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Chapter 2
Cells
Ch 2.1 – Cell Structure
A. Cell size & shape
1. Directly related to cell function
B. Cell Organization
1. Cell Membrane – protective layer around
outside of all cells
a) flexible
b) controls substances moving into and
out of the cell
Cell
Membrane
2. Cell Wall – structure located around the
outside of the cell membrane in some cells
a) found around cells of plants, algae, fungi
and some bacteria
b) much thicker than cell membrane
and made of cellulose to provide extra
protection
Cell Membrane
Cell Wall
3. Cytoplasm – gelatin like substance
inside the cell membrane
a) Has cytoskeleton – internal structure
to help keep the cell’s shape
b) Contains organelles – tiny structures
each with their own job to help with the
cell’s life processes
Cytoplasm
4. Nucleus – control center of the cell
a) organelle that contains a cell’s
hereditary material (DNA)
b) DNA provides instructions for everything
the cell does
Nucleus
C. Two types of cells
1. Prokaryotic cells – simpler than most; lack
a nucleus and organelles
a) example: bacteria cells
2. Eukaryotic cells – contain a nucleus and
organelles
a) example: plant & animal cells
D. Other Organelles
1. Energy processing organelles
a) Chloroplasts - green organelles in
plant and algae cells that make food;
where photosynthesis takes place
Chloroplasts
b) Mitochondria – the powerhouse of the
cell; release energy from food; found in
plant and animal cells
Mitochondria
2. Manufacturing organelles
a) Ribosomes – make proteins
-some float freely in the cytoplasm, others
are attached to the endoplasmic reticulum
Ribosomes
(Dots)
3. Transporting organelles
a) Endoplasmic Reticulum (ER) - series of
membranes to move substances around the
cell
-Rough ER – ribosomes attached
-Smooth ER – no ribosomes attached
ER
(channels)
4. Packaging organelles
a) Golgi bodies – package substances into
vesicles to move things around the cell or out
of it to other parts of the body
Golgi Bodies
(channels)
5. Storage organelles
a) Vacuoles – temporary storage places for
food, water and waste
- large in plant cells
- small in animal cells
Vacuoles
6. Recycling organelles
a) Lysosomes – break down cell waste
products
Lysosomes
E. Organization of Living Things
1. All living things are made of cells
2. Cells working together makes a tissue
3. Tissues working together make an organ
4. Organs working together make an organ system
5. Organ systems working together make up an
organism
Ch 2.2 – Viewing Cells
A. Magnifying Cells
1. Early Microscopes – lenses made images
larger but not always clear
a) first microscope made in 1500’s by
reading glass maker who put two
magnifying glass lenses on top of each
other in a tube
b) In the mid-1600’s Antonie van Leeuwenhoek
created a microscope with a glass bead
powerful enough to see tiny creatures in pond
water that he called “beasties”
c) During the late 1600’s microscope
technology improved as scientists used these
inventions to explore the world in a new way
d) In 1665, Robert Hooke was the first person to
discover and coin the term “cells” after
examining a thin slice of cork under his
microscope
e) In the 1830’s Matthias Schleiden determined
that all plants were made of cells
f) Soon after Theodor Schwann concluded that
all animals were made of cells
2. Modern Microscopes – use lenses to bend
light
a) A simple light microscope has one lens
while a compound light microscope has
multiple lenses
b) Magnification – tells how many times an
image has been magnified from its original
size
c) For compound microscopes, power of the
eyepiece multiplied by the power of the
objective lens determines an objects total
magnification
3. Electron Microscopes – more powerful
than lens microscopes
a) use electron beams to produce photographs
or electronic images of objects magnified up to
one million times their actual size
B. Development of the Cell Theory
1. The cell theory resulted from many
scientists’ observations and conclusions of
microscope studies
2. It states:
-The basic unit of organization is the cell
-All organisms are composed of one or more cells
-New cells come from old cells through cell division
Ch 2.3 - Viruses
A. Virus – a nonliving strand of hereditary
material surrounded by a protein coating
B. Virus multiplication – viruses can make
copies of themselves only inside a living host cell
1. Active virus – immediately makes the host
cell create new viruses which kills the host
cell when it bursts
a) causes illness soon after an organisms
body is infected
b) ex: the common cold & influenza
2. Latent virus – hides inside the host cell
for a period of time before it starts creating
new viruses and destroying it
a) The virus’ hereditary material becomes
part of the host cell’s hereditary material
so that as the host cell divides an
organism’s body begins to have more
cells that contain the viral DNA
b) Latent viruses eventually become
active viruses and then destroy the host
cells
c) ex: HIV virus & herpes viruses
C. Virus effects on organisms
1. Most infect only specific kinds of cells
2. Often carried to the host through the air
3. The virus and host must “fit” together
exactly to begin a viral infection
4. Bacteriophages – viruses that attach to
infect bacteria cells
D. Fighting Viruses
1. Vaccines – made of weakened virus
particles which allow cells to fight off viruses
before they attack and take over
2. Treating viral diseases
a) Antibiotics are not effective treatments for
viral infections (they fight bacterial infections)
b) Antiviral drugs can treat the symptoms of a
viral illness but not the disease
c) Once the bodies immune system combats
the viruses to reverse the illness, the cells
remember this so that the same virus cannot
be contracted twice
E. Gene Therapy – researchers studying good
uses for viruses to replace defective
hereditary material with normal hereditary
material