Quiz 2 QA

Question 1

What type of macromolecule are most enzymes?

Answer 1

Proteins

Enzymes are a type of protein that have the capability of speeding up biochemical reactions. Enzymes have a specific three-dimensional shape that allows them to bond to a specific substrate or substrates for the purpose of increasing the chemical reaction rate. Normally, the chemical reaction would occur at a rate that is too slow to allow physiological processes to function. Enzymes catalyze the reaction, enabling these reactions to occur under normal bodily conditions.

Nucleic acids include DNA and RNA. DNA does not have any catalytic capabilities; however, a few types of RNA has been found to have enzyme like activity. The vast majority of enzymes are proteins. Lipids do not have catalytic capabilities. A substrate is what an enzyme works on, not what the enzyme is composed of. An example of a substrate will be sucrose and the enzyme would be sucrase.

Question 2

How many different elements are present in 3C6H12O6?

Answer 2

3
A total of three elements are present, which includes carbon, oxygen, and hydrogen. This problem did not require any calculations nor using any numbers that are associated with the formula. Always read the question being asked and do not assume that one needs to use numbers if numbers are included in a question.

There are 6 atoms of carbon, 6 atoms of oxygen, and 12 atoms of hydrogen in one molecule of the compound. Adding up the number of carbon atoms, hydrogen atoms, and oxygen atoms adds up to 24, but realize the question is asking for the total number of elements, not the total number of atoms in one molecule of the compound. Multipling 3 by 24 gives 72, which represents the total number of atoms in 3 molecules of the compound.

Question 3

What distinguishes one element from another?

Answer 3

The number of protons

Atoms from different elements vary by the number of protons. The proton is a positively charged subatomic particle that is located in the nucleus of every atom. The number of protons is also known as the atomic number.

The atomic mass is equal to the number of protons and neutrons. The number of neutrons can vary in cases of isotopes, but isotopes are still the same element. When the number of electrons changes, they produce ions, not isotopes.

Question 4

An ionic bond involves the _____ between 2 or more atoms.

Answer 4

Transfer of electrons
Ionic bonds involve the transfer of electrons between 2 or more atoms. One atom loses an electron and becomes positively charged while another atom gains that electron and becomes negatively charged. The opposite charges attract and form an ionic bond.

Covalent bonds involve the sharing of electrons between 2 or more atoms. An unequal sharing of electrons is associated with polar covalent bonds, while an equal sharing of electrons is associated with non-polar covalent bonds. Neither protons nor neutrons are transferred between atoms when chemical bonds are formed. Chemical bonds always involve either the sharing or transfer of electrons between atoms.

Question 5

Which of the following is a characteristic of an acid?

Answer 5

An acid has a high concentration of hydrogen ions.

Acidic solutions are defined by having a high concentration of hydrogen ions. Acids release hydrogen ions into water and the more hydrogen ions that are released, the more acidic the solution will be. Acidic solutions are below 7 on the pH scale.

A pH scale is used to compare the pH of different solutions. Acidic solutions are defined by having a pH below 7, not above 7. Basic or alkaline solutions have a pH above 7. Ammonia has a pH about 11.5, making it a basic compound. Blood has a pH of 7.35-7.45, which makes it slightly basic.

Question 6

Many monomers of amino acids linked together through peptide bonds form a __________.

Answer 6

protein
Amino acids are the building blocks of proteins. Amino acids are bonded together through the process of dehydration synthesis. Individual peptide bonds connect two amino acids together. Many amino acids bonded together will contain many peptide bonds, and once structured in a three-dimensional configuration, they can be referred to as a polypeptide or as a protein.

Fatty acids are long carbon chains containing primarily hydrogen and a little bit of oxygen. Fatty acids combine with glycerol to produce a fat. Do not confuse the words amino acid, nucleic acid, and fatty acid; even though they have the word “acid,” they are distinctly different chemical compounds. Nucleic acids include DNA and RNA, which are produced from monomers of nucleotides. Polysaccharides are made from monomers of monosaccharides.

Question 7

Which of the following is found in the cell walls of plants?

Answer 7

Cellulose
Cellulose is a polysaccharide that is found in the cell walls of plants. It provides structural strength for the plant and also serves as a source of fiber in our diet that aids in proper bowel movements.

Glycogen is a polysaccharide that is found primarily in cells of the liver and skeletal muscle. It functions to store sugars. Starch is a polysaccharide that is found in plants and functions to store sugars. Examples include potato and corn starch. Phospholipids are found in cell membranes and function to form a selectively permeable barrier around cells. Lactose is a disaccharide that is found in milk.

