Ultrastructure of cells 1.2

Essential Idea: Eukaryotes have a much more complex structure than prokaryotes 1.2 Ultrastructure of Cells Understandings: Prokaryotes have simple cell structure without compartmentalization   Eukaryotes have a compartmentalized cell structure Electron microscopes have a much higher resolution that light microscopes Applications: Structure and function of organelles within exocrine gland cells of the pancreas and within palisade mesophyll cells of the leaf Prokaryotes divide by binary fission Skills: Draw the ultrastructure of prokaryotic cells based on electron micrographs Draw the ultrastructure of eukaryotic cells based on electron micrographs Interpret electron micrographs to identify organelles Deduce the function of specialized cells

I. Prokaryotes Pro = Before Karyon = nucleus

Small (1-10um) with no compartmentalization Features 1. Cell Wall – protects & maintains shape a. Composed of peptidoglycan b. Some have additional layer of polysaccharides called a capsule – helps them stick to things (teeth, food, etc) 2. Cell Membrane – controls what enters and leaves the cell 3. Pili – hair-like growths on outside of cell wall a. Used to join together and transfer DNA between bacteria (sexual reproduction) 4. Flagella – movement 5. Ribosomes – 70s, protein synthesis Annotate picture

Nucleoid region – single, long circle of DNA (chromosome) a. NOT associated with proteins Plasmids – extra tiny circles of DNA Replicate independently Not required for normal conditions but helpful adapt under stress (antibiotics, temperature/pH changes)

Binary Fission 1. DNA is replicated 2. Daughter chromosomes attach to different spots on the plasma membrane 3. Cell elongates and pinches in two

E. Prokaryotes are classified into two distinct domains. 1. Archaebacteria (Archaea) - found in extreme environments like high temps, salt concentrations, or pH. 2. Eubacteria (Bacteria)- traditional bacteria including most known pathogenic forms (E. coli, S. aureus)

II. Eukaryotes Larger – 5-100um Contain a nucleus and membrane bound organelles Compartmentalized – separates chemical reactions and increases efficiency

Cytoplasm – region between membrane and nucleus a. Cytosol – jelly-like filler

Endoplasmic Reticulum – network of tubules and channels composed of lipid bilayer that extends throughout cytoplasm (attaches to nuclear membrane and cell membrane) a. Transport of materials through cell

b. Smooth ER – no ribosomes associated -production of lipids and carbs -production of sex hormones (testosterone and estrogen) -detoxification of drugs/toxins in the liver -storage of Ca++ in muscle cells -transport of lipid-based compounds -helps liver release glucose when needed

Rough ER – studded with ribosomes -site of protein synthesis -protein development and transport -usually closer to nucleus than Smooth ER

Ribosomes – site of protein synthesis a. Can be free floating or associated with Rough ER b. No exterior membrane c. Composed of ribosomal RNA and proteins d. Consist of 2 subunits e. 80s size in eukaryotes

Lysosomes – digestive centers -Arise from Golgi apparatus -No internal structures – just a sac of enzymes -Enzymes all hydrolytic -Fuse with old organelles to breakdown and recycle -Acidic pH

Golgi apparatus -Flattened stacks of membrane called cisternae -Collects, modifies, packages, distributes cell products -cis side – near RER, receives proteins -trans side – releases proteins in vesicles -most prevalent in glandular cells that produce and secrete

Mitochondria -About the size of a bacteria cell -Contain their own DNA in circular chromosome -Double membrane – inner membrane folded to increase SA -Converts food to ATP -Produces and contains its own 70s ribosomes -Can reproduce independently

Nucleus -Surrounded by membrane – nuclear envelope -DNA can carry out function without being effected by other cellular processes -Envelop contains pores to allow communication with rest of cell -DNA in form of chromatin/ chromosomes and is associated with histone proteins -Nucleolus – dense region of DNA where rRNA (component of ribosomes) is produced

Chloroplasts -In algae and plant cells -Double membrane, size of bacteria cell, own circular DNA, 70s ribosomes, can reproduce independently -Thylakoids – membrane sacs that can absorb light -Stroma – like cytosol, full of enzymes for photosynthesis

Centrosome – region near nucleus where microtubules are produced -Microtubules provide structure and allow movement -Centrioles – used for cell division in animal cells

Vacuoles – storage vesicles -Can store water, food, waste, toxins -Bud off of Golgi -Very large in plants, small, temporary or not present in animals -Increase a cell’s SA:V ratio

Cell Membrane -Phospholipid bilayer -In animal cells, secretes substances to create an extra cellular matrix (ECM) -Composed mostly of glycoproteins and collagen -Anchored to membrane -Involved in cell-to-cell communication and signaling -Important for cell differentiation

Cell Wall -Gives shape and support -Limits water uptake Organism Type of Cell Wall Bacteria Peptidoglycan Yeast Glucan Other Fungi Chitin Algae & Plants Cellulose Animals No cell wall

D. Eukaryotes have be divided into 4 distinct kingdoms: 1. Protista-unicellular organisms; or multicellular organisms without specialized tissue 2. Fungi-have a cell wall made of chitin and obtain nutrition via heterotrophic absorption 3. Plantae- have a cell wall made of cellulose and obtain nutrition autotrophically (via photosynthesis) 4. Animalia- no cell wall and obtain nutrition via heterotrophic ingestion

Eukaryotes: Animal Cell

Eukaryote: Plant Cells

Based on the notes you have just taken, work together as a table to compile a list of differences between prokaryotes and eukaryotes.

III. Prokaryotes vs. eukaryotes DNA free-floating (nucleoid region) DNA contained in a nucleus Circular DNA Linear DNA DNA not associated with proteins DNA associated with histone proteins No membrane-bound organelles Membrane-bound organelles 70s ribosomes 80s ribosomes Both are surrounded by a cell membrane, contain DNA, and carry out the functions of life

IV. Plant cells vs. animal cells Plants Animals Cell wall & cell membrane Cell membrane only Chloroplasts & mitochondria Mitochondria only Large central vacuole present No or small vacuoles Carbohydrates stored as starch Carbohydrates stored as glycogen No centrioles Contain centrioles during cell replication Fixed shape More flexible, rounded

V. Why use an electron microscope? Light Microscope Electron Microscope Pass light through sample Pass electrons through sample Inexpensive Very Expensive Simple specimen preparation Complex specimen preparation Magnifies up to 2000x Magnifies up to 500,000x Can use live or dead specimens Must use dead specimens (prep would kill them)