Solution Manual For Hole's Essentials of Human Anatomy and Physiology, 14th Edition

Name: Solution Manual For Hole's Essentials of Human Anatomy and Physiology, 14th Edition
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Strengthen your understanding of key topics with Solution Manual For Hole's Essentials of Human Anatomy and Physiology, 14th Edition, a detailed textbook guide.

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1
ANSWERS TO PRACTICE QUESTIONS
Chapter 1
Practice 1.1
1. What factors probably stimulated an early interest in the human body?
Factors include attempting to understand the causes of various injuries, illnesses, and the
loss of function of body parts, and trying to treat these conditions.
2. What kinds of activities helped promote the development of modern medical science?
Activities include dissection of cadavers, the production of prosthetic body parts,
experimentation to improve medical knowledge and techniques, and the discovery of certain
chemicals in nature as treatments for specific conditions.
Practice 1.2
1. Why is it difficult to separate the topics of anatomy and physiology?
Structure is closely related to function; body parts are shaped and arranged (anatomy) in
such a way that they are able to perform their functions (physiology).
2. List examples that illustrate how the structure of a body part makes possible its
function.
The front teeth (incisors) are pointed for grasping and tearing food, while the back teeth
(molars) are flattened for grinding food. The jointed structure of the bones of the fingers
allow us to grasp objects. The cone-shaped, chambered heart pumps blood through the
blood vessels. The tubular blood vessels transport blood to the cells of the body.
Practice 1.3
1. How does the human body illustrate levels of organization?
Larger structures are composed of smaller and smaller components. For example, the body
consists of several systems, such as the cardiovascular system. The cardiovascular system
consists of organs, such as the heart and blood vessels. The heart is composed of tissues,
which consist of layers of cells. Cells are composed of organelles, which consist of
molecules, and finally, atoms.
2. What is an organism?
An organism is a complete unit of life. Organisms range in size from a single cell to a
complex living thing, like a human, which is composed of trillions of cells. Humans, as
complex organisms, are composed of organ systems, organs, tissues, cells, molecules, and
atoms

2
3. How do body parts at different levels of organization vary in complexity?
Typically, the higher the level of organization a structure is part of, the more complex it is.
For example, a molecule is composed of two or more atoms; therefore, a molecule is more
complex than an atom. An organ system, such as the cardiovascular system, is composed
of organs, such as the heart and blood vessels. Therefore, an organ system is more
complex than any of its organs.
Practice 1.4
1. What are the characteristics of life?
The characteristics of life are properties that all living organisms exhibit. They include
movement, reproduction, responsiveness, growth, and metabolism, which in turn consists of
the processes of respiration, digestion, circulation, and excretion.
2. How are the characteristics of life dependent on metabolism?
Metabolism is the sum of all of the chemical reactions that occur in the cells. Metabolism
supports life processes. For example, digestion of food is accomplished by metabolic
reactions that break down the food into smaller particles that can be absorbed across the
membrane of the small intestine. Once absorbed, food particles are circulated, and used for
growth, movement, and reproduction. Wastes from food are excreted.
Practice 1.5
1. Which requirements of organisms does the external environment provide?
The environment provides water, food, oxygen, heat, and pressure.
2. Why is homeostasis important to survival?
Homeostasis is the maintenance of a stable internal environment, which consists of the fluid
around our body cells. Changes in the external environment affect the internal environment,
and therefore, the health of our cells. Cells, tissues, organs, and systems function properly
only in the presence of certain concentrations of water, oxygen, hydrogen ions (pH), and
nutrients, and specific conditions of heat and pressure. Having enough water in our cells
prevents dehydration, shrinkage of cell nuclei, and cell death. Homeostatic pH prevents
irreversible alteration of enzyme structure (denaturation) and function.
3. Describe two homeostatic mechanisms.
Negative feedback is a common homeostatic mechanism. When a variable deviates from its
set point, this mechanism activates effectors that return the variable toward its normal range.
For example, if a person is too hot, sweating and increased blood flow to the skin return the
body temperature to its normal range. A less common mechanism is positive feedback, in
which a change in a variable leads to further change. During blood clotting, certain
chemicals stimulate further blood clotting, to stop the bleeding.

