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3Cells and Tissues

42

Chapter OverviewCells are the basic units of any organism. Although the human body has many differenttypes of cells, they have similar structures and some similar functions. The cell membraneforms the boundary of the cell and keeps the cell contents separated from the fluid outsidethe cell. This membrane is a thin, pliable film composed of two layers of phospholipids andcholesterol molecules. Two types of proteins are also components of the cell membrane.Integral proteins completely penetrate the cell membrane and serve diverse roles; someallow water and water-soluble substances to cross the cell membrane or, as receptors, bindspecific substances to the cell. Peripheral proteins attach to lipids and proteins within themembrane. They attach the cell to other cells or structures or are involved in cell signaling.Carbohydrates combined with membrane lipids and proteins form a sugary outer coating, orglycocalyx, that protects the cell from damage and that helps identify one type of cell fromothers. In some specialized cells, the cell membrane forms hairlike or whiplike projectionsthat have specific purposes.

Within each cell are various structures called organelles that perform distinct functions.The nucleus of each cell controls all the cell’s activities. Deoxyribonucleic acid (DNA), a verylong organic molecule within the nucleus, contains instructions to make proteins. Eachsegment of DNA that codes for making a specific protein is called a gene. When genes issueincorrect instructions, genetic defects result. Other organelles are involved in energygeneration, protein and lipid synthesis, transport, and waste disposal.

Cells reproduce, a process necessary for growth and also for normal functioning of thebody, because cells age and die—either naturally, in a process called apoptosis, or due toinjury or disease, a process called necrosis. Cells reproduce by producing duplicates of theorganelles and DNA and then dividing into two, with half the organelles going to each newdaughter cell. DNA synthesis is called replication. Mitosis describes the division of thenucleus; cytokinesis describes the division of the cytoplasm.

Stem cells are unspecialized cells that can reproduce and give rise to more specialized cells.

• Totipotent stem cells can give rise to an entire organism or to any particular type of cell in the body. A zygote, or fertilized egg, is totipotent.

LWBK765-Ch3_42-72.qxd 9/22/10 10:12 PM Page 42

• Pluripotent stem cells can produce any type of tissue.

• Multipotent stem cells can produce a limited range of specialized cell types. Small numbers ofmultipotent stem cells persist in adults and are used to make replacements for dead or dysfunctional cells.

Cells specialize to perform different tasks. Germ cells, the reproductive cells, found only in theovary or testis, develop into ova (eggs) or sperm. Somatic cells develop into specific types of cells—liver, muscle, brain, and so on—by focusing solely on those genes that perform a set of specializedfunctions and by turning off the genes that would lead them to manufacture other proteins, andthus perform other functions.To carry out these functions, cells must make proteins followinginstructions in the DNA. First, a messenger RNA (mRNA) copy is made of a particular gene by theprocess of transcription. Ribosomes and transfer RNA (tRNA) decode the mRNA transcript toform a protein, a process called translation.

For many cell processes to occur, substances must move from one part of the cell to another orbetween the inside and outside of the cell. Lipids and gases, which are lipid soluble, can pass easilythrough the phospholipids in the cell membrane to enter the cell. Any substances that are watersoluble, however, must be carried through the cell membrane by proteins. Some of these water-soluble substances pass through the cell membrane through channels, or watery tunnels. Channelshave different shapes, which permit the passage of specific substances. Glucose and some othersubstances diffuse across the membrane through carrier proteins, using a process called facilitateddiffusion. Some of the movement must take place up the concentration gradient, from low to highconcentration.This process is called active transport.Transport proteins called pumps use energyfrom ATP to force particles across a membrane from the low concentration side to the highconcentration side.

The concentration of all solutes in a particular compartment is called its osmolarity, measuredin particles of solute per liter of water. The osmolarity of most body cells and fluids is relativelyfixed, at about 300 mOsm (milliosmoles per liter).When substances moved into or out of thecell, they alter the relative osmolarity of the cytosol and the extracellular fluid.This action iscompensated for by osmosis, the movement of water across the cell membrane from the area ofhigh water concentration to the area of low water concentration.

Sometimes, the cell expels or accepts substances in large amounts at one time. The process ofexpelling such substances is called exocytosis and takes place through a vesicle. Taking in suchsubstances is called endocytosis, and this process often takes place when a specific receptor onthe cell membrane binds with a particular substance, usually a molecule too large to enter byother means. In phagocytosis, microbes are brought into specialized cells called phagocytes tobe destroyed.

