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Chapter 7
Cells
7.1 Discovery of Cells
Cell Theory
1. All organisms are composed of one or
more cells
2. The cell is the basic unit of structure and
organization of living things
3. All cells come from preexisting cells
Types of Cells
1. Prokaryotes- cells that lack membranebound organelles, no nucleus
Example- bacteria
2. Eukaryotes- cells that have organelles
and nucleus
Example- plants, animals, fungi, protists
Types of Microscopes
1. Light
Bends light coming through object
Limited to 1000-2000x magnification
Living cells and tissues
Inexpensive, mobile, easy to use
Light Microscope Image
2. Scanning electron microscope (SEM)
Bounces electrons off surface of object
10,000-20,000x magnification
Specimen must be sacrificed
Expensive, large, extensive training
required
SEM Image
Transmission electron microscope (TEM)
Electrons travel through thin sections of
specimen
100,000-200,000x magnification
Specimen must be sacrificed
Expensive, large, extensive training
required
TEM Image
7.2: Plasma Membrane
Plasma membrane- flexible boundary
between a cell and its environment
AKA cell membrane and phospholipid
bilayer
Demonstrate the function of the cell membrane
and explain its role in maintaining homeostasis
Functions:
Allow steady supply of nutrients into the
cell
Examples- oxygen, water, glucose
Allow wastes and products of cell
metabolism to leave the cell
Examples- carbon dioxide, water, wastes
Demonstrate the function of the cell membrane
and explain its role in maintaining homeostasis
Selective Permeability
Membrane allows some molecules to pass
through while keeping others out
The plasma membrane is picky!
Demonstrate the function of the cell membrane
and explain its role in maintaining homeostasis
Structure of the Membrane
Phospholipid- lipid
molecule composed
of:
 Glycerol
 Phosphate group
 2 fatty acids
Demonstrate the function of the cell membrane
and explain its role in maintaining homeostasis
Structure of the Phospholipid Molecule
Head- polar, hydrophilic- “water-loving”
Tail- nonpolar, hydrophobic- “waterfearing”
Phospholipid molecules are arranged in
two layers- tails facing each other to form
the….
Demonstrate the function of the cell membrane
and explain its role in maintaining homeostasis
Phospholipid bilayer- 2 layers of
phospholipid molecules
Because of nonpolar inner layers, cells
can maintain their structure in a water
environment and not dissolve!
Demonstrate the function of the cell membrane
and explain its role in maintaining homeostasis
Other components of the membrane:
Cholesterol- helps stabilize proteins,
keeps tails from tangling
Proteins- move needed substances or
waste materials through the membrane,
attach cell membrane to inner cellular
structures, help to identify cells & chemical
signals (along with surface carbohydrates)
Demonstrate the function of the cell membrane
and explain its role in maintaining homeostasis
Plasma Membrane
Demonstrate the function of the cell membrane
and explain its role in maintaining homeostasis
Domains of Living Things
All living things are divided into two
Domains:
Prokarya
Eukarya
Prokaryotes
Examples- bacteria and Archaea
Small- 2-8 um
Structurally simple
Prokaryotic Cell Structure
Cell wall- composed of lipids,
carbohydrates, & protein- no cellulose
Plasma membrane- encloses cell
Mesosome- in-folding of the plasma
membrane involved in secretion & copying
of chromosome
Singular chromosome- circular, doublestranded DNA
Nucleoid region- general area where
chromosome is located
Plasmids- smaller, circular DNA molecules
Generalized Prokaryote
Great Diversity in Metabolic Processes
Nutrient cyclers
Decomposers
Photosynthetic
Source of antibiotics
Mostly beneficial, some detrimental to
human health
Eukaryotes
 Examples- everything
but bacteria
 10-100 um
 Internally complexorganelles
Organelles
Any part of a eukaryotic cell that has its
own structure and function
Why have organelles?
 Many reactions that occur in cells are not
compatible and need to be separated from each
other
 Division of labor- Specific processes are isolated
in organelles
Cell wall
 Found in plants, fungi, and prokaryotes
 Provides support and protection
 Outside of plasma membrane
Generalized Plant Cell
Cytosol
Protein-rich semifluid
Surrounds and bathes organelles
Mostly water
Cytoplasm
Cytosol plus all the other organelles
Nucleus
 Genetic control center
 Enclosed by two
membranes- nuclear
envelope
 Contains
chromosomes (DNA)
Nucleolus
 Small body inside
nucleus
 Involved in cell
division and RNA
production
Endoplasmic reticulum (ER)
System of membranes and tubes that
connects other organelles
Snuggled up next to nucleus
2 types:
Rough ER- covered in ribosomes
Smooth ER- no ribosomes
Ribosomes
Small, spherical bodies found throughout
cell
Location of protein synthesis
Golgi apparatus or body
System of vesicles and tubes
Next to ER
Final assembly of proteins
Transport of materials throughout cell
Vesicles
Spherical membranes that pinch off of
Golgi body
Carry materials to other organelles and to
plasma membrane for export
Lysosome
Contains enzymes that break down old
molecules for recycling
Vacuole
Contain water, enzymes, & pigments
Plant cells have one large vacuole that
dominates cell; animal cells have several
small vacuoles
Chloroplasts
 Double membrane
 Location of
photosynthesis
 Found in plant cells
and other autotrophic
one-celled organisms
Mitochondria
Double membrane
Where ATP synthesis occurs
Found in animal and plant cells
Centrioles
 Barrel-shaped
organelle
 Involved in cellular
reproduction
 Found in animal cells
Cytoskeleton and Related Structures
Internal skeleton helps organize structure
and activities of the cell
Cytoskeleton
 Functions in support, cell movement, cell
signaling
 Three-dimensional network of:
1. Microfilaments- cell movement
2. Intermediate filaments- anchor organelles
3. Microtubules- guide movement of
organelles through the cell, allow for
movement of cilia and flagella
 All are composed of protein
Cilia
Short extensions of plasma membrane
Composed of microtubules
Move materials across cell surface, cover
surface
Flagella
Long extensions of cell surface
Composed of microtubules
Move cell through the environment