http://www.visualsunlimited.com
Biology Review
Cell Biology
Note
Much of the text material is from, “Essential Biology with
Physiology” by Neil A. Campbell, Jane B. Reece, and Eric J.
Simon (2004 and 2008). I don’t claim authorship. Other
sources are noted when they are used.
2
Outline
•
Cell theory
• Microscopy
• Cells and their components
3
Cell Theory
4
Cell Theory
•
Cells were first described in 1665 by the British scientist, Robert Hooke,
from microscopic examination of thin slices of cork from Mediterranean
oak trees.
•
Over the next two centuries, cells have been found in all organisms that
were examined.
•
The accumulation of evidence led to cell theory: all organisms are composed of cells.
•
Cell theory was later expanded to encompass observations that cells
arise from previously existing cells—that is, cells do not spontaneously
form.
5
Cellular Structure of Cork
http://www.isa.utl.pt
http://farm1.static.flickr.com
Robert Hooke’s drawing.
http://cache.eb.com
6
Microscopy
7
Microscopic World of Cells
•
Every cell in a living organism is intricate and extremely complex.
•
The most elaborate machine, if it were reduced to the size of a cell,
would seem simple in comparison.
•
Cells must be very small for materials to to move in and out to meet
their metabolic needs.
8
Microscopic World of Cells (continued)
•
Organisms are single-cellular (bacteria, archaea, and some protista) or multi-cellular (other protista, fungi, plants, and animals).
•
The human body has many trillions of cells that work cooperatively
to perform their functions, which is a focus of this course on human
physiology.
9
Light Microscope
•
The light microscope was invented during the Renaissance, about 400
years ago.
•
Visible light passes through a specimen—the lens enlarges the image
and projects it onto the retina of the human eye, film camera, or electronic sensing device.
•
Modern light microscopes have compound lenses to reduce chromatic
(color) aberration and spherical aberration to improve the quality of the
viewed image.
10
http://www.meijitechno.com
Light Microscope (continued)
A modern lab and classroom version.
11
Magnification and Resolving Power
•
Two key aspects of microscopes are their magnification and resolving
power.
•
Magnification is the increase in an object’s apparent size compared to
its actual size.
•
Resolving power is the ability to show two or more objects as distinct
entities.
•
Due to limitations in resolving power (about 0.2 m), the maximum
useful magnification of a light microscope ranges between X400 and
X1000.
12
http://www.uwash.edu
Light Micrograph
Red blood cells and a stained white blood cell.
13
Another Light Micrograph
http://www.emsdiasum.com
Coronal cross section of a rat brain under low-power
magnification (about X10).
14
Do you have experience using a light microscope? If so,
what did you discover?
15
Electron Microscope
•
Electron microscopes use electron beams rather than light to access
a very small world.
•
Resolving power is much higher than for light microscopes, allowing
for much higher useful magnifications.
•
Electron micrographs can be produced at magnifications of X100,000
or higher.
•
The study of cells advanced rapidly when electron microscopes were
developed in the 1950s.
16
http://www.usaft.af.mil
Electron Microscope (continued)
A somewhat dated, electron microscopy laboratory.
17
Types of Electron Microscopes
•
Scanning electron microscopes are used to study the surfaces of
cells.
•
Transmission electron microscopes are used to explore the internal structures of cells.
•
Electron microscopes are used with prepared (dead) specimens,
while light microscopes are suited for either live or prepared specimens.
18
http://www.allergy-details.com
Electron Micrograph
A collection of pollens.
19
http:www3.niaid.nih.gov
Another Electron Micrograph
Escherichia coli (E. coli).
20
Cells and Their Components
http://www.steve.gb.com
21
http://www.visualsunlimited.com
http://www.visualsunlimited.com
Prokaryotic and Eukaryotic Cells
Prokaryotic cell
Bacteria and archaea
(bacterium shown)
Not to scale: A prokaryotic cell is
about 1000 times smaller in volume
than a eukaryotic cell.
Eukaryotic cell
Plants, animals, and fungi
(animal cell shown)
22
Cell Comparisons
•
Prokaryotic cells first appeared about 3.5 billion years ago; eukaryotic cells appeared about 1.8 billion years later.