Cells combine to form tissues, in which they work together to perform certain specificfunctions.The body is made of four kinds of tissue: muscle tissue, nervous tissue, connective tissue,and epithelial tissue. (The first two kinds of tissue are discussed in later chapters.) Epithelial tissue,also called epithelium, is a thin layer of cells lining the surface of the skin and hollow internalorgans.The cells making this tissue are packed closely together and function as a barrier. Epithelialtissues have three functions: to act as a barrier, to absorb substances, and to secrete substances. Asheet of these cells, the epithelial membrane, usually rests on a layer of connective tissue thatincludes blood vessels and nerve cells. Epithelial tissue also makes up glands, structures thatsecrete substances into blood (endocrine glands) or onto body surfaces (exocrine glands).Connective tissue is structural or supports the rest of the body, and most connective cells arespaced widely apart, separated by the extracellular matrix.There are five types of connectivetissue: loose connective tissue, which underlies the skin and other epithelial membranes; denseconnective tissue, which is tough and appears in tendons and ligaments; cartilage; bone; and blood.

43


44

Addressing the Learning Outcomes

1. List the components of the cell membrane, and explain the function of each.

Exercise 3.1

Study the diagram of the cell membrane and its environment (Fig. 3.1). Choosing from the list ofterms below, write the name of the feature next to the number in the chart that corresponds to the number in the diagram that shows the feature. Then, in the right-hand column of the chart,explain the function of the feature.

cholesterol hydrophobic headextracellular fluid integral proteinglycolipid peripheral proteinglycoprotein phospholipidshydrophilic tail

1

6 7 8 9

2 3 4 5

Figure 3.1


Chapter 3 Cells and Tissues 45

Feature Function

1.

2. and 3.

4. and 5.

6.

7.

8.

9.


46 Study Guide to Accompany Human Form, Human Function

2. Explain how DNA is organized in dividing and nondividing cells.

Exercise 3.2

Choosing from the words in the list below, write the correct terms in the spaces to complete the paragraph.

chromatin histonechromosome nucleoplasmDNA proteins

The nucleus contains the long organic molecule called (1) ___________________. This molecule

appears in both dividing and nondividing cells. In nondividing cells, it takes the form of

(2) ___________________, a dense tangle of DNA strands. These dark regions of matter are mixed with

(3) ___________________, a semiliquid substance that fills the nucleus. Long threads of the organic

molecule are wound around nuclear organizing proteins called (4) ___________________. In the

nucleus of dividing cells, the molecule is visible as 46 distinct units called (5) ___________________.

These organic molecules contain the instructions—the code—the body must follow to make

(6) ___________________. Each distinct segment of material that encodes a particular protein is

called a(n) (7) ___________________.

3. List the organelles of the cell, and briefly describe the function of each.

Exercise 3.3

Study Figure 3.2, a diagram of a cell. Choosing from the list below, write the name of the featurenext to the number in the chart that corresponds to the number in the diagram. Then, in the right-hand column of the chart, explain the function of the feature. Finally, use a colored pen or pencilto circle the names of the organelles that are surrounded by a membrane. Use a different color tocircle the names of the organelles that are not surrounded by a membrane. Draw a rectanglearound the name of any features that are not organelles.

cell membrane nucleuscytoskeleton mitochondrioncytosol peroxisomesendoplasmic reticulum ribosomeGolgi apparatus vesicleslysosomes



3

4

5

6

7

9

2

10

11

12

13

1

8

Figure 3.2

Feature Function

1.

2.

(continued)


Feature Function

3.

4.

5.

6.

7.

8.

9.

10.

(continued)




4. Briefly describe the form and function of three types ofcytoskeletal filaments.

Exercise 3.4

Match the correct description of a filament in the cytoskeleton in the right column with thecorrect name for the filament in the left column by writing the letter of the appropriatedescription in the space next to the name.

Feature Function

11.

12.

13.

(continued)

________ 1. Intermediate filament

________ 2. Microfilament

________ 3. Microtubule

a. hollow tubes that attach to certain cell parts and act as pulleysto move the parts around in the cell

b. long string, much like a beaded necklace, which forms anetwork supporting the cell membrane, participating in thecontraction of muscle cells, and aiding the movement of somecells that move

c. long, interwoven protein fibers that stabilize the placement oforganelles and strengthen the nuclear envelope


5. Compare apoptosis and necrosis.

Exercise 3.5

Use the lines below to describe apoptosis and necrosis and give an example of each.

