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Biology 130 Midterm 1 Review.docx

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University of Waterloo
BIOL 130
Heidi Engelhardt

Biology Midterm 1 Review Unit 1: Intro to the Cell Cell Theory: A brief History  Robert Hooke (1635-1703)- invented first microscope and viewed slices of cork (“cellula” which means little rooms)  Antoni Van Leeuwenhoek (1632-1723)- worked with glass and made huge improvements in the quality of lenses. Nearly 300x magnification became possible. He was the first to observe single- celled organisms (animalcule), protists from pond water, sperm, bacteria from his own mouth, blood cells, banded pattern in muscle cells. Father of microbiology.  Progress of the microscope stalled for a century or so because of limited resolving power and the emphasis on description rather than explanation.  In the 1830’s the compound microscope was developed with improved magnification and resolution. It allowed visualization of objects less than one micrometer. Beginnings of Cell Theory  Robert Brown (1833)- botanist that noticed every plant cell contained a round structure (kernel)-nucleus  Matthias Schleiden (1838)- another botanist that discovered all plant tissues are composed of cells. He discovered that embryonic plants always arose from a single cell.  Theodor Schwann (1839)- was a zoologist that had similar observations in animal cells. He recognized the structural similarities between plant and animal cells. Formulated Cell Theory. Cell Theory  All organisms consist of one or more cells.  All cells come from pre-existing cells.  The cell is the basic unit of structure for all organisms. Facts and the Scientific Method  Fact: something we know or believe to be true.  Fact (scientific)- An attempt to state our best current understanding based on observations and experiments. Valid only until revised or replaced by a better understanding, based on more careful observations or more discriminating experiments. What is the Scientific method?  Make observations.  Use inductive reasoning to develop tentative explanation (hypothesis)  Make predictions based on your hypothesis.  Make further observations or design and carry out controlled experiments to test your hypothesis.  Interpret your results to see if they support your hypothesis. What is a theory?  A hypothesis that has been tested under many different conditions and by many different investigators using a variety of different approaches.  By the time an explanation is regarded as theory it is widely accepted by most sciences as truth.  The “solid ground” of science- ie cell theory, evolution, germ theory What is more solid than a theory?  If a theory is thoroughly tested and confirmed over many years by such large numbers of investigators and there is no doubt of its validity, it may become law (ie gravity, gas law) Strands of Cell biology  Biochemistry, cytology (light microscopy-bright field, phase contrast, Fluorescence microscopy, electron microscopy- scanning and transmission), and genetics. Scanning allows us to see birds eye view, transmission allows us to see cross sectional view of structures inside the cell. Basic properties of cells  Cells are highly complex and organized. (composed of macromolecules, atoms, molecules, organelles, plasma membrane)  Cells follow the central dogma (DNA synthesis-DNA to RNA to proteins)  Cells are capable of reproducing themselves but must first replicate genetic material  Cells acquire and use energy (glycolysis, krebs cycle) and carry out a variety of chemical reactions (cellular metabolism)  Cells have many processes that are highly conservative at the molecular level: membrane structure, genetic code, ATP synthesis, actin filament, etc.  Cells engage in many mechanical activities (transports of materials within cell, assembly & disassembly of structures, movement of cell)  Cells respond to environmental signals: move away or towards stimuli and respond to hormones, growth factor, etc.  Cells are capable of self regulation (homeostasis) which is most evident when control systems break down. Cells can fix defects in DNA replication, DNA repair, and cell cycle control. Prokaryotes vs. Eukaryotes  Prokaryotes have no membrane bound nucleus. They have “naked” DNA that are single, circular strands. Prokaryotes have a cell wall and plasma membrane.  Eukaryotes have a membrane bound nucleus.  Prokaryotes are the most diverse cell group (ie spherical, rod-shaped, and spiral cells)  Prokaryotes have two domains: eubacteria (all have cell walls except mycoplasma-smallest and most complex cyanobacteria) and archaebacteria (all have cell walls, extremophiles)  Eukaryotes have four groups: 1) Protists- are a very diverse group. They are mostly single celled, some are colonies. Protists include algae, slime mold, protozoa, water molds. 2) Fungi- are single celled (yeast) and multicellular (mushrooms). They have cell walls and are heterotrophs. 