First lecture

By
Dr/ Yasmin Heikal
General Biological Sciences 1

An introduction to biology
&
A Tour of the Cell
Lecture 1:

 From Greek words ~~~ bios means life
logos means knowledge
 Study of living organism ( the Science of life )
 is the science that deals with the study of life
processes of living organisms and the search for
solutions to problems associated with them.
 Biologists: use the scientific method to solve
biological problems
Biology…..

Scientific investigation
Identify problem
Observed situation
Identify variable
State problem
Forming hypothesis
-make general statement about relation
between manipulated variable and responding
variable
Plan the experiment

conduct the
experiment
Collecting data
Analysis and interpreting data
Forming conclusion
Hypothesis is accepted if result support the
hypothesis while rejected if the result do not
support the hypothesis
Writing a report

The study of Biology is important because it helps
us to understand the hows and whys of living
systems
Modern biology is the study of organized
knowledge contributed by many biologists from
different generations.
Biology is divided into many branches and
specialized fields that correlate and overlap with one
another.
Living things exhibit unique characteristics that
make them different from non-living things.

Characteristics of living organisms
1) Nutrition (able to use energy)
2) Respiration/Homeostasis
3) Excretion
4) Growth (GROW AND DEVELOP)
POOP

5) Reproduction (HAVE DNA)
6) Movement/Locomotion
7) Sensitivity/Adaptability
(CHANGE TO FIT THEIR
ENVIRONMENT(ADAPT) and
RESPOND TO A STIMULUS)

These 7 observable characteristics can be remembered
using the mnemonic MRS GREN
Hi, my name is
MRS GREN
M ovement
R espire
S ense
G rowth
R eproduction
E xcretion
N utrition

Divisions of Biology
Two major divisions are:
a. Botany- the study of plants or flora
b. Zoology- the study of animals or fauna

This term we will study :
1.Cytology (Cell Ultra- structure)
2.Physiology
3.Transmission Genetics
4.Microbiology

1. Cytology
(Cell Ultra- structure)

The Fundamental Units of Life
 Cells: which are as fundamental to the living systems of
biology as the atom is to chemistry and the organisms basic
unit of structure and function.
 All organisms are made of cells. In the hierarchy of
biological organization, the cell is the simplest collection of
matter that can be alive.
 Many forms of life exist as single celled organisms. More
complex organisms, including plants and animals, are
multicellular; their bodies are cooperatives of many kinds of
specialized cells that could not survive for long on their own.
Cells Tissues Organs Systems Body

Microscopy
 Biologists use microscopes and the tools of
biochemistry to study cells.
 The discovery and early study of cells progressed
with the invention of microscopes in 1590 and their
refinement during
the 1600s.
 Cell walls were first seen by Robert Hooke in
1665 as he looked through a microscope at dead cells
from the bark of an oak tree.
 Antoni van Leeuwenhoek in 1674 as he was the
first to use microscope; visualize living cells and
discovered microorganisms.

1. Light microscope (LM), visible light is passed through
the specimen and then through glass lenses. The lenses
refract (bend) the light in such a way that the image of the
specimen is magnified as it is projected into the eye or into a
camera.
2. Electron microscope (EM), In the 1950s, the electron
microscope was introduced to biology. Rather than light,
the electron microscope focuses a beam of electrons
through the specimen or onto its surface. Modern electron
microscopes can theoretically achieve a resolution of about
0.002 nm, though in practice they usually cannot resolve
structures smaller than about 2 nm across. Still, this is a
hundredfold improvement over the standard light
microscope.
Types of
Microscope

1. Magnification is the ratio of an objects image size to
its real size. Light microscopes can magnify effectively to about
1,000 times the actual size of the specimen; at greater
magnifications, additional details cannot be seen clearly.
2. Resolution is a measure of the clarity of the image; it is
the minimum distance two points can be separated and still be
distinguished as two points.
For example, what appears to the unaided eye as one star in
the sky may be resolved as twin stars with a telescope, which
has a higher resolving ability than the eye.
Three important parameters in microscopy

Similarly, using standard techniques, the light microscope
cannot resolve detail finer than about 0.2 micrometer ,
or 200 nanometers (nm), regardless of the magnification.
3. Contrast, accentuates differences in parts of the
sample. Improvements in light microscopy have included
new methods for enhancing contrast, such as staining or
labeling cell components to stand out visually.

