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The Study of the cell
Cell: the smallest unit that can
carry on all of life’s processes
EARLY MICROSCOPES
 Zacharias
Janssen - made 1st
compound microscope
 a Dutch maker of reading
glasses (late 1500’s)
Leeuwenhoek
The first to
observe living
cells ( 1675)
 discovered blood
cells, bacteria and
other single-celled
organisms which
he named
“animacules

Leeuwenhoek’s Microscope
made a simple
microscope (mid
1600’s)
 magnified 270X
 Early microscope
lenses made
images larger but
the image was not
clear

Leeuwenhoek's microscope
A) a screw for adjusting the
height of the object being
examined
B) a metal plate serving as
the body
C) a skewer to impale the
object and rotate it
D) the lens itself, which was
spherical
Discovery of cells
Cells were first seen in 1665 by the
early microscopist Robert Hooke.
 Hooke was examining cork wood, and
noticed that the wood was divided into
little squares or “cells”

Hooke’s Microscope
CELL THEORY

A theory resulting from many scientists’
observations & conclusions
CELL THEORY
1. The basic unit of life is the cell. (Hooke)


In 1665, an English scientist
named Robert Hooke made
an improved microscope and
viewed thin slices of cork
viewing plant cell walls
Hooke named what he saw
"cells"
CELL THEORY
2. All living things are made of 1 or more cells.
Matthias Schleiden (botanist studying plants)
 Theodore Schwann (zoologist studying animals)
stated that all living things were made of
cells

Schwann
Schleiden
CELL THEORY
3. All cells divide & come from old cells. (Virchow)
Virchow
MODERN MICROSCOPES


A microscope is simple or compound depending on
how many lenses it contains
A lens makes an enlarged image & directs light
towards you eye

A simple microscope has one lens

Similar to a magnifying glass

Magnification is the change in
apparent size produced by a
microscope
COMPOUND MICROSCOPE

A compound microscope
has multiple lenses

(eyepiece & objective lenses)
STEREOMICROSCOPE

creates a 3D image
ELECTRON MICROSCOPES



More powerful; some can
magnify up to 1,000,000X
Use a magnetic field in a
vacuum to bend beams of
electrons
Images must be
photographed or produced
electronically
Scanning Electron Microscope (SEM)
Electron microscope image of a spider


produces realistic 3D image
only the surface of
specimen can be observed
Electron microscope image of a fly foot
Transmission Electron Microscope (TEM)


produces 2D image of
thinly sliced specimen
detailed cell parts (only
inside a cell) can be
observed
Scanning Tunneling Microscope (STM)

able to show
arrangement of
atoms
Ocular Lens
Body Tube
Nose Piece
Arm
Objective
Lenses
Stage
Clips
Diaphragm
Stage
Coarse Adj.
Fine Adjustment
Light Source
Base
Skip to Magnification Section
Magnification
To determine your magnification…you just
multiply the ocular lens by the objective lens
 Ocular 10x Objective 40x:10 x 40 = 400

So the object is 400 times “larger”
Objective Lens have
their magnification
written on them.
Ocular lenses usually magnifies by 10x
TOTAL MAGNIFICATION

Powers of the eyepiece (10X) multiplied by
objective lenses determine total magnification.
Using a Microscope
Start on the lowest magnification
 Don’t use the coarse adjustment knob on
high magnification…you’ll break the slide!!!
 Place slide on stage and lock clips
 Adjust light source (if it’s a mirror…don’t
stand in front of it!)
 Use fine adjustment to focus

FROM CELL TO ORGANISM
Cell
The basic unit of life
Tissue
Group of cells working together
Organ
Group of tissues working together
Organ System
Group of organs working together
Organism
Any living thing made of 1 or more cells
Two basic cell types:
Eukaryotes (Eu = true) (kary = nucleus) Organisms
whose cells contain a membrane-bound nucleus and
other organelles.
Prokaryotes (Pro = before) Organisms without a
membrane-bound nucleus (bacteria).
* These cells have genetic information,
but not in a nucleus.
* Evolutionists chose the prefix “pro” because
they believe these evolved before others.
Prokaryotic Cells:
Organisms with prokaryotic cells are called
“prokaryotes”
Prokaryotes have no true nucleus or organelles.
Have a single strand of “looped” DNA
Most prokaryotes are single-celled microscopic
organisms.
Some Example Prokaryotes
Coccusshaped
bacterium
Bacillusshaped
bacterium
Spirillumshaped
bacterium

Eukaryotic Cells:
 Organisms
composed of eukaryotic cells
are called “eukaryotes.”
 Have
a membrane bound nucleus which
contains the cell’s DNA.
 Some eukaryotes are one-celled
organisms.
ALL multicellular organisms are
eukaryotes.
 Have organelles, each of which is
surrounded by (or bound in) a “plasma
membrane.”
Some Example Eukaryotes
Plant leaf cells
Yeast cells
Fertilized
human
egg cell
Nerve cells
Prokaryotes vs. Eukaryotes





