DISCOVERING THE CELLChapter 4

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)

• Details of cell surfaces, 3D image

• Uses a beam of electrons = higher resolution• Can’t be used on living cells

Transmission (TEM)• Details of internal cell

structures

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

– 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– 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 TypesAnimal Cells Plant Cells