•
Eukaryotic cells are much larger—they are about ten times the diameter of prokaryotic cells and their volume is even greater (by about
a thousand times).
•
The DNA in eukaryotic cells is in the nucleus surrounded by a membrane, while the DNA in prokaryotic cells is in an unenclosed central
region.
•
Prokaryotic and eukaryotic use different processes for copying their
DNA (replication versus transcription).
23
How do some types of prokaryotic cells affect
our lives?
24
Cell Comparisons (continued)
•
Eukaryotic cells have several types of membrane-enclosed organelles with specialized functions, while prokaryotic cells have far
fewer.
•
Eukaryotic cells use aerobic respiration and anaerobic respiration for
chemical energy production, while prokaryotic cells only use anaerobic respiration.
Organelle = a compartment within a cell that has a specialized
function, for example, ribosome, lysosome, Golgi apparatus, or
mitochondrion.
(http://sis.nlm.nih.gov/enviro/iupacglossary/glossaryo.html)
Most of these membrane-enclosed organelles, as we will discuss,
are unique to eukaryotic cells.
25
Some Animal Cell Types
3. Adipose
1. Blood
4. Intestinal
2. Purkinje (cerebellum)
Images 1 and 2, http://upload.wikimedia.org
Image 3, http://www.proteinpower.com
Image 4, http://focus.harvard.edu
26
Components of Eukaryotic Cells
Component
Plasma membrane
Nucleus
Chromosomes
Cytoplasm
Ribosomes
Endoplasmic reticulum
Golgi apparatus
Lysosomes
Mitochondria
Cytoskeleton
Vacuoles and vesicles
Flagella and cilia
Centrioles
Cell wall
Chloroplasts
Central vacuole
Animal cell
Plant cell
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x•
x
x
x
----
Rare
x
x
x
Rare
x
x
x
x
27
Plasma Membrane
•
A plasma membrane separates the intracellular space of a cell from
its surrounding extracellular space.
•
The plasma membrane defines the cell boundary.
•
The membrane is a double layer (bilayer) of phospholipid molecules.
Computer generated graphic
http://www.sci-design.com
28
Plasma Membrane (continued)
•
The glycerol heads with their attached phosphate groups orient toward
the fluids in the intracellular and extracellular spaces because they are
hydrophilic.
•
The two lipid tails attached to the glycerol molecule orient inward since
they are hydrophobic.
•
Phospholipid membranes are self-organizing because of their hydrophilic
and hydrophobic properties.
29
Plasma Membrane (continued)
•
Chemical receptors and other protein molecules are embedded in
the plasma membrane.
•
The plasma membrane is not a static structure of molecules fixed in
place.
•
Phospholipids and most proteins are drift about in the plane of the
membrane, much like icebergs floating in the high-latitude oceans.
•
Therefore, the plasma membrane is described as a fluid mosaic.
30
Selective Permeability, Membrane Transport
•
The plasma membrane and membranes that enclose organelles are
selectively permeable.
•
The membranes allow some substances to pass while blocking others
from entering a cell.
•
Some substances can diffuse across the plasma membrane including
O2, CO2, and some nutrients.
•
The passage of other substances requires the use of transport proteins
through the plasma membrane.
•
Glucose, a major source for cellular energy, is attached to a transport
protein to enter cells.
31
Nucleus
•
The nucleus of a cell has the genetic code of life in the form of DNA.
•
The nucleus is enclosed in a double membrane known as the nuclear
envelope—it is similar in molecular structure to the cell’s plasma membrane.
•
Pores in the nuclear envelope permit the passage of material between
the nucleus and cytoplasm (messenger RNA and components of ribosomes).
Electron micrograph
http:.//www.science.org.au
32
Nucleus (continued)
•
DNA molecules and proteins in the nucleus form long fibers called
chromatin.
•
Each fiber makes-up one chromosome—humans usually have 46
chromosomes in somatic cells of their bodies.
•
A ball-like mass in the nucleus, called the nucleolus, produces the
components of ribosomes.
