5 Cell Growth and Division

5

CHAPTER

Cell Growth

and Division

GETTING READY TO LEARN

Preview Key Concepts

5.1 The Cell Cycle

Cells have distinct phases of growth, reproduction, and normal functions.

5.2 Mitosis and Cytokinesis

Cells divide during mitosis and cytokinesis.

5.3 Regulation of the Cell Cycle

Cell cycle regulation is necessary for healthy growth.

5.4 Asexual Reproduction

Many organisms reproduce by cell division.

5.5 Multicellular Life

Cells work together to carry out complex functions.

Review Academic Vocabulary

Write the correct word for each definition.

homeostasis

nucleus

centrosome

cell membrane

1.

: forms spindle ?bers

2.

: described by the ?uid mosaic model

3.

: maintaining constant internal conditions

4.

: largest organelle in a cell

Preview Biology Vocabulary

See how many key terms from this chapter you already know. Rewrite

each phrase, using a different word or words for the words in bold.

PHRASE

REWRITTEN WITH DIFFERENT WORDS

1. The formation of skin and nerves and The formation of skin and nerves and musmuscles in a developing embryo is an cles in a developing embryo is an example

example of cell differentiation.

of

.

2. Bacteria reproduce asexually through

binary fission.

3. Organisms that reproduce sexually

use mitosis for growth, development, and repair.

Bacteria reproduce asexually through

.

Organisms that reproduce sexually use

for growth, development, and repair.

73

SECTION

5.1

The Cell Cycle

KEY CONCEPT

normal functions.

Student

text pages

@E;@8E8JK8E;8I;J

134¨C137

B.6.1

Cells have distinct phases of growth, reproduction, and

The cell cycle has four main stages.

Cells grow and divide in a regular pattern, or cycle*. If you cut your

finger, your cells grow and divide to make more cells. This is how your

finger heals.

The cell cycle is a regular pattern of growth, DNA duplication*, and

cell division* that occurs in eukaryotic cells. Recall that your cells are

eukaryotic cells, and they have a nucleus. There are four main stages of

the cell cycle:

? gap 1¡ªnormal growth

Together, these three stages

? synthesis¡ªDNA is copied

make up a part of the cell

? gap 2¡ªmore growth

cycle called interphase.

? mitosis¡ªnuclear division

Each stage is described below.

Gap 1 (G1 ) In G1 cells do their normal functions. For example,

VISUAL VOCAB

your muscle cells contract, and intestinal cells absorb

Mitosis is the division of the cell

nutrients.

nucleus and its contents.

Synthesis (S) Synthesis means ¡°the combining of parts to

parent cell

make a whole.¡± During the S stage, a cell puts together, or

synthesizes, a whole copy of its nuclear DNA. In eukaryotes,

mitosis

DNA is in the nucleus. At the end of this stage, there are two

cytokinesis

complete sets of DNA in a cell¡¯s nucleus.

Gap 2 (G2 ) In G2 cells grow and continue their normal funcdaughter cells

tions. If the cell is healthy, it will continue to the next stage.

Cytokinesis divides the cell cytoplasm.

Mitosis (M) There are two parts of this stage: mitosis and

cytokinesis. Mitosis (my-TOH-sihs) is the division of the cell

Daughter cells is a term to describe

these resulting cells, but it does not

nucleus and the DNA inside it. Cytokinesis (SY-toh-kuhmean that they are female.

NEE-sihs) is the division of the contents of the rest of the

cell¡ªthe cytoplasm.

These four main stages are shown in the graph at the top

of page 75.

* ACADEMIC VOCABULARY

cycle a pattern of events that is repeated

duplication the process of doubling, or copying

division separating

74

McDougal Littell Biology

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