Types of Electron microscope (EM)
1. Scanning electron microscope
(SEM) is the electron beam scans
the surface of the sample, usually
coated with a thin lm of gold. The
beam excites electrons on the
surface, and these secondary
electrons are detected by a device
that translates the pattern of
electrons into an electronic signal
to a video screen. The result is an
image of the specimens surface that
appears three-dimensional.

2. Transmission electron
microscope (TEM) is used to
study the internal structure of
cells. The TEM aims an electron
beam through a very thin section
of the specimen, similar to the way
a light microscope transmits light
through a slide. The specimen has
been stained with atoms of heavy
metals, which attach to certain
cellular structures, thus enhancing
the electron density of some parts
of the cell more than others.

What are the cells?
Both living and non-living things are composed of molecules
made from chemical elements such as Carbon, Hydrogen,
Oxygen, and Nitrogen. The organization of these molecules
into cells is one feature that distinguishes living things from
all other matter.
The cell is the smallest unit of matter that can carry on all the
processes of life.
Cell Theory consists of three principles:
a. All living things are composed of one or more cells.
b. Cells are the basic units of structure and function
in an organism.
c. Cells come only from the replication of existing cells.

CELL DIVERSITY: Not all cells are alike. Even cells within
the same organism show enormous diversity in size, shape, and
internal organization. Your body contains around 1013 to 1014
cells of around 300 different cell types.

CELL SIZE: Most cells are small for two main reasons:
cell’s nucleus and Cells have large surface area-to-volume
ratio. A group of small cells has a relatively larger surface
area than a single large cell of the same volume.

CELL SHAPE: Cells come in a variety of shapes –
depending on their function: The neurones from your toes
to your head are long and thin; Blood cells are rounded
disks, so that they can flow smoothly.
INTERNAL ORGANIZATION Cells contain a variety of
internal structures called organelles. An organelle is a cell
component that performs a specific function in that
cell.
Cells are of two distinct types: prokaryotic and
eukaryotic.

 Organisms of the domains Bacteria and Archaea consist of
prokaryotic cells. Protists, fungi, animals, and plants all
consist of eukaryotic cells.
ALL cells (PROKARYOTIC ,EUKARYOTIC) have
several basic features in common:
1-all bounded by membrane (plasma membrane).
2-all have genes made of DNA.
3-all contain ribosome's tiny structures which made protein.
Prokaryotes vs. Eukaryotes

Plant Cell
Nuclear envelope
Ribosome (free)
Ribosome (attached)
Mitochondrion
Golgi apparatus
Vacuole
Nucleolus
Nucleus
Smooth
endoplasmic
reticulum
Rough endoplasmic
reticulum
Cell wall
Cell membrane
Chloroplast

Animal Cell
Smooth endoplasmic
reticulum
Ribosome (free)
Ribosome (attached)
Golgi apparatus
Mitochondrion
Rough
endoplasmic
reticulum
Cell membrane
Nucleus
Nuclear envelope
Nucleolus
Centrioles

A Panoramic View of the
Eukaryotic Cell

Cell wall is an extracellular structure of plant cells that
distinguishes them from animal cells.
The wall functions: protects the plant cell, maintains its
shape, and prevents excessive uptake of water. On the
level of the whole plant, the strong walls of specialized cells
hold the plant up against the force of gravity.
Plant cell walls are much thicker than the plasma membrane,
ranging from 0.1 to several micrometers.
The chemical composition of the wall varies from species to
species and even from one cell type to another in the same
plant, but the basic design of the wall is consistent.
Cell Wall:
Supporter and protector

