Chapter 2 (chemical level of organization)
What can result if body fluid pH fluctuates outside the normal range of 7.35 to 7.45? (2.7)
Variations in pH outside the normal range can damage cells and disrupt normal cellular functions. For example, blood pH below 7 can produce coma, and blood pH above 7.8 usually causes uncontrollable, sustained muscular contractions.
Discuss ionization as it relates to living organisms (2.6)
Within organisms, solutes (which may be organic or inorganic) are typically dissolved in water, forming an aqueous solution. Inorganic compounds held together by ionic bonds in solution undergo ionization (or dissociation). In this process, ionic bonds are broken apart as individual ions interact with the positive or negative ends of polar water molecules. The high concentration of water molecules prevents re-forming of the original bonds, resulting in a solution.
Which of the following substances removes hydrogen ions from a solution? (2.8)
a base
Glucose is an example of __________. (2-9)
a monosaccharide
In proteins, the bond between the carboxyl group of one amino acid and the amino group of another is called __________. (2.11)
a peptide bond
In order to create a high-energy compound within cells, a high-energy bond usually connects an organic molecule to __________. (2-13)
a phosphate group
A substance that dissociates in solution to release hydrogen ions (H+) is called a(n) __________. (2.8)
acid
A solution with a pH below 7 is __________. (2.7)
acidic
Enzymes promote chemical reactions by lowering the _________ required (2.4)
activation energy
Before enzymes can function as catalysts, reactants must bind to a special region of the enzyme called the __________. (2.11)
active site
The hydrolysis of ATP yields the molecule ________.
adenosine diphosphate
Which of the following is/are a function(s) of DNA? (2-12)
all of the above (carbohydrate destruction, protein synthesis, lipid creation)
Proteins are long chains of ____________, each of which consists of a central carbon atom bonded to several components (2.11)
amino acids
Which of the following is connected by peptide bonds and function as a building block for proteins?
amino acids
Which of the following substances has the lowest hydrogen ion (H+) concentration? (2.7) milk grapes saliva ammonia
ammonia
Which of the following processes requires energy to create a chemical bond? (2-3)
anabolism
A(n) _______ solution containing anions and cations can conduct an electric current. (2.6)
aqueous
The number of protons in an atom is its ___________. (2.1)
atomic number
The number of protons in an atom is known as the atom's __________.
atomic number
Which of the following properties takes into account the masses of subatomic particles and the relative proportions of any isotopes? (2.1)
atomic weight
A solution with a pH above 7 is termed _________. (2.7)
basic (alkaline)
Which of the following is an anion? (2-2)
bicarbonate (calcium, magnesium, potassium are cations)
Atoms are so small that measurements are reported in __________. (2.1)
billionths of a meter (nanometers)
Which of the following compounds are very soluble in water? (2-9, 2-10)
both monosaccharides and disaccharides
Which of the following substances keep the pH of most body fluids within a range of 7.35 to 7.45? (2.8)
buffers
Which of the following compounds provides energy for vital activities? (2-14)
carbohydrates
The term ________ indicates that a carbon and a hydroxyl group are important features of fatty acids (2.10)
carboxyl
Enzymes belong to a class of substances called _____________, compounds that accelerate chemical reactions without being permanently changed themselves (2.4)
catalysts
Among the following compounds, which is a steroid? (2.10) triglyceride glycerol phospholipid cholesterol
cholesterol
Chemical bonding produces molecules and _______________. (2.2)
compounds
Hydrolysis is a form of __________. (2-3)
decomposition
A condensation reaction is an example of __________. (2-3)
dehydration synthesis
Which of the following reactions results in the formation of a complex molecule by the removal of water? (2.3)
dehydration synthesis
Water molecules are released during which of the following reactions? (2-6)
dehydration synthesis of large molecules
Which of the following lists is in the correct order of increasing hydrogen ion concentration? (2-7)
eggs, saliva, vinegar, stomach HCl
Buffers stabilize pH by __________. (2-8)
either removing or replacing hydrogen ions
Salts are examples of __________, inorganic compounds whose ions can conduct an electrical current (2.8)
electrolytes
What does the conversion of ATP to ADP via hydrolysis represent? (2-13)
energy release
Catalyst is a term used to describe __________. (2-4)
enzymes
Which type of reaction generates heat that maintains body temperature? (2.4)
exergonic
A single hemoglobin molecule is composed of __________. (2-11)
four globular protein subunits
Glycogen is a polysaccharide composed of interconnected __________ molecules (2.9)
glucose
Which of the following sugars is the most important "fuel" in the body? (2.9)
glucose
Of the following important substances in the body, which is NOT an inorganic compound? (2.5)
glucose (water, carbon dioxide, oxygen are inorganic compounds)
A triglyceride consists of three fatty acids attached to __________. (2-10)
glycerol
Each time an energy exchange occurs in chemical reactions, some of the energy is released as __________. (2.3)
heat
A salt is an ionic compound consisting of any cation except a(n) ___________ ion and any anion except a hydroxide ion (2.8)
