Cells units of life
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CELLS: UNITS OF LIFE. Chapter 4 Hyperlink is the 3 rd one that says component of cells – same as above, but narrated!. The Discovery of Cells. All organisms consist of cells. The Discovery of Cells. Cells – the place where biochemical activity occurs. The Discovery of Cells.

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CELLS: UNITS OF LIFE

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CELLS: UNITS OF LIFE

Chapter 4

Hyperlink is the 3rd one that says component of cells – same as above, but narrated!


The Discovery of Cells

  • All organisms consist of cells


The Discovery of Cells

  • Cells – the place where biochemical activity occurs


The Discovery of Cells

  • Cells – have ALL characteristics of life

    • All made of cells – and have levels of organization

    • All grow, develop, and reproduce

    • All use energy

    • All adapt

    • All respond to stimuli

    • Maintain internal constancy


The Discovery of Cells

  • Cells – cell membrane – separates living matter from the environment and limits size of organism


The Discovery of Cells

  • Organelles – structures where life processes occur to keep cell alive


The Discovery of Cells

  • Cellular Cytoplasm- remainder of interior of cell besides organelles


The Discovery of Cells

  • Cells can specialize (examples : muscle cells, leaf cells, root cells)


The Discovery of Cells

  • Stem cells – from which all cells differentiate in many celled organism


Lenses Reveal the World of the Cell

  • 13th Century – world recognized glass magnifies


Lenses Reveal the World of the Cell

  • 16th Century – began using paired lenses (Jansen and church spire)


Lenses Reveal the World of the Cell

  • Robert Hooke (1660)

    • 1st person to see the outlines of cells

    • Spun glass and looked at bee stingers, fish scales, fly legs, insects and CORK

  • Antonie van Leeuwenhoek (1673)

    • developed over 500 high magnification lenses

    • 1st record of microorganisms- he called “animalcules” found in tooth tartar


The Cell Theory Emerges – not till 19th Century

  • Robert Brown – discovered cellular nucleus

    • Houses DNA

  • Schleiden

    • Cells were basic unit of plants

  • Schwann

    • Cells were basic unit of animals

  • Together

    • Cells were elementary particles of all organisms, the unit of structure and function


The Cell Theory Emerges – not till 19th Century

  • Virchow

    • All cells come from pre-existing cells

    • Believed abnormal cells cause diseases


Cell Theory

1. All living things are composed of cells. [Schleiden & Schwann]

2. All cells come from preexisting cells. [Virchow]

Cell Theory still evolving: Organelles have precise locations in cells


Variations on the Cellular Theme

C. Types of Cells

3 basic types:

  • Bacterial

  • Archaean

Prokaryotic

  • Eukaryotic


Variations on the Cellular Theme

Review surface area to volume relationship – Large volume justifies the need to have organelles


Variations on the Cellular Theme

Folding membranes also increase surface area for reactions


1. Bacterial cells

  • 1-10 m in diameter

  • NO membrane-bound organelles

  • Some photosynthetic – use pigment only

  • Some cause illness some don’t

  • Vital to life on earth

  • 1 circular DNA molecule located in nucleoid region

    • MAKE PROTEINS RAPIDLY DUE TO CLOSE LOCATION OF ORGANELLS

  • plasma membrane, cytoplasm & ribosomes

  • most have a cell wall (peptidoglycan)

    • Many antibiotics interfere with cell wall construction

  • may have a polysaccharide capsule to protect or attach

    • Film on teethn morning

      Ex. bacteria & cyanobacteria


Bacterial Shapes

  • Cocci

  • Bacilli

  • Spirilla

  • Fibrios

  • fusiform


Gram-staining

Distinguishes 2 types of bacteria

  • Gram – negative – thin cell wall

  • Gram positive – thick cell wall

Structure of a Gram-Negative Cell Wall

Gram positive cell wall


Archaean cells represent a distant ancestor???

  • 1-10 m in diameter

  • Use carbon dioxide and hydrogen to make methane (methanogens)

  • Have co-enzymes that make methane

  • NO membrane-bound organelles

  • cell walls lack peptidoglycan

  • have characteristics of both bacteria & eukaryotic cells

  • Half of genes are same as bacteria, other half totally different

  • mRNA and tRNA are different than in other domains

Methanogen


Archaean Extremophiles, con’t

Ex. Extremophiles: extreme environments: temp, pressure, pH, salinity

methanogens, extreme halophiles & extreme thermophiles

  • Live in Swamps, rice paddies and oceans

Extreme halophile


3. Eukaryotic cells

  • 10-100 m in diameter

  • Includes plants, animals, fungi and protists

  • nucleus & other membrane-bound organelles

  • Nucleus

    • Protects and organizes the cell’s linear DNA

    • DNA combined with protein forming chromosomes

  • plasma membrane, cytoplasm & ribosomes

  • some have a cell wall (cellulose or chitin)

  • Animal cells: half the volume of a cell is organelles

  • Plant cells: 90% may be water (found in vacuole)

  • Cytoskeleton – rods and tubules within cells to give cell shape or appendages to move


Introduction to Organelles

  • Organelles –

    • improve efficiency,

    • protect contents,

    • secrete substances,

    • derive energy

    • Degrade debris

    • reproduce


Introduction to Organelles

  • Organelles Synthesize and Process Proteins

    • Enzymes – key to determining function of cell

    • Endomembrane system

      • Rough endoplasmic reticulum

        • Compartments use enzymes that assist with protein production and transportation

      • Smooth endoplasmic reticulum

        • Lipids synthesized, modified and toxins neurtalized


Generalized Generalized

Animal Cell Plant Cell


Introduction to Organelles’s cont

  • Golgi apparatus

    • Sorts proteins for exports out of cell or into lysosomes

    • links simple carbohydrates together to form starch

    • links simple carbohydrates to proteins (glycoprotein) or lipids (glycolipid)

    • completes folding of proteins

    • temporarily stores secretions (milk)


Organelle interaction in a mammary gland cell.


