Section 1F - Prokaryotes, eukaryotes and cellular evolution F2024_p.pdf

Section 1: Introduction to Cell Biology A The basic building blocks of life B Chemical information (DNA, RNA, making proteins) C Protein Structure and Function D Regulating protein function (phosphorylation and GTP binding) E Cellular Organization: organelles F...

Section 1: Introduction to Cell Biology A The basic building blocks of life B Chemical information (DNA, RNA, making proteins) C Protein Structure and Function D Regulating protein function (phosphorylation and GTP binding) E Cellular Organization: organelles F Prokaryotes, Eukaryotes and cellular evolution G Cellular Energetics H Experimental Methods - Studying gene function For reference reading (optional): Alberts 7e, Chapter 1, pages 10-22, 26-31 1  Section 1F: Prokaryotes, eukaryotes and cellular evolution 1. Domains of life - Differences between prokaryotes & How did eukaryotic cells evolve? eukaryotes - Last universal common ancestor 2. Evolution of a) the nuclear envelope b) Mitochondria c) chlotoplasts 2  PROKARYOTES vs EUKARYOTES Plasma membrane DNA Yeast cell is an eukaryote: Have membrane-bound organelles, E. Coli is a prokaryote; cell including the nucleus which membrane no nucleus or sequesters the DNA 3 other membrane organelles  DOMAINS OF LIFE Fig 1-9 4  PROKARYOTES AND EUKARYOTES Prokaryotic cell: lacks a nucleus enclosing the genetic information (DNA) lacks other membrane-bound organelles. the plasma membrane is the only membrane structure of these cells. are mainly bacteria and archea Eukaryotic cell: Genetic information (DNA) is enclosed by the nucleus, a (double) membrane-bound organelle Contain various membrane-bound organelles with distinct functions Contain a cytoskeleton, a network of filaments Mitochondria and chloroplasts are organelles with their own genome 5  Last universal common ancestor (LUCA) of all living organisms The last organism that was a common ancestor to Bacteria, Eukayotes and Archae Lived about 3.5 billion years ago Was a fairly complex cell already: Had enzymes that could synthesize lipids to make cell membranes Had complex metabolic enzymes and pathways Had translation (and ribosomes) Number of changes Kim and Caetano-Anollés. 2011. The proteomic complexity and rise of the primordial ancestor of diversified life. BMC Evolutionary Biology. 11:140 6 SINGLE AND MULTICELLULAR ORGANISMS THE CELL IS THE BRICK THAT BUILDS ALL ORGANISMS Or a few to trillions of cells = one organism One cell = one organism Bacteria (prokaryote) Yeast (eukaryote) Plant Mouse (Eukaryotes) 7  Plausible Origin of Eukaryotic Cells Primordial eukaryotic cells may have been predatorial, eating other cells White blood cell, neutrophil, eating a red blood cell by phagocytosis http://vimeo.com/70326148 8  Plausible Origin of Eukaryotic Cells Primordial pre-eukaryotic cells (archae) may have been predatorial, eating other cells The process by which cells eat other cells is called phagocytosis Many current cells do this: from amoeba to our immune cells Requires change in cell shape driven by the cytoskeleton filaments Likely, nuclear enclosure would be advantageous to protect DNA from entanglement and breakage when cells are “eating” during phagocytosis 9  Predatorial eukaryotic cells may also explain the origin of mitochondria and chloroplasts 10  Mitochondria and chloroplasts are unique among other organelles Mitochondria Chloroplasts Fig. 1-25, 1-28 1. Energy organelles 2. Are defined (surrounded) by a DOUBLE MEMBRANE (like the nucleus) 3. Have their own genome. 4. Have their own ribosomes and transfer RNAs to make proteins (like cells) 11 Plausible Origin of Mitochondria and chloroplasts Early eukaryotic-lineage Some bacteria taken in by cells that ”eat” other phagocytosis didn’t get smaller cells by digested and “lived” in early phagocytosis eukaryote: endosymbiosis 12  Plausible Origin of Mitochondria and Chloroplasts Mitochondria Primordial cell relied on predation (eating) of oxidizing bacteria After an “attempt” at eating an oxidizing bacterium, the “digestion” stalled and the two organisms became symbiotic: large cell provided protection and food molecules and bacteria oxidized food to release energy (ATP) Symbiotic relationship eventually became permanent by loss of redundant genomes Chloroplasts Predation of photosynthetic bacteria (e.g. cyanobacteria) Became symbiotic: cyanobacteria converted sunlight to food while large eukaryotic cell with mitochondria oxidized food molecules to chemical energy Symbiotic relationship eventually became permanent by loss of redundant genomes 13 Plausible Origin of Eukaryotic Cells Stage 1 (nucleus): Ancestral pre-eukaryotic cells were likely predatorial, eating other cells by phagocytosis. Evolved the nucleus to protect DNA molecules from damage Stage 2 (mitochondria) Predation of oxidizing bacteria lead to endosymbiosis and eventually mitochondria. Stage 3 (chloroplasts) A line of mitochondria-containing eukaryotic cells may have internalized photosynthetic bacteria (cyanobacteria), which became chloroplasts. 14  Summary Section 1F: Prokaryotes, eukaryotes and cellular evolution There are key differences between prokaryotes and eukaryotes Presence of a nucleus Presence of mitochondria and/or chloroplasts Presence of many other membrane-bound organelles Prokaryotes and eukaryotes evolved from a common ancestor Organelles in eukaryotic cells have many important functions Evolution each of the following occurred in this order after appearance f phagocytosis Nuclear envelope Mitochondria chloroplasts 15