Very simple cells(no
organelles)
Always single-celled
No nucleus
DNA arranged in
one single loop
Found only in
kingdom Monera
(bacteria)





Complex cells(
have organelles)
Can be singlecelled or
multicellular
Have a nucleus
DNA arranged in
many separate
strands
Found in Animal,
Plant, Protists, and
Fungi kingdoms

Bacteria

Eukaryotic cell
1.0-10.0
micrometers
 10.0-100.0
micrometers

Prokaryotic bacteria cells
surrounding a eukaryotic cell
(possibly a white blood cell?)
-
Size is limited by ratio between outer surface
area and inner volume.
(Volume increases with the cube of the
side length)
(Surface area increases by the square of
the side length)
- So, as it grows, the surface area is too small
to allow enough materials to pass through the
membrane (water, food, waste).





Remember cells are not really cubes or even
perfect spheres. We use cubes only as examples.
When a side of a cube equals "s",
then the area of only one face is (A = s2).
The total surface area (T.S.A.) of a cubed cell is
(T.S.A. = 6 x s2).
The volume of a cubed cell is (V = s3).
The distance from the center of the cell to each
wall is (Distance = s divided by 2).
** Be able to calculate T.S.A., V, and distance if
given “s” for a cell.
** Note the smallest cell has the largest T.S.A. to V
ratio, and the smallest distance from center to
membrane.
•
•
• EXAMPLES: Nerve
cells (for many
connections), skin
(for a flat covering),
white blood cells (to
travel & clean up)




1. No cell wall
2. No chloroplast
3. No vacuole
4. shape is different




1. have cell wall
2. have chloroplast
3. have vacuole
Between the two
Structure
Prokaryote Plant
Animal
Cell Wall
Yes
Yes
No
Cell
Membrane
Yes
Yes
Yes
Organelles No
Yes
Yes
Nucleus
No
No
Yes
Centrioles
No
No
Yes
Eukaryotic Cell
Ch 4.2 - Parts of Eukaryotic Cells
Endoplasmic Reticulum
Nucleolus
Cytoplasm
DNA
Mitochondria
Vesicles
Golgi Complex
Ribosomes
Nucleus
Cell Membrane
Ch 4.2 - Parts of Eukaryotic Cells
Internal Organization:
Organelles = perform specific functions.
- function like tiny organs, analogous to organs
of a multicellular body.
Cell Membrane = surrounds, contains, and
protects the cell
Nucleus = large organelle containing most of the
genetic information
CELL WALL




protects the cell
gives shape
is made of cellulose
A cell wall is found in plants, algae, fungi, &
most bacteria.
CELL MEMBRANE (Plasma membrane)



Outer covering, protective
layer around ALL cells
For cells with cell walls,the
cell membrane is inside the
cell wall
Allows food, oxygen, & water
into the cell & waste products
out of the cell.
CELL MEMBRANE (Plasma membrane)


The boundary of the
cell…separates inside from
outside of cell
Is Semipermeable Membrane:
allows some substances into
cell and keeps others out of
cell.
CELL MEMBRANE (Plasma membrane)

Has a phospholipid bilayer.
The lipid molecules are fluid
and can move past one
another in a fluid
manner…also allows proteins
to move and change in this
layer thus scientist explain
cell membrane and call it a
Fluid Mosaic Model
Cell Membrane are made of a
phospholipid bilayer
CYTOPLASM




gelatin-like inside cell membrane
constantly flows
aka protoplasm
It contains the various
organelles of the cell
CYTOSKELETON



scaffolding-like
structure in cytoplasm
helps the cell maintain
or change its shape
made of protein
NUCLEUS




Directs all cell activities
Contains instructions
for everything the cell
does
These instructions are
found on a hereditary
material called DNA
Usually the largest
organelle
Actual Cell Nucleus
NUCLEOLUS



Aka “little nucleus”
Found in the nucleus
Contains RNA and
proteins for ribosome
synthesis
CHROMATIN



contains genetic code that controls cell
made of DNA & proteins
Condenses to form chromosomes
during cell division
ENDOPLASMIC RETICULUM



A series of folded
membranes that move
materials (proteins)
around in a cell like a
conveyor belt
Smooth ER – ribosomes
not attached to ER,
functions in lipid
synthesis
Rough ER – ribosomes
attached to ER, functions
in producing proteins
RIBOSOMES



Make proteins
Float freely or attached to
the endoplasmic
reticulum (ER)
Ribosomes are made in
the nucleolus and are
small particles of RNA
GOLGI BODIES (GAWL jee)