Microfibrils made of the polysaccharide cellulose which
are secreted to the extracellular space, where they become
embedded in a matrix of other polysaccharides and proteins.
A young plant cell first secretes a relatively thin and flexible
wall called the primary cell wall. Between primary walls of
adjacent cells is the middle lamella, a thin layer rich in sticky
polysaccharides called pectins. The middle lamella glues
adjacent cells together.
When the cell matures and stops growing, it strengthens its
wall. Some plant cells add a secondary cell wall between the
plasma membrane and the primary wall. The secondary
wall (lignified), often deposited in several laminated layers,
has a strong and durable matrix that affords the cell protection
and support. Wood, for example, consists mainly of secondary
walls.

Plasmodesmata:
Cell Junctions
Plant cell walls are usually perforated by channels between
adjacent cells called plasmodesmata (singular,
plasmodesma; from the Greek desmos, to bind).
It is membrane-lined channels filled with cytoplasm.
Cytosol passes through the plasmodesmata and joins the
internal chemical environments of adjacent cells.

CYTOPLASM:
Area of Movement
1. Everything within the cell membrane which is not the
nucleus is known as the cytoplasm.
2. Cytosol is the jelly-like mixture in which the other
organelles are suspended, so
Cytosol + Organelles = Cytoplasm.
3. Organelles carry out specific functions within the cell. In
Eukaryotic cells, most organelles are surrounded by a
membrane, but in Prokaryotic cells there are no membrane-
bound organelles.

The nucleus is normally the largest organelle within a
Eukaryotic cell. It contains most of the genes in the cell.
The nuclear envelope encloses the nucleus, separating its
contents from the cytoplasm. It is a double membrane,
perforated by pore structures that are about 100 nm in
diameter. These dimples make it look like a golf ball.
An intricate protein structure called a pore complex lines
each pore and plays an important role in the cell by regulating
the entry and exit of proteins and RNAs, as well as large
complexes of macromolecules.
NUCLEUS:
Control Center

Except at the pores, the nuclear side of the envelope is lined by
the nuclear lamina, a netlike array of protein filaments that
maintains the shape of the nucleus by mechanically
supporting the nuclear envelope.
Within the nucleus, the DNA is organized into discrete units
called chromosomes, structures that carry the genetic infor-
mation.
Each chromosome contains one long DNA molecule associated
with many proteins. Some of the proteins help coil the DNA
molecule of each chromosome, reducing its length and
allowing it to t into the nucleus. The complex of DNA and
proteins making up chromosomes is called chromatin.
Most nuclei contain at least one nucleolus (plural, nucleoli).
The nucleoli are where ribosomes are synthesized. Ribosomes,
you remember, translate mRNA into proteins.

The Endoplasmic Reticulum:
Biosynthetic Factory
The endoplasmic reticulum (ER) is such an extensive
network of membranes that it accounts for more than half the
total membrane in many eukaryotic cells. (The word
endoplasmic means within the cytoplasm, and reticulum is
Latin for little net. )
The ER consists of a network of membranous tubules and sacs
called cisternae (from the Latin cisterna, a reservoir for a
liquid).
The ER membrane separates the internal compartment of the
ER, called the ER lumen (cavity) or cisternal space, from the
cytosol. ER membrane is continuous with the nuclear
envelope.

