Name __________________________________ Test Date___Oct 1st ______
CELL STRUCTURE AND FUNCTION
I. DISCOVERY OF CELLS
A. History of Microscopes
The invention and development of the microscope in the 1600’s enabled
scientists to discover and study cells - basic unit of structure and function in
in all living things
1. Anton von Leeuwenhoek – was the first to try stacking several
lenses_ together to view tiny objects. He looked at pond water_
through his lenses and became known as the first scientist to describe
living cells as seen through a microscope.
2. Robert Hooke - In 1665, he used a _microscope_ to examine thin
slices of cork and then described what he saw and called them _cells__.
He chose the name “cells” because the chambers he saw reminded him
of the rooms in a monastery which were called cells.
B. Cell Theory
Nearly a century after Hooke’s findings, several other scientists discoveries led
to the formation of the _cell theory_.
1. Matthias Schleiden (botanist) & Theodor Schwann (zoologist) –
together they reached the conclusion that _all living things__; from oak
trees to violets, and from worms to tigers; were composed of cells_.
2. Rudolf Virchow – elaborated on Schleiden & Schwann’s proposal and
added “omnia cellula e cellula” : all cells come from cells_
These discoveries, confirmed by other biologists, are summarized in the
cell theory, a fundamental concept in Biology…..
The cell theory states that:
a. All organisms are ____composed of cells______
b. Cells are the smallest working units of life.
c. All cells come from ____pre-existing cells________
II. TYPES OF CELLS
Living organisms are made of either _prokaryotic__ or _eukaryotic_cells –
the two major kinds of cells which can be distinguished by _structural
organization__
A. Types of Prokaryotic Cells – (All Uni-Celled)
1. Eubacteria – have shapes such as cocci (round), bacilli (rod), spirilla
(spiral); ex. include E.coli,Streptococcus. Have a cell wall made of
___peptidoglycan__.
2. Archaebacteria – “ancient” bacteria; live in extreme environments (salty,
hot, acidic); ex. methanogens. Have a cell wall made of _other
polysaccharides_.
B. Types of Eukaryotic Cells – (Uni or Multi-celled)
1. Protista – ex. Amoeba, Euglena, Paramecium
2. Fungi - ex. Penicillium, yeasts, molds, mushrooms. Have a cell wall made
of ___chitin___.
3. Plants – ex. Mosses, ferns, flowering plants. Have a cell wall made of
__cellulose__.
4. Animals – ex. Sponges, worms, snails, insects, mammals. No _cell wall_.
III. CELL BOUNDARIES
A. Cell Wall
Cell Walls are the outer most boundary in _bacteria_, _plants_, and
_fungi_. They are not found in __animal cells_____. The primary function
of the cell wall is to _provide support and structure__.
B. Cell Membrane
Every cell is surrounded by the cell membrane. Its function is to maintain
homeostasis__ in the cell by separating and protecting the cell from its
environment. It also regulates exchange with the environment. The cell
membrane is also called the __plasma membrane_. It is _selectively
permeable_ which means that it allows some substances to pass through;
acts a barrier to others.
IV. INSIDE A EUKARYOTIC CELL
Within the cell membrane, the cell is composed of the nucleus with its
corresponding structures, the _nucleolus_ and _nuclear envelope__.
The cytoplasm includes all the rest of the material inside the cell membrane.
The cytoplasm includes two components:
Cytosol – a semi-gelatinous substance that contains dissolved nutrients and
wastes
Organelles – means “little organs”. Each has a specific role in the overall
function of the cell.
Structure
Plant,
Prokaryotic
Animal
Eukaryotic
or
or Both?
Both
General Characteristics and Functions
Control center of the cell. Contains genes
that control cell activities. Contains most of
the cell's DNA, which is stored as chromatin
(DNA wrapped in protein).
Nucleus
Eukaryotic
Both
Small, dense region in the nucleus. Involved
in the synthesis of ribosomes which are
important in protein synthesis. "Little
nucleus"
Nucleolus
Eukaryotic
Both
Double membrane, each consisting of a
phospholipid bilayer. Perforated by nuclear
pores which allow RNA molecules to leave
the nucleus.
Nuclear
Envelope
Eukaryotic
Ribosomes Both
Both
Both
Constructed in the nucleolus, these tiny,
non-membrane bound organelles are
located in prokaryotic and eukaryotic cells.
These organelles function in protein
synthesis, and can be either free
(suspended in the cytosol), or bound
(attached to rough ER). Free ribosomes aid
in the production of proteins that will stay in
the cell, and bound ribosomes aid in the
production of proteins that will be
transported out of the cell.
Rough
Endoplasmi Eukaryotic
c Reticulum
Both
Extensive network continuous with the
nuclear envelope. Appear "rough" due to
the presence of ribosomes all along the
membrane. Function of the rough ER is to
modify and transport proteins. Most of these
proteins are packaged into vesicles (pieces
of the membrane that act as a protective
sac) and shuttled to the Golgi Apparatus.