6. Name the four phases of the cell cycle and the four stages of mitosis,and describe events that occur in each.

Exercise 3.6

Describe the process of cell division in the chart below. For each phase and subphase of theprocess listed in the chart, write the correct letter or number from Figure 3.3 illustrating that partin the process. Then, in the third column of the chart, describe the phase or subphases.


3

2

A

4

5

67

8

B

1

Figure 3.3



Letter or Number Phase or Subphase Description

anaphase

DNA synthesis phase (S phase)

first growth phase (G1 phase)

interphase

metaphase

mitosis

prophase

second growth phase (G2 phase)

telophase

cytokinesis



7. Use a diagram to explain how DNA replication works.

Exercise 3.7

Use the lines below to describe the process by which DNA replicates itself. Refer to Figure 3.4 asyou write your description.

1 Chromatid

Template strand

Sense strand

Centromere

Free nucleotide

Direction of replication

Direction of replication

1 Chromatid

T

AT

ATA

A

G

G

CG

C

C

G

T

T

A

T

A

T

A

AT

GC

GC

GC

C

G

G

C

T

A

TC

1 Chromosome:before the S phase

1 Chromosome:after the S phase

Figure 3.4



8. Compare and contrast multipotent, pluripotent, and totipotent stem cells.

Exercise 3.8

Match the correct description of a type of stem cell in the right column with the correct name forthat type of cell in the left column by writing the letter of the appropriate description in the spacenext to the name.

________ 1. Multipotent

________ 2. Pluripotent

________ 3. Totipotent

a. can produce any type of tissue—heart, brain, liver, skin, youname it—but cannot form an entire new human being

b. can give rise to an entire organism or to any particular type ofcell in the body

c. specialized stem cells that can produce only a limited range ofcell types

9. Name the four types of RNA and the function of each.

Exercise 3.9

Complete the chart by describing the function of the four kinds of RNA found in cells.

Type of RNA Function

Messenger RNAs (mRNAs)

Transfer RNAs (tRNAs)

Ribosomal RNAs (rRNAs)

Small nuclear RNAs (snRNAs)


10. Draw a diagram illustrating the steps of transcription and translation of a very short gene.The sense strand of this gene is TTT CCC TTT.

Exercise 3.10

Listed below, out of sequence, are the 10 steps describing the process of transcription andtranslation of the gene TTT CCC TTT. Place the steps in the correct order by writing each step in the correct box in the diagram.

Steps:

• The proline tRNA with its CCC anticodon attaches to the mRNA’s GGG, and the ribosome transfers the phenylalanine to bind to this proline.

• RNA polymerase joins uracils and guanines into a complementary mRNA codons: UUU CCC UUU.

• When the ribosome reaches a stop codon, it releases both the mRNA and the new protein.

• The ribosome reads the next codon, GGG, and signals for its tRNA carrying proline.

• The DNA helix separates, exposing the DNA triplet AAA GGG AAA on the antisense strand.

• The second phenylalanine tRNA attaches to the mRNA, and the growing polypeptide chain isattached to this phenylalanine.

• The tRNA anticodon attaches and binds to the first UUU codon on the mRNA.

• The ribosome moves right again and signals for a second phenylalanine-carrying tRNA.

• The mRNA carries the full coded message from the nucleus into a ribosome.

• Reading the mRNA code, the ribosome signals for a tRNA that carries the amino acidphenylalanine.


Step 1

Step 2



Step 3

Step 4

Step 5

Step 6



Step 7

Step 8

Step 9

Step 10



13. Draw a diagram showing how the normal CFTR protein moves fromthe Golgi apparatus to the cell membrane by exocytosis.

Exercise 3.12

Study Figure 3.5 below showing the formation and transport of the normal CFTR protein. Usingthe list below, label the structures in the diagram. Then use the lines that follow to describe eachof the six numbered steps shown in the diagram.

11. Identify the mutation that is the cause of Julia’s cystic fibrosis.

Note: Objective 11 is covered in Exercise 3.13.

12. Prepare a table comparing simple diffusion, facilitated diffusion,osmosis, and active transport under the following categories:Relation to gradient; Energy requirement; Membrane proteinrequirement; Transported substance; Example.

