The CellThe Cell

Oops, different type of cellOops, different type of cell

The CellThe Cell

There that’s better!There that’s better!

I. Discovery of the CellI. Discovery of the CellA. Robert Hooke (1665) used a A. Robert Hooke (1665) used a

microscope to look at dead plant cells microscope to look at dead plant cells (“little boxes”) (“little boxes”)

thin slices of corkthin slices of cork

B. Anton van Leeuwenhoek (1673) first B. Anton van Leeuwenhoek (1673) first person to look at living cells.person to look at living cells.

c. c. The cell theoryThe cell theory

1.1.Living things are composed of Living things are composed of one or more cells.one or more cells.

2.2.In organisms cells are the In organisms cells are the basic units of structure and basic units of structure and function.function.

3.3.New cells can only be made by New cells can only be made by existing cells.existing cells.

D. Evidence for the cell theoryD. Evidence for the cell theory

1. Matthias Schleiden (1838) 1. Matthias Schleiden (1838) concluded plants were made of cells.concluded plants were made of cells.

2. Theodor Schwann (1839) concluded 2. Theodor Schwann (1839) concluded animals were made of cells.animals were made of cells.

3. Rudolf Virchow (1855) found that 3. Rudolf Virchow (1855) found that cells only come from other cells.cells only come from other cells.

II. Cell DiversityII. Cell Diversity

A.A. Size Size 1.1. Nerve cells can be very large.Nerve cells can be very large.

2.2. Most plant and animal cells are 10-50 Most plant and animal cells are 10-50 micrometers (0.002 inches)micrometers (0.002 inches)

3.3. Bacterial cells 0.2 micrometers Bacterial cells 0.2 micrometers (0.000008 inches)(0.000008 inches)

4.4. Cells are limited in size by the ratio of Cells are limited in size by the ratio of their outer surface area to their volumetheir outer surface area to their volume

a. Surface area= 2 (La. Surface area= 2 (L××H + LH + L××W + W + HH××W)W)

b. Volume= Lb. Volume= L××WW××HH

c. Volume is a measure of space c. Volume is a measure of space (increases by the cube of the (increases by the cube of the

sides)sides)

d. Surface area is the amount of d. Surface area is the amount of exposed exposed surface (increases by the surface (increases by the square of square of the sides)the sides)

e. Volume increases more rapidly than e. Volume increases more rapidly than surface areasurface area

f. Many materials essential to the cell f. Many materials essential to the cell must enter through the must enter through the

surfacesurface

Side Side LengthLength

Surface Surface AreaArea

VolumeVolume Surface Surface Area to Area to Volume Volume RatioRatio

1 mm1 mm 6 mm6 mm22 1 mm1 mm33 6:16:1

2 mm2 mm 24 mm24 mm22 8 mm8 mm33 3:13:1

3 mm3 mm 54 mm54 mm22 27 mm27 mm33 2:12:1

B. ShapeB. Shape1. Variety of shapes1. Variety of shapes

a. Nerve cella. Nerve cell b. Skin Cellb. Skin Cell

c. White and redc. White and redblood cellsblood cells

C. Internal OrganizationC. Internal Organization1. Cells contain internal structures 1. Cells contain internal structures called organelles.called organelles.

2. Cells are surrounded by a cell 2. Cells are surrounded by a cell membrane called a phospholipid membrane called a phospholipid bilayerbilayer

3. The Nucleus contains genetic 3. The Nucleus contains genetic information and controls cell information and controls cell function.function.

4. Eukaryotes: organisms that contain a 4. Eukaryotes: organisms that contain a membrane bound nucleus and membrane bound nucleus and

organelles.organelles.

5. Prokaryotes: no membrane bound 5. Prokaryotes: no membrane bound nucleus or membrane bound organelles nucleus or membrane bound organelles (bacteria)(bacteria)

Although new studies Although new studies have shown they have have shown they have “microcompartments” “microcompartments” on the molecular level on the molecular level that may act as that may act as organellesorganelles