2.2 Prokaryotic Cells IB Biology

Prokaryotic Cells First organisms to evolve on Earth –3.5 billion years ago –cyanobacteria Simplest cell structure Eubacteria and Archaea

Origin of Life Miller-Urey Experiment Stimulated pre-biotic life conditions in the lab for 1 week –Ammonia (NH3) –Methane (CH4) –Hydrogen (H2) –Water (H2O) –Spark of electricity (simulate lightning)

Origin of Life Experiment Results Organic compounds found –Amino acids which make up proteins of living things –Experiment not supported today other than to show that life can arise from a chemical origin –Recall: This is evidence supporting the cell theory “all cells come from preexisting cells”

DVD: Cosmos, Carl Sagan 1980s TV series narrated and produced by Carl Sagan He was an astronomer, cosmologist, astrophysicist Episode 2: Chapter 10 One Voice in the Cosmic Fugue Time: min

Prokaryotes: Eubacteria vs. Archaea No true nucleus Heterotrophs or autotrophs Most have cell wall with peptidoglycan Live everywhere Eg. Bacteria –cyanobacteria No true nucleus Heterotrophs Cell wall with no peptidoglycan Live in extreme environments –Salt (halophiles) –Heat (thermophiles) –Methane (methanogens)

Prokaryote Properties Small size Unicellular –One cell must carry out all the functions of life Found everywhere –Can live in various extreme environments –Found in soil, water, volcanoes, intestines and skin

Metabolic Properties 1. Fermentation –Convert lactose (sugar) into lactic acid for yogurt production 2. Photosynthesis –Blue-green bacteria produce their own food 3. Nitrogen Fixation –Convert nitrogen from air into nitrogen compounds useful in soil

Prokaryotic Structures No nucleus No mitochondria No membrane bound organelles

Escherichia coli Scanning Electron Microscope Transmission Electron Microscope Found in your gut

Cell wall –Carbohydrate and protein –Protection –Maintains shape –Prevent bursting Cell (plasma) membrane –Phospholipid bilayer –Partially permeable controls what enters and exits the cell CELL MEMBRANE CYTOPLASM E. Coli Micrograph

Cytoplasm –Fluid, gel-like –Contains free floating molecules Enzymes, ribosomes –Location of chemical reactions of metabolism Nucleiod –Small amount of circular DNA with no protein –Controls cell activities Ribosomes (70s) –Make proteins from RNA messages CELL MEMBRANE CYTOPLASM

Motion Flagella –Protein propeller –Attached to cell wall –Use energy to move cell –Not very flexible Pili –Protein filaments attached to cell wall –Pulled in or pushed out –Used to adhere or “stick” to other bacteria cells to exchange DNA conjugation PILI FLAGELLA

Reproduction Binary Fission –Bacterium replicates its DNA and then divides the cytoplasm –One copy of DNA on each side Cytokinesis

Identify Prokaryotic Structures cytoplasm nucleiod Cell membrane Cell wall ribosome

Homework E. coli handout