Human Anatomy & physiology Chapter 2

After the transfer of the electron, sodium will form an ion with __________.

a charge of +1 If sodium loses an electron, it will be positively charged. Although not shown explicitly in the figure, the element sodium contains 11 protons within its nucleus. If sodium forms a cation containing 10 electrons, it will have a charge of +1

Which of the following best describes an isotope?

a structural variation in which different atoms of the same element have different numbers of neutrons Nearly all known elements have two or more structural variations called isotopes, which have the same number of protons and electrons but differ in the number of neutrons they contain.

Which of the following is a chemical that has an amine group and an organic acid group, but does not contain a peptide bond?

amino acid An amino acid contains an amine group and an organic acid group, but does not contain a peptide bond. Peptides bonds are used to join amino acids (monomers) together, forming larger molecules (polymers) ranging in size from small polypeptides to large proteins.

Which particle is indicated by the arrow?

proton Note how the number of the indicated particles in each of the three atoms defines each as a unique element

Which type(s) of subatomic particles can be located within the nucleus of an atom?

protons and neutrons In a typical atom, the protons and neutrons "hang out" together in the center of the atom—the nucleus. Electrons are always found orbiting around the nucleus.

Bonds between carbon and hydrogen atoms (as depicted on the right side of the figure) are generally __________.

single covalent bonds Each shared pair of electrons represents a single covalent bond

What is represented by the chemicals at A?

substrates The substrate is a reactant in an enzyme-catalyzed reaction

A patient voices concern that her normal cholesterol level is dangerous. "I eat no cholesterol at all. That stuff is toxic!" she declares. What is your best response?

"A normal cholesterol level is a good thing. Your cells depend on cholesterol to stay healthy, and you can't make vital hormones without it."

Except for elements with atomic number 1 and 2, all other elements are stable with how many electrons in their outermost (valence) energy level?

18 Elements 1 and 2 are stable with a maximum of two electrons in their outermost (valence) energy level (electron shell). All other elements are stable with eight electrons in their valence shell

What is the mass number of the helium atom?

4 amu The helium atom shown contains two protons and two neutrons, which contribute to a total mass number of 4 amu.

An atom of oxygen has an atomic number of 8 and a mass number of 18. How many of each type of subatomic particle does it contain?

8 protons, 8 electrons, and 10 neutrons The atomic number is the number of protons in an atom, and it will have the same number of electrons, to balance the electrical charge. Mass number is the number of protons plus the number of neutrons, so subtracting atomic number from mass number reveals the number of neutrons. The number of protons and electrons is constant for all atoms of any element, but the number of neutrons can vary. Atoms of the same element that differ in the number of neutrons are called isotopes.

In a covalent bond,

Atoms share one or more pairs of electrons. In covalent bonds, atoms share ("co") their valence electrons ("valent"). These bonds are strong because to maintain stability the atoms must stay close enough together to continue sharing their electrons.

Which of the following statements is true regarding the reactions shown?

Both reactions are exergonic. Both of the illustrated reactions are exergonic and release the same amount of energy during product formation. The difference is the amount of energy input (activation energy) required to initiate the reactions depending on the presence or absence of enzyme.

What explains the negative charge on the oxygen atom within the water molecule?

Electrons are transferred from hydrogen to oxygen during the formation of an ionic bond Oxygen atoms are highly electronegative and pull electrons away from the electropositive hydrogen atom. Also, the nonbonding (lone) electron pairs on the oxygen, which are responsible for bending the molecule, are negative.

Polar molecules are electrically balanced, due to the equal sharing of electrons between the atoms of the molecules.

False

Rank the chemical bonds from relatively weakest to strongest .I. Ionic II. Covalent III. Hydrogen

III < I < II Covalent bonds are the strongest because they involve sharing electrons. Ionic bonds are weaker and involve attractions between oppositely charged ions. Hydrogen bonds are the weakest and involve attractions between partial charges.

Which of the following is true of an isotope?

Isotopes have the same number of protons, but differ in the number of neutrons they contain

Why can dehydration be such a life-threating event?

It significantly alters the ratio of body water (solvent) to dissolved substances (solutes), such as sodium ions.

Which of the following statements is true regarding the reaction without an enzyme compared to the one with an enzyme?

Less energy input is required to start the reaction in the presence of enzyme. Enzyme-catalyzed reactions require less activation energy and therefore are initiated with a lower input of energy. This activation energy represents the energy necessary for driving the early stages of the reaction: creating contact between properly oriented substrates, breaking original bonds, and so on.

Atoms of oxygen have a total of 8 electrons. Are these atoms stable, and why or why not?

