The Cell CycleThe Cell CycleChapter 5.1: The Cell Cycle and Mitosispp. 150-155

What am I?What am I?A: Dust!

What What am I am I really???really???A: Dead skin cells!Over 70% of the dust in your home is made

up of tiny flakes of skin we lose on a daily basis.

Each day, you shed millions of skin cells per hour. Each month, you replace the outer layer (the epidermis) of your skin.

Note:Note:Terms in green are definitions

– these are key terms to know

Terms in blue are important words or concepts – please make note

Introduction to the Cell Introduction to the Cell CycleCycleQ: Ever wonder how we as humans can

grow from a single cell into trillions? How do you think it happens?

A: Cells must divide and multiply in number in order to create all of our tissues, organs, organ systems, etc.

Cell division allows one cell to become many cells!

A single cell (fertilized

egg)

Billions of cells (single organism)

Cell Replacement and Cell Replacement and DevelopmentDevelopmentCells divide as a human body grows. A body must also replace cells that take a lot of wear and tear.

Which body cells are replaced most frequently?Cell Type Rate Of Cell

DivisionReason For Cell

Replacement

Stomach lining cells

Every 2 days Destroyed by stomach acid

Intestinal lining cells

Every 3 days Destroyed by bacteria or during digestion

Skin cells Every 20 days Wear and tear during everyday activities or

accidents such as scratches

p. 152

The Cell CycleThe Cell CycleThe life of a cell is divided into 3 stages known as the cell cycle:

1

31)Interph

ase2)Mitosis3)Cytokin

esis

2

p. 153

The Cell CycleThe Cell Cycle1)interphase: the first and longest stage of

the cell cycle, in which cells carry out life functions and cells that divide prepare for cell division

2)mitosis: the second and shortest stage of the cell cycle; the process in which the duplicated contents of the cell’s nucleus divides into two equal parts

3)cytokinesis: the final stage of the cell cycle, which separates the two nuclei and cell contents into two daughter cells

InterphaseInterphase

interphase: “inter” = between between phases

Interphase is the time where the cell obtains nutrients, grows, reads its DNA, and conducts other essential cell functions.

Interphase can be divided into 3 parts:1) Growth and preparation2) Replication3) Continued growth and preparation

1)Growth and preparationCell increases in size and makes the

proteins and molecules necessary for the cell to function.

Some organelles begin to duplicate.

2) Replicationreplication: the cell copies the 3 billion

base pairs of DNA information in the nucleus the cell temporarily has two complete sets of DNA

Step 1: Enzyme separates DNA

sides

Step 2: New bases pair

with original bases on

original DNA

Step 3: Two new identical

DNA molecules

are produced

p. 154

3) Continued growth and preparation

After DNA replication, the cell continues to grow and make materials (ex. proteins) for the future new cells.

Chromatin (containing the replicated DNA) is in a loosely coiled form can be copied into RNA proteins can be made.

Organelles such as mitochondria and chloroplasts will be duplicated.

p. 155

Activity: Video – Introduction to

Mitosis

Homework for next class:Homework for next class:Complete ‘Identifying stages of the

cell cycle’ (p. 71 of the worksheet)Answer Reading Check questions 1-6

(p. 155)Complete student questionnaireBring field trip forms and $Read over class notes and check out the

class blog: http://msoonscience.blogspot.com/

Works CitedWorks CitedImages taken from the following

sources:http://www.historyoftheuniverse.com/celldivi.html

http://www.cartoonstock.com/directory/s/single_cell.asp

http://www.ias.unt.edu/~tpp001/Mitosis_Diagram_Page.main.html