3
Practice 1.6
1. Which organ occupies the cranial cavity? The vertebral canal?
The brain occupies the cranial cavity, and the spinal cord occupies the vertebral canal.
2. What does viscera mean?
“Viscera” refers to the organs within the thoracic and abdominopelvic cavities.
3. Name the cavities of the head.
The small cavities of the head include the oral cavity, nasal cavity, orbital cavities, and
middle ear cavities. The cranial cavity is the large cavity of the head; it is occupied by the
brain.
4. Describe the membranes associated with the thoracic and abdominopelvic
cavities.
Double-layered serous membranes line the walls of the thoracic and abdominopelvic
cavities and surround each organ. The parietal layer lines the wall of the cavity, and the
visceral layer surrounds an organ. Between the layers is a potential space, or cavity,
filled with lubricating fluid. The pleural membranes surround the lungs, the pericardial
membrane surrounds the heart, and the peritoneal membrane surrounds the
abdominopelvic organs.
5. Name and list the organs of the major organ systems.
Integumentary system: skin, hair, nails, sweat and sebaceous glands
Skeletal system: bones
Muscular system: muscles
Nervous system: brain, spinal cord, nerves, and sense organs
Endocrine system: endocrine glands
Cardiovascular system: heart, arteries, veins, capillaries, and blood
Lymphatic system: lymph nodes, thymus, and spleen
Digestive system: mouth, teeth, tongue, pharynx, esophagus, stomach, small intestine,
large intestine, salivary glands, liver, pancreas, and gallbladder
Respiratory system: nasal cavity, pharynx, larynx, trachea, bronchi, and lungs
Urinary system: kidneys, ureters, urinary bladder, and urethra
Reproductive system of male: scrotum, testes, epididymides, ductus deferentia, seminal
vesicles, prostate gland, bulbourethral glands, penis, and urethra

4
Reproductive system of female: ovaries, uterine tubes, uterus, vagina, clitoris, and vulva
6. Describe the general functions of each organ system.
Integumentary system: Protects internal structures, regulates body temperature, detects
changes in environment via sensory receptors, and synthesizes specific chemicals, such as
vitamin D
Skeletal system: Provides a framework for the body, supports and protects internal organs
and soft tissues, helps with body movements, produces blood cells, and stores inorganic
salts, such as calcium salts
Muscular system: Provides force to move body parts, maintains posture, and produces most
of the body heat
Nervous system: Regulates and adjusts organ function for homeostasis; communicates via
nerve impulses to help detect changes in the environment, integrate information, and
respond to this information by stimulating muscles and glands
Endocrine system: Regulates and adjusts organ function for homeostasis, and
communicates via hormone secretion into body fluids; each hormone alters metabolism of
specific target cells
Cardiovascular system: Transports red and white blood cells, platelets, respiratory gases,
nutrients, hormones, and wastes throughout the body
Lymphatic system: Defends the body against infection and disease, transports some tissue
fluid back to the bloodstream, and carries large fats from the digestive system to the general
circulation
Digestive system: Receives nutrients from the environment, breaks down food particles into
smaller molecules that can be absorbed across cell membranes and enter body fluids,
eliminates wastes, and produces hormones to regulate digestive processes
Respiratory system: Moves air into and out of the lungs, and exchanges oxygen and carbon
dioxide between the lungs and the blood
Urinary system: Removes blood wastes, helps maintain water, electrolyte, and acid-base
balance, produces urine, and transports urine to the outside of the body
Reproductive system of male: Produces and maintains sperm, produces hormones that
develop male body type, and transfers sperm to the female reproductive tract
Reproductive system of female: Produces and maintains oocytes (eggs), produces hormones
that develop female body type, receives sperm for fertilization, supports development of the
embryo and fetus, functions in birth process, and nourishes infant

