classification of cells lecture 2. what is exactly is life? from the biological perspective- life is...
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CLASSIFICATION OF CELLSCLASSIFICATION OF CELLS
Lecture 2Lecture 2
What is exactly is life?What is exactly is life?
• From the Biological perspective- Life is described with 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 metabolism to convert materials and energy for its needs
• EVOLUTION: Life undergoes evolution to different forms
• From the Biological perspective- Life is described with 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 metabolism to convert materials and energy for its needs
• EVOLUTION: Life undergoes evolution to different forms
LIFELIFE
• 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?
• 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?What is living?
• Animals
• Plants
• Fungi
• Bacteria
• Viruses
• Prions
• Atoms
• Animals
• Plants
• Fungi
• Bacteria
• Viruses
• Prions
• Atoms
What is living?What is living?
• Animals - yes
• Plants - yes
• Fungi - yes
• Bacteria - yes
• VIRUSES - no
• PRIONS - no
• ATOMS - no
• Animals - yes
• Plants - yes
• Fungi - yes
• Bacteria - yes
• VIRUSES - no
• PRIONS - no
• ATOMS - no
Classification of cellsClassification of cells
• Two main classes of cells - so far!
• Nucleus - Do they have or not have?
• Prokaryotic cells - All Bacteria & Archaea - no 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.
• Two main classes of cells - so far!
• Nucleus - Do they have or not have?
• Prokaryotic cells - All Bacteria & Archaea - no 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. EukaryotesProkaryotes vs. Eukaryotes
PROPERTY
Nucleus
Cell Diameter
Cytoskeleton
Organelles
DNA content (bp)
Chromosomes
PROPERTY
Nucleus
Cell Diameter
Cytoskeleton
Organelles
DNA content (bp)
Chromosomes
Eucaryotes
• Present
• 10 - 100 um
• Present
• Present
• 1.5x10E7 to 5x10E9
• Multiple linear DNA molecules
Eucaryotes
• Present
• 10 - 100 um
• Present
• Present
• 1.5x10E7 to 5x10E9
• Multiple linear DNA molecules
Procaryotes
• Absent
• 1 um
• Absent
• Absent
• 1x10E6 to 5x10E6
• Single circular DNA molecule
Procaryotes
• Absent
• 1 um
• Absent
• Absent
• 1x10E6 to 5x10E6
• Single circular DNA molecule
KNOW YOUR SI UNITSKNOW YOUR SI UNITS• Each student of science must be at ease with the SI unit scale• 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 E 9 giga G• 106 E 6 mega M• 103 E 3 kilo k• 102 E 2 hecto h• 101 E 1 deca da• 10-1 E -1 deci d• 10-2 E -2 centi c• 10-3 E -3 milli m• 10-6 E -6 micro オ• 10-9 E -9 nano n• 10-12 E-12 pico p
• Each student of science must be at ease with the SI unit scale• 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 E 9 giga G• 106 E 6 mega M• 103 E 3 kilo k• 102 E 2 hecto h• 101 E 1 deca da• 10-1 E -1 deci d• 10-2 E -2 centi c• 10-3 E -3 milli m• 10-6 E -6 micro オ• 10-9 E -9 nano n• 10-12 E-12 pico p
The First CellThe First Cell
• 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! ????????
• 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 CellThe First Cell
• Proteins and RNA were thought to be the first 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
• Proteins and RNA were thought to be the first 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 MetabolismEvolution of Metabolism
• 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
• 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 todayProkaryotes today
• 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
• 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.jpg01_10_Bacteria shapes.jpg
01_11_E. Coli.jpg01_11_E. Coli.jpg
01_13_Sulfur bacterium.jpg01_13_Sulfur bacterium.jpg
Eukaryotic CellsEukaryotic Cells
• Also have a plasma membrane and ribosomes - 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
• Also have a plasma membrane and ribosomes - 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.jpg01_14_Yeasts.jpgYeast Cell budding
01_15_Nucleus.jpg01_15_Nucleus.jpgNucleus
Origin of EukaryotesOrigin 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
• 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.jpg01_18_folds mito.jpg
01_19_engulfed bacteria.jpg01_19_engulfed bacteria.jpg
01_20_Chloroplasts.jpg01_20_Chloroplasts.jpg
01_21_Chloro.engulfed.jpg01_21_Chloro.engulfed.jpg
Mitochondria & ChloroplastsMitochondria & 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.
• 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.
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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
PREVIEW OF WHAT’S TO COMEPREVIEW OF WHAT’S TO COME
01_22_ER.jpg01_22_ER.jpg
01_23_Golgi apparatus.jpg01_23_Golgi apparatus.jpg
01_24_Organelles.jpg01_24_Organelles.jpg
01_25_endocytosis exoc.jpg01_25_endocytosis exoc.jpg
01_27_cytoskeleton.jpg01_27_cytoskeleton.jpgActin, microtubules, intermediate filaments
01_29_eucaryotes origin.jpg01_29_eucaryotes origin.jpg
Multicellular OrganismsMulticellular Organisms
• Many eucaryotes are unicellular just like bacteria• Single cells capable of self-replication• Simplest eucaryotes are the yeasts (6um & 12 million
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.
• Many eucaryotes are unicellular just like bacteria• Single cells capable of self-replication• Simplest eucaryotes are the yeasts (6um & 12 million
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)Multicellular Volvox (algae)
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Multicellular Organisms cont…Multicellular Organisms cont…
• Plants have fewer specialized cells than do 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
• Plants have fewer specialized cells than do 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…Multicellular Organisms cont…
• Animal cells are more diverse & specialized• Human body contain over 200 different kinds of
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
• Animal cells are more diverse & specialized• Human body contain over 200 different kinds of
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 currentReading assignments to stay current
Read Chapter 1 of textbook to page 23 & visit website for supplemental information (time @ 55 minutes)
Read Chapter 1 of textbook to page 23 & visit website for supplemental information (time @ 55 minutes)