Types: There are two distinct, though connected, regions of
the ER that differ in structure and function: smooth ER and
rough ER. Smooth ER is so named because its outer surface
lacks ribosome. Rough ER is studded with ribosomes on the
outer surface of the membrane and thus appears rough
through the electron microscope.
Functions of Smooth ER
The processes include synthesis of lipids, metabolism of
carbohydrates, detoxification of drugs and poisons, and
storage of calcium ions.
Functions of Rough ER
1. Many types of cells secrete proteins produced by ribosomes
attached to rough ER. For example, certain pancreatic cells
synthesize the protein insulin in the ER and secrete this
hormone into the bloodstream

2. Rough ER is a membrane factory for the cell; it grows
in place by adding membrane proteins and phospholipids to
its own membrane. As polypeptides destined to be membrane
proteins grow from the ribosomes, they are inserted into the
ER membrane itself and anchored there by their hydrophobic
portions.
3. Like the smooth ER, the rough ER also makes membrane
phospholipids; enzymes built into the ER membrane
assemble phospholipids from precursors in the cytosol. The
ER membrane expands and portions of it are transferred in
the form of transport vesicles to other components of the
endomembrane system.

The Golgi Apparatus:
Shipping and Receiving Center
After leaving the ER, many transport vesicles travel to the
Golgi apparatus. We can think of the Golgi as a
warehouse for receiving, sorting, shipping, and even
some manufacturing. Here, products of the ER, such as
proteins, are modified and stored and then sent to other
destinations. Not surprisingly, the Golgi apparatus is
especially extensive in cells specialized for secretion.
The Golgi apparatus consists of attened membranous sacs
cisternae looking like a stack of pita bread. The membrane of
each cisterna in a stack separates its internal space from the
cytosol.

The two sides of a Golgi stack are referred to as the cis
face and the trans face; these act, respectively, as the
receiving and shipping departments of the Golgi apparatus.
The cis face is usually located near the ER.
Transport vesicles: move material from the ER to the Golgi
apparatus. A vesicle that buds from the ER can add its
membrane and the contents of its lumen to the cis face by
fusing with a Golgi membrane. The Golgi manufactures its
products in stages, with different cisternae containing unique
teams of enzymes.
Secretory vesicles: before a Golgi stack dispatches its
products by budding vesicles from the trans face, it sorts
these products and targets them for various parts of the cell.

LYSOSOMES:
Digestive Compartments
Lysosome is a membranous sac of hydrolytic enzymes that an
animal cell uses to digest (hydrolyze) macromolecules.
Lysosomal enzymes work best in the acidic environment found
in lysosomes. If a lysosome breaks open or leaks its contents,
the released enzymes are not very active because the cytosol
has a neutral pH. However, excessive leakage from a large
number of lysosomes can destroy a cell by self-digestion.
Function: Amoebas and many other protists eat by engulfing
smaller organisms or food particles, a process called
phagocytosis (from the Greek phagein, to eat, and kytos,
vessel, referring here to the cell). The food vacuole formed in
this way then fuses with a lysosome, whose enzymes digest the
food.

Lysosomes also use their hydrolytic enzymes to recycle the cell
own organic material, a process called autophagy. During
autophagy, a damaged organelle or small amount of cytosol
becomes surrounded by a double membrane (of unknown
origin), and a lysosome fuses with the outer membrane of this
vesicles.

Peroxisomes:
Oxidation
The peroxisome is a specialized metabolic compartment
bounded by a single membrane. Peroxisomes contain enzymes
that remove hydrogen atoms from various substrates
and transfer them to oxygen (O2), thus producing
hydrogen peroxide (H2O2) as a by-product (from which the
organelle derives its name). These reactions have many
different functions.
Function: some peroxisomes use oxygen to break fatty
acids down into smaller molecules that are transported to
mitochondria and used as fuel for cellular respiration.
Peroxisomes in the liver detoxify alcohol and other harmful
compounds by transferring hydrogen from the poisons to
oxygen. The H2O2 formed by peroxisomes is itself toxic, but the
organelle also contains an enzyme that converts H2O2 to water.