No, because the atoms have only 6 valence electrons, but need 8 for stability. To be stable, by the Octet Rule an atom must have 8 electrons in its outermost orbital. With only 6 valence electrons, oxygen atoms are unstable and will seek ways to get or share two more electrons to become stable.

Would water still be a polar molecule if it were NOT in the form of a V but rather were linear like carbon dioxide?

No, because the difference in the pull of oxygen on the bonding electrons would be neutralized. Like in carbon dioxide, the difference in electronegativity of the oxygen and hydrogen atoms would be neutralized by being in a straight line.

Which of the following distinguishes hydrogen bonds from covalent bonds?

Only hydrogen bonds can form between molecules. Because hydrogen bonds are not true bonds, they do not always join atoms together within a single molecule. In water, for example, hydrogen bonds link water molecules together. This is referred to as an intermolecular attraction—it is between different atoms

Blood loss due to a moderate hemorrhage has several adverse effects on patient wellbeing. Why would administering IV fluids alone not be sufficient to return a patient to health?

Oxygen-carrying red blood cells lost along with the fluid component must also be replaced.

Which of the following is true of protein structure?

Secondary protein structures involve hydrogen bonding between amine and carboxyl groups.

Which of the following is true of protein structure?

Secondary protein structures involve hydrogen bonding between amine and carboxyl groups. Hydrogen bonding between certain amine and carboxyl groups creates alpha helices and beta-pleated sheets.

Which of the following statements about a dipole is INCORRECT?

The dipole molecules are electrically balanced. Nonpolar molecules, not dipole molecules, are electrically balanced

Which of the following is true of polar covalent bonds?

The electrons are shared unequally. Because the electrons are shared unequally, they spend more time around one atom than the other, causing a slight negative charge where they tend to hang out the most, and a slight positive charge where they spend the least time

Which response provides the best explanation as to why ionic compounds easily dissociate in water?

The polarity of water easily breaks the charges between the oppositely charged ions in the compound

How are the oxygen atoms bonded together in a molecule of oxygen gas (O2)(O2)?

They are bonded by a double covalent bond. Since the oxygen atoms have a valence number of 6, they each need to gain two electrons to satisfy the octet rule. Neither can transfer electrons, so they must share two electrons each, forming a double covalent bond.

Which of the following is not a result of hydrogen bonds?

Two hydrogen atoms join together to form a molecule of hydrogen gas. Hydrogen bonds occur when there are polar covalent molecules present, but hydrogen atoms join with each other through nonpolar covalent bonds.

Carbon atoms have four valence electrons. Are they likely to react with other atoms, and why or why not?

Yes, because they can become more stable by doing so. Atoms react with other atoms to gain stability, typically by gaining, losing, or sharing electrons to attain a full outermost orbital. Atoms with full outermost electron orbitals are less likely to react and are referred to as being inert.

The presence of what group differentiates most amino acids from each other

an R group The identity of each unique amino acid is determined by the structure of its R group—note differences within the green rectangular area in amino acids (b) through (d).

All amino acids, such as the four represented in the figure, contain __________.

an amine group and an acid group

What holds the sodium and chloride ions together in a chemical bond?

an electrical attraction between opposite charges The transfer of an electron results in ions with opposite charges that are electrically attracted to each other.

Which of the following would represent the attraction between an anion and a cation?

an ionic bond Ionic bonds form between ions, atoms that have gained or lost electrons in order to become more stable. Anions have gained one or more electrons and thus have a negative charge; cations have lost one or more electrons and thus have a positive charge.

Chemical bonds __________.

are energy relationships between the electrons of the reacting atoms

Which of the following is not produced through chemical bonding?

atoms Atoms react through chemical bonding to form larger structures. Chemical bonding begins with atoms; it does not produce them. All of the structures that we cover in A&P are made from atoms through chemical bonding.

Water is an important molecule because it __________.

can form hydrogen bonds Because of its polar nature, water is able to form hydrogen bonds. In fact, many of the special properties of water derive from its extensive hydrogen bonding capacity. In addition, water has a high heat capacity and is considered a universal solvent since it dissolves more substances than any other known solvent

Which four elements comprise approximately 96% of our body weight?

carbon, oxygen, hydrogen, and nitrogen. The four elements carbon, oxygen, hydrogen, and nitrogen make up about 96% of our body weight; 20 others are present in the body, some in trace amounts

Which of the following correctly ranks the types of chemical bonds, in order, from strongest to weakest?

covalent, ionic, hydrogen In covalent bonds, electrons are shared between atoms; in ionic bonds electrons are lost or gained; but hydrogen bonds are not true chemical bonds—they are weak attractions due to slight electrical imbalances. No electrons are directly involved.