Exercise 3.11

Fill in the missing information in the chart below to describe the four types of transport across the cell membrane.

MembraneRelation to Energy Protein Transported

Type of Transport Gradient Requirement Requirement Substance Example

Simple diffusion

Facilitated diffusion

Osmosis

Active transport



2

1

3

4

5

6

Figure 3.5

CFTR intestine lumenCFTR gene nucleusCFTR mRNA rough endoplasmic reticulumCFTR protein secretory vesicleGolgi apparatus

1. ___________________________________________________________________________________________________________

___________________________________________________________________________________________________________

___________________________________________________________________________________________________________

___________________________________________________________________________________________________________



2. ___________________________________________________________________________________________________________

___________________________________________________________________________________________________________

___________________________________________________________________________________________________________

___________________________________________________________________________________________________________

3. ___________________________________________________________________________________________________________

___________________________________________________________________________________________________________

___________________________________________________________________________________________________________

___________________________________________________________________________________________________________

4. ___________________________________________________________________________________________________________

___________________________________________________________________________________________________________

___________________________________________________________________________________________________________

___________________________________________________________________________________________________________

5. ___________________________________________________________________________________________________________

___________________________________________________________________________________________________________

___________________________________________________________________________________________________________

___________________________________________________________________________________________________________

6. ___________________________________________________________________________________________________________

___________________________________________________________________________________________________________

___________________________________________________________________________________________________________

___________________________________________________________________________________________________________

14. Explain why the deletion of three nucleotides of the CFTR gene canresult in viscous mucus; and 11. Identify the mutation that is thecause of Julia’s cystic fibrosis.

Exercise 3.13

Study Figure 3.6 below, and then read the two paragraphs that follow. Use the words from the listto fill in the missing words from the explanations of the genetic cause of Julia’s cystic fibrosis andof why this mutation produces its particular effect.



amino acids normalcodons osmosisconcentration proteindeleted sequencedestroyed transcribesmRNA transportmutation viscous

The gene involved is called the cystic fibrosis transmembrane conductance regulator, or the CFTR

gene, found on chromosome 7. In a(n) (1) ___________________ CFTR gene (left side of figure), the

DNA sense strand reads “ATC TTT GGT” and the (2) ___________________ reads “AUC AAA GGU.”

These three (3) ___________________ encode the (4) ___________________ isoleucine (Ile),

phenylalanine (Phe), and glycine (Gly). In the (5) ___________________ that causes cystic fibrosis,

the short DNA sequence “C TT” is (6) ___________________ (right side of figure), making the DNA

U U GG G UAUUG GU UU UA C

U

Ile Phe Gly Ile Gly Val

Chromosome 7

CFTR gene

Deletion site

DNA template

DNA sense strand (triplets)

Deleted

FPO FPO

mRNA (codons)

Translation

Folding

Amino acid# 508

(a) NORMAL (b) CYSTIC FIBROSIS

T

A

T

A

T

A

T

A

G

C

G

C

G

C

G

C

G

C

T

A

A

T

T

A

T

A

T

A

T

A

T

A

A

T

C

G

Figure 3.6

Au: Pls.conformFig. 3.6



sequence now read “ATT GGT GTT.” Enzymes (7) ___________________ this sequence into RNA

with the sequence “AUU GGU GUU,” producing the amino acid (8) ___________________

“Ile-Gly-Val.” As a result, one amino acid—Phe—is deleted.Because an amino acid is missing, the

(9) __________________ coded by the defective CFTR gene has a surface different from normal and

it is destroyed by barrel-shaped organelles called (10) __________________. Because of this, the

protein cannot take its normal place in the cell membrane or do its normal job, which is to

(11) __________________ chloride molecules out of the cell across the cell membrane. Without the

integral protein to make a channel for them, however, they remain in the cell, increasing the

(12) __________________ of these molecules inside the cell. Just as less chloride moves out

of the airway cells to the airway lumen, so less water moves out of the cell through

(13) __________________. The lack of water means respiratory secretions cannot be diluted,

so they become (14) __________________, or thick.

15. Prepare a chart describing the form and function of six types of epithelial membranes and five types of connective tissue.

Exercise 3.14

Complete the chart to identify the six types of epithelial tissue, describe the form of each, andindicate a location where such cells are typically found.