Vacuoles & vesicles
Vacuoles are large vesicles derived from the endoplasmic
reticulum and Golgi apparatus. Thus, vacuoles are an integral
part of a cell s endomembrane system.
Like all cellular membranes, the vacuolar membrane is
selective in transporting solutes; as a result, the solution
inside a vacuole differs in composition from the cytosol.
Vacuoles perform a variety of functions in different kinds of
cells. Food vacuoles, formed by phagocytosis.
Many freshwater protists have contractile vacuoles that
pump excess water out of the cell, thereby maintaining a
suitable concentration of ions and molecules inside the cell

Mature plant cells generally contain a large central vacuole,
which develops by the coalescence of smaller vacuoles. The
solution inside the central vacuole, called cell sap, is the
plant cell s main repository of inorganic ions, in-cluding
potassium and chloride.
The central vacuole plays a major role in the growth of
plant cells, which enlarge as the vacuole absorbs water,
enabling the cell to become larger with a minimal investment
in new cytoplasm.

Food & water storage
contractile
vacuole
central vacuole
food vacuole

Mitochondria:
Chemical Energy Conversion
The mitochondrion is enclosed by two membranes, each a
phospholipid bilayer with a unique collection of embedded
proteins. The outer membrane is smooth, but the inner
membrane is convoluted, with in foldings called cristae.
The inner membrane divides the mitochondrion into two
internal compartments. The first is the inter-membrane
space, the narrow region between the inner and outer
membranes. The second compartment, the mitochondrial
matrix, is enclosed by the inner membrane.

The matrix contains many different enzymes as well as the
mitochondrial DNA and ribosomes. Enzymes in the matrix
catalyze some of the steps of cellular respiration. Other
proteins that function in respiration, including the enzyme
that makes ATP, are built into the inner membrane.
As highly folded surfaces, the cristae give the inner
mitochondrial membrane a large surface area, thus
enhancing the productivity of cellular respiration. This is
another example of structure fitting function.
Function:
• Make ATP energy from cellular respiration
• sugar + O2  ATP
• fuels the work of life

Chloroplasts:
Capture of Light Energy
The chloroplast is a specialized member of a family of closely
related plant organelles called plastids. One type of plastid,
the amyloplast, is a colorless organelle that stores starch
(amylose), particularly in roots and tubers. Another is the
chromoplast, which has pigments that give fruits and owers
their orange and yellow hues.
Chloroplasts contain the green pigment chlorophyll, along with
enzymes and other molecules that function in the
photosynthetic production of sugar. These lens-shaped
organelles are found in leaves and other green organs of plants
and in algae.

It surrounded by an envelope consisting of two membranes
separated by a very narrow inter-membrane space. The
membranes of the chloroplast divide the chloroplast space into
three compartments: the inter-membrane space, the
stroma, and the thylakoid space.
Inside the chloroplast is another membranous system in the
form of attened, interconnected sacs called thylakoids. In
some regions, thylakoids are stacked like poker chips; each
stack is called a granum (plural, grana). The fluid outside the
thylakoids is the stroma, which contains the chloroplast DNA
and ribosomes as well as many enzymes.
Function:
• make energy from photosynthesis
sunlight +water + CO2 ATP + sugar+ oxygen
• build leaves & roots & fruit out of the sugars

University of Arizona. (2002) The biology project. Retrieved December 1, 2001
from http://www.biology.arizona.edu.
Sullivan, J. & Sullivan, G. (2002). Cells alive! Retrieved December 1, 2001 from
http://www.cellsalive.com.
Fenteany, G. (2002) WWW virtual library of cell biology. Retrieved December 1,
2001 from http://vlib.org/Science/Cell_Biology/.
Konda, S., Rogers, S. & Weber, D. (2001). A Web atlas of cellular structures
using light and confocal microscopy. Retrieved December 1, 2001 from
http://www.itg.uiuc.edu/technology/atlas/.
Childs, G.V. (2002) Cell biology. University of Arkansas Medical Sciences
Department. Retrieved December 1, 2001 from
http://www.cytochemistry.net/Cell-biology/.
References

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Membrane Structure
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