UNITY OF LIFE
A STUDY OF CELLS
Despite vast differences in
appearance and ways of life, all
living things have a unity of life.
They are all composed of cells
that are similar in structure and
function. Some organisms such
as Paramecuim and Euglena, are
made of only one cell. In more
complex, multicellular organisms,
the cells may perform more
specialized functions, but all have
certain features in common.
Before we begin our study of
cells. It is necessary to discuss
the instrument that allowed
people to see cells in the first
place!
This discovery lead to our modern
Cell Theory
MICROSCOPES
• 1590- The first microscope is built by
Zacharias Janssen
• 1670’s Anton von Leeuwenhoek built a
simple microscope that could magnify
objects 270X.
Compound light microscope
• The compound light microscope is widely used in
science. The term light refers to the method by
which light transmits the image to your eye.
Compound deals with the microscope having
more than one lens. Microscope is the
combination of two words; "micro" meaning small
and "scope" meaning view.
Stereomicroscope
•
•
•
•
Also called dissecting scope
Has two eyepieces (binocular)
Objects are seen in 3-D
Does not have high power, use to observe
relatively large objects such as insects or
crystals
Phase-contrast microscope
• Allows observer to distinguish different
structures within a cell, without staining,
using light waves.
Electron microscope
• Uses a beam of electrons instead of light
rays
• Can provide magnifications of 200,000X
• Tissues must be thinly sliced, dry and in a
vacuum chamber, therefore electron
microscopes cannot be used to view living
specimens
The surface
of a
strawberry
Bacteria
on the
surface
of the
human
tongue
Head of
zebra
fish
embryo
Stem
surface
of a
black
walnut
tree
Lettuce
leaf,
showing
stomate
with
E.coli
bacteria
inside
Micro-dissection apparatus
Centrifuge
Cell Theory
• 1665- Robert Hooke looked at cork with his
compound light microscope and saw walled
compartments, he called “CELLS”
1831- Robert Brown ( Scottish botanist)
• Discovers the nucleus of the cell.
• 1838- Matthias Schleiden ( German
botanist) concluded “All plants are made of
cells”
• 1839- Theodor Schwann (German
zoologist) said “All animals are composed
of cells”
• 1839- Johannes Purkinje- (Czech
physiologist) discovered cytoplasm.
• 1858- Rudolph Virchow (German biologist)
said “Cells arise from other cells by cell
reproduction”
CELL THEORY
•
•
•
•
1. Cells are the basic unit of life
( How else could we express this idea?)
2. Cells come from pre-existing cells.
(How else could this idea be expressed?)
Exceptions to cell theory
• Viruses
• First cell?
• Mitochondria and chloroplasts
CELLS
• There are two basic types of cells
• Prokaryotic and Eukaryotic
• Prokaryotic cells- (also called prokaryotes) belong
to the kingdoms Eubacteria & Archaebacteria, are
very small, 1-10 micrometers, have no nucleus
and few organelles. They are primitive cells.
Bacteria are prokaryotic cells.
Eukaryotic cells (also called
eukaryotes)
• Larger than prokaryotes, 10100micrometers
• Have nucleus
• Have organelles
• Complex cells
• Protists, Fungi, Plants and Animals all have
eukaryotic cells
Cell Organelles
• Tiny structures within a cell that perform
various, specialized functions , such as
transporting materials, building important
biological substances, secreting products,
releasing energy from food molecules, etc.
Cell Organelles
• Cell (plasma) membrane- separates the
cell from its environment.
• Consists of a double layer of phospholipids
with embedded proteins.
• Called fluid-mosaic model
• Selectively permeable membrane
protein
steroid glycoprotein
Head of
lipid
Tail of
lipid
phospholipid
protein
Transport
protein
CYTOPLASM
• Jelly-like fluid that fills the interior of the
cell
Endoplasmic reticulum (ER)
• Network of tubes found throughout
cytoplasm
• Transports materials around the cell
Ribosomes
• Site of protein synthesis
• Rough ER has ribosomes attached to its
walls
• Smooth ER has no ribosomes attached to its
walls
GOLGI COMPLEX
• Look like flattened sacs
• Function in the secretion of products
produced in the cell.
• Act like the “packaging and shipping
department “
MITOCHONDRIA
• Look like short rods or tiny spheres
• Site of cellular respiration, (chemical
reactions that release energy from food
molecules)
• “powerhouse of the cell”
MICROTUBULES
• Long, slender tubes that give the cell
structure and support
MICROFILAMENTS
• Long thin threads attached to cell
membranes
• Aid in cell movement
Lysosomes
•
•
•
•
Small, oval organelles
Contain digestive enzymes
Digest food molecules
Destroy old cells
NUCLEUS
• Contains chromosomes
• Directs the activities of the cell
• “Control center of the cell”
NUCLEOLUS
• Found inside the nucleus
• Produces ribosomes
• Produces nucleotides
<>
CENTRIOLES
• Found in the cytoplasm of animal cells
• Cylinder of tiny tubes
• Important in cell division
CILIA & FLAGELLA
• Cilia are tiny hair-like structures on outside
of cell
• Flagella are long projections from cell
membrane
• Aid in movement of cell and in movement
of materials
VACUOLE
• Storage sacs in the cell
• May store many different materials. Ex:
Food, water ,wastes
CHLOROPLAST
• Found in
photosynthetic
organisms- plants,
algae, some bacteria
• Site of photosynthesis
• Contain chlorophyll
CELL WALL
• Found in plant cells, fungi and bacterial
cells
• Surrounds and protects the cell
• Composed of cellulose
• Supports the cell
DIFFERENCES BETWEEN PLANT
& ANIMAL CELLS
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•
•
•
Plant cell
Cell wall
Chloroplasts
Large vacuole
• Animal cell
• Centrioles
• Small vacuoles
WHERE DO CELLS COME
FROM??????????