33
Cytoplasm
•
The cytoplasm is the region between the cell’s plasma membrane and
its nucleus.
•
It contains organelles suspended in a fluid known as cytosol.
•
Each type of organelle performs specific functions, as we will discuss.
•
Most organelles in eukaryotic cells have their own phospholipid membranes.
Electron micrograph
http://www.danforthcenter.org
34
Ribosomes
•
Ribosomes are found in the cytoplasm, and often in close proximity
to the cell nucleus.
•
These organelles synthesize the polypeptides that make up proteins
from amino acids.
Computer generated graphic
http://rna.ucsc.edu
35
Ribosomes (continued)
•
The genetic information of DNA is transferred via messenger RNA
(mRNA) to the ribosomes to provide instructions for the synthesis
of polypeptides that form proteins.
•
Some ribosomes synthesize proteins for use in the cytoplasm or
plasma membrane.
•
Other ribosomes make proteins for secretion by the cell for use by
other cells.
36
Endoplasmic Reticulum
•
The endoplasmic reticulum (ER) synthesizes many types of biological
molecules.
•
ER is made-up of an elaborate system of tubes and sacs in the cytoplasm.
•
The two types of endoplasmic reticulum are rough ER and smooth ER.
Electron micrograph
http://www.bu.edu
37
Rough ER
•
Rough ER has the appearance of roughness due to the ribosomes
that stud its surface.
•
Rough ER produces proteins found in the plasma membranes of
cells and organelles, and for secretion by the cell.
•
Cells that secrete substantial amounts of proteins, such as salivary
glands of the mouth, are rich in rough ER.
•
Products are sent to other locations in the cell in membrane covered
packages called transport vesicles—the vesicles bud and separate
from the ER.
38
Smooth ER
•
Smooth ER lacks the ribosomes that stud the surface of rough ER.
•
One function is the synthesis of steroids in the testes, ovaries, and
adrenal glands.
39
Smooth ER (continued)
•
Smooth ER in liver cells (known as hepatocytes) produce enzymes
that detoxify drugs and poisons in the blood.
•
The amount of smooth ER increases (up-regulates) with exposure
to certain drugs.
•
The body increases its tolerance to the drug, which requires higher
dosages to achieve the same physiological effect.
•
One hallmark of addiction is increased drug tolerance (along with a
psychological component).
40
Golgi Apparatus
•
The Golgi apparatus works with the endoplasmic reticulum to refine,
store, and distribute molecules synthesized by the cell.
•
Products synthesized in the ER reach the Golgi apparatus via transport vesicles.
•
Enzymes in the Golgi apparatus modify many of the products synthesized by the ER.
Electron micrograph
http://www.bu.edu
41
Golgi Apparatus (continued)
•
The Golgi apparatus is named for its discoverer, Camillo Golgi.
•
They work with the ER to refine, store, and distribute chemical products.
•
The Golgi apparatus tags proteins with addresses of their destinations
within the cell.
•
Vesicles that bud from the Golgi apparatus distribute products to other
organelles.
•
Other products are sent to the plasma membrane for secretion by the cell.
42
Lysosomes
•
Lysosomes are membrane-enclosed sacs of enzymes for digestion to
prevent self-destruction of the cell.
•
The enzymes breakdown macromolecules including proteins, glycogen,
fats, and nucleic acids.
•
Molecules from this process nourish the cell.
Electron micrograph
http://biology.unm.edu
43
Lysosomes (continued)
•
Other lysosomes function as recycling centers by engulfing and digesting damaged organelles and making some of these molecules available
for the synthesis of new organelles.
•
Lysosomes in white blood cells ingest bacteria—their enzymes destroy
bacterial cell walls.
•
Another type of lysosome destroys the webbing that joins the fingers in
human embryos.
44
Mitochondria
•
Mitochondria perform cellular respiration to harvest chemical energy
for cellular work.
•
The processes, known as the Krebs or citric acid cycle and the electron transport chain, are aerobic since as require a continuing supply
of oxygen molecules.
•
Sugars and other types of food molecules are converted to a form of
energy known as ATP.
