A Tour of the Cell

1
Chapter 7

• A Tour of the Cell

2
How cells are studied

• Microscopy
• Cell Fractionation

3
Microscopy

• light microscope (LM) (1600s)
• electron microscope (EM) (1950s)
• (TEM, SEM)

4
Cell Fractionation

• Isolate organelles to study their function
• isolation is accomplished by centrifugation
• reductionist approach

5
Cell Size

• Prokaryotic
• most bacteria are 1-10 ?m

• Eukaryotic
• 10-100 ?m
• RBC 7.5
• WBC 10-12
• ovum 170

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Cell size cont.

• Cell size and shape is related to its function
• upper limit (not too large)
• lower limit (not too small)

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Contributions to the Cell

• Robert Hooke (1665), English
• coined cell
• first to see cells, cork cells
• magnified 30X

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Contributions cont.

• Antonie van Leeuwenhoek
• (1600s), Dutch
• first to see living cells
• microorganisms in pond water
• blood cells
• animal sperm cells
• magnified 300X

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Contributions cont.

• Matthias Schleiden (1838)
• botanist
• all plant tissue is made of cells

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Contributions cont

• Theodor Schwann (1839)
• zoologist
• all animal tissue is made of cells

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Cell Theory

• all living things are made of cells (inductive
  reasoning)

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Principles of the Cell Theory

• all organisms are made of cells
• cells are the smallest living things
• life is a continuous line of descent from early
  cells
• cells come from other cells

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Prokaryotic Cells

• Ubiquitous
• 3.5 billion years
• 4000 species recognized
• (400K to 4 M estimated)
• most numerous
• size - 1-10 ?m
• largest 0.5 mm

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Prokaryotic Cellbranches

• Archaeobacteria
• inhabit extreme environments
• (hot springs, salt ponds)
• Eubacteria
• larger group

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Archaeobacteria Eubacteria

• Different
• structurally
• biochemically
• physiologically
• Arch
• w/ introns (protein synthesis)
• not inhibited by antibiotics
• more like eukaryotes

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Prokaryotic Cellcomposite

• Plasma membrane
• cell wall-peptidoglycan
• cytosol, cytoplasm
• nucleoid
• circ dsDNA
• plasmid

• ribosomes
• flagella
• pili
• capsule
• mesosome

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Prokaryotic Cellbasic cell shapes

• coccus - sphere
• bacillus - rod
• spirillum - spiral

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Gram Stainingeubacteria

• Hans Christian Gram
• separates eubacteria into 2 groups based on their
  cell wall differences
• 2 groups are
• Gram positive
• Gram negative

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Gram Staining cont.

• Procedure
• crystal violet (purple) iodine
• decolorize, acetone/alcohol
• counterstain, safranin (red)

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Gram Staining cont.

• purple-colored cells G
• red-colored cells G-
• G large amount of peptidoglycan
• G- less peptidoglycan

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Evolution of Eukaryotes

• Prokaryotes (prok) evolved 3.5 billion years ago
• eukaryotes (prok) evolved 1.5 billion years ago
• prok euk

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Eukaryotic Cellscomposite
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structural elements

• plasma membrane
• selectively permeable
• cell wall
• cellulose in Plantae
• chitin in Fungi

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structural elementscont.

• glycocalyx (Animalia)
• oligosaccharide coat
• strengthens cell surface
• aids with id of cell
• helps glue cells together

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Eukaryotic Cells cont. organelles

• Ribosomes
• function make protein
• RNA proteins
• free (for cytosol) or
• bound (for organelle or export)
• two subunits (lg and sm)

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organellescont.

• endoplasmic reticulum (ER)
• divides cells into compartments
• forms vesicles
• rough ER (RER) - protein
• smooth ER (SER) - lipids, metabolizes carbo.,
  detoxifies

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Organelles cont.

• Nucleus
• function control center
• nuclear envelope
• nuclear pores
• DNA (chromosomes, chromatin)
• nucleolus
• nucleoplasm
• largest animal cell organelle

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Organelles cont.

• Golgi apparatus
• flat stacks of membranes
• func collects, modifies, packages, transports
• cis face trans face

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Organelles cont.

• lysosomes (A)
• Golgi derived
• function breakdown of macromlc.
• autodigestion

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Organelles cont.

• vacuoles
• food vacuoles (A)
• contractile vacuoles (A)
• central vacuoles (P)
• tonoplast
• largest P cell organelle

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DNA-Containing Organelles

• These organelles resemble bacteria
• endosymbiotic theory
• Lynn Margulis, Univ of Mass.
• chloroplasts (P)
• mitochondria

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Mitochondria

• small ribosomes
• circular dsDNA
• size 1-10 ?m
• self-replicating
• func energy production

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Mitochondria cont.

• membranes
• outer smooth membrane
• inner folded membrane
• cristae
• compartments
• intermembrane space
• mitochrondrial matrix

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Plastids

• Closely related plant organelles
• amyloplast - colorless, store starch
• chromoplast - with xanthophylls and carotenes
• chloroplast - with chlorophylls

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Chloroplasts

• small ribosomes
• circular dsDNA
• size 2-5 ?m
• self-replicating
• func photosynthesis

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Chloroplasts cont.

• membranes
• outer membrane
• inner membrane
• thylakoids - granum - grana
• compartments
• intermembrane space
• stroma

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Structural Elements

• Peroxisomes (A P)
• contain enzymes that detoxify and form H2O2
  (hydrogen peroxide)
• enzymes that breakdown fats

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Structural Elements cont.

• Cytoskeleton
• func movement support
• 3 types of fibers
• microtubules
• microfilaments
• intermediate filaments

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Microtubules

• function movement
• protein unit tubulin, ? ?
• thickest, 25 nm in diameter
• forms flagella, cilia, centrioles, and spindle
  apparatus

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Microfilaments

• function contraction and movement
• protein unit actin
• thickness 7 nm

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Intermediate Filaments

• function reinforcement
• protein unit fibrous
• thickness 8-12 nm

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Structural Elements cont.

• Centrioles (A)
• function movement
• found in pairs, at right angles
• 9 sets of triplet microtubules in a ring
• location centrosome

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Structural Elements cont.

• Flagella and Cilia
• function movement
• 9 2 microtubular arrangement
• 0.25 ?m diameter

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• Cilia
• Beat in one direction
• numerous

• Flagella
• Undulate
• one or few

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Chapter 7

• The End

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Symbiosis

• Relationship between 2 different species
• larger organism host
• symbionts - organisms involved

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Symbiotic Relationships

• mutualism - both benefit
• commensalism - one benefits, other not harmed
• parasitism - one benefits at the expense of the
  other

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Endomembrane System

• Related membranes
• nuclear envelope, ER, Golgi apparatus, lysosome,
  vacuoles, plasma membrane
• lumen compartment
• cisternae sacs