Which of the following statements about stem cells is true?

They are able to differentiate into a variety of cell types.

They are found only in embryos.

They are "perpetual" parent cells that never produce daughter cells.

They are found only in embryos and in the bone marrow of adults.

Which of the following is an example of asexual reproduction in eukaryotes?

The union of sperm and egg in sea urchins

As a result of mitosis, each of your body cells

is genetically identical to all others.

contains unique genetic information.

contains only the genetic information needed for that type of cell.

changes genetically as you grow and develop.

The genetic material in bacteria consists of

several circular DNA molecules.

many rod-like DNA molecules with protein.

What is the longest-lasting phase of the prokaryotic cell cycle?

Fission of the plasma membranes at the cell equator

How do prokaryotic and eukaryotic chromosomes differ?

Prokaryotic chromosomes are not contained in a membrane-bound organelle.

Eukaryotic chromosomes occur singly, and prokaryotic chromosomes occur as pairs.

Genetic information is stored as DNA in eukaryotic cells and as proteins in prokaryotic cells.

Prokaryotic chromosomes are not made from nucleotides.

In prokaryotes, the DNA molecule is

more than 1.8 meters (6 feet) long when uncoiled.

What is the function of the histones that are found in a chromosome?

They bind the DNA into a supercoiled structure.

They bind nucleotides together to form a single strand of DNA.

They contain the genes that code for various traits.

They hold the DNA strands together in a form called the double helix.

Meiotic cell division in animals occurs in the ________ and results in the production of ________.

testes and ovaries; diploid cells

Which of the following is the correct sequence of stages in mitotic cell division?

Prophase-metaphase-anaphase-telophase

Metaphase-prophase-anaphase-telophase

Telophase-anaphase-prophase-metaphase

Anaphase-telophase-prophase-metaphase

chromatids to spindle microtubules.

sister chromatids to each other.

What would be a consequence of a mutation that disables the production of cyclin-dependent kinases (Cdks)?

Cell-cycle control would not be possible.

The nuclear envelope would disintegrate.

Telomere length would be shortened significantly.

DNA would not contain any phosphate groups.

Growth factors stimulate

the cell to ignore the checkpoints of the cell cycle.

Cdks to synthesize enzymes that digest cyclins.

the cell to skip the S and G1 phases of interphase and undergo mitosis directly.

Cancer is essentially

unregulated mitotic cell division.

a never-ending repetition of the S phase of the cell cycle.

the creation of extra checkpoints in the cell cycle.

the binding of cyclins and Cdks.

Sexual reproduction allows for

greater genetic diversity in offspring, compared to asexual reproduction.

random mutations to occur at a faster rate than does asexual reproduction.

haploid individuals to pass their genes on to the next generation.

clones of parent cells to be produced more quickly and efficiently than does prokaryotic fission.

Which of the following occurs during meiosis?

Haploid nuclei with unpaired chromosomes are produced from diploid parent nuclei with paired chromosomes.

Haploid nuclei with paired chromosomes are produced from diploid parent nuclei with unpaired chromosomes.

Diploid nuclei with paired chromosomes are produced from haploid parent nuclei with unpaired chromosomes.

Diploid nuclei with unpaired chromosomes are produced from haploid parent nuclei with paired chromosomes.

Chapter 9 evaluation. The Continuity of Life: Cellular Reproduction.

Chapter 9: LESSON 27 THE PROCESS OF EVOLUTION

Some substances, such as macromolecules and nutrients, are too large to pass through the cell membrane by the transport processes you have studied so far. Cells employ two other transport mecha- nisms—endocytosis and exocytosis—to move such substances into or out of cells. Endocytosis and exocytosis are also used to transport large quantities of small molecules into or out of cells at a single time. Both endocytosis and exocytosis require cells to expend energy. Therefore, they are types of active transport. Endocytosis Endocytosis (EN-doh-sie-TOH-sis) is the process by which cells ingest external fluid, macromolecules, and large particles, including other cells. As you can see in Figure 5-7, these external materials are enclosed by a portion of the cell’s membrane, which folds into itself and forms a pouch. The pouch then pinches off from the cell membrane and becomes a membrane-bound organelle called a vesicle. Some of the vesicles fuse with lysosomes, and their con- tents are digested by lysosomal enzymes. Other vesicles that form during endocytosis fuse with other membrane-bound organelles. Two main types of endocytosis are based on the kind of material that is taken into the cell: pinocytosis (PIEN-oh-sie-TOH-sis) involves the transport of solutes or fluids, and phagocytosis (FAG-oh-sie-TOH-sis) is the movement of large particles or whole cells. Many unicellular organisms feed by phagocytosis. In addition, certain cells in animals use phagocytosis to ingest bacteria and viruses that invade the body. These cells, known as phagocytes, allow lysosomes to fuse with the vesicles that contain the ingested bacteria and viruses. Lysosomal enzymes then destroy the bacteria and viruses before they can harm the animal. CYTOSOL EXTERNAL ENVIRONMENT During endocytosis, the cell membrane folds around food or liquid and forms a small pouch. The pouch then pinches off from the cell membrane to become a vesicle. FIGURE 5-7 vesicle from the Latin vesicula, meaning “bladder” or “sac” Word Roots and Origins www.scilinks.org Topic: Endocytosis Keyword: HM60505 mb06se_homs02.qxd 5/18/07 11:03 AM Page 105 106 CHAPTER 5 1. Explain the difference between passive trans- port and active transport. 2. What functions do carrier proteins perform in active transport? 3. What provides the energy that drives the sodium-potassium pump? 4. Explain the difference between pinocytosis and phagocytosis. 5. Describe the steps involved in exocytosis. 6. How do endocytosis and exocytosis differ? How can that difference be seen? CRITICAL THINKING 7. Analyzing Information During intense exercise, potassium tends to accumulate in the fluid surrounding muscle cells. What membrane protein helps muscle cells counteract this tendency? Explain your answer. 8. Evaluating Differences How does the sodium- potassium pump differ from facilitated diffusion? 9. Relating Concepts The vesicles formed during pinocytosis are much smaller than those formed during phagocytosis. Explain. SECTION 2 REVIEW Vesicle Cell membrane EXTERNAL ENVIRONMENT CYTOSOL During exocytosis, a vesicle moves to the cell membrane, fuses with it, and then releases its contents to the outside of the cell. FIGURE 5-8 INSIDE OF CELL Vesicle OUTSIDE OF CELL Exocytosis Exocytosis (EK-soh-sie-TOH-sis) is the process by which a substance is released from the cell through a vesicle that transports the sub- stance to the cell surface and then fuses with the membrane to let the substance out of the cell. This process, illustrated in Figure 5-8, is basically the reverse of endocytosis. During exocytosis, vesi- cles release their contents into the cell’s external environment. Figure 5-8 also shows a photo of a vesicle during exocytosis. Cells may use exocytosis to release large molecules such as pro- teins, waste products, or toxins that would damage the cell if they were released within the cytosol. Recall that proteins are made on ribosomes and packaged into vesicles by the Golgi apparatus. The vesicles then move to the cell membrane and fuse with it, deliver- ing the proteins outside the cell. Cells in the nervous and endocrine systems also use exocytosis to release small molecules that control the activities of other cells.

chapter 9

110.31.b.17.C

Topic: Reading/Vocabulary Development

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