Electron micrograph
http://is2.okcupid.com
45
Mitochondria (continued)
•
The inner membrane of a mitochondrion contains enzymes and other
molecules for cellular respiration.
•
The membrane has many folds to increase its surface area and maximize ATP output.
•
Mitochondria may have been invaders in the earliest eukaryotic cells.
•
Now, a symbiotic relationship exists between mitochondria and eukaryotic cells.
Mitochondria—plural; mitochondrion—singular.
Symbiotic = an interaction between dissimilar organisms,
especially when they benefit each other.
46
Mitochondria (continued)
•
Mitochondrial DNA is passed through maternal lineage from mother to
daughter.
•
The DNA maintains remarkable stability from generation to generation.
•
These aspects enable mitochondrial DNA to be used in tracing population groups 10,000 years or more back in time as they have migrated.
47
Cytoskeleton
•
Microtubules of several different proteins form a network of fibers
known as the cytoskeleton.
•
The cytoskeleton is found in the cytoplasm.
•
It provides structural support for a cell and a means for specialized
movements.
Color enhanced electron micrograph
http://www.bcsb.org
48
Cytoskeleton (continued)
•
Microtubules also hold the organelles in place in the cytoplasm and
guide the movement of vesicles.
•
Other microtubules guide the movement of individual chromosomes
when cells divide.
49
Cytoskeleton (continued)
•
Unlike a bony skeleton, a cytoskeleton can be rapidly dismantled in
one location to reform in a new location of the cell.
•
This process occurs through the removal and replacement of its protein units.
•
It contributes to the crawling motion of single-cell amoeba and movement of white blood cells.
50
Vacuoles and Vesicles
•
Vacuoles and vesicles are membrane enclosed sacs that bud from
a cell’s plasma membrane, endoplasmic reticulum, and Golgi apparatus.
•
They differ in their functions—for example, vacuoles in the plasma
membrane of a cell engulf food molecules for transportation to the
lysosomes.
In neurons, vacuoles known as synaptic
vesicles store neurotransmitters to communicate with other neurons, muscles,
and glands.
Electron micrograph
http://www.pharmacology.com
51
Flagella
•
Some eukaryotic cells have appendages and specialized microtubules that enable movement.
•
Flagella (singular: flagellum) propel cells by an undulating, whip-like
motion.
•
Flagella usually occur singly—for example, in sperm that must travel
the length of the female reproductive tract to fertilize an egg released
by an ovary.
Human sperm,
Electron micrograph
http://www2.sunysuffolck.edu
52
Cilia
•
Cilia, which are usually shorter and more numerous than flagella, produce motion through rhythmic back-and-forth movements (think of the
rows of oars on an ancient galley ship).
•
The cilia of cells in the oviducts (fallopian tubes) can sweep a fertilized
egg along the reproductive path for implantation in the uterus.
http://www.gibinquirer.net
Electron micrograph
http://www.talbotcentral.ucr.edu
53
Cilia (continued)
•
Tobacco smoke can damage or destroy the cilia in the bronchial
tubes, which interferes with the body’s normal means for removing
pollutants from the lungs.
•
Smoker’s cough is the body’s compensatory attempt to cleanse the
respiratory system.
54
Extracellular Matrix
•
Most animal cells secrete a thick, sticky substance called extracellular matrix.
•
It helps hold cells together in tissues, and provides protective and
supportive functions.
55
Cell Junctions
•
The cells in many animal tissues are connected by cell junctions.
•
Tight junctions bind cells to form a leak-proof sheet of tissue such as
in the small intestine and large intestine to prevent fluids from leaking
into the abdominal cavity.
•
Anchoring junctions bind cells together while allowing some molecules
to pass among the spaces between them.
•
Communicating junctions contain channels to permit water and other
small molecules to flow among neighboring cells.
56
Centrioles
•
Centrioles are can-shaped structures of microtubules in the cytoplasm that support cell division.
•
We will cover their functions when we discuss mitosis and meiosis
in the next lecture.
Computer generated graphic
http://www.sparkleberrysprings.com
57
Can you describe the components of an animal eukaryotic
cell and their basic functions?
58