Question 1

The ultimate source of energy for life on earth is __________.
A) The sun
B) Geothermal heat
C) Carbohydrates
D) Fats
E) Other organisms

Accepted Answer

The sun is the primary source of energy for Earth's climate system and is the source of energy for all life on Earth, directly or indirectly. Photosynthesis in plants captures the energy from sunlight to produce carbohydrates, which serve as an energy source for other organisms.

Question 2

Which of the following is not a common component of biomolecules?
A) Carbon
B) Hydrogen
C) Oxygen
D) Nitrogen
E) Chlorine

Accepted Answer

Chlorine is not a common component of biomolecules. Biomolecules, such as proteins, carbohydrates, lipids, and nucleic acids, are primarily composed of carbon, hydrogen, oxygen, and nitrogen. Chlorine is not typically found in the structures of these molecules.

Question 3

Which of the following is the basic structural unit of living organisms?
A) Nucleus
B) Cell membrane
C) Tissue
D) Cell
E) Cytoskeleton

Accepted Answer

The cell is the basic structural and functional unit of all living organisms, often called the "building block of life."

Question 4

Which of the following is not an organelle?
A) Mitochondria
B) Chloroplast
C) Nucleus
D) Plasma membrane
E) Golgi complex

Accepted Answer

The plasma membrane is not an organelle but a biological membrane that separates the interior of all cells from the outside environment, which is a fundamental structure for all living cells, not a specialized structure within the cell like an organelle.

Question 5

Which of the following is not a role played by carbohydrates in living cells?
A) Energy source
B) Structural support
C) Intercellular communication
D) Both A and B are correct
E) All are roles played by carbohydrates in living cells

Accepted Answer

Carbohydrates serve as an energy source, provide structural support, and are involved in intercellular communication, making all the listed options roles played by carbohydrates in living cells. Therefore, the statement that both A and B are correct does not apply as an answer to the question asking for a role not played by carbohydrates.

Question 6

Metabolism is best defined as the _________.
A) Reactions of living cells
B) Reactions that synthesize large molecules in living cells
C) Reactions that degrade molecules in living cells
D) Conversion of food molecules to energy
E) Reactions that synthesize and degrade molecules in living cells

Accepted Answer

Metabolism encompasses all chemical reactions within living cells, including both the synthesis (anabolism) and degradation (catabolism) of molecules.

Question 7

The average life span of a species is about ________years
A) One million
B) Ten million
C) Five hundred thousand
D) Five million
E) One hundred thousand

Accepted Answer

The answer of The average life span of a species...

Question 8

Which of the following is not a waste product of living organisms
A) Carbon dioxide
B) Water
C) Urea
D) Ammonia
E) Glycine

Accepted Answer

Glycine is an amino acid, not a waste product. It is used in the biosynthesis of proteins.

Question 9

Biochemistry is defined as
A) The study of life processes
B) The study of the molecular basis of life
C) The study of living organisms
D) The study of organic compounds in living organisms
E) The study of living compounds

Accepted Answer

Biochemistry is specifically focused on understanding the molecular basis of life, including the chemical processes and substances that occur within living organisms.

Question 10

One of the principal methods that organisms use to obtain energy from chemical bonds is by ___________.
A) Substitution reactions
B) Dehydration reactions
C) Oxidation/reduction reactions
D) Hydration reactions
E) Addition reactions

Accepted Answer

Organisms primarily use oxidation/reduction reactions (also known as redox reactions) to obtain energy from chemical bonds. In these reactions, one molecule is oxidized (loses electrons) and another is reduced (gains electrons), facilitating the transfer of energy.

Question 11

The following is an example of which reaction class? CH₃Br + HSCH₂CH(NH₂)COOH $\rightarrow$CH₃SCH₂CH(NH₂)COOH + Br^- + H⁺ A) Substitution B) Elimination C) Addition D) Isomerization E) Oxidation/Reduction

Accepted Answer

This reaction is an example of a substitution reaction, where a bromine atom (Br) is replaced by a thiol group (-SH) on the organic molecule.

Question 12

The following is an example of which reaction class HOOCCH=CHCOOH + H₂O $\rightarrow$HOOCCH₂CH(OH)COOH A) Substitution B) Elimination C) Addition D) Isomerization E) Oxidation/Reduction

Accepted Answer

This is an example of an addition reaction, where a molecule (in this case, sulfur dioxide, SO2) adds across the double bond of maleic acid (HOOCCH=CHCOOH) to form a single product, sulfurous acid (HOOCCH(SO2)CH(OH)COOH).