hydrogen
Water has a high heat capacity due to the linking of water molecules by __________. (2-6)
hydrogen bonds
During _________, complex molecules are broken down by the addition of water molecules. (2.6)
hydrolysis
Neutral solutions have equal numbers of hydrogen ions and _________ ions (2.7)
hydroxide
In which of the following cell types is glycogen found? (2.9)
in animal cells
Weak and irregular heartbeats can be caused by __________. (2-8)
increased concentrations of potassium
Small molecules that generally lack both carbon and hydrogen atoms are called ______________ compounds (2.5)
inorganic
Chemical bonds created by the electrical attraction between anions and cations are __________ bonds. (2.2)
ionic
Atoms that are of the same element but contain different numbers of neutrons are called
isotopes
Which of the following elements is required for the activation of several enzymes? (2-1)
magnesium
Enzymes are responsible for which of the following? (2-11)
metabolic regulation
___________ refers to all the chemical reactions in the body. (2.3)
metabolism
Saliva has a pH similar to that of a(n) __________. (2-7)
milk
Isotopes differ in the number of __________ they contain (2-1)
neutrons
In DNA, the two strands twist around each other in a double helix resembling a spiral staircase; the "stair-steps" correspond to __________. (2.12)
nitrogenous base pairs
In which type of bond do the atoms remain electrically neutral? (2-2)
nonpolar covalent bonds
Large organic molecules composed of carbon, hydrogen, oxygen, nitrogen, and phosphorus are called ____________. (2.12)
nucleic acids
Long chains of nucleotides form complex molecules called __________. (2-12)
nucleic acids
Essential elements and molecules obtained from the diet are called __________. (2.5)
nutrients
Which of the following substances is defined as a large, complex compound composed of carbon bonded with other atoms, including hydrogen atoms? (2.5)
organic compound
Which of the following compound(s) is/are inorganic? (2-5)
oxygen and carbon dioxide
What is the most abundant lipid component of cell membranes? (2.10)
phospholipids
An unequal sharing between atoms of different elements creates a ___________. (2.2)
polar covalent bond
Which of the following lipids contain multiple double bonds between carbon atoms? (2-10)
polyunsaturated fatty acids
Polypeptides containing more than 100 amino acids are called __________. (2-11)
proteins
The simplest element is hydrogen, which has an atomic number of 1 because its atom contains one ______________. (2.1)
proton
Lowering the activation energy affects only the __________ of a reaction, NOT the __________ of the reaction (2.4)
rate; direction
In a chemical reaction, the interacting participants are termed ______________, and the reaction generates one or more products. (2.3)
reactants
Many biological reactions are freely __________. (2.3)
reversible
The opposite of decomposition is known as __________. (2.3)
synthesis
A carbohydrate is an organic molecule that contains carbon, hydrogen, and oxygen in a ratio near __________. (2.9)
1:2:1
Discuss the concept of complementary base pairs regarding nucleotides in DNA (2.12)
A DNA molecule has two nucleotide chains held together by weak hydrogen bonds between opposing nitrogenous bases. Due to their shapes, adenine can bond to thymine only, and cytosine can bond to guanine only.
How many hydrogen bonds exist between cytosine and guanine? (2.12) [figure 2-20]
three
The nitrogenous base that binds to adenine and is present in DNA (but not in RNA) is ______________. (2.12)
thymine
A disaccharide contains how many monosaccharides? (2-13)
two
Oxygen atoms reach stability by sharing __________. (2-2)
two pairs of electrons
What is the subatomic particle makeup of an atom of helium with an atomic number of two and a mass (sum of protons and neutrons) number of four? (2-1)
two protons, two neutrons, two electrons
Which of the following types of lipid is/are liquid at room temperature? (2-10)
unsaturated fats
An atom with a full electron shell is __________ stable and thus is __________ reactive. (2.2)
very; not
Most inorganic molecules and compounds in the human body exist in association with which of the following substances? (2.5)
water
What is the single most important constituent of the human body? (2.6)
water
Which of the following is an excellent solvent? (2.6)
water
Which of the following is/are NOT an organic compound(s)? (2-5)
water and carbon dioxide
Which of the following do NOT dissociate completely in solution? (2.8)
weak acids and weak bases
Why is a solution containing table salt considered to be a neutral solution? (2.8)
A solution of table salt (sodium chloride, or NaCl) is considered to be neutral because its dissociation does not affect the concentration of either hydrogen ions or hydroxide ions
Define activation energy as it refers to chemical reactions (2.4)
Activation energy is the amount of energy required to start a reaction.
Why is anabolism considered to be an "uphill" process? (2.3)
Anabolism, the synthesis of new compounds, is considered to be an "uphill" process because energy is required to make chemical bonds.
Discuss how the heat capacity of water affects body temperature. (2.6)
Because water molecules are linked by hydrogen bonds, water has a very high heat capacity; that is, it takes a lot of energy to change the temperature of a quantity of water. This property allows body temperature to remain stable over a range of environmental temperatures.