Stacked flattened
membranes
Sort and package
proteins
Called dictyosomes in
plants
LYSOSOMES (LI suh sohmz)



The word "lysosome" is Latin for "kill body."
The purpose of the lysosome is to digest things.
They might be used to digest food or break down
the cell when it dies.
Break down food molecules, cell wastes & worn
out cell parts
Microbodies




Various membrane bound organelles that
contain specialized teams of enzymes for
specific metabolic pathways
2 important types:
1. peroxisomes: break down H2O2 and
detoxify alcohol
2. Glyoxysomes: found in fat-storing
tissues of germinating seeds.
VACUOLES
Temporary
storage spaces
 Store food,
water, waste

MITOCHONDRIA



Organelles that
release energy from
food (power house of
cell)
This energy is
released by breaking
down food into
carbon dioxide
AKA the powerhouse
b/c they release
energy (ATP) from
Folds of mitochodria are called:
www.soulcare.org
Galloway
Sid
Centrioles



Short cylinder near nuclear envelope
There generally are 2 at right angles to
each other
They control cell division
CHLOROPLASTS


Green organelles that
make food
found only in plant
cells
Cilia

Short hair like projections from the cell
that by beating produce organized
movement. Ex paramecium
Flagella
 Long
whiplike organelle
whose action produces
movement.
Microtubules
 Found
in cytoplasm of all
eukaryotic cells and function in
cell support
Microfilaments
 Built
from actin, a globular
protein and function in
support of cytoskeleton and
localized contraction of cell
Intermediate filaments
 Size
intermediate to
microtubules and
microfilaments.
 Function in reinforcing cell
shape
Extracellular material

Found outside cell

Material secreted by cell into the cell
matrix, ranging from saliva, to gastric
juices, ext…
1- Nucleus
2- Chromosomes
3- Mitochondria
4- Ribosomes
5- Chloroplasts
6- Vacuoles
7- ER
8- Cell
Membrane
The process by
which cells
reproduce
themselves.
Two types (Mitosis and Meiosis)
I. Mitosis = produces body cells with identical
genetic material as the original.
II. Meiosis = reduces the chromosome number
by half in the sex cells. (haploid)



Chromosomes – composed of 2 sister
chromatids connected by centromere
During cell division in eukarotic cells the
DNA is coiled into very compact
chromosomes, made of both DNA and
proteins.
Chromatid – each chromosome consists
of two identical halves called chromatids
(= copies
Chromatin - Before cell division, the DNA is not
tightly coiled, but loosely arranged, and its codes
can then be read by the cell to direct the cell’s
activities.
chromosome
centromere
chromatids
Homologues or homologous chromosomes
Mitosis Animation/Video Links

McGraw-Hill Mitosis Movie
http://highered.mcgraw-hill.com/sites/0072437316/student_view0/chapter11/animations.html#
The cycle = repeating set of events
composing the life of a cell.
* There are two periods: Interphase
and Cell Division
*




Interphase is the time between divisions, and is
divided into three phases.
1. G1 phase – offspring cells grow to mature
size
(= Gap after division and before DNA
replication)
2. S phase – The DNA is copied
3. G2 phase – Gap after DNA synthesis &
before division.
 Chromosomes
duplicate
 Chromosomes are not visible
 Nucleus has clearly defined
nucleus
LOOKS SPAGHETTI LIKE, longest phase
The DNA which was copied in S phase, now
supercoils.
Nucleolus and nuclear membrane break down.
Centrosomes with centrioles move to poles.
(Plants have no centrioles.)
Spindle fibers (microtubules) radiate from them.
Mitotic spindle is this array of fibers.


Metaphase – CHROMOSOMES line up in a
straight line in the center ( equatorial
plane) of the cell .
Centromere of each pair of chromatids
attaches to a separate spindle fiber.
 Anaphase
– centromeres &
chromatids separate.
 (Each new chromosome moves
slowly to opposite poles
 Shortest phase
 Looks like they have wiped out
waters skiing




Telophase – spindle fibers disassemble,
chromatin forms, nucleus reappears.
(new nuclear envelope forms for each set of
chromosomes
Cell plate forms in plant cell
Cleavage furrows appear in animal cells
Meiosis is a process in which gonad cells
divide twice to produce haploid cells.
* Gonads are sex organs (ovaries and
testicles).
* Gametes (sex cells – sperm and eggs) are
the resulting haploid cells.

* Cells preparing for meiosis first undergo
the G1, S, and G2 phases of interphase.

Meiosis I and Meiosis II are the names for the
two divisions of Meiosis.
–
There are some important differences in the
stages compared to mitosis.

Similar to mitotic prophase except for Synapsis.

Synapsis is where the homologues pair up &
twist around
one another.

Tetrads is the term for these paired
homologues
(4 chromatids).

Crossing-Over then occurs where parts of
the chromatids exchange genes.

