are produced in an inactive form to prevent unintended effects.
What is the general structure of an enzyme-substrate interaction?
Answer: Enzyme and substrate form an enzyme-substrate complex, which leads to the transformation of substrate into product(s).
How are products transferred between enzymes in a metabolic pathway?
Answer: Substrate molecules are passed from one enzyme to another in a specific order, forming an enzyme-to-enzyme chain.
What is the role of the active site in enzyme-substrate interactions?
Answer: The active site is where an enzyme and its substrate interact. It has a specific charge and shape formed by amino acids, enabling binding and catalysis.
How are the amino acids within the active site arranged?
Answer: The amino acids in the active site are brought closer and arranged through the coiling and folding of the enzyme’s polypeptide chain.
What are the two definite regions of the enzyme’s active site and their functions?
Answer: The two regions are the binding site and the catalytic site. The binding site recognizes and binds the substrate, leading to the formation of an ES complex, which then activates the catalytic site responsible for converting substrate to product.
How does Emil Fischer’s Lock and Key model describe enzyme-substrate interaction?
Answer: According to the Lock and Key model, enzymes and substrates have specific complementary shapes, analogous to a key fitting into a lock. The active site is considered a rigid structure that acts as a template for substrate transformation.
Why did later studies not support the Lock and Key model for all reactions?
Answer: Later studies found that the Lock and Key model didn’t explain all enzyme-substrate interactions, as it did not account for certain types of enzyme flexibility or induced fit.
Where are most enzymes located within a cell and how are they arranged?
Answer: Most enzymes are attached to membrane systems inside the cell in specific and orderly arrangements. Mitochondria and chloroplasts are examples of such organized enzyme locations.
What is the role of the aqueous medium in enzyme activity?
Answer: Enzymes require an aqueous medium for their activity. This medium provides the necessary environment for enzyme-substrate interactions and catalysis to occur.
What did Koshland (1959) propose based on new evidence, and what is it known as?
Answer: Koshland proposed the Induced Fit Model, which suggests that substrate binding induces changes in enzyme structure, enhancing its catalytic activity.
How does an increase in enzyme concentration affect the reaction rate?
Answer: Increasing the enzyme concentration leads to an increase in the reaction rate, as more active sites are available to convert substrate molecules into products.
What happens to the reaction rate when substrate concentration is low?
Answer: At low substrate concentrations, the reaction rate is directly proportional to the amount of substrate available.
What is the significance of the point where further increase in substrate concentration doesn’t affect the reaction rate?
Answer: When all active sites on the enzyme are occupied due to high substrate concentration, additional substrate increase won’t increase the reaction rate.
Name some factors that can affect the rate of enzyme action.
Answer: Concentration of enzyme, concentration of substrate, temperature, and pH of the medium.
What is the optimum temperature for enzymes in the human body?
Answer: 37°C
How does an increase in temperature affect enzyme-controlled reactions?
Answer: Enzyme-controlled reactions initially increase in rate with higher temperature up to a certain limit.
What happens if the vibrations of atoms within an enzyme become too violent due to heat?
Answer: The enzyme’s globular structure, essential for activity, is lost, and the enzyme is denatured.
What is the significance of the optimum pH for enzyme function?
Answer: Enzymes function most effectively within a narrow pH range known as the optimum pH.
How does a change in pH affect enzyme activity?
Answer: A slight pH change can alter amino acid ionization at the active site, potentially retarding or blocking enzyme activity.
What happens when pH extremes are reached?
Answer: Extreme pH values can cause enzyme denaturation by breaking the bonds within the enzyme.
Can all enzymes work at their maximum rate at any temperature?
Answer: No, enzymes have specific optimum temperatures where they function at their maximum rate.
What is the role of heat in enzyme-catalyzed reactions?
Answer: Heat provides activation energy and accelerates chemical reactions by increasing the kinetic energy of reacting molecules.
Provide some examples of enzymes along with their optimum pH values.
Answer: Pepsin (pH 2.00), Sucrase (pH 4.50), Enterokinase (pH 5.50), Salivary amylase (pH 6.80), Catalase (pH 7.60), Chymotrypsin (pH 7.00-8.00), Pancreatic lipase (pH 9.00), Arginase (pH 9.70).
What impact does denaturation have on enzyme structure and function?
Answer: Denaturation disrupts the enzyme’s structure, causing loss of function and activity.
What is an inhibitor?
An inhibitor is a chemical substance that can react with an enzyme’s active site but doesn’t get transformed into products, thus blocking the site temporarily or permanently.
Give an example of an inhibitor.
Cyanide is an example of an inhibitor, acting as a poison that blocks enzyme activity.
How are irreversible inhibitors different from reversible inhibitors?
Irreversible inhibitors permanently occupy active sites or destroy the enzyme’s structure, while reversible inhibitors form weak linkages and can be neutralized by increasing substrate concentration.
What is the primary effect of irreversible inhibitors on enzyme activity?
Irreversible inhibitors either occupy the active site by forming covalent bonds or physically block the site, leading to a reduction in enzyme activity.
How can reversible inhibitors be neutralized?
Reversible inhibitors can be partially or completely neutralized by increasing the concentration of the substrate.
Name the two major types of reversible inhibitors.
Competitive and non-competitive are the two major types of reversible inhibitors.
Explain competitive inhibitors.
Competitive inhibitors have a structural resemblance to the substrate and can bind to the enzyme’s active site, but they can’t activate the catalytic sites, preventing product formation.
What is the outcome of the interaction between a competitive inhibitor and an enzyme?
