Introduction to the Cell (Ch. 1)- More than 10 million specieso Common threads: Growth and reproduction Communication with the environment Acquisition and assimilation of energy Homeostasis- Cell Theoryo Cells are the functional units of lifeo All living organisms are composed of cells- 8 common features of all cells1. Highly complex and organized2. Possess a genetic program3. Capable of producing more of themselves4. Biochemical factories that constantly acquire and utilize energy5. Engage in mechanical activities6. Able to respond to stimuli7. Capable of self regulation8. Evolution first happens at the level of molecules and cells1. Cells are constructed from a hierarchy of molecular organization2. Cells possess a genetic programa. Organisms are built according to information stored in a collection of genesb. Hereditary information defines a speciesc. Genesi. Store informationii. Blue prints for constructing cellular materialiii. Directions for running cellular activitiesiv. Program for making more cellsv. the fundamental molecular mechanisms by which genetic programs arecarried out are identical among all cell typesvi. All cells speak the same hereditary language1. Can place a gene from one organism into cell of another organism and it will be able to read itd. Cells duplicate their hereditary information by way of ‘Templated Polymerization’i. Cells transcribe their hereditary information in chemically similar, short-lived copies1. Fixed set of DNA molecules Working RNA copiesii. Proteins carry out the tasks specified by DNA and are the work horsesof the cell 1. “Central Dogma” Flow of information a. DNA RNA protein2. Proteins carry out a cell’s activitiesa. Widely varied in structure and functionb. Many proteins are catalystsi. Cells use special classes of proteins as chemical catalysts (enzymes)3. Cells are capable of producing more of themselvesa. Growth and reproduction ultimately occur at the cellular levelb. 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 cellsi. Identical copies mitosisii. Genetic change meiosis4. Cells are biochemical factories constantly acquiring and assimilating energya. Cells must accomplish biological order in a universe that favors disorder5. Cells engage in mechanical activitiesa. Of the astonishing variety of protein classes that carry out the cells activities, motor proteins are among the most fascinating- All cells fall into one of two major categories of existence:o 1. Eukaryotic Cells Animal Cells, Plant Cells 10-100um in diameter Nucleus Highly structured internal organizationo 2. Prokaryotic Cells 1-5um Lack distinct nucleus Lack detailed internal organization- Cell size constraints: surface area to volume ratioo 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 folding- Prokaryoteso Evolutionarily optimized for rapid and efficient reproductiono 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 material- Genome Analysis provides a direct means of deducing evolutionary relationships among specieso DNA accumulates random changes through mutation over long periods of timeo The number of differences between the DNA sequences of two organisms is proportional to the evolutionary distance between them- The Tree of Lifeo 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 Changeo New genes arise from existing genes by intragenic mutation or gene duplicationo Some genes evolve rapidly, others are highly conservedo 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 membraneso Evolved as a predator—engulfed other cells (>1 billion years ago), including prokaryotes, resulting in symbiotic relationshipso Some prokaryote symbionts evolved into mitochondria, chloroplasts As a result, eukaryotes have hybrid genomeso Eukaryotic genomes are large—20,000 genes and 10,000 times as much non-coding DNA- Model Eukaryoteso “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 knowno Examples Yeast –the minimal eukaryote Arabidopsis (Common Thale Cress) C. elegans – a nematode worm Drosophila melanogaster – the fruitfly MouseVisualizing Cells (Ch.9)- The Big Pictureo 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)- Visualizing Cellso Many techniques are used to study cellular functions, but the ability to visualize cells and
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