Question 8

What type of bond is shown in the figure?

Answer 8

Hydrogen bonds are drawn as dotted lines between a hydrogen atom with a partial positive charge and another atom such as oxygen, which has a partial negative charge. The polarity of water molecules accounts for the partial charges found on the oxygen and hydrogen atoms. The opposite charges create an attraction known as a hydrogen bond that forms between separate water molecules.

Water molecules contain single covalent bonds within a water molecule and hydrogen bonds between separate water molecules. Double and triple covalent bonds hence are not associated with water molecules. While water will dissolve ionic compounds, ionic bonds do not form within water molecules nor between separate water molecules. Water molecules are polar due to the partial charges. Non-polar covalent bonds have an equal sharing of electrons, and therefore lack a partial charge.

Question 9

Which of the following is not a property of water?
Ability to dissolve many substances
High heat capacity
Its molecules exhibit polarity
Low heat of vaporization

Answer 9

Low heat of vaporization…
is not a property of water. Heat of vaporization describes the amount of heat energy required to turn a given amount of liquid into a vapor. Water requires a lot of heat in order to turn into a vapor. The hydrogen bonds between water molecules hold the water molecules close together, keeping them in a liquid state.

All properties of water derive from the fact that it is a polar molecule. There is an unequal sharing of electrons that creates partial charges within the water molecule. The oxygen atom has a partial negative charge and the hydrogen atoms have partial positive charges. Hydrogen bonds form between the oxygen from one water molecule and the hydrogen atoms of a different water molecule due to attraction of the opposite partial charges. High heat capacity means that water can hold heat without turning into a gas. The hydrogen bonds account for the high heat capacity. The polarity of the water molecules enables it to dissolve polar and ionic solutes.

Question 10

Which of the following is a difference between DNA and RNA?

Answer 10

RNA has the base uracil while DNA has the base thymine.

One of the differences between RNA and DNA is that RNA has the base uracil while DNA has the base thymine. Both DNA share the bases adenine, guanine, and cytosine but they differ when it come to uracil and thymine. Other key differences include DNA being double-stranded while RNA is single-stranded. DNA is what genes are composed of while it is RNA that works directly to make proteins. DNA has the sugar deoxyribose while RNA has the sugar ribose.

DNA has a double-stranded structure appearing as a twisted ladder while RNA is single-stranded. The name DNA stands for deoxyribonucleic acid and RNA stands for ribonucleic acid. The first part of their names comes from the type of sugar that each contains. Deoxyribose is found in DNA while ribose is found in RNA. Both RNA and DNA contain the base guanine. DNA is the genetic material that is found in genes, while RNA is used to directly make proteins.

Question 11

An atom has an atomic mass of 20 and an atomic number of 15. How many neutrons does it have?

Answer 11

5
The number of neutrons is equal to the difference between the atomic mass and the atomic number, and in this case 20-15 = 5. Recall that the atomic mass equals sum of the number of protons and the number of neutrons, while the atomic number is equal to the number of protons. Subtracting the latter from the former leaves the number of neutrons.

The atomic mass equals the number of protons plus the number of neutrons, which is 20 in this example. The atomic number is equal to the number of protons, which is 15 in this example. The adding up of the atomic mass and atomic number does not produce a useful number. Since the atomic number and atomic mass is known, there is enough information to calculate the number of neutrons.

Question 12

Which of the following is the weakest bond?

Answer 12

Hydrogen
Hydrogen bonds are the weakest bonds in the list. They are due to weak attractions between a partially positive hydrogen atom and a partially negative atom. Hydrogen bonds are found between different water molecules and are found within molecules of DNA, holding the separate strands together.

Ionic bonds form stronger bonds than hydrogen bonds. Ionic bonds result from the transfer of electrons from one atom to another, producing an ion with a full charge. The opposite charges that attract form an ionic bond, which only breaks down when dissolved in water. Single, double, and triple covalent bonds all involve the sharing of electrons between two or more atoms. These are the strongest types of chemical bonds. They do not break down when the molecule is dissolved in water.

Question 13

The atomic mass is equal to the number of _____ _____.

Answer 13

Protons + neutrons
The number of protons + the number of neutrons equals the atomic mass. This comes from the fact that each proton and each neutron has a weight of one atomic mass unit, while the electron weighs practically nothing, hence all of the weight resides with the protons and neutrons.
Electrons weigh practically nothing, thus adding them up with protons will only add up to the weight of the protons. Neutrons by themselves will not give the complete weight of an atom; they must be added to the total number of protons. Protons by themselves will not give the complete weight of an atom; they must be added to the total number of neutrons. Recall that the total number of protons does give the atomic number of an atom. Since electrons weigh practically nothing, all the electrons added together gives a mass that equals about zero.

