Introduction to the Cell Ch 1 More than 10 million species o Common threads Growth and reproduction Communication with the environment Acquisition and assimilation of energy Homeostasis Cell Theory o Cells are the functional units of life o All living organisms are composed of cells 8 common features of all cells 1 Highly complex and organized 2 Possess a genetic program 3 Capable of producing more of themselves 4 Biochemical factories that constantly acquire and utilize energy 5 Engage in mechanical activities 6 Able to respond to stimuli 7 Capable of self regulation 8 Evolution first happens at the level of molecules and cells 1 Cells are constructed from a hierarchy of molecular organization 2 Cells possess a genetic program a Organisms are built according to information stored in a collection of genes b Hereditary information defines a species c Genes i Store information ii Blue prints for constructing cellular material iii Directions for running cellular activities iv Program for making more cells v the fundamental molecular mechanisms by which genetic programs are carried out are identical among all cell types vi All cells speak the same hereditary language 1 Can place a gene from one organism into cell of another d Cells duplicate their hereditary information by way of Templated organism and it will be able to read it Polymerization short lived copies i Cells transcribe their hereditary information in chemically similar 1 Fixed set of DNA molecules Working RNA copies ii Proteins carry out the tasks specified by DNA and are the work horses of the cell 1 Central Dogma Flow of information a DNA RNA protein 2 Proteins carry out a cell s activities a Widely varied in structure and function b Many proteins are catalysts i Cells use special classes of proteins as chemical catalysts enzymes 3 Cells are capable of producing more of themselves a Growth and reproduction ultimately occur at the cellular level b Genetic programs enable 2 classes of reproduction that either preserve identical copies of pre existing cells or generate genetic change that lead to variations among individual cells Identical copies mitosis i ii Genetic change meiosis 4 Cells are biochemical factories constantly acquiring and assimilating energy a Cells must accomplish biological order in a universe that favors disorder 5 Cells engage in mechanical activities a Of the astonishing variety of protein classes that carry out the cells activities All cells fall into one of two major categories of existence motor proteins are among the most fascinating o 1 Eukaryotic Cells Animal Cells Plant Cells 10 100um in diameter Nucleus Highly structured internal organization o 2 Prokaryotic Cells 1 5um Lack distinct nucleus Lack detailed internal organization Cell size constraints surface area to volume ratio o Surface area to volume ratio requires that cells be relatively small As cells get larger in volume relative surface area actually decreases Limits how large actively metabolizing cells can become Larger cells needing greater surface area use modifications such as membrane Prokaryotes folding o Evolutionarily optimized for rapid and efficient reproduction o Most biochemically diverse among all organisms Organotrophs obtain energy by feeding on living things or organic material Phototrophs obtain energy by using sunlight to convert inorganic substances into organic material Lithotrophs obtain energy by converting inorganic chemicals into organic Genome Analysis provides a direct means of deducing evolutionary relationships among material species o DNA accumulates random changes through mutation over long periods of time o The number of differences between the DNA sequences of two organisms is proportional to the evolutionary distance between them The Tree of Life o Three different domains in the tree of life o Eukaryotes protists fungi plants animals o Prokaryotes Archea Bacteria Archea and Eukaryotes may have had a common ancestor Archea and Bacteria generally have 1000 6000 genes 1 10Mbp o More than 200 gene families are common to all 3 primary branches of life Genetic Change o New genes arise from existing genes by intragenic mutation or gene duplication o Some genes evolve rapidly others are highly conserved o Not gene is ever entirely new Innovation can occur in several ways Repeated rounds of the process of duplication and divergence over many millions of years have enabled one gene to give rise to a family of genes that may all be found within a single genome How did Eukaryotic cells arise o Endosymbiosis ancestral eukaryotic cell engulfed bacterial cell mitochondria Eukaryotic Cells o By definition have a nucleus and other organelles bounded by internal membranes o Evolved as a predator engulfed other cells 1 billion years ago including prokaryotes resulting in symbiotic relationships o Some prokaryote symbionts evolved into mitochondria chloroplasts As a result eukaryotes have hybrid genomes o Eukaryotic genomes are large 20 000 genes and 10 000 times as much non coding DNA Model Eukaryotes o Model organisms have been chosen in which The genome has been sequences Site directed and tissue specific mutagenesis is possible Expression of multiple genes can be tracked across many cells simultaneously The developmental sequences is known o Examples Yeast the minimal eukaryote Arabidopsis Common Thale Cress C elegans a nematode worm Drosophila melanogaster the fruitfly Mouse Visualizing Cells Ch 9 The Big Picture o Understanding cellular function requires techniques for visualizing individual cells The small size and transparency of cells make this challenging o Light microscopy can be used to image large scale cellular structures but resolution is limited Chemical stains and fluorescent molecules can be used to provide contrast and sensitivity o Electron microscopy allows much higher resolution imaging of cells in much finer detail than light microscopy but requires special cellular preservation and staining techniques o Flow cytometry uses fluorescent labels to measure cellular levels of specific biomolecules and ions and to sort cells based on expression levels or other criteria o Many techniques are used to study cellular functions but the ability to visualize cells and subcellular compartments remains central to the field of cell biology o Cellular structures and most animal cells are too small to see with the naked eye so they must be magnified for study o Development of high quality light microscopes in 19th
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