1.
Choose the element that is found in all organic compounds:
Correct Answer
A. Carbon
Explanation
Carbon is found in all organic compounds because it is the key element that forms the backbone of organic molecules. Carbon has a unique ability to form strong covalent bonds with other carbon atoms, as well as with other elements such as hydrogen, oxygen, nitrogen, and sulfur. These bonds allow carbon to form a wide variety of complex and diverse organic compounds, including carbohydrates, lipids, proteins, and nucleic acids. Therefore, carbon is essential for the existence and functioning of organic life.
2.
The following structural formula is representative of which functional group?
Correct Answer
B. Carboxyl
Explanation
The given structural formula contains a carbon atom bonded to both an oxygen atom and a hydroxyl group. This arrangement is characteristic of the carboxyl functional group, which is found in carboxylic acids. Carboxyl groups are important in various biological molecules such as amino acids and fatty acids, and they are involved in processes such as protein synthesis and metabolism.
3.
Which of the functional groups illustrated below would you expect to find in an amino acid?
Correct Answer
B. 1 and 4
Explanation
Amino acids are the building blocks of proteins and contain an amino group (-NH2) and a carboxyl group (-COOH). Option 1 and 4 both have these functional groups. Option 1 has a carboxyl group (COOH) and option 4 has an amino group (NH2). Therefore, these functional groups are expected to be found in an amino acid.
4.
In humans, the function of glycogen is to:
Correct Answer
E. Keep glucose available
Explanation
The function of glycogen in humans is to keep glucose available. Glycogen is a polysaccharide that serves as a storage form of glucose in the body. It is stored in the liver and muscles and can be broken down into glucose when the body needs energy. This ensures a constant supply of glucose is available for various metabolic processes and to maintain blood sugar levels within the normal range.
5.
When a molecule of glycerol reacts with one or more fatty acids, an ester linkage results. The formation of this linkage is a result of a reaction between:
Correct Answer
E. An alcohol and a carboxylic acid
Explanation
When a molecule of glycerol reacts with one or more fatty acids, an ester linkage is formed. This ester linkage is the result of a reaction between an alcohol (glycerol) and a carboxylic acid (fatty acid). The hydroxyl group (-OH) of the alcohol reacts with the carboxyl group (-COOH) of the carboxylic acid, resulting in the formation of an ester bond (-COO-). This reaction is known as esterification and is a common process in the synthesis of lipids, such as triglycerides.
6.
When two organic molecules are joined together, and a water molecule is removed, the reaction is called which of the following?
Correct Answer
C. Dehydration synthesis (condensation)
Explanation
Dehydration synthesis (condensation) is the correct answer because when two organic molecules are joined together, a water molecule is removed in the process. This type of reaction is commonly known as dehydration synthesis or condensation reaction. In this reaction, a covalent bond is formed between the two molecules, resulting in the formation of a larger molecule and the release of a water molecule as a byproduct. This process is essential for building complex biological molecules such as proteins, carbohydrates, and nucleic acids.
7.
The hydrolysis (breakdown) of an ester results in:
Correct Answer
D. An acid and an alcohol
Explanation
When an ester undergoes hydrolysis, it is broken down into its constituent components, which are an acid and an alcohol. This process involves the addition of water to the ester molecule, leading to the cleavage of the ester bond. The oxygen atom in the ester bond forms a bond with a hydrogen atom from water, resulting in the formation of an alcohol. Simultaneously, the carbon atom in the ester bond becomes a part of a carboxylic acid, leading to the formation of an acid. Therefore, the correct answer is "An acid and an alcohol."
8.
The hydrolysis (breakdown) of a dipeptide results in the production of which of the following?
Correct Answer
A. Two amino acids
Explanation
The hydrolysis of a dipeptide involves the breaking of the peptide bond between two amino acids. This process results in the production of two separate amino acids.
9.