Question 13

The following is an example of which reaction class? CH₃CH₂OH $\rightarrow$CH₃CHO + H₂O A) Substitution B) Elimination C) Addition D) Isomerization E) Oxidation/Reduction

Accepted Answer

The reaction involves the conversion of ethanol (CH3CH2OH) to acetaldehyde (CH3CHO), which is an oxidation process as the alcohol is oxidized to an aldehyde.

Question 14

Which of the following is not a component of nucleic acid?
A) Nucleotides
B) Glucose
C) Phosphate group
D) Purines
E) Pyrimidines

Accepted Answer

Glucose is not a component of nucleic acids. Nucleic acids, such as DNA and RNA, are composed of nucleotides, which in turn are made up of a sugar (deoxyribose in DNA and ribose in RNA), a phosphate group, and a nitrogenous base (purines or pyrimidines).

Question 15

The largest molecules in living organisms are _________.
A) proteins
B) lipids
C) nucleic acids
D) carbohydrates
E) steroids

Accepted Answer

Nucleic acids, which include DNA and RNA, are the largest molecules in living organisms due to their long chain-like structures that can contain millions of atoms.

Question 16

All of the following classes of compounds are lipids except _______.
A) fats
B) sterols
C) fatty acids
D) phosphoglycerides
E) nucleotides

Accepted Answer

Nucleotides are not lipids; they are the basic building blocks of nucleic acids like DNA and RNA, not involved in the same biological functions or structures as lipids.

Question 17

Which of the following classes of biomolecules are the most abundant in nature?
A) Lipids
B) Amino acids
C) Carbohydrates
D) Proteins
E) Nucleotides

Accepted Answer

Carbohydrates are the most abundant class of biomolecules in nature, primarily because they serve as energy sources and structural components in plants (e.g., cellulose) and are widespread in both plant and animal tissues.

Question 18

Consider the following molecule. Which arrow is pointing to a peptide bond? 
A) A
B) B
C) C
D) D
E) E

Accepted Answer

The answer of Consider the following molecule. Which arrow is...

Question 19

The following molecule is an example of which single class of compounds? CH₃CH₂CH(NH₂)COOH A) Amine B) Acid C) Ester D) Amino acid E) Alcohol

Accepted Answer

The molecule contains both an amino group (-NH2) and a carboxylic acid group (-COOH), which are characteristic functional groups of amino acids.

Question 20

The following molecule is an example of which class of compounds? CH₃CH₂CH₂COOCH₂CH₃ A) Hydrocarbon B) Acid C) Ester D) Ether E) Aldehyde

Accepted Answer

The molecule described is an ester, characterized by the presence of a COO group linking two hydrocarbon chains.

Quiz 1: Biochemistry: an Introduction

The ultimate source of energy for life on earth is __________.

Which of the following is not a common component of biomolecules?

Which of the following is the basic structural unit of living organisms?

Which of the following is not an organelle?

Which of the following is not a role played by carbohydrates in living cells?

Metabolism is best defined as the _________.

The average life span of a species is about ________years

Which of the following is not a waste product of living organisms

Biochemistry is defined as

One of the principal methods that organisms use to obtain energy from chemical bonds is by ___________.

The following is an example of which reaction class? CH₃Br + HSCH₂CH(NH₂) COOH $\rightarrow$ CH₃SCH₂CH(NH₂) COOH + Br^- + H⁺

The following is an example of which reaction class HOOCCH=CHCOOH + H₂O $\rightarrow$ HOOCCH₂CH(OH) COOH

The following is an example of which reaction class? CH₃CH₂OH $\rightarrow$ CH₃CHO + H₂O

Which of the following is not a component of nucleic acid?

The largest molecules in living organisms are _________.

All of the following classes of compounds are lipids except _______.

Which of the following classes of biomolecules are the most abundant in nature?

Consider the following molecule. Which arrow is pointing to a peptide bond?

The following molecule is an example of which single class of compounds? CH₃CH₂CH(NH₂) COOH

The following molecule is an example of which class of compounds? CH₃CH₂CH₂COOCH₂CH₃