This set of Class 11 Biology Chapter 9 Multiple Choice Questions & Answers (MCQs) focuses on “Biomolecules – Enzymes and Biocatalysts-1”.
1. Which of these enzymes are not proteinaceous?
a) Kinases
b) Endonucleases
c) Ligases
d) Ribozymes
View Answer
Explanation: Kinases, endonucleases and ligases are proteins in nature. They are made out of repeating units of amino acids. However, ribozymes are not proteins but are nucleic acids that act as enzymes.
2. At which part of the enzyme does the substrate fit in?
a) Left end
b) Right end
c) Active site
d) Binding site
View Answer
Explanation: In order to catalyze a reaction, the substrate must bind to enzyme at its active site. Following this, an enzyme-substrate complex is formed which ultimately leads to the formation of the product.
3. How are enzymes different from catalysts?
a) Enzymes are active at high temperatures
b) Catalysts are active at subzero temperatures
c) Catalysts are efficient at high temperatures and high pressures
d) Enzymes are denatured at room temperature
View Answer
Explanation: Enzymes are organic catalysts or biocatalysts. However, inorganic catalysts work at high temperatures and high pressures efficiently. Enzymes, being proteinaceous in nature, get denatured under such conditions.
4. Up to what temperature does the enzymes of thermophilic organisms stay active?
a) 90°C
b) 40°C
c) 35°C
d) 200°C
View Answer
Explanation: Thermophilic organisms can survive at very high temperatures. Therefore, the enzymes produced by them are thermally stable. The enzymes produced by them are active up to temperatures such as 90°C.
5. Which of these statements is true about physical changes?
a) It involves the breaking of bonds
b) It involves a change in shape
c) It does not involve a change in shape
d) Melting of ice is a physical change
View Answer
Explanation: Physical changes involve a change in the shape of a substance but it does not involve the breaking of bonds. Physical changes are reversible, unlike chemical changes. The melting of ice is a physical change.
6. Which of these is an example of a chemical change?
a) Melting of ice
b) Evaporation of water
c) Hydrolysis of glucose
d) Rusting of iron
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Explanation: The melting of ice into water, the evaporation of water to water vapor and the freezing of water are examples of physical changes. However, the hydrolysis of glucose involves the breaking of bonds. It is a chemical change.
7. How can we express the rate of a physical or chemical process?
a) Amount of product formed per unit time
b) Amount of precipitate formed per unit time
c) Amount of substrate used per unit product
d) Amount of time taken per unit product
View Answer
Explanation: The rate of a physical change or a chemical change can be expressed by the amount of product formed per unit time. Physical changes are reversible but chemical changes are not reversible.
8. What happens to the rate of a chemical reaction when that is a 10°C change in either direction?
a) The rate does not change
b) The rate becomes half
c) The rate doubles
d) The rate doubles or becomes half
View Answer
Explanation: The temperature of a reaction is one of the factors that affect the rate of a reaction. When there is a 10°C change in either direction then the rate of the reaction doubles or becomes half of its original value.
9. What reaction is catalyzed by carbonic anhydrase?
a) Breakdown of lipids
b) Formation of cholesterol
c) Formation of carbonic acid
d) Breakdown of carbohydrates
View Answer
Explanation: Carbonic anhydrase is an enzyme that catalyzes the formation as well as the breakdown of carbonic acid. Carbonic anhydrase is proteinaceous in nature and it can be denatured at high temperatures.
10. When the direction is specified, then the rate of a reaction is also called its velocity. True or false?
a) True
b) False
View Answer
Explanation: The rate of a reaction is defined as the amount of product formed per unit time. When the direction of the reaction is specified, then the rate of the reaction is also known as the velocity of the reaction.
11. If the formation of carbonic acid is uncatalyzed, how many product molecules are formed every hour?
a) 25
b) 50
c) 100
d) 200
View Answer
Explanation: The formation of carbonic acid can be catalyzed by the enzyme carbonic anhydrase. When this reaction is uncatalyzed, 200 molecules of carbonic acid are formed every hour. The presence of a catalyst increases the rate by about 10 million times.
12. How many molecules of pyruvic acid are formed from 8 molecules of glucose?
a) 8
b) 24
c) 16
d) 32
View Answer
Explanation: Glucose is converted to pyruvic acid via a metabolic pathway known as glycolysis. 1 molecule of glucose yields 2 molecules of pyruvic acid. Thus, 8 molecules of glucose yield 16 molecules of pyruvic acid.
13. How many carbon atoms do five molecules of pyruvic acid contain?
a) 25
b) 5
c) 15
d) 20
View Answer
Explanation: Pyruvic acid contains three atoms of carbon. Therefore, five molecules of pyruvic acid contain 15 atoms of carbon. Pyruvic acid is the end product of glycolysis, which is a ten-step metabolic pathway.
14. What is the end product of glycolysis under anaerobic conditions?
a) Lactic acid
b) Pyruvic acid
c) Oxalic acid
d) Ascorbic acid
View Answer
Explanation: Glycolysis is a ten-step metabolic pathway that converts one molecule of glucose into two molecules of pyruvic acid. Under anaerobic conditions, glucose is converted into two molecules of lactic acid.
15. Yeast ferments glucose into _____
a) aldehyde
b) ethanol
c) ketone
d) lactic acid
View Answer
Explanation: Yeast is the simplest unicellular eukaryotic organism and belongs to the kingdom Fungi. It anaerobically digests or ferments glucose to produce ethanol or ethyl alcohol, along with carbon dioxide.
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