Copyright Pearson Prentice Hall. The larger a cell becomes, the more demands the cell places on its...

Copyright Pearson Prentice Hall

The larger a cell becomes, the more demands the cell places on its DNA.

Larger cells have more trouble moving enough nutrients and wastes across the cell membrane.

Ratio of Surface Area to Volume (SA:V ratio)◦ As the length of a cell increases, its volume

increases faster than the surface area.◦ As a cell grows, this SA:V ratio gets smaller.

◦ When the cell divides, the SA:V ratio increases.

◦ Before it becomes too large, a growing cell divides forming two “daughter” cells.

◦ Before a cell divides, the cell replicates, or copies, all of its DNA. Each daughter cell gets one complete set of

genetic information.


◦ As a cell increases in size, which of the following increases most rapidly? surface area volume


◦ If an imaginary cube-shaped cell has a length of 6 cm, its ratio of surface area to volume is 1 : 1. 6 : 1. 36 : 1. 1 : 6.


◦ The process by which a cell divides into two new daughter cells is called cell growth. cell division. DNA replication. cell multiplication.


◦ When one cell divides in two, what happens to the surface area to volume ratios in the new cells?a. There is no change in the amount of material

exchanged.b. Each new cell can exchange more material than the

original cell.c. Each new cell can exchange less material than the

original cell.d. The two new cells cannot be compared to the

original cell.


◦ When a growing cell undergoes cell division, each new cell gets half the DNA from the original cell. twice as much DNA as the original cell. a random sample of the DNA in the original cell.

a full copy of all the DNA in the original cell.


2 Stages of Cell Division in eukaryotes:1. Mitosis: division of the cell nucleus.2. Cytokinesis: division of the cell cytoplasm

Genetic information is passed from one generation to the next on chromosomes.◦ Dark-staining structures that contain DNA and

protein.◦ Chroma- Greek for “colored”◦ Soma- Greek for “body”

Before cell division, each chromosome is duplicated, or copied.

Each chromosome consists of two identical “sister” chromatids.

Centromere- holds sister chromatids together

When the cell divides, the chromatids separate.

Each new cell gets one chromatid.


Sister chromatids

Centromere

Cell cycle- sequence of growth and division of a cell.

Interphase is the period of growth that occurs between cell divisions. 3 stages:◦ G1◦ S◦ G2

During the cell cycle:◦ a cell grows◦ prepares for division◦ divides to form two daughter cells

1. G1 (First Gap Phase)◦ Cell grows◦ synthesizes new proteins and organelles

2. S Phase◦ chromosomes are replicated◦ DNA synthesis takes place

3. G2 (Second Gap Phase)◦ Organelles (ie. Mitochondria, chloroplast)

and molecules required for cell division are produced

4. Mitosis


1. Prophase2. Metaphase3. Anaphase4. Telophase


The centrioles separate and move to opposite sides of the nucleus.

A spindle begins to form◦ Microtubules that help

separate the chromosomes.

Chromatin condenses to form visible chromosomes.

The nuclear envelope breaks down.


Spindle forming

CentromereChromosomes(paired chromatids)

Centriole

The second phase of mitosis

The chromosomes line up across the center (equator)of the cell.

Microtubules connect the centromere of each chromosome to the poles of the spindle.


Centriole

Spindle

Centromere

Equator (imaginary midline)

the third phase of mitosis.

The sister chromatids separate into individual chromosomes.

The chromosomes move toward opposite poles.


Individualchromosomes

the fourth and final phase of mitosis.

Chromosomes gather at opposite ends of the cell and lose their distinct shape.

A new nuclear envelope forms around each cluster of chromosomes.


the cytoplasm pinches in half.

Each daughter cell has an identical set of duplicate chromosomes.



In plants, the cell plate forms at the equator. The cell plate develops into a cell membrane. A cell wall then begins to appear in the cell plate.

Cell wall

Cell plate

◦ The series of events that cells go through as they grow and divide is called a. the cell cycle.b. mitosis.c. interphase.d. cytokinesis.


◦ The phase of mitosis during which the chromosomes line up across the center of the cell is a. prophase.b. metaphase.c. anaphase.d. telophase.


◦ Cytokinesis usually occurs at the same time as telophase. after telophase. during interphase. during anaphase.


◦ DNA replication takes place during the S phase of the cell cycle. G1 phase of the cell cycle. G2 phase of the cell cycle. M phase of the cell cycle.


◦ During mitosis, “sister” chromatids separate from one another during telophase. interphase. anaphase. metaphase.


Copyright Pearson Prentice Hall. The larger a cell becomes, the more demands the cell places on its...

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