Transcript CLASSIFICATION of CELLS

CLASSIFICATION OF CELLS
Lecture 2
What is exactly is life?
• From the Biological perspective- Life is described with
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ALL the following 4 properties (at this time)
CELLULAR: Firstly, every living thing is cellular
– it is either a single-celled creature (unicellular - bacterium,
brewers yeast, amoeba)
– or a creature composed of many cells (muticellular toadstool, frog, plant, man)
• PROPERGATE: Living things reproduce themselves
– Either individually (asexual reproduction)
– In sexual pairs (sexual reproduction
• METABOLIZE: Life uses processes collectively called
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metabolism to convert materials and energy for its needs
EVOLUTION: Life undergoes evolution to different forms
LIFE
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There is no hard and fast definition of life!
Scientists are manipulating life at this time!
New life is being created in test tubes!
NASA is looking for new life forms at this
time
– Was McCoy right when he found silicon based
life-forms?
What is living?
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Animals
Plants
Fungi
Bacteria
Viruses
Prions
Atoms
What is living?
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Animals - yes
Plants - yes
Fungi - yes
Bacteria - yes
VIRUSES - no
PRIONS - no
ATOMS - no
Classification of cells
• Two main classes of cells - so far!
• Nucleus - Do they have or not have?
• Prokaryotic cells - All Bacteria & Archaea - no
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nucleus
Eukaryotic cells - Plants, animals, fungi, and
protists - all have a nucleus
Prokaryotes also lack organelles or cytoskeleton
Otherwise, they function very much the same.
Prokaryotes vs. Eukaryotes
PROPERTY
Nucleus
Cell Diameter
Cytoskeleton
Organelles
DNA content (bp)
Chromosomes
Procaryotes
• Absent
• 1 um
• Absent
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• 1x10E6 to 5x10E6
• Single circular
DNA molecule
Eucaryotes
• Present
• 10 - 100 um
• Present
• Present
• 1.5x10E7 to 5x10E9
• Multiple linear DNA
molecules
KNOW YOUR SI UNITS
• Each student of science must be at ease with the
SI unit scale
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Length metre: m (the correct English spelling of the unit is "metre", but the variant "meter"
is frequently used in the United States)
Mass kilogram: kg
Time second: s
electric current ampere: A
thermodynamic temperature kelvin: K
SI Prefixesexponent (base 10) of decimal numbers: E n = 10nFactor
109
106
103
102
101
10-1
10-2
10-3
10-6
10-9
10-12
E 9
E 6
E 3
E 2
E 1
E -1
E -2
E -3
E -6
E -9
E-12
giga
mega
kilo
hecto
deca
deci
centi
milli
micro
nano
pico
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da
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The First Cell
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Earth formed @ 4.5 billion years ago
Life emerged @ 3.8 billion years ago
No or little oxygen
CO2 and N2; H2, H2S and CO
Add heat and water
Organic molecules
LIFE! ????????
The First Cell
• Proteins and RNA were thought to be the first
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macromolecules produced
Only RNA capable of directing its self-replication,
acting as both template and catalyst
“RNA World” existed for a period of time
The FIRST CELL is thought to have arisen when
RNA became enclosed in a phospholipid
membrane, and was able to self-replicate
Evolution of Metabolism
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The early Earth lacked O2
Early Cells took food and energy by absorption
Glycolysis - glucose to lactic acid
Photosynthesis - sunlight, water, CO2 to
Glucose and O2
Oxidative metabolism - Glucose and O2 to CO2
and water
ATP is generated
All Cells use ATP for energy to drive their cellular
machinery
Prokaryotes today
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Two groups
Archaea and the Eubacteria (true bacteria)
Archaea live in many harsh environments
Eubacteria populate many places
Bacterial shapes vary, as does their size
and DNA content
01_10_Bacteria shapes.jpg
01_11_E. Coli.jpg
01_13_Sulfur bacterium.jpg
Eukaryotic Cells
• Also have a plasma membrane and ribosomes •
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just as do Prokaryotes
Nucleus, with linear chromosomes
Organelles - mitrochondria, chloroplasts,
lysosomes, peroxisomes.
Plant cells have vacuoles for storage, waste, or
digestion of macromolecules
ER (endoplasmic reticulum) & Golgi apparatus
Cytoskeleton - network of protein filaments
01_14_Yeasts.jpg
Yeast Cell budding
Nucleus
01_15_Nucleus.jpg
Origin of Eukaryotes
• Hypothesis that a critical step in the
evolution of eukaryotic cells took place
possibly via two endosymbiotic events one cell living inside another
• Some of the organelles are thought to
have evolved from prokaryotes living
inside eukaryotes
01_18_folds mito.jpg
01_19_engulfed bacteria.jpg
01_20_Chloroplasts.jpg
01_21_Chloro.engulfed.jpg
Mitochondria & Chloroplasts
• Same size as bacterial cells
• Reproduce by dividing into two, like
bacteria
• Both contain their own DNA, coding for
some of their own components
• Have own ribosomes too, which more
closely resemble those of bacteria, then
those in the cell cytoplasm.
PREVIEW OF WHAT’S TO COME
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TIFF (Uncompressed) decompressor
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QuickTime™ and a
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Schematic of typical animal cell, showing subcellular components.
Organelles: (1) nucleolus (2) nucleus (3) ribosome (4) vesicle (5) rough
endoplasmic reticulum (ER) (6) Golgi apparatus (7) Cytoskeleton (8)
smooth ER (9) mitochondria (10) vacuole (11) cytoplasm (12) lysosome
(13) centrioles
01_22_ER.jpg
01_23_Golgi apparatus.jpg
01_24_Organelles.jpg
01_25_endocytosis exoc.jpg
01_27_cytoskeleton.jpg
Actin, microtubules, intermediate filaments
01_29_eucaryotes origin.jpg
Multicellular Organisms
• Many eucaryotes are unicellular just like bacteria
• Single cells capable of self-replication
• Simplest eucaryotes are the yeasts (6um & 12 million
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bps)
Amoeba is 100,000x the volume of typical E.coli bacteria
Over a Billion years ago (> 1 x 10E9) multi-cellular
organisms evolved from single celled eukaryotes
Volvox shows an evolutionary transition phase, of
multiple cells aggregating for the greater good.
Multicellular Volvox (algae)
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
QuickTime™ and a
TIFF (Uncompressed) decompressor
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Multicellular Organisms cont…
• Plants have fewer specialized cells than do
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animals
Ground tissue - includes parenchyma cells
(metabolism including photosynthesis), and
collenchyma and sclerenchyma cells (which are
rigid and provide structure)
Dermal tissue - covers the surface of the plant
and provides protection and diffusion
Vascular tissue - elongated cells form the xylem
and phloem for transport
Multicellular Organisms cont…
• Animal cells are more diverse & specialized
• Human body contain over 200 different kinds of
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cells
Epithelial cells - sheets that cover the body and
line the gut
Connective tissues - bone, cartilage, adpose
Blood and immune systems
Nerve cells and brain
Reading assignments to stay
current
Read Chapter 1 of textbook to page 23 & visit
website for supplemental information
(time @ 55 minutes)