The competitive inhibitor competes with the substrate for binding to the active site, reducing the overall enzyme activity and product formation.
How do irreversible inhibitors block enzyme activity?
Irreversible inhibitors either covalently bind to the active site or physically obstruct it, leading to a lasting reduction in enzyme function.
Give an example of a reversible non-competitive inhibitor.
Non-competitive inhibitors bind to a site other than the active site. An example is an antibiotic that affects enzyme activity indirectly.
What is the primary characteristic of non-competitive inhibitors?
They form enzyme inhibitor complexes away from the active site.
Where do non-competitive inhibitors bind to the enzyme?
They bind to a location other than the active site.
How do non-competitive inhibitors affect the enzyme’s structure?
They modify the enzyme’s structure, hindering catalytic function.
Even if the actual substrate is present, what happens when non-competitive inhibitors are bound?
Catalysis is disrupted and fails to occur.
What is the consequence of the enzyme inhibitor complex formation by non-competitive inhibitors?
Genuine substrate binding to the active site doesn’t result in catalysis.
(i) List two conditions that destroy enzymatic activity by disrupting bonds between the atoms in an enzyme.
Extreme pH levels
High concentrations of denaturing agents like urea or guanidine hydrochloride
(ii) How do low and high temperatures affect enzyme activity?
Low temperature: Enzyme activity generally decreases due to slower molecular movement and reduced kinetic energy.
High temperature: Enzyme activity initially increases, but at a certain point (optimal temperature), the enzyme denatures and loses activity due to disrupted bonds.
(iii) What is a prosthetic group?
A prosthetic group is a non-polypeptide molecule that is tightly and permanently attached to an enzyme. It plays a critical role in the enzyme’s function, often participating in catalysis or binding specific substrates.
(iv) Define inhibitors of enzymes.
Inhibitors are molecules that can bind to enzymes and decrease their catalytic activity. They can be competitive (competing for the active site) or non-competitive (binding elsewhere on the enzyme).
(v) How does an enzyme accelerate a metabolic reaction?
Enzymes accelerate metabolic reactions by lowering the activation energy required for the reaction to occur. They achieve this by providing an alternative pathway with a lower energy barrier, allowing the reaction to proceed more easily and at a faster rate.
Unit 3 Biology of 1st Year Long Answers Questions
Question: Describe in detail the mechanism of enzyme action.
Answer: Mechanism of Enzyme Action:
Enzymes facilitate chemical reactions by lowering the activation energy required for the reactions to occur. This enables the reactions to happen more efficiently and at biologically relevant rates. The mechanism of enzyme action can be described in a few steps:
Substrate Binding: The substrate, which is the molecule the enzyme acts upon, binds to the active site of the enzyme. The active site is a specific region on the enzyme’s surface that matches the shape and properties of the substrate.
Formation of the Enzyme-Substrate Complex: As the substrate binds to the active site, an enzyme-substrate complex forms. This complex is stabilized by various interactions, including hydrogen bonds, ionic interactions, and hydrophobic interactions.
Catalysis: The enzyme catalyzes the conversion of the substrate(s) into product(s). It does so by facilitating the formation or breaking of chemical bonds in the substrate molecule(s). The enzyme’s active site provides an optimal environment for these reactions to occur, allowing them to happen more readily than they would without the enzyme.
Product Formation: After the reaction is complete, the products are released from the active site, and the enzyme is ready to bind to another substrate molecule and repeat the process.
Enzyme Recycling: Enzymes are not consumed in the reactions they catalyze. Once the products are released, the enzyme is free to bind to another substrate molecule and continue catalyzing reactions.
Question: Give the effect of pH and temperature on the efficiency of an enzyme action.
Answer: Effect of pH and Temperature on Enzyme Efficiency:
pH: Enzymes have an optimal pH at which they function most effectively. Deviating from this pH range can disrupt the enzyme’s structure through changes in ionization of amino acid residues, affecting its active site and overall stability. Extreme pH values can denature enzymes, rendering them non-functional.
Temperature: Enzymes also have an optimal temperature at which they work best. Low temperatures slow down enzymatic activity due to reduced molecular motion, while high temperatures can denature enzymes by breaking the weak interactions that maintain their structure.
Question: Write a note on inhibitors of enzymes.
Answer: Inhibitors of Enzymes:
Enzyme inhibitors are molecules that can bind to enzymes and reduce their activity. They can be classified into two main types:
Competitive Inhibitors: These inhibitors compete with the substrate for binding at the active site. They do not affect the enzyme’s catalytic ability directly but reduce the chance of a substrate binding to the active site.
Non-competitive Inhibitors: These inhibitors bind to an allosteric site (a site other than the active site) on the enzyme, causing a conformational change that reduces the enzyme’s catalytic activity.
Question: What is the importance of enzymes in life?
Answer: Importance of Enzymes in Life:
Enzymes play crucial roles in virtually all biological processes. They are essential for life because they:
- Regulate metabolic pathways by controlling the rates of biochemical reactions.
- Enable digestion by breaking down complex molecules into absorbable forms.
- Facilitate DNA replication, transcription, and translation, which are vital for genetic inheritance and protein synthesis.
- Play a key role in energy production through processes like glycolysis, the citric acid cycle, and oxidative phosphorylation.
- Are involved in signal transduction and cell communication, mediating responses to external stimuli.
- Participate in immune responses, blood clotting, and many other physiological processes.
- In summary, enzymes are central to life processes due to their ability to accelerate biochemical reactions and control essential cellular activities.