Lecture 3 Prokaryotes Eukaryotes 1 Components of ALL

Lecture 3 Prokaryotes & Eukaryotes 1

Components of ALL cells Plasma membrane = lipid bilayer that forms a physical barrier to all cells Cytoplasm = the semisolid components within the cell (Cytosol = Fluid portion) Chromosomes = DNA structure containing genes Ribosomes = tiny structures of RNA/protein that synthesize new proteins using instructions from the genes 2

Prokaryotes v. Eukaryotes nucleoid versus a nucleus Cell size - Prokaryotic cells are smaller (Most 0. 2 - 5 µm) 1000 X magnification - Eukaryotic cells are larger (Most 10 - 100 µm) 200 to 500 X magnification Membrane-bound organelles - Almost none in prokaryotes - Eukaryotic cells have many organelles of specialized form and function - Complex cytoskeleton composed of various types of filaments - Large ribosomes 3

Distinguishing Features of Prokaryotes • Nucleoid • No histones • No numerous organelles • Cell walls • Peptidoglycan • Binary fission • Pili or fimbriae • Single Circular Chromosome • Some exceptions • Plasmids • Smaller usually circular pieces of DNA 4

The Prokaryotic Cell Wall Many Types of Bacterial Cell Walls but Two Main Types… 1. Gram Positive 2. Gram Negative Both contain peptidoglycan but differ on amount 5

Hans Christian Gram (1853 -1938) Hans Christian Gram was a Danish doctor studying in Berlin who studied lung tissues of pneumonia victims. He noticed that different bacteria behaved differently when stained with a cationic dye and classified them as Gram positive (stained) or Gram negative (didn’t stain). 6

Fig. 4. p 097 7

Gram Stain Slide Gram + have a thick layer of peptidoglycan 8

N-acetylmuramic acid (NAM) Peptidoglycan • Macromolecule composed of a repeating framework of long chains cross-linked by short peptide fragments – Unique to bacteria – Composed of 2 sugars: NAG & NAM – Sugars alternate in the backbone N-acetylglucosamine – Rows linked by polypeptides (NAG) • Provides strong, flexible support to keep bacteria from bursting or collapsing because of changes in osmotic pressure 9

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Be able to identify all the parts of a Gram + & - cell wall for the next exam. 11

Gram-positive versus Gram-negative Cell Walls Fig. 4. 16 Thick – 20 -80 nm Thin – 8 -11 nm Teichoic acids are found only in Gram-positive cell walls. They are negatively charged and their function is unknown. 12 Lipopolysaccharide and outer membrane are only found in Gram-negative cell walls.

Eukaryotic Cell Wall • Many eukaryotes have a cell • Animal cells have no cell wall composed of a • Elaborate extracellular matrices carbohydrate • Collagen & glycoproteins • Cell wall of algae & plants is • No eukaryotic cell has made of cellulose peptidoglycan in their cell • A carbohydrate chain wall • Cell wall of fungi is made of • Peptidoglycan is unique to bacteria chitin • A carbohydrate chain • Cell wall of yeasts is made of glucan and mannan • A carbohydrate chain 13

Plant Cell Wall Cellulose 14

Fungal cell Illustration shows relationship between the cell membrane and cell wall. Glycocalyx is the outermost section. 15

All Cells have a Membrane Plasma membrane functions as a selective barrier O 2 & nutrients must enter the cell Waste products must exit the cell 16

Lipid Bilayer • Two layers of phospholipids • Main component of cell membranes • Membrane has fluid properties • Most phospholipids and some proteins can drift through membrane – It’s FLUID & not static 17

Fig. 2. 18 18

Fluid Mosaic Model • Membrane is a mosaic of – Phospholipids – Glycolipids – Sterols Carbohydrates • Eukaryotes – Proteins 19

Cell Membrane Pro v. Euk • Prokaryotes – Lipid bilayer – Selectively permeable – Allows secretion – Site for metabolic rxns • Respiration • Photosynthesis – Nutrient processing – Synthesis of proteins & other molecules • Eukaryotes – Lipid bilayer – Selectively permeable – Endocytosis – Exocytosis – Sterols • Cholesterol • Reinforces cell wall – All organelles have a membrane very similar to the cell membrane 20