Type Form Location (Example)

Simple squamous epithelium

Flat, many layers

Lining the ducts of glands, e.g., pancreas

(continued)


Exercise 3.15

Complete the chart to identify the five types of connective tissue and to describe the contents andform and the function of each.


Type Contents and Form Function

_____________ connective Contains a few _____________ and Loosely binds _____________ to

tissue _____________, some fat cells, and a thin _____________ _____________, fills gaps

mixture of _____________ and elastin; between _____________ bundles and

lacy and _____________ between some _____________, forms a

layer of the _____________ and large arteries

Dense _____________ Packed with _____________ _____________ Withstands strong forces in _____________,

_____________ woven into thick parallel bundles _____________, the capsules that encase

many organs, and ______________

Cartilage Contains _____________ _____________ (or Provides _____________ _____________

chondrocytes), varying amounts of _____________ where bones meet and shape

_____________ and _____________ fibers, to certain structures such as the

and a _____________ ground substance _____________

Contains bone cells (or _____________) Serve as _____________ for body

and a calcified _____________ _____________;

is rigid but not rocklike; is very

slightly _____________

Cells suspended in a liquid called Circulates throughout the body carrying

plasma water, cells, and dissolved molecules

Type Form Location (Example)

Stratified cuboidal epithelium

Tall, thin, upright, and in a single layer

Intestines

(continued)



Down

1. Structure that contains epithelial cells that secretetheir product into ducts

2. Chemicals secreted into blood vessels to act as mes-sengers

3. Type of junction formed of a band of proteins that fusethe membranes of neighboring cells to make a water-proof seal

4. Type of junction that holds cells tightly together atspecific points but do not block the movement of sub-stances between the cells

5. Structure in the breast that, following childbirth, se-cretes milk

Across

6. Ductless, solid masses of epithelial cells that se-crete their products into blood vessels

7. Special collection of cells that synthesizes andsecretes a product

8. Type of junction that connects neighboring cellsto serve as a means of communication

9. Gland in the mouth that secretes liquid that aidsin digesting food

1 2 3

4 5

6

7 8

9

16. Compare and contrast desmosomes and tight junctions; and 17.Compare exocrine and endocrine glands and provide an example of each.

Exercise 3.16

Complete the following crossword puzzle by writing the correct terms from the word list thatcorresponds to each definition.

desmosome glandduct hormoneendocrine gland mammaryexocrine gland salivarygap tight



Testing Your Knowledge

Building Understanding

I. Multiple Choice

Select the best answer and circle the letter of your choice.

1. What type of organic molecule provides the bulk of the cell membrane?

a. carbohydratesb. lipidsc. nucleotidesd. proteins

2. How do the cilia promote health in the airways?

a. They attack foreign bodies that enter the airways.b. They help identify molecules as belonging to the body or not.c. Their movement sweeps mucus that holds trapped particles out of the airways.d. They attach to foreign particles and by whiplike motion carry them away.

3. The functions of cells are carried out by specialized structures that collectively are called what?

a. cytoplasmb. cytosolc. inclusionsd. organelles

4. In RNA, the nucleotide uracil replaces what nucleotide in DNA to bond with adenine?

a. adenineb. cytosinec. guanined. thymine

5. What activity takes place in ribosomes?

a. DNA replicationb. protein synthesisc. RNA transcriptiond. zygote formation

6. Which of these is not a characteristic of integral proteins that allows them to support facilitated diffusion?

a. ability to change from being channels to carriersb. being both lipid soluble and water solublec. combined protein–carbohydrate makeupd. position extending across the entire cell membrane



7. In which environment would water leave the cell?

a. atonicb. hypertonicc. hypotonicd. isotonic

8. What is the name of the process by which the cell destroys invading microbes and cleans updead cell debris in diseased or injured tissue?

a. endocytosisb. exocytosisc. phagocytosisd. transcytosis

9. Which of these is not a function of epithelial cells?

a. serving as a barrierb. secreting substancesc. destroying substancesd. absorbing substances

10. Which of these is not a description of connective tissue?

a. is structural or supportiveb. connects body systems through the nervous systemc. derived from a kind of tissue called mesodermd. has a large amount of extracellular matrix

II. Completion

Write the word or phrase that correctly completes each sentence.

1. Water cannot pass from extracellular fluid into the cell because the outer-facing side of

phospholipids and cholesterol molecules is .

2. Water and water-soluble molecules are able to pass through the cell membrane by way of the

, channels, or carriers.

