1.2 Ultrastructure of cells

1.2 Ultrastructure of cells Understandings Prokaryotes have a simple cell structure without compartments Eukaryotes have a compartmentalized cell structure Prokaryotes divide by binary fission Electron microscopes have a much higher resolution than light microscope Nature of Science Developments in scientific research follow improvements in apparatus: the invention of electron microscopes led to greater understanding of cell structure Applications The structure & function of organelles within exocrine gland cells of the pancreas The structure & function of organelles within palisade mesophyll cells of the leaf Skills Drawing the ultrastructure of prokaryotic cells based on electron micrographs Drawing the ultrastructure of eukaryotic cells based on electron micrographs Interpretation of electron micrographs to identify organelles & deduce the function of specialized cells

Discoveries due to electron microscopes in 1930’s Nature of Science: Developments in scientific research follow improvements in apparatus: the invention of electron microscopes led to greater understanding of cell structure. Discoveries due to improved light microscope in 1850’s Discoveries due to electron microscopes in 1930’s Bacteria Chromosomes Mitosis & meiosis Fusion of gametes Organelles within cells Images of things as small as 0.2μm More intricate details of chloroplasts & mitochondria Existence of ribosomes, lysosomes, & ER Images of things as small as 0.001μm

Understanding: Electron microscopes have a much higher resolution than light microscopes Resolution = the ability of a microscope to distinguish 2 separate points as 2 separate entities Naked eye can see things 0.1mm (100μm or 100,000 nm) as separate objects Light Microscope Electron Microscope * Max resolution = 0.2 μm (200 nm) even if you keep increasing the magnification (limited by wavelength of visible light), you would just get a blurry image Max mag on light scope = 400x Reveal structure of cells Can see bacteria Resolution = 0.001 μm (1 nm) 200X higher than light scope Use beams of electrons with shorts wavelengths, so higher magnification will have higher resolution Reveal ultrastructure of cells (ultra = high definition/extreme) Can see viruses

Understanding: Prokaryotes have a simple cell structure without compartments Pro = before Karyon = nut or kernel Prokaryote = before a nucleus (no nucleus) Cell membrane Cell wall – protects, maintains shape, prevents bursting, made of peptidoglycan, extracellular All cytoplasm One organelle = ribosomes (70S size, S = Svedberg unit) DNA in middle of cytoplasm in “nucleoid” (nucleus-like) DNA is “naked” = not associated with proteins (so appears lighter than cytoplasm, which has proteins (enzymes)) DNA usually one circular piece

Name the parts!

Understanding: Prokaryotes divide by binary fission Binary fission = asexual reproduction DNA replicates The 2 DNAs move to opposite ends of cell Division of cytoplasm

Bacterial conjugation = exchange of genetic material http://youtu

Skill: Draw the ultrastructure of prokaryotic cells based on electron micrographs

Escherichia coli http://www.cellsalive.com/cells/bactcell.htm

Understanding: Eukaryotes have a compartmentalized cell structure Eu = true Karyon = nucleus Instead of one continuous structure, cell is divided into compartments Compartments are single or double membranes Compartments = organelles = little organs with specific functions Advantages: enzymes & substrates can be localized to one area so more concentrated Harmful substances can be compartmentalized in a lysosome pH can be compartmentalized in one organelle Organelles can move around cell, carrying contents

Skill: Draw the ultrastructure of eukaryotic cells based on electron micrographs http://www.cellsalive.com/cells/cell_model.htm http://www.youtube.com/watch?v=k0YqEpA-62A

Let’s practice!

Application: The structure and function of organelles within exocrine gland cells of the pancreas Gland cells = cells that secrete (release) substances thru cell membrane Endocrine glands Exocrine glands Have no ducts secrete hormones directly into bloodstream Have ducts Secrete substances into a duct that carries them somewhere else (Pancreas cells secrete digestive enzymes thru duct into small intestine)

What organelles are needed in a pancreas exocrine gland cell?

Application: The structure and function of organelles within palisade mesophyll cells of the leaf. What organelles are needed for photosynthesis?

Skill: Interpret electron micrographs to identify organelles and deduce the function of specialized cells. https://sites.google.com/a/canacad.ac.jp/sl-hl-1-biology-4- ferguson/unit-1-cells/1-2-ultrastructure-of-cells