Introduction to Organelles’s cont

  • Lysosomes (suicide sacs)

    • Contain digestive enzymes – 40 types

    • Function to recycle damaged organelles, break down cellular by products & destroy invading microbes


The Nucleus

  • Exports RNA instructions

    • Genes: instructions on DNA are copied onto mRNA

    • mRNA exits nucleus through nuclear pores (found in nuclear envelope

      • Not just holes

      • Channels with 100 types of proteins (importins and exportins)


The Cytoplasm

  • Site of Protein synthesis and other reactions

    • mRNA binds to ribosomes

      • A complex of MANY proteins surrounding an rRNA

        • rRNA + proteins are assembled in the nucleolus then exit the nucleus through pores

        • Remainder of section completes milk production example


Lysosomes and Peroxisomes: Cellular Digestion Centers – and more

  • Lysosomes are cellular recycling centers

    • Lyse – cut apart

    • Enzymes within organelle – lyse targets

      • Dismantle bacteria

      • Dismantle worn out organelles and debris

      • Break down large nutrients into useable monomers

      • Fuse with vesicles carrying debris

      • Made in rough ER

      • Function in very acidic environment


Lysosome’s con’t

  • Numbers very based on cell function

    • White blood cells have many

    • Liver have MANY – process cholesterol

  • Human cells have more than 40 enzyme types

  • Balance of enzyme related to health

    • Too many, causes storeage problems in cell – crowds other organelles

    • Tay Sachs – missing an enzyme in a lysosome


Tay Sachs events


PeroxisomesFacilitate oxidative Reactions

  • Contain enzymes that oxidize other molecules

  • Enzymes made in the cytoplasm – then transported to vesicles

  • Environmental toxins: cause explosion of peroxisome production

    • Toxins are oxidized and removed

  • Synthesize bile acids


Leopard spot retinal pigmentation

Peroxisomes, con’t

  • Break down lipids

  • Degrade rare biochemicals

  • Metabolize free radicals

  • Some produce hydrogen peroxide

    • Produces free radicals

    • So contain catalase – removes oxygen from hydrogen peroxide to make water

  • Found in leaves

  • Adrenoleukodystrophy (Lorenzo’s disease) – two proteins missing in peroxisomes outer membrane pg 59


Mitochondria – organelle of energy

  • Mitochondria Extract Energy from nutrients

    • Numbers vary from few to 1000’s

    • Cristae – inner folds contain enzymes

    • Site of cellular respiration (ATP)

      • Converts glucose into ATP energy

    • Has own genetic material (DNA)

      • Inherited only from female


Chloroplast – organelle of energy

  • Chloroplasts provide plant cells with nutrients (THEREFORE ENERGY)

  • Chloroplast

    • carry out photosynthesis

    • Form glucose or other carbohydrates

    • Have stroma – space inside chloroplast for reactions

    • Thylakoids – membrane system of stacked sacks called grana where reactions take place

    • Has own DNA

    • See Table pg 60


Origin of Complex Cells

  • Endosymbiont theory – large celled critters engulfed smaller simpler cells. Simple cells became organelles in the larger critter

    • Structure and DNA sequences provide evidence

      • Evidence in FAVOR of EST

        • Resemblance between mitochondria and chloroplasts to certain kinds of bacteria

          • Size

          • Shape

          • Membrane structure

          • Presence of pigments

          • Reproduction method

          • Relative relationship of DNA, RNA and ribosomes


Origins of Complex Cells, con’t

  • Technology Evidence

  • DNA evidence – bacteria and archaea contributed

    • Theory: archaean cells enveloped bacterial cells that became mitochondria and chloroplasts

    • Theory: bacteria share genes with bacteria and vice versa

      • Ricettsia


Endosymbiant Theory


Origins of Complex Cells, cont

  • How Endosymbiosis May have worked, pg 61


2. Endoplasmic reticulum (ER)

interconnected network of membranes extending from nucleus to plasma membrane


3. Golgi apparatus

  • stacks of membrane-enclosed sacs


4. Lysosomes (suicide sacs)

  • vesicles containing > 40 types of digestive enzymes

  • function to recycle damaged organelles, break down cellular byproducts & destroy invading microbes


5.Perixisomes

  • vesicles containing several types of enzymes (produced in cytoplasm)

  • found in all eukaryotic cells

  • function to help cell use oxygen & metabolize potentially toxic compounds

    • hydrogen peroxide is produced as a by-product of peroxisome activity

    • the enzyme catalase converts hydrogen peroxide to water


6. Mitochondria

  • double-membrane

    • outer is smooth

    • inner is highly folded (cristae)

  • #/cell varies

  • contain DNA

  • inherited from female parent

  • site of cellular respiration (production of ATP)


7. Chloroplasts

  • possess 3 membranes

    • outer/inner membranes surround stroma

    • 3rd membrane system folded into flattened sacs (thylakoids)

  • #/cell varies

  • contain DNA

  • found in plants & protists

  • function in photosynthesis


E. The Endosymbiont Theory

Proposes that chloroplasts and mitochondria evolved from once free-living bacteria engulfed by larger archaea.

Based on fact that mitochondria & chloroplasts resemble certain bacteria (size, shape, membrane structure & method of making proteins).


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