3. In helping identify cells as structures that belong to the body, glycocalyx prevents the cell

from being attacked by the body’s .

4. The cytosol, in which organelles are embedded, is a viscous, solution containing salts,

bicarbonate, oxygen, CO2, and minerals in which the solvent is .

5. The DNA in a cell’s nucleus is organized into 23 pairs of structures, with one structure from each

pair inherited from each biological parent.Those structures are called .


6. Unlike the smooth endoplasmic reticulum, the rough endoplasmic reticulum is covered by

. The two structures differ in function as well. The rough endoplasmic

reticulum modifies ; the smooth endoplasmic reticulum makes

.

7. Because cells die and must be replaced, cells must .

8. The phase of cell reproduction in which the chromosomes condense into visible structures

is called .

9. Cells manufacture most of the ATP required for cellular activities in organelles called

.

10. When people discuss embryonic stem cells, they are referring to the powerful but slightly

limited type of stem cells called .

11. In the process of transcription, RNA forms a sequence of nucleotides complementary to the

strand of DNA so that it is a copy of the strand of

DNA, which is the strand that carries the permanent code.

12. The chain of amino acids that indicates a protein’s destination is its

, which usually occurs at the beginning of the protein .

13. Because of a certain characteristic of cells and the composition of cell membranes, some, but

not all, substances can pass into and out of the cell. That characteristic is called

.

14. The proteins that facilitate diffusion of substances into cells by changing shape are called

.

15. When an intestinal cell absorbs glucose, it also absorbs water, in a demonstration of the

principle that .

16. Both endocytosis and exocytosis are processes that require energy supplied by

.




17. The walls of capillaries and the air sacs of the lungs have a simple squamous epithelium

because this structure makes it easier to exchange oxygen and carbon dioxide between the

lungs and .

18. Exocrine glands, like the mammary glands that produce milk, make substances and secrete

them into .

19. The thick, parallel bundles that make up tendons and ligaments are rich in the protein

called .

20. Three locations where cartilage is found include , ,

and .

Understanding Concepts

I. True/False

For each question, write T for true or F for false in the blank to the left of each number. If astatement is false, correct it by replacing the underlined term and writing the correct statement inthe blank below the question.

________ 1. The two functions of the glycocalyx are to protect the cell from damage and to serveas an identifier.

__________________________________________________________________________________

________ 2. The interphase stage of cell reproduction, when structures other than the nucleusare prepared for duplication, lasts much less time than the mitosis phase.

__________________________________________________________________________________

________ 3. When multipotent stem cells divide, they frequently produce one daughter cell thatis a new stem cell to maintain the stem cell population.

__________________________________________________________________________________

________ 4. Translation refers to the process by which the nucleotide sequence of mRNA is readto produce the right amino acid sequence for a particular protein.

__________________________________________________________________________________


_______ 5. If a mutation occurs in any cell, the defect is inheritable and can be transmitted tooffspring.

__________________________________________________________________________________

________ 6. The osmolarity of most body cells and fluids is relatively fixed, at about 300 mOsm.

__________________________________________________________________________________

_______ 7. Like connective tissue, epithelial tissue has a large extracellular matrix separatingthe cells.

__________________________________________________________________________________

_______ 8. Bone is slightly flexible and yields a bit under force, a feature that promotes fragilityand fractures.

__________________________________________________________________________________

II. Practical Applications

Study each discussion. Then write the appropriate word or phrase in the space provided.

1. Red blood cells cannot reproduce after maturing because they have lost their .

2. At 6 months of age, Eliot was diagnosed with Tay-Sachs disease. This degenerative condition,

which affects the nervous system and usually leads to death by around age 4, results from the

buildup of damaging ganglioside on nerve cells. These fatty substances build up because they

are not removed, as in a normal human, by the cell’s .

3. Nicholas and Alexandra, the last emperor and empress of Russia, were killed along with their

children in the Russian Revolution of 1918. When remains thought to be those of these

individuals were found, they were identified through genetic testing that compared DNA

in a part of their cells to the DNA of known relatives through female lines of their families.

The structure that contains this DNA is the .

4. Andrea has thyroid cancer. One cause of her cancer is the dysfunction of molecules in the

cell that maintain a balance in the rate of cell reproduction. Those molecules are called

.