5
Practice 1.7
1. Describe the anatomical position.
A person in the anatomical position is standing up straight, facing forward, has upper limbs
at the sides, and the palms are facing forward.
2. Using the appropriate terms, describe the relative positions of several body parts.
The head is superior to the neck.
The foot is inferior to the knee.
The toes are anterior to the heel.
The brain is posterior to the nose.
The great toe is medial to the smallest toe.
The thumb is lateral to the smallest finger.
The kidneys are bilateral.
The left kidney and the spleen are ipsilateral.
The left kidney and the right kidney are contralateral.
The knee is proximal to the foot.
The knee is distal to the thigh.
The skin is superficial to the subcutaneous layer.
The lens of the eye is deep to the cornea.
3. Describe the three types of body sections.
A sagittal section divides the body into left and right portions. If the portions are equal, it is
called a median or midsagittal plane. If the portions are unequal, it is called a parasagittal
plane.
A transverse or horizontal plane divides the body into top and bottom portions.
A frontal or coronal section divides the body into front and back portions.
4. Name the nine regions of the abdomen.
Epigastric, left and right hypochondriac, umbilical, left and right lateral (lumbar), pubic
(hypogastric), and left and right inguinal (iliac) regions

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1
ANSWERS TO PRACTICE QUESTIONS
Chapter 2
Practice 2.2
1. What are elements?
Elements are pure substances, either found in nature or artificially produced, which
represent the simplest forms of matter that have certain chemical characteristics.
2. Which elements are the most common in the human body?
The 4 most common elements are oxygen, carbon, hydrogen, and nitrogen. Together, they
make up about 95% of the human body.
3. Where are electrons, protons, and neurons located in an atom?
Protons and neutrons are found in the centrally located nucleus of an atom, while electrons
are in constant motion around the nucleus.
4. What is the difference between atomic number and atomic weight?
The atomic number of an atom is the number of protons in its nucleus. All atoms of a
particular element have the same atomic number. The atomic weight is approximately equal
to the number of protons plus the number of neutrons. Atoms of the same element may
have different numbers of neutrons, and therefore, different atomic weights.
Practice 2.3
1. What is an ion?
An ion is an atom that has gained or lost one or more electrons in a chemical reaction, and
now carries a positive or negative charge.
2. Describe two ways that atoms bond with other atoms.
Atoms can form ionic bonds, in which oppositely charged ions attract each other and unite,
forming arrays or crystals, instead of discreet molecules. Atoms can also share electrons,
forming covalent bonds. As the shared electrons move around the nuclei of both atoms,
both achieve stability.
3. Distinguish between an ion and a polar molecule.
An ion contains unequal numbers of protons and electrons. A polar molecule contains equal
numbers of protons and electrons, but the shared electrons reside closer to the nucleus of
one of the bonded atoms than to the other. This results in the polar molecule having one
slightly negative end and one slightly positive end.

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2
Practice 2.4
1. Distinguish between a molecule and a compound.
A molecule is any particle formed by the bonding of two or more atoms. The atoms may be
either identical or different. If the bound atoms are different elements, the molecule is called
a compound.
2. What is a molecular formula? A structural formula?
A molecular formula shows the types of atoms in a particular molecule, and the number of
each type of atom. The formula for water is H2O; this shows that a water molecule contains
two atoms of hydrogen and one atom of oxygen. A structural formula shows the
arrangement of atoms within a molecule, and uses lines to represent pairs of shared
electrons. The structural formula for a molecule of hydrogen is H – H; this shows that two
atoms of hydrogen are bound together by sharing one pair of electrons.
3. Describe three types of chemical reactions.
In a synthesis reaction, two or more atoms (reactants) bond together, forming a larger or
more complex particle (product). For example, two atoms of hydrogen and one atom of
oxygen bind to synthesize a molecule of water. In a decomposition reaction, bonds break
within a reactant molecule, resulting in the formation of smaller or simpler particles.
Decomposition occurs when a large starch molecule is broken down into individual glucose
molecules during the digestion process. During an exchange reaction between two
molecules, chemical bonds are broken and new ones are formed. Parts of the reactants
switch places, producing new molecules. When an acid and base react, producing water
and a salt, this is an exchange reaction.
Practice 2.5
1. Compare the characteristics of an acid with those of a base.
Acids are electrolytes that release H+ ions in water, and have a pH of <7. Bases are
electrolytes that release ions that can bind to H+ ions in water, and have a pH of >7.
2. What does pH measure?
The pH is a measurement of H+ ion concentration in a solution. The lower the pH of the
solution, the higher the H+ concentration is, and the more acidic the solution is. The higher
the pH, the lower the H+ concentration is, and the more basic, or alkaline, the solution is.
3. What is a buffer?
A buffer is a chemical that resists or minimizes pH changes. Buffer components bind to H+
ions when they are present in excess, and release them when they are deficient.