Which of the following is a primary function of molecule B?

energy storage

How many valence shell electrons does the element carbon have?

four Carbon has an atomic number of 6 and has four electrons in its outermost (valence) electron shell

How many hydrogen atoms will a single carbon atom bond with to form a stable molecule?

four Carbon has four electrons in its valence (outermost) electron shell. Therefore, it will form covalent bonds with four hydrogen atoms. The four electrons contributed by the hydrogen atoms will fill the valence shell of carbon.

Which of the following factors would speed up the rate of a chemical reaction?

high concentration of reagents Chemical reactions take place faster if the reacting particles are present in a high number

What type of bond is formed between the oxygen atom of one water molecule and the hydrogen atom of another water molecule?

hydrogen bond The attraction between the slightly negative oxygen atom of one molecule and the slightly positively charged hydrogen atom within a separate water molecule is the basis of hydrogen bond formation. It is a form of dipole-dipole interaction.

Covalent bonds:

involve the sharing of one to three pairs of electrons. In single covalent bonds, one pair of electrons is shared; in double covalent bonds two pairs are shared; and triple covalent bonds involve sharing of three pairs of electrons. Double covalent bonds are common between carbon atoms in some organic molecules.

Which type of bond would most likely form between lithium and fluorine to make lithium fluoride?

ionic bond Lithium has three electrons, two in the first energy level and one in the second. Fluorine has nine electrons, two in the first energy level and seven in the second. They would both satisfy the octet rule if lithium transferred its valence electron to fluorine, forming an ionic compound.

The three atoms shown represent different __________.

isotopes These three atoms have the same number of protons and are therefore different variations of the same element. They vary because each contains a different number of neutrons; therefore, they are different isotopes of the element hydrogen (atomic number = 1).

Which of the following is NOT a subatomic particle?

molecule Atoms are comprised of subatomic particles: protons, electrons, and neutrons. Most atoms do not exist in the free state but instead are chemically combined with other atoms. Such a combination of two or more atoms held together by chemical bonds is called a molecule.

Which subatomic particles contribute to an atom's mass number but not its atomic number?

neutrons Atomic number is the number of protons in an atom, but mass number is calculated by adding both the number of protons and the number of neutrons in an atom

Which of the following is not a fundamental subatomic particle that forms elements?

nucleus

Sulfur has an atomic number of 16. Sulfur will form chemical bonds in a similar manner as __________.

oxygen Oxygen and sulfur both have six electrons in their valence (outermost) electron shells. Therefore, they will form similar types and numbers of bonds with other atoms

Molecule A is a __________.

phospholipid Phospholipids consist of a glycerol backbone linked to two fatty acid chains and a phosphorus-containing group

Formation of hydrogen bonds requires hydrogen atoms and what else?

polar covalent bonds Hydrogen gets a slight positive charge from the unequal sharing of electrons in polar covalent bonds, and it bonds to another atom with a slightly negative charge, again resulting from unequal electron sharing due to a polar covalent bond

A molecule of water (H2O) is formed by what type of bond?

polar covalent bonds The unequal electron distribution produces a slight negative charge on the oxygen and a slight positive charge on the hydrogens. These slight charges give water many unique characteristics that make it ideal for many physiological processes.

Hydrogen bonds would be found in which of the following?

the complex, three-dimensional structure of protein molecules Proteins are long chains of amino acids. Some of these amino acids are polar, and others are not. The chain of amino acids will adopt a specific shape according to the hydrogen bonds formed between the polar parts of the protein.

The superscript preceding each hydrogen atomic symbol (H) represents which of the following?

the mass number of the corresponding atom Note how the sum of the number of protons and neutrons in the corresponding atomic structures is equal to the indicated atomic mass

What is the most significant factor in the formation of a covalent bond?

the sharing of electron pairs between two atoms Covalent bonds are formed by the sharing of electrons between two reactive atoms.

Which of these elements would be MOST likely to be radioactive?

tritium Tritium is the heaviest isotope and is the most likely of the three to be radioactive.

Which parts of atoms can interact (react) to form chemical bonds?

valence electrons Only the outermost parts of atoms interact (react) with each other, and those are the valence electrons. If the outermost orbital is full, the atom is stable and less likely to react with another atom.

In biochemistry, and thus in the body, the universal solvent is __________.

water

Which of the following is considered the universal solvent?

water Water is a solvent and makes up 60-80% of the volume of most living cells