• Cell membranes of both Prokaryotes and Eukaryotes perform • Diffusion, osmosis & active transport • Endocytosis is unique to Eukaryotes • Phagocytosis • Uses pseudopods - surround and engulf • Pinocytosis • Cell drinking • Plasma membrane folds in on itself • Often times receptor mediated • Exocytosis 21

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Cell Membranes Show Selective Permeability Diffusion Other Mechanisms 23

Plasma Membrane • Passive Transport – Diffusion • Active Transport – Requires energy as ATP (adenosine triphosphate) • Cell membrane proteins carry out many tasks – Highly specialized proteins • Enzymes • Recognition and signaling • Energy Reactions (Prokaryotes) 24

Osmosis • Diffusion of water molecules across a selectively permeable membrane • Direction of net flow is determined by water concentration gradient • Side with the most solute molecules has the lowest water concentration 25

Biological Relevance of Osmosis Cells can be in one of 3 conditions Cell lysis = death Isotonic - solutes balanced Good Situation! Hypotonic - more solute inside cell Plasmolysis = death Hypertonic - more solute outside cell 26

Animal Cell [H 2 O] is greater in the cell than outside [H 2 O] is greater outside the cell than inside 27

Plant Cell Hypertonic [H 2 O] is greater in the cell than outside Isotonic Hypotonic [H 2 O] is greater outside the cell than inside 28

Flagella & Cillia Prokaryotic & Eukaryotic flagella are not similar in size or structure 29

Prokaryotic Flagella • Long filamentous projections used to propel bacteria – 18 -20 nm • Several types of flagella arrangements Monotrichous – One flagellum usually at one pole (Polar) Amphitrichous - tufts of flagella at both poles Lophotrichous - two or more flagella at one pole Petritrichous - flagella distributed over entire surface 30

• Filament - main body of flagella, made of flagellin Parts of the Flagellum • Hook - attaches flagella to basal body • Basal body - attaches flagella to cell • Movement is accomplished by rotating basal body • ATP • Results in rotation of filament • Smooth running or tumbling 31

Direction of Flagellar Rotation Important for Motility • Counterclockwise rotation results in movement • Clockwise results in tumbling • Responds to chemo and phototaxis possible • Attractants induce “running” • Repellants induce “tumbling” • This model is for Escherichia coli 32

Axial Filaments • Spirochetes • Endoflagella • Bundle of fibrils • Run length of organism • Drives spirochete forward in a spiral motion 33

Eukaryotic Flagella and Cilia • Flagella - long (~40 um), few • 10 X larger (diameter) than Pro flagella (~180 -200 nm in width) • Cilia – short (10 um long), many • Oars • Ciliated protozoa & animal cells • Both used for motility • Both have 9+2 microtubule structure • Hollow tubes that slide past one another (made up of tubulin) • Waves and whips • Doesn't rotate - different from bacterial flagella • Pull & push 34

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Motor Protein Dynein ATP 36

Prokaryotic Genome Size Bacteria Escherichia coli Bacillus subtilis Streptococcus pyrogenes Mycobacterium genitalium Archaea Methanococcus jannaschii Sulfolobus solfactaricus Pyrococcus furiosus Size (Mbp) 4. 64 4. 20 1. 85 0. 58 Size (Mbp) 1. 66 2. 25 1. 75 Genome consists of usually one circular chromosome and plasmids (if present) 37

Eukaryotic Genome Size Organism Mbp Homo sapiens Drosophilia melanogaster Plasmodium falciparum Saccharomyces cerevisiae 3000 165 23 12. 07 Eukaryotes also have Mitochondrial DNA Chloroplast DNA Genome usually consists of a number of linear chromosomes 38

Glycocalyx, Capsule & Slime Glycocalyx Outermost layer of cell that come into contact with environment This term is used for both Eukaryotes and Prokaryotes Sticky carbohydrates attached to proteins Important in protection & adhesion Capsule Repeating units of polysaccharide, protein or both (a polymer) Adheres tightly, thick & gummy Mostly a Prokaryotic term – interchangeable with glycocalyx Slime Layer Polysaccharide, protein or both that is easily washed off Mostly a Prokaryotic term 39

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Pili & Fibriae • Prok surface appendages – Pilus is longer • Gram negative bacteria • Conjugation – Fibria is shorter • Bristlelike • Stick to surfaces • Colonize host tissue • Euk do not produce these structures 41