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3
Practice 2.6
1. How do inorganic and organic molecules differ?
Organic molecules contain carbon and hydrogen; inorganic molecules do not.
2. How do electrolytes and nonelectrolytes differ?
Electrolytes are substances that dissolve and dissociate in water and release ions; most
inorganic substances are electrolytes. Nonelectrolytes are substances that dissolve in
water, but do not release ions; this includes many organic substances.
3. Name the inorganic substances common in body fluids.
Water, oxygen, carbon dioxide, and salts are common inorganic substances in cells.
4. Compare the chemical composition of carbohydrates, lipids, proteins, and nucleic
acids.
Carbohydrates consist of carbon, hydrogen, and oxygen, with approximately a 2 to 1 ratio of
hydrogen to oxygen atoms. Lipids (triglycerides) also consist of carbon, hydrogen, and
oxygen, but they contain a much higher ratio of hydrogen to oxygen atoms. Some lipids also
contain phosphorus. Proteins are also mainly composed of carbon, hydrogen, and oxygen,
but they also contain nitrogen, and some contain sulfur. Nucleic acids consist of carbon,
hydrogen, oxygen, nitrogen, and phosphorus.
5. How does an enzyme affect a chemical reaction?
An enzyme catalyzes a chemical reaction, meaning that it greatly increases the reaction rate.
Metabolic reactions are able to occur quickly enough to support life processes only because
of the presence of enzymes.
6. What is the chemical basis of the great diversity of proteins?
All proteins are composed of various combinations of 20 different amino acids. Proteins
contain chains of <100 to >5000 amino acids. Some consist of only one polypeptide chain,
while others consist of several. The length and order of amino acids, as well as the pleated
or coiled secondary structure and the 3-deminsional shape, or conformation, of the protein,
all contribute to the great diversity of proteins in the body.
7. What are the functions of nucleic acids?
Deoxyribonucleic acid, or DNA, stores the genetic information, or genetic code, on
chromosomes. This information is used to construct proteins for the cell. Various types of
ribonucleic acid, or RNA, function in the process of protein synthesis.

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1
ANSWERS TO PRACTICE QUESTIONS
Chapter 3
Practice 3.1
1. What is a cell?
A cell is the smallest unit of life. To be classified as a cell, the structure must display all of
the characteristics of life: responsiveness, respiration, digestion, growth, absorption,
assimilation, circulation, excretion, movement, and reproduction. An organism may consist
of one cell or trillions, as in humans.
2. Give three examples of how a cell’s shape makes possible the cell’s function.
A skeletal muscle cell is long and cylindrical; this enables it to shorten during muscle
contraction, leading to a specific type of body movement. A cell in the alveoli (air sacs) of
the lungs is broad and flattened; this provides a large surface area for the rapid exchange of
oxygen into the blood. The many branches (dendrites and axons) and threadlike shape of
neurons (nerve cells) allow them to communicate with several other cells at the same time.
Practice 3.2
1. Name the three major parts of a cell and their functions.
The 3 major parts of a cell are the cell membrane, nucleus, and cytoplasm. The cell
membrane is the outer boundary of the cell; it protects the structural integrity of the cell,
regulates entry and exit of substances, communicates and interacts with other cells, and
transports messages into the cell. The nucleus stores the DNA, or genetic material, directs
the cell’s activities, and produces ribosomes. The cytoplasm consists of fluid and organelles,
which perform basic cell functions, such as processing and using nutrients, and producing
substances for the cell or for export.
2. Define organelles and explain their general functions in a cell.
Organelles are tiny structures found in the cytoplasm, which perform specific functions for
the cell. They conduct activities such as food breakdown to produce energy and heat,
protein and lipid production and packaging, and maintenance of cell shape.
3. What is a selectively permeable membrane?
A selectively permeable membrane is one that regulates which substances enter or leave
the cell.

