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)