5. Collecting embryonic stem cells as the basis for research and possible development of

genetic-based treatments is controversial because an embryo must be destroyed to obtain the

cells.There is little or no controversy involving another kind of stem cell, as these cells can be

collected without harming anyone.Those stem cells, possessed by all people, have the ability to

produce limited numbers of different cells.They are

.

6. An oxygen molecule reaches the cell membrane from the extracellular fluid, where it meets

the phospholipids and cholesterol of the membrane. Does it pass through the membrane?

Why or why not?

__________________________________________________________________________________________________________

__________________________________________________________________________________________________________

7. Antonio enters the emergency room after experiencing vomiting and diarrhea due to a

gastrointestinal infection.To restore his body’s balance of water and solute, the emergency room

staff gives Antonio intravenous fluids that have the same osmolarity, or concentration of solutes in

the watery solution, as the body.The tonicity of these fluids is described as

8. Eight-year-old Sandra gets a splinter in a finger. To get better hold on the splinter with

sterilized tweezers, her father picks away a bit of skin around the spot with the tweezers. This

action doesn’t cause Sandra bleeding or pain because her father does not cut past the first

layer of skin, which means he does not reach blood vessels or nerve cells. That first layer of

skin is called the .

9. In a bicycle accident, Jesse suffers both cuts and bruises. Why does a nurse apply germ-killing

antibiotic to the cut but not to the bruise?

__________________________________________________________________________________________________________

__________________________________________________________________________________________________________

__________________________________________________________________________________________________________

__________________________________________________________________________________________________________


10. A surgeon uses a scalpel to cut into the abdomen of Rajiv, who needs an appendectomy. Be-

neath the skin, the doctor finds a layer of fat, also called .

III. Short Essays

1. How do genetic defects affect cell function?

__________________________________________________________________________________________________________

__________________________________________________________________________________________________________

__________________________________________________________________________________________________________

2. Describe the structure of DNA and what happens to DNA just before mitosis.

__________________________________________________________________________________________________________

__________________________________________________________________________________________________________

__________________________________________________________________________________________________________

3. Describe how RNA works with DNA to instruct cells on how to manufacture proteins.

__________________________________________________________________________________________________________

__________________________________________________________________________________________________________

__________________________________________________________________________________________________________

4. How is blood similar to and different from other connective tissue?

__________________________________________________________________________________________________________

__________________________________________________________________________________________________________

__________________________________________________________________________________________________________

IV. Conceptual Thinking

1. The body has trillions of cells, and many of them reproduce by cell division every day, whichmeans that mutations—defective copies of the cell’s DNA—happen frequently. Why are mostof these mutations not dangerous?

__________________________________________________________________________________________________________

__________________________________________________________________________________________________________

__________________________________________________________________________________________________________




2. Joe, a 50-year-old man, suffers a stroke that leaves his right arm paralyzed. With physical ther-apy, Joe is able to recover some, but not all, of his motor function. Why?

__________________________________________________________________________________________________________

__________________________________________________________________________________________________________

__________________________________________________________________________________________________________

3. Why can traditional medical treatments, such as antibiotics or surgery, not completely cureJulia, the subject of the chapter’s Case Study?

__________________________________________________________________________________________________________

__________________________________________________________________________________________________________

__________________________________________________________________________________________________________

Expanding Your HorizonsThe buildup of free radicals in cells is potentially dangerous. These free electrons can seek toform a bond with the first available molecule, no matter if the cell is damaged in the process. Freeradicals are a product of normal cellular metabolism, but they must be kept in low concentrationbecause they can damage any part of the cell. The body has natural defenses against free radicals,enzymes in the peroxisome that combine the free radicals with oxygen, which neutralizes them and produces a nontoxic molecule. Popular writings on diet and nutrition, and manyadvertisements, warn of links between free radicals and serious diseases, such as cancer andheart disease. Many reports and ads tout the benefits of eating foods with antioxidants orconsuming supplements with these substances.

Critical ThinkingAs you read more about this issue, consider these questions:

1. To what extent are free radicals connected to serious diseases such as cancer and heart disease?

2. How effective are consuming large amounts of antioxidants, or taking supplements with antioxidants, toward preventing disease?

Jot down your thoughts in the space below.


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Cells and Tissues - Lippincott Williams & Wilkinsdownloads.lww.com/wolterskluwer_vitalstream_com/... · Cells and Tissues 42 Chapter Overview ... Cells reproduce, a process necessary