Biochemistry Question bank

Question 1

Glycosidic bonds are considered which of the following types of bonds?

Answer 1

covalent
Note: think of co within glycosidic

Glycosidic bonds (shown below), also called glycosidic linkages, are considered covalent bonds formed via dehydration/condensation reactions occurring between two monosaccharides that join resulting in a loss of a water molecule for each covalent bond formed.

Covalent bonds are a type of bond where electrons are shared either between atoms of identical electronegativities equally (non-polar covalent) or with differing electronegativities (polar covalent) unequally.

Question 2

Alpha helices and beta sheets are connected to their respective strands with which of the following bonds?

Answer 2

Hydrogen bonds

Alpha helices (shown below) and beta sheets are connected to their respective strands with the use of hydrogen bonds (bonds occurring when hydrogen is bonded to either fluorine, oxygen, or nitrogen).

Hydrogen bonding is the most prevalent interaction that occurs between carboxyl and amino groups of adjacent amino acids forming a polypeptide’s most common secondary structures, the alpha helix and beta sheets

Question 3

The bonds to create the tertiary structure of proteins can be associated with all of the following EXCEPT one. Which one is the EXCEPTION?
A. Vander der Waals [5%]
B. Ionic bonds [11%]
C. Hydrogen bonds [4%]
D. Metallic bonds [74%]
E. Disulfide bonds [6%]

Answer 3

D. Metallic bonds [74%]

The tertiary structure of a protein (shown below) represents the three-dimensional or overall shape of a protein caused by interactions of amino acid side chains, such as hydrophobic interactions, Vander der Waals interactions, ionic bonds, hydrogen bonds, and disulfide bridges.

Question 4

Which of the following connects the amino acids of the primary structure of proteins?

Answer 4

covalent bonds

The primary structure of a protein (shown below) is comprised of a linear sequence of amino acids. These amino acids are linked via a peptide or covalent bond that attaches one AA’s carboxyl group and the other AA’s amino group together by undergoing dehydration reactions.

Question 5

Which of the following compounds contain the strongest bonds?
A. NaCl
B. H2O
C. HNO3
D. CH4
E. HF

Answer 5

A. NaCl
Ionic bonds are formed between ions with opposite charges, as shown below. The electrons are not shared between the atoms as seen in covalent bonding, but rather are associated more with one ion than the other. Although hydrogen bonding may be seen in choices B, C, and E, it is not as strong as ionic bonding.

Question 6

Which of the following lists the correct order from smallest to largest?
PAM

Answer 6

Proton, atom, molecule

Protons are subatomic particles with a +1 electrical charge. Atoms, shown below, are known as the smallest unit of matter that still retains the properties of an element. They are comprised of protons, neutrons, and electrons. Finally, molecules form when two or more atoms join by chemical bonds.

Question 7

Which of the following best describes a molecule?
A. Made up of protons, neutrons, and electrons
B. Group of two or more atoms
C. Group of two or more neutrons
D. Group of two or more protons
E. Group of two or more electrons

Answer 7

B. Group of two or more atoms
Molecules are formed when two or more atoms join together by the use of chemical bonds (covalent bonds), as shown below:

Question 8

Fluorine can strongly attract electrons because of its:
A. Atomic radius
B. Neutrons
C. Electronegativity
D. Electron affinity
E. Atomic mass

Answer 8

C. Electronegativity
The attraction an atom has for electrons is called its electronegativity. In other words, it is “how thirsty” an element is for electrons. The more electronegative an atom is (fluorine being the most electronegative element on the periodic table), the more it can pull electrons toward itself.

Question 9

Answer 9

Polar covalent bonds are chemical bonds formed between atoms that share electrons and have different electronegativities. On the other hand, hydrogen bonds are a type of bond formed when a Hydrogen (H) atom is bound to a highly electronegative atom (such as F, O, or N), causing the Hydrogen atom to take on a more positive charge. The more positively charged hydrogen atom is then attracted to another highly electronegative atom with at least one lone pair of electrons (typically F, O, or N).

You may be wondering why the bond in red is not a hydrogen bond. The hydrogen bond shown in the picture is polar covalent because it is a direct covalent bond between N and H atoms. A hydrogen bond would only be formed in this case if this ammonia molecule interacted with another ammonia molecule, as seen below:

Question 10

Covalent bonds can have all the following properties EXCEPT one. Which one is the EXCEPTION?
A. Non-polar [1%]
B. Polar [1%]
C. Single bond [0%]
D. Double bond [1%]
E. Ionic bond [97%]

Answer 10

E. Ionic bond [97%]

Depending on the number of electrons being shared, covalent bonds can be single, double, or triple bonds, as shown below. Furthermore, non-polar covalent bonds involve the equal sharing of electrons between atoms whereas polar covalent bonds involve the unequal sharing of electrons.