Genetic Recombination is the result, which
increases
variation.
tetrads line up randomly at the midline of cell
 - Spindle fibers from one pole attach
to one centromere
of one
homologue.

- Spindle fibers from the other
pole attach to the other
homologue’s centromere.

* the spindle fibers randomly pull the
homologues to separate poles.
- Independent Assortment is the term
for the random
separation.
- Note that the centromeres do not split
the chromatids at this point.
- The homologous chromosome
(consisting of two chromatids) stays intact.
I – is the final phase of
Meiosis I, and the chromosomes
reach the poles.
 Telophase


Cytokinesis then begins to separate the
cytoplasm into TWO new cells.
At this point, the TWO new cells contain a
Haploid number of chromosomes, yet each
has two sister chromatids (copies) attached
by a centromere.
Formation of Gametes* Spermatogenesis = male testes cell produces four
gametes called spermatids.
* Oogenesis = female ovaries produce eggs (ova), but
only one ova (not four) is produced from the meiotic
divisions of each ovary cell.
- The other three “donate” most of their cytoplasm
to the one mature ova, so that it has plenty of
energy reserves to grow once it is fertilized by a
sperm.
A Phospholipid Bilayer
Phospholipids can form:
BILAYERS
-2 layers of
phospholipids with
hydrophobic tails
protected inside by the
hydrophilic heads.
The PHOSPHOLIPID
BILAYER is the basic
structure of membranes.
Structure of the cell membrane
Cell membranes are
made mainly of
phospholipids. They
have:
HYDROPHILIC heads
(water liking)
-Attracted to the
water POLAR
HYDROPHOBIC tails
(water fearing)
-Not attracted to the
water NON-POLAR
Diagram representing the cell membrane
Remember the membrane is 7nm wide
Fluid mosaic model
Cell membranes also contain proteins within the phospholipid
bilayer.
This ‘model’ for the structure of the membrane is called the:
FLUID MOSAIC MODEL
FLUID- because individual phospholipids and proteins can move
around freely within the layer, like it’s a liquid.
MOSAIC- because of the pattern produced by the scattered
protein molecules when the membrane is viewed from above.
Diagram of a cell membrane
Summary

Cell membranes have a basic structure composed of a
PHOSPHOLIPID BILAYER.

Phospholipds have HYDROPHOBIC (non-polar) tails and
HYDROPHILIC (polar) heads.

The best model of the cell membrane is called the FLUID
MOSAIC MODEL

The average thickness of the membrane is 7nm.

The fatty acid tails of phospholipids can be SATURATED
(straight) or UNSATURATED (bent)

Proteins can float or be fixed and also have hydrophobic and
hydrophilic portions.
Summary continued

Some proteins and phospholipids have carbohydrates
attached to them to form GLYCOPROTEINS AND
GLYCOLIPIDS.

Phospholipids form the bilayer, act as barrier to most
water soluble substances

Cholesterol regulates the fluidity of the membrane,
gives mechanical stability and help to prevent ions
from passing through the membrane.

.
Summary continued
 Proteins
act as transport proteins to
act as channels for substances to move
into or out of the cell.
Transport through cell
membranes

There are 5 basic mechanisms:
1.
DIFFUSION
2.
OSMOSIS
3.
ACTIVE TRANSPORT
4.
FILTRATION
5.
ENDOCYTOSIS
 Diffusion
is the net movement of
molecules (or ions) from a region of
their high concentration to a region of
their lower concentration.
The molecules move down a
concentration gradient.
DIFFUSION
Diffusion is a PASSIVE process which means no energy is
used to make the molecules move, they have a natural
kinetic energy.
Osmosis = Water diffusion,
moving “down” the gradient
The net direction of osmosis depends on
the solute concentrations on both
sides.
 Hypotonic = lower solute
concentration
 Hypertonic = higher solute
concentration
 Isotonic = equal concentrations on
both sides of
the membrane
Osmosis in Red Blood Cells
Plants use osmosis in hypotonic soil to maintain
rigidity.
-Turgor Pressure = the pressure of water
molecules
against the cell wall.
- Plasmolysis is when a plant wilts (sags) in a
hypertonic
environment, since the water in
the cells diffuses out and turgor pressure is lost.
Plant Cell Osmosis
Passive Transport Review
Active Transport
 requires
energy use to move materials
up their concentration
 Moves from an area of low
concentration to an area of high
concentration
 Example: sodium-potassium pump
Ion Pump for Na+ and K +

process by which cells ingest external
fluid, macromolecules, and large
particles, including other cells
Two Types of Endocytosis
- Pinocytosis = Cell drinking
- Phagocytosis = Cell eating
Exocytosis of Vesicle
Contents
Filtration
 Molecules
pass through a membrane by
physical force during filtration
 Ex blood pressure forces substances to
leave circulation