Similar to rough ER in structure, except that
it lacks ribosomes. Smooth ER functions in
the synthesis of lipids (steroids), breaks
down glycogen, and detoxifies drugs, and
poisons. Smooth ER (esp. in muscle and
liver cells) also stores Ca+ ions that are
used for muscle contraction.
Smooth
Endoplasmi Eukaryotic
c Reticulum
Both
Flattened, round sacs with the appearance
of pita bread. Golgi is sometimes called the
"UPS man" because it functions in
modifying, storing, and re-routing the
products of the ER. Golgi is packed with
enzymes that aid in modifying the products
before they are shipped out by way of a
transport vesicle into the cytosol.
Golgi
Apparatus
Lysosome
Eukaryotic
Eukaryotic
Both
Membrane bound bag of hydrolytic enzymes
that help to digest macromolecules, as well
as recycle used cell components.
Lysosomes are made from parts of the ER
(enzymes) and Golgi apparatus
(phospholipid membrane). Also used as a
Animal defense against bacteria and viruses.
??
Sacs that may be used as storage for ions,
molecules, water, or wastes. Plants have a
very large central vacuole for maximum
water storage.
Vacuole
Eukaryotic
Both
Double membrane structure that has its own
proteins embedded in phospholipid bilayers,
as well as its own DNA. This DNA programs
a small portion of the mitochondria's protein
synthesis; however, a majority of their
proteins are synthesized according to the
directions from nuclear DNA. Has inner
folds called cristae. Uses glucose to
manufacture energy in the form of ATP.
Mitochondri
a
Eukaryotic
Both
Chloroplast
s
Eukaryotic
Plant
Found in plant cells. Bound by a double
membrane that helps partition its contents
from the cytosol. Contain the green pigment
chlorophyll which is used to harvest energy
from the sun to produce glucose
(photosynthesis). Also contains its own
DNA. The three functional compartments of
the chloroplast are the intermembrane
space, the thylakoid, and the stroma.
Found only in animal cells. Made up of
bundles of microtubules that play a role in
cell division. Centrioles help to organize the
assembly of the spindle fibers for cell
division. This organelle is part of the
cytoskeleton.
Centrioles
Eukaryotic
Animal
Network of fibers throughout the cytoplasm
that forms a framework for
support/movement. Enables the cell to
maintain or change shape and anchors the
organelles. Provide motility for some cells
in the form of cilia or flagella. There are
three types of fibers that make up the
cytoskeleton: microtubules (thickest),
microfilaments (thinnest), and intermediate
filaments (intermediate).
Cytoskeleton
Eukaryotic
Both
V. VIRUSES (pg 478-483)
Viruses are not considered alive because they do not exhibit any of the
characteristics of life; rather, they are thought to be the bridge between the
non-living and living. Because of this, they are not included in a kingdom and
should not be referred to as an organism. The correct term for describing a
virus is a particle. A viral particle is simply genetic information enclosed in a
protein coat. A virus lacks enzymes for metabolism and ribosomes for
making proteins. It requires a host cell to reproduce.
A. Structure of Viruses
1. Genetic Material – The genome of a virus may be either DNA or RNA,
but never both. Viral genes carry information for reproduction only – a
virus carries out no other activities.
2. Protein Coat – The DNA or RNA is surrounded by a protein coat called
a capsid. The shape of the virus is important in the
infection process. Some viruses are enclosed by a protective protein
envelope.
Viruses are classified by shape, type of genetic info (DNA or RNA), enveloped or no
envelope (outer lipid membrane), and type of cell it infects.
RNA
capsid
DNA
RNA
capsid
capsid
proteins
tail
sheath
tail fiber
surface
proteins
envelope
II. Viral Replication
B. Viral Cycles
There are three initial steps that are common to all viral infections:
 Virus attaches to the cell membrane of the host cell
 Virus penetrates, or fuses with, the host cell’s cell membrane
 Virus releases its genetic information (DNA or RNA) into the host cell
Once inside the host cell, there are two ways that a virus can take over
and use the host to reproduce. These two mechanisms are:
1. Lytic infection – Upon release of genetic material into host cell, virus
destroys host cell DNA, and then reprograms the host cell to copy viral
genes and make viral proteins (transcription and translation), using all
the enzymes, raw materials, and energy from the host cell. After this
replication, the new viral genes and proteins are assembled & the new
virus mature. Finally, the new viruses lyse the host cell and are
released to attack other cells. This viral cycle is virulent and
symptomatic, because it results in death of the host cell.
2. Lysogenic infection – In a lysogenic infection, also known as viral
latency, viral genome becomes incorporated into the host cell’s
chromosomes. This incorporated viral DNA is known as a prophage.
This prophage does not interfere with the host cell’s normal activities.
Every time the host cell replicates, the virus is replicated as well. This
virus is asymptomatic and can remain latent (inactive) in the host cell
for many generations. At some point, a lysogenic infection can switch
to a lytic infection and become symptomatic. Example of lysogenic
infections include HIV, Herpes, Chicken pox.