Ionic bonds on the other hand are formed between ions with opposite charges. The electrons are not shared between the atoms as seen in covalent bonding, but rather are associated more with one ion than the other.

Question 11

Which of the following bonds occurs due to the even sharing of electrons between two atoms with similar electronegativity?

Answer 11

Covalent nonpolar bonds

Covalent non-polar bonds are involved with the even or equal sharing of electrons between two atoms of similar or the same electronegativity. Different types of covalent bonds are shown below:

Question 12

Which of the following bonds occur due to the uneven sharing of electrons between two atoms with different electronegativity?

Answer 12

Covalent polar bonds

Covalent polar bonds occur when an atom is bonded to another more electronegative atom preventing equal sharing of electrons between atoms, as shown below:

Question 13

What would be the best biological solvent?

Answer 13

water

Solvents can be described as a substance’s dissolving agent, while the thing that gets dissolved is described as the solute.

In the scenario of putting sugar in water, water acts as the solvent while sugar acts as the solute. The image below shows NaCl mixed with water. Note that hydrogen will encircle negatively charged ions, while oxygen will encircle positively charged ions.

Water is a very reliable solvent primarily due to the polarity it contains. However, it is important to note that, although the versatility of water as a solvent is vast, water is not a universal solvent. If it was, any container holding water, including our cells would be dissolved.

Question 14

Which of the following properties of water make it the best biological solvent?
A. High heat capacity
B. Dipoles of H2O
C. Surface tension
D. Adhesion
E. Cohesion

Answer 14

B. Dipoles of H2O

Water’s polarity caused by the dipoles of H2O allows it to function as a great solvent for polar substances and ions. This is due to polar molecules being more attracted to water i.e., being hydrophilic. Whereas non-polar molecules are repelled by water i.e., they are hydrophobic. This results in water making non-polar molecules aggregate together to avoid other water molecules, while polar substances dissolve further in the polar water. Shown below is an image of a water molecule:

Question 15

The high heat of vaporization of water is explained by its:

Answer 15

High heat capacity

The heat of vaporization of a substance can be described as the quantity of heat a liquid must absorb to transition from a liquid to a gaseous state. As a result of the same reason that water contains a high specific heat, i.e., because of its ability to form hydrogen bonds, it too contains a high heat of vaporization. This means, that due to requiring more heat to increase the temperature of water, it will also require more heat to vaporize the water.

Question 16

If a large body of water is surrounded by a very high atmospheric temperature, which of the following will occur?

Answer 16

The temperature will be stable

The specific heat capacity of a substance is defined as the amount of heat that must be absorbed or lost for 1 g of that substance to change its temperature by 1 degree Celsius.

The ability of water to stabilize temperatures comes from its relatively high heat capacity. Because of the high specific heat of water relative to other materials — water contains the ability to minimize temperature changes of organisms living in large bodies of water and the environment.

Question 17

If a large body of water is surrounded by a very high atmospheric temperature, which of the following will occur?

Answer 17

The temperature will be stable

The specific heat capacity of a substance is defined as the amount of heat that must be absorbed or lost for 1 g of that substance to change its temperature by 1 degree Celsius.

The ability of water to stabilize temperatures comes from its relatively high heat capacity. Because of the high specific heat of water relative to other materials — water contains the ability to minimize temperature changes of organisms living in large bodies of water and the environment.

Question 18

Why is ice able to float in liquid water?

Answer 18

Ice is less dense

Unlike most substances you will encounter, water is one of the select few that are less dense as a solid than it is as a liquid due to the lattice structure of ice (shown below in (a)).

This means that while other substances may contract and become denser as they solidify, water instead expands due to the presence of extensive hydrogen bonding. This allows ice to float (shown below in (b)), as its density in the solid phase is less than water’s density when present in the liquid phase.

Question 19

Which of the following occurs on a molecular level as water freezes?

Answer 19

. H-bonds become more structured

At low enough temperatures, water molecules begin to get locked into a crystal-like lattice structure (shown below in (a)) of hydrogen bonds, resulting in the formation of ice.

As the H-bonds become more structured, ice becomes less dense than liquid as water molecules get spaced further apart causing ice to float (shown below in (b)).