When fatty acids and glycerol chemically combine to for a fat, one other product is produced. This product is:
Correct Answer
B. Water
Explanation
When fatty acids and glycerol chemically combine to form a fat, the process is called esterification. In this process, a condensation reaction occurs, where a water molecule is released as a byproduct. Therefore, the correct answer is water.
10.
Many people are aware that water is the most abundant substance in all organisms. However, next to water, what is the major component of living cells?
Correct Answer
E. Proteins
Explanation
Proteins are the major component of living cells, second only to water. They play crucial roles in various cellular functions such as structural support, enzymatic reactions, and transportation of molecules. Proteins are made up of amino acids and are essential for the growth, repair, and maintenance of tissues in organisms. They are involved in almost every biological process and are responsible for the diversity and complexity of living organisms.
11.
Of the following, which are reasons why molecular models are useful to biologists? Models help:1. Visualize the shape of functional groups2. Visualize geometric isomers3. Visualize the three-dimensional shapes of molecules4. Determine the presence of symmetry in molecules5. Predict products of chemical reactions
Correct Answer
D. 1, 2, 3, 4, and 5
Explanation
Molecular models are useful to biologists because they can help visualize the shape of functional groups, visualize geometric isomers, visualize the three-dimensional shapes of molecules, determine the presence of symmetry in molecules, and predict products of chemical reactions. Therefore, the correct answer is 1, 2, 3, 4, and 5.
12.
Which of the following is the essential characteristic of a polar molecule?
Correct Answer
B. Has an asymmetrical distribution of electrical charge
Explanation
A polar molecule is characterized by having an asymmetrical distribution of electrical charge. This means that the molecule has a positive end and a negative end, resulting in a dipole moment. This occurs when there is an uneven sharing of electrons between atoms in a molecule, causing one end to be more electronegative than the other. The presence of double or triple bonds, the element oxygen, or ions as part of the structure may contribute to the polarity of a molecule, but they are not the essential characteristic.
13.
Which three of the following are characteristics of hydrogen bonds?1. They are responsible for the surface tension properties of water.2. They are responsible for the relatively high boiling point of water.3. They are stronger than ionic bonds.4. They are present in all substances.5. They are weaker than covalent bonds.
Correct Answer
A. 1, 2, and 5
Explanation
Hydrogen bonds are responsible for the surface tension properties of water because they cause the water molecules to stick together, creating a cohesive force at the surface. They are also responsible for the relatively high boiling point of water because the hydrogen bonds require more energy to break, resulting in a higher boiling point. Additionally, hydrogen bonds are weaker than covalent bonds, as they involve an electrostatic attraction between a hydrogen atom and a highly electronegative atom. Therefore, the correct characteristics of hydrogen bonds are 1, 2, and 5.
14.
A chemical bond involving carbon and hydrogen (C-H) is present in many biological molecules. Based upon their electronegativities, the bond could be described as:
Correct Answer
B. A covalent bond
Explanation
A covalent bond is the correct answer because a bond involving carbon and hydrogen is typically formed by the sharing of electrons between the two atoms. In a covalent bond, the electrons are shared rather than transferred, which is consistent with the nature of the C-H bond. This type of bond is commonly found in biological molecules such as carbohydrates, lipids, and proteins.
15.
In terms of maintaining the shape of an enzyme, the strongest bonds involved are:
Correct Answer
C. Covalent (disulfide) bonds
Explanation
Covalent (disulfide) bonds are the strongest bonds involved in maintaining the shape of an enzyme. These bonds form between two cysteine residues in the enzyme's polypeptide chain, creating a covalent link called a disulfide bond. Disulfide bonds are highly stable and can withstand harsh conditions, allowing them to provide structural support to the enzyme. This helps the enzyme maintain its specific shape, which is crucial for its proper functioning. The other bond types listed, such as dipole-dipole interactions, hydrogen bonds, hydrophobic bonds, and ionic interactions, are also important for enzyme structure but are generally weaker than covalent bonds.