Discovering the Cell

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Chapter 4

• Discovering the Cell

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Discovering the Cell

• Contemporaries in the late 1600s
• Robert Hooke
• Simplistic microscope to examine cork
• Referred to compartments as cellulae
• Origin for todays term cell
• Antoni Van Leeuwenhoek
• Invented many simplistic microscopes
• 1st to observe and describe bacteria
• termed animalcules

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Cell Theory

• Smallest unit to demonstrate properties of life
• All living things are composed of cells
• Schleiden and Schwann
• 1 to many billions with different functions
• New cells are formed from existing cells
• Virchow
• Mitosis and meiosis

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Compound Light Microscope

• Visible light is refracted (bent) through glass
  lenses
• Magnification apparent size
• Resolution clarity between 2 points

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Electron Microscope (EM)

• Scanning (SEM)

• Transmission (TEM)

Details of cell surfaces, 3D image
Details of internal cell structures

• Uses a beam of electrons higher resolution
• Cant be used on living cells

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Simplicity of Cells

• Metabolic activity related
• to cell volume and surface
• area
• Volume increases faster
• than surface area
• Ratio constrains size
• Limits amount and speed of stuff (waste and
  nutrients) across membranes
• Larger cell volume needs more nutrients and
  produces more waste
• Eventually the cell becomes big enough that the
  membrane cant transport stuff fast enough
• Effects shapes and body plans too

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Cellular Classification

• Prokaryotes
• NO nucleus (nucleoid region)
• NO membrane bound organelles
• Single, circular DNA
• Smaller, less complex
• E.g bacteria, archaea
• Eukaryotes
• Nucleus
• Membrane bound organelles
• DNA arranged on multiple
• chromosomes
• Larger
• E.g protists, fungi, plants,
• animals

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The Basic Cell

• Plasma membrane
• Phospholipid bilayer
• Regulates movt in and out
• Cytoplasm
• Fills cell
• Contains organelles and surrounding substances
• DNA
• Genetic material
• Location varies in cell types
• Ribosomes
• Synthesize proteins
• Composition varies in cell types

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Prokaryotic Cells

• Nucleoid region
• Chromosome/DNA (see previous)
• Cell membrane
• Cell wall (peptidoglycan)
• Capsule (glycocalyx)
• Cytoplasm
• Ribosomes (antibiotic actions)
• Pili
• Flagellum/Cilia

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Eukaryotic Cells

• Most living organisms
• Protists
• Fungi
• Plants
• Animals
• Organelles allow compartmentalizing
• Different areas carrying on reactions
  independently of rest of cell
• Endomembrane system connects
• Nuclear membrane ? rough ER ? smooth ER ? golgi
  apparatus ? lysosomes/vacuoles ? plasma membrane

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Nucleus

• Control center
• Nucleolus
• Constructs ribosomes
• Chromatin
• All DNA in cell
• Organized into chromosomes
• 6 Feet of DNA in one nucleus!!!
• Nuclear envelope/membrane
• Regulates transport of molecules
• Receptors for signaling
• Nuclear pores
• Allow communication with cytoplasm

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Endoplasmic Reticulum (ER)

• Smooth ER
• No ribosomes
• Lipid synthesis
• Carbohydrate synthesis
• Rough ER
• Ribosomes attached
• Protein and rRNA
• Free or attached
• Synthesize proteins

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Golgi Apparatus (Body)

• Package and process proteins lipids
• Warehouse finishing factory
• Polarity
• Receives vesicles from ER
• Produces vesicles for finished products

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Cellular Production

• Vesicles are sacs containing enzymes
• Lysosomes
• Intracellular digestion
• Destroy bacteria in white blood cells
• Breaks down damaged organelles
• Peroxisomes
• Break down fatty acids proteins
• Detoxify alcohol other toxic substances
• Vacuoles are large storage vesicles
• Varies between eukaryotic cells
• Food vacuoles
• Contractile vacuoles
• Central vacuoles

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Cellular Energy

• Chloroplast
• Photosynthesis
• Plants only
• Mitochondria
• Forms ATP (energy) from carbohydrates
• Site of cellular respiration
• Similar to bacteria have their own DNA
  ribosomes
• May be artifact of ancient symbiotic
• relationship between prokaryotes
• eukaryotes

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Cytoskeleton

• Protein fibers that extend throughout the
  cytoplasm
• Microfilament
• Rods of actin
• Supports shape
• Intermediate filament
• Reinforce shape
• Anchor organelles
• Microtubule
• Produce movement
• Centrioles cilia and flagella

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movement

• Flagella long outer structures for movement
• Usually only a few
• Cilia short outer structures for movement
• Usually many
• Pseudopod
• False foot

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Eukaryotic Cell Types

• Animal Cells

• Plant Cells

Lysosomes and centrioles are only in animal cells
Cell wall and central vacuole only In plant
cells Chloroplasts only in plants