cell division

The process by which a cell divides into two new daughter cells; includes mitosis & cytokinesis (243).

The larger a cell becomes, the more demands the cell places on its DNA and the more trouble the cell has moving enough nutrients and wastes across the cell membrane.

What problem does

growth cause for cells?

The cell's volume

The rate at which food and oxygen

are used up and waste products are made 

depends on ______?

The relationship between a cell's volume and its surface area.  The smaller the cell the higher the SA:V ratio.

What is the key to understanding

why cells must divide as they grow?

Volume

As a cell increases in size,

which increases more rapidly, its surface area or its volume?

chromatid

One of two identical "sister" parts of a duplicated or copied chromosome that consists of genes of the same type and form. (p. 244)

centromere

A structure which connects two sister chromatids together (p. 244)

interphase

A period of the cell cycle when the cell is actively metabolizing & growing, but not dividing or reproducing (245).

cell cycle

A series of events that cells go through as they grow and divide; includes interphase (G₁, S, G₂) and mitosis(245).

Mitosis

A part of eukaryotic cell division

during which the cell nucleus divides (p. 245)

prophase

The first and longest phase of mitosis, during which the chromosomes become visible and the centrioles separate and take up positions on the opposite sides of thenucleus (p. 246)

centriole

One of two tiny structures located in the cytoplasm of animal cells near the nuclear envelope.

spindle

A fanlike microtubule structure that helps separate the chromosomes during mitosis.

metaphase

The 2nd stage of mitosis in which the paired chromatids line up along the equator of the cell.

anaphase

The third phase of mitosis,

during which the chromosome pairs separate

and move toward opposite poles.

telophase

The fourth and final phase of mitosis,

during which the chromosomes

begin to disperse into a

tangle of dense material.

cytokinesis

The division of the cytoplasm

during cell division; usually begins in late anaphase and is completed in telophase.

What are the main events

of the cell cycle?

What are the stages of the life cycle of a cell

M phase (mitosis), the division of the cell nucleus and cytokinesis take place.

S phase (synthase) coping of the chromosomes

These are the "landmark" phases.

(The G stands for gap) 

What are chromosomes

 made of?

DNA & histone proteins

How do prokaryotic cells divide?

Every cell must first copy its genetic information before cell division begins.  Each daughter cell then gets a complete copy of that information. 

In most prokaryotes, the rest of the process of cell division is a simple matter of separating the contents of the cell into two parts.

How is cytokinesis in plant cells similar

 to cytokinesis in animal cells? 

How is it different?

Cytokinesis can take place in a number of ways.

In most animal cells, the cell membrane is drawn inward until the cytoplasm is pinched into two nearly equal parts.  Each part contains its own nucleus and cytoplasmic organelles.

In plants, a structure known as the cell plate forms midway between the divided nuclei.  The cell plate gradually develops into a separating membrane.  A cell wall then begins to appear in the cell plate.

How is the cell cycle regulated?

Cyclins regulate the timing of the cell cycle in eukaryotic cells.

(There are two types of regulatory proteins: internal regulators and external regulators.)

How are cancer cells

 different from other cells?

Cancer cells do not respond to the signals that regulate the growth of most cells.  As a result, they form masses of cells called tumors that can damage the surrounding tissues.

cyclin

One of a family of closely related proteins that regulate the cell cycle in eukaryotic cells

cancer

A disorder in which some

 of the body's own cells lose the ability to control growth.

What chemicals regulate the cell cycle? 

 How do they work?

Cyclins (proteins) 

The amount of cyclin protein in the cell rose and fell in time with the cell cycle.  They decided to call this protein cyclin because it seemed to regulate the cell cycle. 

What happens when

cells do not respond

 to the signals that normally regulate their growth?

Cancer

Cancer cells do not respond to the signals that regulate the growth of most cells.  As a result, they form masses of cells called tumors that can damage the surrounding tissues.