3) Plants- are multicellular autotrophs and have cell walls. 4) Animals- are multicellular heterotrophs. Organelles of Eukaryotes  Cytoplasm: everything between plasma membrane and nuclear membrane. Includes all membrane bound organelles except the nucleus.  Cytosol: the fluid component of cytoplasm.  Endomembrane system: involved in cells transport- nuclear envelope, endoplasmic reticulum, golgi apparatus, lysosomes, vacuoles.  Nucleus- stores genetic info  Mitochondria- generate energy to power the cell  Chloroplasts- capture energy from sunlight, convert to carbohydrate (only in plants)  Cytoskeleton: regulates cell shape, movement of materials and organelles within cell, movement of the cell itself  Transcription (making of mRNA) occurs in nucleus while translation occurs in cytoplasm via nuclear pore. The mRNA runs through the ribosome and connects amino acids in a sequence creating a polypeptide chain.  Flow of traffic within endomembrane system: rough ER-synthesis of proteins for export, insertion into membranes, and lysosomes. Golgi apparatus- collection, packaging and distribution.  Lysosomes: cell stomachs- contain enzymes that digest old organelles and material brought in by phagocytosis.  Mitochondria and chloroplasts contain DNA that encodes some of their own proteins. They have unusual double layered membranes. Endosymbiont theory: Eukaryotes engulfed mitochondria (which were aerobic prokaryotic cells) and some engulfed chloroplasts (which were photosynthetic cyanobacterium). Advantage to host- aerobic respiration, photosynthesis. Advantage to bacteria- protected environment and a supply of carbon compounds from host cell’s prey. Evidence supporting Endosymbiont theory: Mitochondria and chloroplasts:  Are similar sizes to bacteria, reproduce by fission like bacteria  Have double membranes  Have their own ribosomes  Have their own genomes (like prokaryotic genomes) Organisms used in research  E. Coli- DNA replication, gene transcription and translation  Brewers yeast- cell cycle  Arabidopsis thaliana- all flowering plants closely related  Worm- first animal genome to be sequenced  Mouse- genetics well understood and similar to humans Unit 2a-Intro to Cellular Chemistry  Chemistry dictates biology- living organisms are complex chemical systems built from inanimate matter. The chemistry that sustains life must obey the same physical principles as non-living matter.  Cells are made of C, H, N, and O (99%). These elements are combined mostly in macromolecules that make up cell but are also present in simple forms such as water and carbon dioxide. Parts of an atom  Nucleus- dense core made of protons and neutrons  Electrons- continually orbit around nucleus  Atomic number=number of protons  Mass number= number of protons +number of neutrons  And isotope of an element has same number of protons but diff number of neutrons  #of protons= #of electrons in a neutral element  Electrons travel around nuclei in orbitals. Orbitals are grouped into layers or shells, based on how far the electron travels from the nucleus  Electron, Shells, and Valence electrons: innermost shells fill first. Once the first shell is filled (2), the next shell fills in pairs (8), etc. Outermost valence electrons influence an atoms reactivity. Unpaired valence electrons determine the number of bonds an atom can make (valence #)  Unpaired valence electrons and reactivity: completely filled valence electrons are non-reactive (inert gases). Closest to being full are most reactive (Cl, F, O). Elements abundant in living organisms have at least one unpaired valence electron.  How can atoms achieve full valence shells?- By sharing electrons (covalent bond), or transferring electrons (ionic bond)-> negatively charged-anion (gained e-), positively charged- cation (lost e-).  Covalent bonds are strongest and the kinds of bonds present in living organisms most of the time.  Molecule- a group of atoms held together by energy in a stable association.  Compound- molecule composed of two or more different types of atoms.  Polar covalent bonds- electrons are shared unequally b/c one element is more electronegative than the other.  Water is polar, a good solvent, able to form H-bonds. Humans are 70% water.  H-bonding: electrical attraction between electronegative atoms and partial positive charge of H.  Hydrophilic means has an affinity for water, hydrophobic means has no affinity for water. Polar compounds are hydrophilic.  Dissociation: dissolving into ions in water. Water is not completely stable and dissociates into H3O+ and OH-.  Short bonds =stronger, longer bonds= weaker. Bond length determined by atom’s properties, and when repulsive and attractive forces are equal.  Pka: When ph=Pka, species is 50% ionized. When ph>pka, equilibrium lies to the right (ionized form dominates). When ph
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