Ribosomes – RNA and Protein Prok Euk All ribosomes are made up of two subunits 42

• Prok Ribosomes • Smaller – 70 S • 50 S & 30 S • Free ribosomes – Located in the cytosol • Euk Ribosomes • Larger – 80 S • 60 S & 40 S • Free ribosomes – Located suspended in the cytosol – Synthesize proteins that function within the cytosol • Bound ribosomes – Are attached to the outside of the endoplasmic reticulum – Synthesize proteins that are included into membranes or 43 exported from the cell

Organelles • • • Membrane-bounded functional units Compartmentalized tasks instead of a mixture Allows for much more variety of functionality Present in Euk Absent in Prok • Prok conduct the similar activities at the cell membrane 44

A View of the Eukaryotic Cell Much more complex - many levels of compartmentalization 45

The Nucleus • Largest organelle - contains DNA • Enclosed by double layered lipid envelope • Pores allow transport of various cytoplasmic substances • Contain nucleoli - sites of r. RNA synthesis • DNA organized by histones • Further organized into chromatin - thread like • Further condenses to chromosomes for replication 46

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The Endoplasmic Reticulum • Extensive network of flattened cisterns continuous with the nuclear envelope • Rough ER - studded with ribosomes • Protein entry point • Modifications made, lipids and carbohydrates attached • Smooth ER - no ribosomes • More enzymatic diversity • Synthesize lipids, oils, phospholipids, steroids 48

Be able to identify all structures listed in this illustration 49

The Golgi Complex • Receives all proteins transported from RER • Mail station of the cell - all proteins sorted for transport • Composed of cisterns - flattened membranous stacks • Many post-translational modifications made • Determines fate of protein • Packaged into secretory vesicle • Can be packaged into transport vesicle (transfer between stacks, transfer to storage vesicles) 50

Lysosomes • Single membrane enclosed vesicles • Contain many digestive enzymes • Play important role in immune response • White blood cells engulf bacteria • Phagosome fuses with lysosome • Digestive enzymes kill bacteria 51

Central Vacuoles • Found in many mature plant cells • Can occupy up to 90% of plant cell cytoplasm • Surrounded by a tonoplast that can • Selectably transport solutes • Functions • Stockpiling proteins or inorganic ions • Storing pigments • Storing defensive compounds against herbivores • Increase the surface to volume ratio for the whole cell 52

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Mitochondria • Generates ATP • Double membrane - structure similar to plasma membrane • Inner membrane - complex folds (cristae), large surface area • Center is matrix • Reactions occur on cristae - ATP generation • Have own ribosomes • Have some DNA • Divide by binary fission 54

Chloroplasts • Found in algae and green plants • Membrane enclosed structure • Contains chlorophyll • Contains other enzymes required for photosynthesis • Chlorophyll contained in flattened sacs - thylakoids • Stacks of thylakoids make grana • Have DNA • Have ribosomes • Divide by binary fission 55

Peroxisomes - Degrade hydrogen peroxide (H 2 O 2) - Unavoidable by-product of oxygen respiration - Peroxisomes convert H 2 O 2 to water - Some break down fatty acids to smaller molecules that are transported to mitochondria for fuel - Others detoxify alcohol and harmful compounds 56

Cytoskeleton • Complex in Eukaryotes • Various-sized thin protein “microfilaments” and microtubules • Maintain cell shape • Used for cellular movement – Cytoplasmic streaming – Pseuodpodia • Support motor proteins – Move molecules in & out of the cell 57

Cytoplasm • Everything inside plasma membrane and outside nucleus • Fluid portion termed cytosol • Packed with enzymes, structural proteins, ribosomes, t. RNA, m. RNA, DNA, pigments • Eukaryotes show cytoplasmic streaming • Prokaryotes do not show streaming 58

Cell Divsion • Eukaryotes undergo mitosis – consists of several steps involving a number of specific structures… is complex because a number of chromosomes must divide and thus be separated • Prokaryotes do not… one circular chromosome… binary fission or “budding” 59

Centrioles • Near nucleus • Organizing center for mitotic organizing apparatus • 9 + 0 array organization • Produces microtubules that separate chromosomes & chromatids • Starting material for flagella & cilia • Found in almost all Eukaryotes, never in prokaryotes 60