Question 14

Which of the following is function of protein?

Answer 14

Provide movement
One function of proteins is to provide movement. Muscles move because of the interaction between actin and myosin proteins. Proteins called microtubules help structures move within cells.

DNA stores genetic information in the form of genes. Triglycerides, a type of lipid, serves the functions of insulation to help with thermoregulation and acts as a cushion to protect internal organs. The job of ATP is to store chemical energy that will be released to provide energy for cellular processes, such as movement, dehydration synthesis, and transporting materials into and out of cells.

Question 15

Please identify the molecule shown in the following image.

Answer 15

Cholesterol is a sterol that is composed of four carbon rings. Cholesterol comes from meat in our diets as well as being made by our cells. Cholesterol is found in cell membranes. Cholesterol is used to produce steroids such as estrogen and testosterone.

Proteins are usually represented in one of a manner of depictions including a linear chain of beads, a spiral helix, a tube bent over itself in multiple positions, or multiple bent-over tubes bonding together. ATP is distinguished by the presence of three phosphate groups attached to a ribose sugar, which itself is bonded to an adenine base. Disaccharides are made of two carbon ring structures that are bonded together. Phospholipids are typically depicted with a spherical phosphate head that is connected to two elongated fatty acid tails.

Question 16

What distinguishes one isotope from another?

Answer 16

The number of neutrons
Atoms that are isotopes are atoms of the same element but vary in the number of neutrons. Isotopes will share the same atomic number but will have different atomic masses. Some isotopes are unstable and give off energy to achieve stability, and thus are ‘radioactive,’ and these radioisotopes play important roles in medical applications.

Atoms of the same element do not differ in their atomic number since it is the number of protons that distinguishes one element from another. When the number of electrons changes, they produce ions, not isotopes. The atomic number deals with the number of protons, which does not vary from atoms of the same element. Hydrogen ions deal with the pH of a solution and don’t have any influence on the number of neutrons in an atom.

Question 17

An unknown compound was analyzed and found to contain fatty acids and glycerol. What is it?

Answer 17

fat
Fats are composed of fatty acids and glycerol. Fats play important functions in the body including energy storage, forming a protective cushion, and insulation. Fats are named as either mono-, di-, or triglycerides depending on whether they have one, two, or three fatty acids bonded to a glycerol molecule.

Proteins are made from amino acids bonded together. Polysaccharides are made from many monosaccharides that are bonded together. Nucleic acids are built from many nucleotides that are bonded together. Cholesterol is a sterol that is composed of four carbon rings.

Question 18

Which is a function of ATP?

Answer 18

Provides chemical energy for cellular functions
ATP’s main function in the cell is to provide chemical energy for cellular processes such as synthesis reactions, movement, and transport of materials into and out of cells. ATP contains three phosphates attached to the sugar ribose. Chemical energy is released when a phosphate is broken off of the ATP molecule. The breaking off of the phosphate releases chemical energy that the cell can then use for various processes.

Enzymes speed up chemical reactions, but they do not provide chemical energy to the chemical reaction. Buffers minimize pH changes. DNA stores genetic information. Some proteins, such as collagen and keratin, provide structural support.

Question 19

What bond is shown in the figure below?

Answer 19

Double covalent bond
Double covalent bonds are identified by having two pairs of electrons being shared between atoms. The sharing of electrons helps the carbon atom and the oxygen atoms attain a complete outer shell, which is filled when it has 8 electrons.

Ionic bonds involve a transfer of electrons between atoms. The image shows an overlap of electrons between the atoms, hence they are not being transferred.
A single covalent bond has one pair of electrons being shared, not two pairs.
A triple covalent bond has three pairs of electrons being shared between atoms.
Hydrogen bonds are drawn with dotted or dashed lines between a hydrogen atom and another atom. This image did not have dotted or dashed lines and it did not have hydrogen as part of the reaction.

Question 20

Which molecule forms cell membranes and is typically drawn as a sphere with two “tails” attached to it?

Answer 20

phospholipids

Question 21

Which substance is hydrophobic and functions as a cushion around organs in the body?

Answer 21

fats

Question 22

What best describes a secondary protein structure?

Answer 22

Helix or pleated sheet

Question 23

An unknown liquid called X has a pH of 8 while a different unknown liquid called Y has a pH of 12. Liquid X is _____ than liquid Y.

Answer 23

10,000 times more acidic

Question 24

Maltase is a type of __________.

Answer 24

enzyme