Prokaryotes Objective 1.2 Ultrastructure of cells Image: Hospital-associated MRSA by NIAID on Flickr http://flic.kr/p/a4RLq5

Prokaryotes “Before nucleus:” evolutionary precursors to eukaryotes. Escherichia coli (E. coli) http://en.wikipedia.org/wiki/Escherichia_coli

Prokaryotic Cell Parts mesosome cell wall plasma membrane pili cytoplasm nucleoid ribosomes flagella Prokaryotic cell parts are not generally membrane-bound, so we don’t refer to them as organelles. Cell structures animation: http://www.wiley.com/legacy/college/boyer/0470003790/animations/cell_structure/cell_structure.swf

Prokaryotic Cell Parts mesosome cell wall: protective protein-based coating (Gram + / Gram -) plasma membrane: selectively permeable, controls entry & exit of materials to and from the cell. pili: attach to other bacteria for DNA transfer cytoplasm: contains enzymes for metabolic reactions nucleoid: closed-loop of bacterial DNA in a condensed area ribosomes: protein synthesis (transcription & translation) flagella: whiplash-like motion causes movement Cell structures animation: http://www.wiley.com/legacy/college/boyer/0470003790/animations/cell_structure/cell_structure.swf

Prokaryotic Cell Parts mesosomes These don’t really exist naturally as bacterial cell parts, and could be an example of a paradigm shift in thinking. They were observed in some electron micrographs and thought to be in-folds of membrane used for division, respiration or making cell walls… … turns out they are an artifact of the preparation method for some electron microscope images. Cell structures animation: http://www.wiley.com/legacy/college/boyer/0470003790/animations/cell_structure/cell_structure.swf http://en.wikipedia.org/wiki/Mesosome

Past-paper question: E. coli TEM image Identify these structures: I. II. III. IV. Calculate the magnification of the image. Image from IB Biology QuestionBank CDRom – get a copy here: https://store.ibo.org/biology

Past-paper question: E. coli TEM image Identify these structures: I. Plasma membrane II. Cell wall / pili III. Nucleoid IV. Cytoplasm / ribosomes Calculate the magnification of the image. 1. Measure the scale bar in mm. 2. Multiply x 1000 to convert to μm. That is the magnification. How long is the bacterium? Image from IB Biology QuestionBank CDRom – get a copy here: https://store.ibo.org/biology

PROKARYOTES E P R O D U C through binary fission two-parts splitting

binary fission PROKARYOTES E through P R O D U C The closed-loop DNA of the bacterium makes copies through semi-conservative DNA replication. New plasmids are pulled to opposing poles by the spindle fibres. The bacterium divides in two.

http://www.youtube.com/watch?v=gEwzDydciWc

What about conjugation?

Eukaryotes Life with a nucleus Image: Hela Cell nuclei via http://en.wikipedia.org/wiki/File:HeLa_cells_stained_with_Hoechst_33258.jpg

Eukaryotic vs. Prokaryotic Cells Eukaryotic Cells DNA in ring form without protein DNA with proteins: chromosomes/chromatin DNA free in cytoplasm (nucleoid region) DNA enclosed within a nuclear envelope (nucleus) No mitochondria Mitochondria 70s ribosomes 80s ribosomes No membrane bound organelles Membrane bound organelles

Animal Cells

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EUKARYOTIC CELLS

NUCLEUS

Nucleus Structure: Double membrane, continuous with ER Contains DNA and proteins DNA wound around proteins organized into chromosomes Perforated by pores Nucleolus inside Function: DNA is code for proteins, genetic information Nucleolus made up of ribosomal RNA, which makes up the ribosomes where protein synthesis happens Pores allow mRNA and rRNA to leave nucleus

RIBOSOMES

Ribosomes Structure: Made of rRNA and protein Small and large subunits Some are attached to endomembranous system, some are free Function Site of protein synthesis Proteins made on bound ribosomes are secreted outside the cell Proteins made on free ribosomes are used inside the cell.

ENDOMEMBRANE SYSTEM Endoplasmic reticulum

Endoplasmic Reticulum Smooth ER has no ribosomes, has enzymes embedded in the membrane Rough ER has ribosomes Smooth ER: synthesis of lipids, metabolism of carbohydrates, detoxification of drugs and poisons. Stores Ca++ in muscle cells Rough ER: synthesis of proteins and glycoproteins Makes membrane proteins and phospholipids that makes up its own membrane

Golgi Apparatus

Golgi apparatus Function: Structure: Flattened, membranous sacs called cisterns Function: Proteins and phospholipids are modified Products leave in vesicles, these can go to other places in the cell or to the membrane for secretion. Products are tagged chemically so they go to the correct places

Lysosome

lysosome Structure: Membranous sac with digestive enzymes Only in animal cells Functions: Intracellular digestion of macromolecules Recycling of damaged organelles called autophagy

Mitochondria Structure: more detail when we learn about respiration Function: cellular respiration Why I am obsessed with my mitochondrial function

Vacuoles Similar to lysosomes, have hydrolytic enzymes Present in plant and fungi, protista Functions: Food vacuoles store food Contractile vacuoles in protists control water and salts Plants have central vacuole that gives internal support, stores organic molecules, pigments, poisons

chloroplast Structure: more detail when we learn about photosynthesis Function - Photosynthesis

Page 24 in your textbook

Animal Cell vs. Plant Cell Feature Animal Plant Cell wall Not present Present- composed of cellulose Carbohydrate storage Glycogen Starch Chloroplast Present in plant cells that photosynthesize Vacuole Small if present at all Large, fluid filled vacuoles Centrioles Centrioles within a small centrosome area No centrioles

Grab a whiteboard…quick quiz :) A cell has cytoplasm, a cell wall, naked DNA and ribosomes. Based on this information, what type of cell could this be? A. A cell from a pine tree B. A grasshopper cell C. A human red blood cell D. A bacterium Prokaryotic cells lack a true a) ribosome b) mesosome c) cytoplasm d) nucleus

Quick quiz….

Identify the labeled structures in this liver cell TEM image. Calculate: The magnification of the image The maximum diameter of the nucleus Source: http://www.udel.edu/biology/Wags/histopage/empage/empage.htm

Identify the labeled structures in this liver cell TEM image. golgi apparatus plasma membrane ribosome vesicles rough er nucleus Scale bar measures 33mm Actual = Measured/magnification Mag = 16,500x Diameter measures 85mm Actual = 5.15 µm Calculate: The magnification of the image The maximum diameter of the nucleus Source: http://www.udel.edu/biology/Wags/histopage/empage/empage.htm

What you’ll see under your microscope Today’s :ab This is what your drawings should look like!