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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


Chapter 4

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

the discovery of cells
The Discovery of Cells
  • All organisms consist of cells
the discovery of cells1
The Discovery of Cells
  • Cells – the place where biochemical activity occurs
the discovery of cells2
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 cells3
The Discovery of Cells
  • Cells – cell membrane – separates living matter from the environment and limits size of organism
the discovery of cells4
The Discovery of Cells
  • Organelles – structures where life processes occur to keep cell alive
the discovery of cells5
The Discovery of Cells
  • Cellular Cytoplasm- remainder of interior of cell besides organelles
the discovery of cells6
The Discovery of Cells
  • Cells can specialize (examples : muscle cells, leaf cells, root cells)
the discovery of cells7
The Discovery of Cells
  • Stem cells – from which all cells differentiate in many celled organism
lenses reveal the world of the cell
Lenses Reveal the World of the Cell
  • 13th Century – world recognized glass magnifies
lenses reveal the world of the cell1
Lenses Reveal the World of the Cell
  • 16th Century – began using paired lenses (Jansen and church spire)
lenses reveal the world of the cell2
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 19 th century
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


  • 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
  • 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
Bacterial Shapes
  • Cocci
  • Bacilli
  • Spirilla
  • Fibrios
  • fusiform


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


archaean extremophiles con t
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
Introduction to Organelles
  • Organelles –
    • improve efficiency,
    • protect contents,
    • secrete substances,
    • derive energy
    • Degrade debris
    • reproduce
introduction to organelles1
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
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)
introduction to organelles s cont1
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
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
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 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
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
peroxisomes facilitate oxidative reactions
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
peroxisomes con t

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 – 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
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
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
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
origins of complex cells cont
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
  • 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).