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CELLS
Chapter 3
A. The Early Years
 Robert
Hooke (1660)
 1st person to see the outlines of cells
 Antonie van Leeuwenhoek (1673)
 developed high magnification lenses
 1st record of microorganisms
 Matthias Schleiden & Theodore
Schwann (1839) & Rudolph Virchow (1855)
 contributed to the cell theory
Cell Theory
1. All living things are composed of
cells. [Schleiden & Schwann]
2. All cells come from preexisting
cells. [Virchow]
B. Cell Size
 Most
are 1-100m in diameter
 Smallest?
 Largest?
 Why can’t cells grow to be as large as
a car?
- surface area/volume ratio
- as cell grows, its volume increases
more rapidly than its surface area
C. Types of Cells
3 basic types:
 Bacterial
Prokaryotic
 Archaean
 Eukaryotic
1. Bacterial cells
 1-10
m in diameter
 NO membrane-bound organelles
 1 circular DNA molecule located in
nucleoid region
 plasma membrane, cytoplasm &
ribosomes
 most have a cell wall (peptidoglycan)
 may have a polysaccharide capsule
Ex. bacteria & cyanobacteria
2. Archaean cells
 1-10
m in diameter
 NO membrane-bound organelles
 cell walls lack peptidoglycan
 have characteristics of both
bacteria & eukaryotic cells
Ex. methanogens,
extreme halophiles &
extreme thermophiles
3. Eukaryotic cells
 10-100
m in diameter
 nucleus & other membrane-bound
organelles
 2 or more linear DNA molecules
located in nucleus
 plasma membrane, cytoplasm &
ribosomes
 some have a cell wall (cellulose or chitin)
Ex. plants, animals, fungi, protista
Generalized
Animal Cell
Generalized
Plant Cell
D. Organelles of Eukaryotic Cells
Organelles compartmentalize a cell’s
activities.
1. Nucleus
 surrounded
by a double membrane
(nuclear envelope), perforated with
nuclear pores
 contains DNA & nucleolus (stores RNA
nucleotides)
 functions
of cell
to separate DNA from rest
Nucleolus
2. Endoplasmic reticulum (ER)
 interconnected
network of
membranes extending from nucleus
to plasma membrane
Rough ER - studded with ribosomes
 site of protein synthesis (most will be
exported out of the cell)
Free ribosomes in the cytoplasm synthesize
proteins that remain in cell.
Smooth ER - lacks ribosomes
 site of lipid synthesis
 contains enzymes that detoxify
drugs & poisons
3. Golgi apparatus
 stacks
of membrane-enclosed sacs
Functions:
 links simple carbohydrates together
to form starch
 links simple carbohydrates to
proteins (glycoprotein) or lipids
(glycolipid)
 completes
folding of proteins
 temporarily stores secretions (milk)
Organelle interaction in a mammary
gland cell.
4. Mitochondria
 double-membrane
outer
is smooth
inner is highly
folded (cristae)
 #/cell
varies
 contain DNA
 inherited from female parent
 site of cellular respiration (production
of ATP)
5. Chloroplasts
 possess
3 membranes
outer/inner
membranes surround stroma
3rd membrane system folded into
flattened sacs (thylakoids)
 #/cell
varies
 contain DNA
 found in plants & protists
 function in photosynthesis
6. Lysosomes (suicide sacs)
 vesicles
containing > 40 types of
digestive enzymes
 function
to recycle damaged organelles,
break down cellular byproducts &
destroy invading microbes
7. Peroxisomes
 vesicles
containing several types of
enzymes (produced in cytoplasm)
 found in all eukaryotic cells
 function to help cell use oxygen &
metabolize potentially toxic
compounds
E. The Endosymbiont Theory
Proposes that chloroplasts and
mitochondria evolved from once
free-living bacteria engulfed by
larger archaea.
Based on fact that mitochondria &
chloroplasts resemble certain
bacteria (size, shape, membrane
structure & method of making proteins).