Cellular Growth Section 9.1

Cell SizeQuestion:Are the cells in an elephant bigger, smaller, or about the same size as those in a mouse?

2

Factors Affecting Cell Size∙ Surface area (plasma membrane surface) is determined by multiplying length times width (L x W)∙ Volume of a cell is determined by multiplying length times width times height (L x W x H)∙ Therefore, Volume increases FASTER than the surface area

3

Cell Size• When the surface area is no longer great enough to get rid of all the wastes and to take in enough food and water, then the cell must divide• Therefore, the cells of an organism are close in size

4

Cell SizeQuestion:Are the cells in an elephant bigger, smaller, or about the same size as those in a mouse?

5

About the same size, but …

The elephant has MANY MORE cells than a mouse!

The Cell Cycle

6

Five Phases of the Cell Cycle

∙ G1 - primary growth phase∙ S – synthesis; DNA replicated∙ G2 - secondary growth phasecollectively these 3 stages are called interphase∙ M – mitosis – division of the nucleus∙ C – cytokinesis – division of the cytoplasm

7

Cell Cycle

8

Interphase - G1 Stage• 1st growth stage after cell division• Cells mature by making more cytoplasm & organelles• Cell carries on its normal metabolic activities

9

Interphase – S Stage• Synthesis stage• DNA is copied or replicated

10

Two identical copies of DNA

Original DNA

Interphase – G2 Stage• 2nd Growth Stage• Occurs after DNA has been copied• All cell structures needed for division are made (e.g. centrioles• Both organelles & proteins are synthesized

11

What‛s Happening in Interphase?

copyright cmassengale

What the cell looks like

Animal Cell

What’s occurring

12

Mitosis

∙ Division of the nucleus

∙ Also called karyokinesis

∙ Only occurs in eukaryotes

∙ Has four stages

∙ Doesn’t occur in some cells such as brain cells

Nucleolus

Chromosmes

Cytoplasm

Nuclear envelope

Chromosmes

Kinetochore Fiber