Transcript Cell Structure

Chapter 4
DISCOVERING THE CELL
Discovering the Cell
• Robert Hooke
– Simplistic microscope to examine
cork
– Referred to compartments as
‘cellulae’
• Origin for today’s term cell
• Antoni Van Leeuwenhoek
– Invented many simplistic
microscopes
– 1st to observe and describe bacteria
• Termed ‘animalcules’
• Contemporaries in the late 1600’s
Cell Theory
• All living things are composed of cells
– Schleiden and Schwann
– 1 to many billions with different functions
• Smallest unit to demonstrate properties of life
• New cells are only formed from existing cells
– Virchow
– Mitosis and meiosis
Compound Light Microscope
• Visible light is refracted (bent) through glass lenses
• Apparent size seen is magnification
• Clarity to discern 2 points as distinct is resolution
– HD TV’s, DVD players, and Blue-Ray players
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
• Can’t be used on living cells
Limits on Cell Size
• Communication time b/w inside and outside
• Interaction of with environment
– Ratio of surface area to volume
• Larger volume needs more nutrients = more wastes
• More surface area speeds mov’t of ‘stuff’
– Volume increases faster than surface area with
growth
• Cell so big transport can’t keep up
• Effects shapes and body plans too
Cellular Classification
• Prokaryotes
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NO nucleus (nucleoid region)
NO membrane bound organelles
Single, circular DNA
Smaller, less complex
E.g. bacteria and archaea
• Eukaryotes
– Nucleus
– Membrane bound organelles
– DNA arranged on multiple
chromosomes
– Larger, more complex
– E.g. protists, fungi, plants, and animals
The Basic Cell
• Plasma membrane
– Phospholipid bilayer
– Regulates mov’t 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
Prokaryotic Cells
• Nucleoid region
• Chromosome/DNA (see
previous)
• Cell membrane
• Cell wall (peptidoglycan)
• Capsule (glycocalyx)
• Cytoplasm
• Ribosomes (antibiotic functions
• Pili
• Flagellum/cilia
Eukaryotic Cells
• Most living organisms
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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
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
Endoplasmic Reticulum (ER)
• Smooth ER
– No ribosomes
– Lipid synthesis
– Carbohydrate
synthesis
• Rough ER
– Ribosomes attached
• Protein and rRNA
• Free or attached
– Synthesize proteins
Golgi Apparatus (Body)
• Package and process proteins
& lipids
– “Warehouse & finishing factory”
• Polarity
– Receives vesicles from ER
– Produces finished vesicle
products
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  protists
• Central vacuoles  plants
Cellular Energy
• Mitochondria  eukaryotic cells
– Site of cellular respiration
• Forms ATP (energy) from carbohydrates
– Similar to bacteria  have their own
DNA & ribosomes
– Double membrane, matrix, cristae
• Chloroplast  plants and algae
– Site of photosynthesis
• Forms sugars from sunlight
– Double membrane, thylakoids, grana,
stroma
• Theorized as both results of
endosymbiosis
Cytoskeleton
• Protein fibers that extend
throughout the cytoplasm
• Microfilaments
– Supports shape and allows change
• Intermediate filaments
– Reinforce shape and anchors
organelles
• Microtubules
– Produce movement
• Cilia, flagella, and pseudopodia
– Assembled by centrioles
Eukaryotic Cell Types
Animal Cells
Plant Cells