Discuss the physiological concept of buffers (2.8)
Buffers are compounds that stabilize the pH of a solution by either removing or replacing hydrogen ions. An example of a buffer is sodium bicarbonate.
Describe the differences between DNA and RNA in terms of their structure, number of nucleotides, and function (2.12)
DNA consists of paired strands arranged in a double helix and always contains more than 45 million nucleotides; RNA consists of a single strand containing fewer than 100 nucleotides or up to about 50,000 nucleotides. DNA stores genetic information that controls protein synthesis, whereas RNA performs protein synthesis as directed by DNA.
Compare the pH of fluid within the stomach to that of blood, in terms of both hydrogen-ion (H+) and hydroxide-ion (OH-) concentrations (2.7)
Due to the presence of HCl, the fluid within the stomach has an extremely acidic composition, at a pH of about 1.0, with a high concentration of H+ and a low concentration of OH-. Blood, at a pH of about 7.35 to 7.45, has a lower H+ concentration and a higher OH- concentration (by a factor of 107).
Describe the concept of surface tension as it relates to hydrogen bonds. (2.2)
Hydrogen bonds are too weak to create molecules, but they can alter molecular shapes or pull molecules together. This type of interaction between water molecules on a free surface slows the rate of evaporation and creates the phenomenon known as surface tension, which acts as a barrier to the entry of small objects into the water.
Why do oxygen atoms in a water molecule display a slight negative charge? (2.2)
In a water molecule, an oxygen atom forms covalent bonds with two hydrogen atoms. However, because the oxygen atom has a much stronger attraction for the shared electrons than do the hydrogen atoms, those electrons spend most of their time with the oxygen atom. Because of the two extra electrons, the oxygen atom develops a slight negative charge.
Describe exchange reactions in terms of their reactants and products. (2.3)
In exchange reactions, parts of the reactants are shuffled (AB + CD → AD + CB). In such reactions, the reactant molecules undergo decomposition, whereas the products are formed by synthesis.
Which of the following sentences best describes glycogen? (2-9)
It is a branching chain of glucose molecules.
Explain why the control of cholesterol levels in the body is difficult through dietary restrictions alone (2.10)
It is difficult to control blood cholesterol levels by dietary restrictions alone because cholesterol is obtained not only through dietary intake (especially in animal products such as meat, cream, and egg yolks) but also through synthesis by the liver. Cholesterol is important in maintaining cell membranes and manufacturing steroid hormones.
Discuss the difference between weight and mass. (2.1)
Mass is the amount of matter that an object contains. Mass is the physical property that determines the weight of an object in the Earth's gravitational field. On Earth, weight and mass are the same, but in orbit, although an object would have no weight, its mass would be unchanged.
What happens to energy in a chemical reaction? (2.4)
Once a reaction has begun, it may absorb energy or release energy (as heat); however, energy cannot be created.
Define phospholipids in terms of their structure and solubility in water (2.10)
Phospholipids consist of a glycerol and two fatty acids (a diglyceride) linked to a nonlipid group by a phosphate group (PO43-). The nonlipid portion of a phospholipid is soluble in water, whereas the fatty acid portion is relatively insoluble.
Which subatomic particles are found in the nucleus of the atom?
Protons and neutrons
The characteristics of a particular protein are determined in part by the ___________ groups on its amino acids (2.11)
R
__________ fats—triglycerides containing saturated fatty acids—are usually solid at room temperature (2.10)
Saturated
Describe the general structure, source, and uses of starches (2.9)
Starches are glucose-based polysaccharides that are important energy sources in our diets. Most starches, including potatoes and grains, are manufactured by plants. To be used by the body, starches must be broken down into simple sugars by the digestive tract.
List the seven major categories of protein function (2.11)
Support (through structural proteins) Movement (via contractile proteins) Transport (via transport proteins and other specialized proteins) Buffering action Metabolic regulation (through the actions of enzymes) Coordination and control (provided by protein hormones) Defense (against environmental hazards)
Describe the primary function and sources of the disaccharides sucrose and lactose (2.9)
The disaccharides sucrose and lactose are complex carbohydrates that must be broken down to their constituent monosaccharides (simple sugars) before they can be absorbed and serve as energy sources in the body. Sucrose is table sugar, whereas lactose is milk sugar.
Describe how the composition of an atom's outer electron shell affects that element's chemical properties. (2.1)
The number of electrons in an atom's outer electron shell determines the element's chemical properties; atoms with an unfilled outer electron shell are unstable and thus react with other atoms, whereas atoms with a filled outer electron shell are stable and will not react with other atoms.
Describe the factors that can alter the shape of a protein and thus its function (2.11)
The shape of a protein can be altered by small changes in the ionic composition, temperature, or pH of its surroundings. At very high body temperatures (over 43°C, or 110°F), for example, proteins undergo denaturation, a change in their 3D shape. Such denatured proteins are nonfunctional, and the loss of structural proteins and enzymes causes irreparable damage to organs and organ systems.
How do enzymes affect the activation energy and/or rate of reactions? (2-4)
They lower the level of the required activation energy.