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2
4. Describe the chemical structure of a cell membrane.
The cell membrane consists of a double layer, or bilayer, of phospholipids. The phospholipid
molecules are oriented such that their water-soluble heads face the surfaces of the
membrane, and their lipid-soluble tails face the membrane interior. The membrane also
includes proteins that span the width of the bilayer or are associated with one of the
surfaces, and smaller amounts of cholesterol and carbohydrates.
5. What are the functions of ribosomes, the endoplasmic reticulum, vesicles, and the
Golgi apparatus?
Ribosomes provide a physical site on which amino acids bond together during protein
synthesis, and the enzymatic function to support the process. Vesicles store substances in a
cell, or transport them throughout a cell or from one cell to another. Endoplasmic reticulum
provides a transportation system for molecules in the cell, and also performs protein and lipid
synthesis. The Golgi apparatus modifies proteins produced on the ribosomes of the rough
endoplasmic reticulum, packages them, and transports them in vesicles to other organelles
or to the cell membrane for export.
6. Explain how organelles and other structures interact to secrete substances from the
cell.
The rough endoplasmic reticulum, which contains ribosomes, produces proteins. The
smooth endoplasmic reticulum produces lipids and some sugars. Some of these substances
are directly secreted from the cell in vesicles consisting of cell membrane. Others enter the
Golgi apparatus, are combined with other molecules, and are then secreted from the cell
inside vesicles that bud off the Golgi apparatus.
7. What is the function of mitochondria?
Mitochondria break down food molecules for energy and heat. The energy is stored mainly
in a molecule called ATP (adenosine triphosphate). The heat is used to maintain normal
body temperature.
8. What are the functions of lysosomes and peroxisomes?
Lysosomes and peroxisomes use their enzymes to break down certain cell contents and
components. Lysosomes maintain acidic pH for optimal activity of their enzymes, and break
down nutrient molecules, some drugs and toxins, and damaged cell parts. Peroxisomes
contain different enzymes than lysosomes; they break down hydrogen peroxide, fatty acids,
and alcohol.
9. How do microfilaments and microtubules differ?
Both are thin and threadlike, and both help form the cytoskeleton of the cell. But
microfilaments consist of the protein actin, and help in cellular movements. Microtubules

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3
consist of the protein tubulin, are 2-3 times the diameter of microfilaments, and participate in
cell division.
10. What is a centrosome and what does it do?
A centrosome is an organelle that is composed of two hollow, cylindrical centrioles. It lines
up and distributes the dividing chromosomes to the forming daughter cells during mitosis.
11. Locate cilia and flagella and explain what they are composed of and what they do.
Cilia and flagella are both fingerlike extensions from the cell membrane of certain cells.
When cilia are present, they occur in large numbers; they beat in a coordinated pattern, to
move fluids, such as mucus, in a certain direction. A flagellum is much longer than a cilium,
and is used to propel the cell. Most cells have only one flagellum, but some microorganisms
have more than one. The only human cell with a flagellum is a sperm cell.
12. Identify the structure that separates the nuclear contents from the cytoplasm.
The nuclear envelope separates the nuclear contents from the cytoplasm. It is double-
layered, and contains nuclear pores, which regulate which substances enter and leave the
nucleus.
13. What is produced in the nucleolus?
The nucleolus produces ribosomes.
14. Describe chromatin and how it changes.
Chromatin is composed of DNA and protein in a loose array of coiled fibers. This is the
form in which DNA exists when the cell is at rest. When the cell enters cell division, the
fibers condense and coil tightly, forming DNA strands called chromosomes.
Practice 3.3
1. What types of substances diffuse most readily through a cell membrane?
Lipid-soluble substances diffuse most readily through a cell membrane, since they can easily
pass through the phospholipid bilayer. Also, substances that are present in higher
concentration on one side of the cell membrane diffuse more readily than those of equal
concentrations.
2. Explain the differences among diffusion, facilitated diffusion, and osmosis.
Diffusion is the passive random movement of a substance from a region of higher
concentration to a region of lower concentration. Lipid-soluble substances diffuse across cell
membranes. Facilitated diffusion is similar to diffusion, but requires the help of a membrane
protein, such as an ion channel, to help transport the substance across the cell membrane.
Water-soluble substances, such as ions, cross cell membranes by this method. Osmosis
refers to the movement of water molecules across a cell membrane, into a region containing

