CELLS LEC

Cell Structure and
Function

Chapter Outline
 Cell theory
 Properties common to all cells
 Cell size and shape – why are cells so small?
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Prokaryotic cells
Eukaryotic cells
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Organelles and structure in all eukaryotic cell
Organelles in plant cells but not animal

Cell junctions

History of Cell Theory
 mid 1600s – Anton van Leeuwenhoek
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Improved microscope, observed many living cells

 mid 1600s – Robert Hooke
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Observed many cells including cork cells

 1850 – Rudolf Virchow
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Proposed that all cells come from existing cells Cell Theory
All organisms consist of 1 or more cells. 2. Cell is the smallest unit of life.
3. All cells come from pre-existing cells. 1.

Observing Cells (4.1)
 Light microscope
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Can observe living cells in true color
Magnification of up to ~1000x
Resolution ~ 0.2 microns – 0.5 microns

Observing Cells (4.1)
 Electron Microscopes
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Preparation needed kills the cells
Images are black and white – may be colorized Magnifcation up to ~100,000
• Transmission electron microscope (TEM)
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2-D image

• Scanning electron microscope (SEM)
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3-D image

SEM

TEM

Cell Structure
 All Cells have:

an outermost plasma membrane
 genetic material in the form of DNA
 cytoplasm with ribosomes
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1. Plasma Membrane
• All membranes are phospholipid bilayers with embedded proteins
• The outer plasma membrane isolates cell contents
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controls what gets in and out of the cell
 receives signals
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2. Genetic material in the form of DNA
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Prokaryotes – no membrane around the DNA
Eukaryotes – DNA is within a membrane 3. Cytoplasm with ribosomes
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Cytoplasm – fluid area inside outer plasma membrane and outside
DNA region
Ribosomes – make proteins

Cell Structure
 All Cells have:

an outermost plasma membrane
 genetic material in the form of DNA
 cytoplasm with ribosomes


Why Are Cells So Small? (4.2)
 Cells need sufficient surface area to allow

adequate transport of nutrients in and wastes out.
 As