ABIOGENESIS
• Spontaneous generation
• Living organisms can come from non living
things
Spontaneous Generation
•The idea that organisms originate directly from nonliving matter.
•"life from nonlife"
•abiogenesis - (a-not bio-life genesis-origin)
These Scientist ran experiments to prove or disprove the theory of spontaneous generation.
Review their experiments and attempt to answer the questions on the end.
Listen to this story
Fancesco Redi
One of the first to disprove spontaneous generation. An Italian doctor
who proved maggots came from flies. (Italian 1668)
Lazzaro Spallanzani - One of the first to disprove spontaneous
generation. An Italian scientist who proved microorganisms could be
killed by boiling. (Italian 1767)
Louis Pasteur - One of the first to disprove spontaneous generation. A
French scientist who proved that micro organisms were carried by dust
not air. (French 1864)
Redi's Problem
Where do maggots come from?
Hypothesis: Maggots come from flies.
Redi put meat into three separate jars.
Jar 1 was left open
Jar 2 was covered with netting
Jar 3 was sealed from the outside
Redi's Experiment Step 1
Jar-1
Left open
Maggots developed
Flies were observed laying eggs on the meat in the open jar
Redi's Experiment Step 2
Jar-2
Covered with netting
Maggots appeared on the netting
Flies were observed laying eggs on the netting
Redi's Experiment Step 3
Jar-3
Sealed
No maggots developed
Spallanzani's Problem
What causes microbes to form in decaying broth?
Hypothesis: Microbes come from the air. Boiling will kill
microorganisms.
Spallanzani put broth into four flasks
Flask 1 was left open
Flask 2 was sealed
Flask 3 was boiled and then left open
Flask 4 was boiled and then sealed
Spallanzani's Experiment Step 1
Flask-1
Left Open
Turned cloudy
Microbes were found
Spallanzani's Experiment Step 2
Flask-2
Sealed
Turned cloudy
Microbes were found
Spallanzani's Experiment Step 3
Flask-3
Boiled and left open
Turned cloudy
Microbes were found
Spallanzani's Experiment Step 4
Flask-4
Boiled and sealed
Did not turn cloudy
Microbes not found
What did Spallanzani's experiment show?
Was his hypothesis correct or incorrect?
Pasteur's Problem
Where do the microbes come from to cause broth to decay.
Hypothesis: Microbes come from cells of organisms on dust particles in
the air; not the air itself.
Pasteur put broth into several special S-shaped flasks
Each flask was boiled and placed at various locations
Pasteur's Experiment Step 1
S-shaped Flask
Filled with broth
The special shaped was intended to trap any dust particles coming in.
Pasteur's Experiment Step 2
Flasks boiled
Micropes Killed
Pasteur's Experiment Step 3
Flask left at various locations
Did not turn cloudy
Microbes not found
Pasteur's Experiment Step 3
Flask Left Out
Notice the dust that collected in the neck of the flask
Pasteur's Experiment Results
What did Pasteur's experiment show?
Was his hypothesis correct or incorrect?
• The theory of abiogenesis or spontaneous
generation was disproved!!!
BIOGENESIS
• LIFE COMES FROM LIFE
Questions: If you can answer the following questions you indicate a
good understanding of this material.
Why did early people believe in spontaneous generation?
In Redi's experiment why did the flies lay their eggs on the netting?
What important process in canning did Spallanzani teach us?
How has the information from these scientists been used to protect our
food from going bad? (application of information-technology)
What process was named after Pasteur?
Approximately how many years apart were the experiments of these
three famous scientists?
What does the phrase "Life From Life" Mean?
Is the theory of spontaneous generation considered to be correct or
incorrect? Why?
CELL DIVISION
• For life to continue, cells must replicate
(make copies) of themselves.
• New cells must have the exact same genetic
info as the parent (original) cell
• The number and types of chromosomes
must be exactly the same.
Stages of the Cell Cycle
• Interphase- the cell spends most of its life in
this phases
• Mitosis- The period in a cell’s life when the
cell divides to form two new cells. This
includes the division of genetic
information.
INTERPHASE
• the period in a cell’s life when the cell
performs its function and grows
• At the end of interphase , the cell replicates
(makes a copy) of its chromosomes.
Stages of MITOSIS
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•
•
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Prophase
Metaphase
Anaphase
Telophase
PROPHASE
• Nuclear membrane disappears
• Replicated chromosomes become visible
METAPHASE
• Chromosomes line up at the equator of the
cell
ANAPHASE
• Replicated chromosomes separate and
moved toward opposite poles of the cell.
TELOPHASE
• Nuclear membrane forms
• Cytoplasm division occurs