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4
a dissolved substance (solute) that cannot cross the membrane. Water moves from higher
to lower water concentration, and from lower to higher solute concentration.
3. Distinguish among hypertonic, hypotonic, and isotonic solutions.
Isotonic solutions have the same osmotic pressure; cells in an isotonic extracellular fluid
neither gain nor lose water. A hypertonic solution is one with a higher osmotic pressure
(higher solute concentration and lower water concentration) than that of the cells or another
solution; cells in a hypertonic solution lose water by osmosis and shrink. A hypotonic
solution is one with a lower osmotic pressure (lower solute concentration and higher water
concentration) than that of the cells or another solution; cells in a hypotonic solution will gain
water by osmosis and swell.
4. How does filtration happen in the body?
During diffusion, molecules pass through a membrane due to random molecular movement.
During filtration, molecules are forced to move across a membrane due to pressure. Blood
pressure derived from the pumping action of the heart causes filtration of water and small
molecules out of capillaries to deliver nutrients to the cells.
5. Explain the mechanism that maintains unequal concentrations of ions on opposite
sides of a cell membrane.
The sodium potassium pump uses the energy of ATP to move Na+ and K+ ions across cell
membranes at certain times. This movement occurs against the concentration gradients of
these ions, and functions to maintain gradients that can be used by the cell for specific
purposes, such as the conduction of nerve impulses.
6. How are facilitated diffusion and active transport similar and different?
Facilitated diffusion and active transport both use membrane proteins to transport
substances across cell membranes. Facilitated diffusion moves substances from higher to
lower concentration, and does not require energy from ATP. Active transport moves
substances from lower to higher concentration, and requires ATP for energy.
7. How do endocytosis and exocytosis differ?
Endocytosis moves molecules into a cell inside a vesicle composed of a small portion of the
cell membrane. Exocytosis transports molecules stored inside a vesicle out of a cell, by
fusion of the vesicle with the cell membrane and release of its contents into the extracellular
fluid.
8. Explain how receptor-mediated endocytosis is more specific than pinocytosis or
phagocytosis.
In pinocytosis, the cell indents when approached by droplets of liquid, forms a vesicle, and
takes in the liquid. Phagocytosis does the same with solid particles. These processes
engage in nonspecific uptake of molecules from the extracellular fluid. In receptor-mediated

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endocytosis, however, only molecules that can bind to specific receptors on the cell
membrane cause the membrane to indent, and form a vesicle to engulf them.
Practice 3.4
1. Outline the cell cycle.
During the life cycle of a cell, it goes through a sequence of certain changes. The phases of
the cell cycle are interphase, mitosis, and cytokinesis. After a cell forms, grows, and
specializes into a mature, functional cell, at a certain point, the cell divides into two identical
daughter cells. During interphase, a cell grows, metabolizes nutrients, and duplicates the
DNA, organelles, membranes, and chemicals that it will need when it divides. In mitosis, the
contents of the nucleus divide, distributing the DNA to both of the forming daughter cells.
Cytokinesis involves the division of the cytoplasm that occurs during the latter portion of
mitosis.
2. Explain regulation of the cell cycle.
Hormones and growth factors can stimulate cell division at the proper times. During
interphase, restriction checkpoints determine if the cell lives, dies, or proceeds into cell
division. The telomeres on the ends of chromosomes limit the number of times a cell can
divide by keeping a mitotic clock.
3. Describe the events that occur during mitosis.
Mitosis consists of 4 stages. During prophase, chromatin changes in chromosomes, the
nuclear envelope disassembles, the centriole pairs migrate to opposite sides of the cell, and
microtubules begin organizing into spindle fibers. During metaphase, the spindle fibers
stretch between the centriole pairs, and the chromosomes attach to them and line up along
the midline of the cell. In anaphase, the chromosome pairs split; one chromatid from each
pair migrates along the spindle fibers to opposite sides of the cell. During telophase, the
chromatids, now called chromosomes, reach the vicinity of the centrioles, and change back
to their chromatin form. The spindle fibers disassemble, and a nuclear envelope forms
around each newly forming nucleus.
4. Why must cells divide and specialize?
Cells divide to provide new cells for growth of an organism, and to replace cells that have
been damaged or lost by injury or disease, or have worn out. Cells must specialize, or
differentiate, in order to become functional as one of the almost 300 cell types in the human
body.

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5. Distinguish between a stem cell and a progenitor cell.
A stem cell has the ability to divide over and over without specializing. A stem cell can divide
to form either two more stem cells or one stem cell and one progenitor cell, which is partly
differentiated (specialized). A progenitor cell can produce daughter cells that differentiate
into a limited number of cell types.
6. How are new cells generated and how do they specialize?
New cells are generated through the division of other cells, by the processes of mitosis and
cytokinesis. Cells specialize by activating only the genes that synthesize the particular types
of proteins needed by that type of cell.
7. How is cell death a normal part of development?
Cell death, called apoptosis, occurs naturally during fetal development, to remove neurons in
the brain that have not established healthy nerve pathways, and prevent organs from
overgrowth. After birth, apoptosis removes skin cells, damaged by sunburn, that may
become cancerous, and helps shape organs in growing children.

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ANSWERS TO PRACTICE QUESTIONS
Chapter 4
Practice 4.1
1. What is cellular metabolism?
Cellular metabolism is a group of chemical reactions that obtain, store, and release energy in
cells. Energy stored in the chemical bonds of nutrient molecules can be used by the cells for
a variety of purposes, such as copying DNA for cell division, and transporting molecules
across cell membranes during active transport.
2. What are enzymes?
Enzymes are proteins that catalyze, or speed up, all of the chemical reactions that occur in
cellular metabolism. They are necessary for reactions in the body to proceed at a rate that
can maintain life.
Practice 4.2
1. What are the general functions of anabolism and catabolism?
In anabolism, chemical bonds are formed, producing larger molecules that are used for
growth and repair. These reactions require energy. Catabolism is the process by which
large nutrient molecules are decomposed into smaller ones, by breaking chemical bonds.
These reactions occur in the process of digestion, and provide the energy and building
blocks needed for anabolism.
2. What are the products of the anabolism of monosaccharides, glycerol and fatty acids,
and amino acids?
Anabolism of monosaccharides produces long chains of glucose, forming glycogen in
animals and starch in plants. When glycerol and 3 fatty acids bond together, they form
triglycerides. When anabolic reactions join amino acids together, dipeptides, polypeptides,
and proteins are produced. Dipeptides contain 2 amino acids, and proteins contain 100 or
more amino acids.
3. Distinguish between dehydration synthesis and hydrolysis.
Dehydration synthesis is a type of anabolic reaction in which molecules are joined together
by removing a H+ ion from one molecule and a OH- ion from the other. The 2 ions then bind
together to produce a molecule of H2O, or water. This occurs when 2 molecules of glucose
bind together to form the disaccharide maltose and a molecule of water. Hydrolysis is a type
of catabolic reaction in which a water molecule is split in order to break down another type of
molecule. For example, in order to decompose a molecule of maltose into 2 molecules of
glucose, one molecule of water is split. Then, as the bond is broken in the maltose
molecule, the H+ ion is added to one glucose molecule and the OH- ion is added to the other.

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