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Biology 121 exam Review.docx

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BIOL 121
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Biology Midterm 1 Review All about Cells Cell History  1665: Robert Hooke discovers cells, Leeuwenhoek observes cells such as Paramecium  1838: Schwann and Schleiden formulate the cell theory: 1. Cell is the unit of structure, physiology and organization in living things 2. Cell is a distinct entity and building block in construction of organisms 3. Spontaneous generation(Virchow 1858) NOT TRUE 4. Cells pass hereditary information from one generation to another(modern) 5. All cells are based on the same chemistry(modern) 6. Cells trap and use energy to build molecules that make them up(modern)  Louis Pasteur disproved spontaneous generation using broth and a swan-necked flask Cell Types Eukaryotic Cells Prokaryotic Cells Nucleus in center of cell No nucleus Have ER and mitochondria No ER or mitochondria Means ‘before nucleus’ Larger in size Smaller in size(with exceptions) Cell Composition  C, H, O, N, P and S make [lipids, polysaccharides](CHO), [nucleic acids](nucleotides), [proteins](amino acids). All these are dry weight of the cell or macromolecules. Make up 20-30% of cell.  Water(wet weight of the cell) makes up 70-80%. Cell Size  Surface area squares, volume cubes each time the cell divides  Limiting factor to cell growth is SA to Volume ratio, inability to transport quickly or efficiently Cells’ Population Growth  Cells replicate through budding(daughter cells are smaller) or binary fission(divides into 2 equal-sized daughter cells) following the cell cycle: 1. Cell mass doubles, DNA replicates 2. DNA separate, septum forms 3. Septum or cell wall is complete. 4. Cells separate 5. Repeat process  Bacteria replicate in four general phases: 1. Lag phase: cells adapt to the medium. May be shortened if cells come from a previously identical condition 2. Exponential/log phase: cells divide quickly or slowly(depends on number, or type of energy cell) for an amount of time 3. Stationary phase: cells still divide, but more slowly. Some die, and growth and death rate level out 4. Death phase: cell death rate increases and most cells die. Some adapt and use less energy.  During log growth, =population at the time t g=time taken for population to double =initial population size =number of generation per unit time t=time allowed for growth unit time N=# of times for population to double Macromolecules Phospholipids and Lipid Bilayers  Phospholipids compose vesicles, micelles and the cytoplasmic membrane  Are amphipathic(dual-sympathy); have hydrophobic(water-hating) tails and hydrophilic(water-loving) heads Micelles Lipid Bilayers/Vesicles Created by hydrophilic heads facing water and hydrophobic tails facing each other Slender tails Stalky tails Self-assemble Plain surface Have transport proteins etc. on leaflet(surface of a bilayer) Single-layered Bilayered Nucleic Acids  Polymers of nucleotides. Either RNA(ribonucleotides) or DNA(deoxyribonucleotides). Deoxy means lacking oxygen.  Purines: A, G. Pyrimidines: T, U, C(T in DNA only, U in RNA only)  Contain a sugar-phosphate backbone. DNA  Discovered by James Watson and Francis Crick in 1953. They also discovered complementary base pairing(G-C is stronger than A-T due to 1 more H-bond), or Watson-Crick pairing.  Shape of double helix with major(large) grooves and minor(small) grooves was discovered.  Needs a template strand to copy itself into a complementary strand. RNA  More reactive than DNA due to an extra hydroxyl group on 2’ side. Also less degrading.  Possibly the first life-form on Earth.  RNA only has 1 strand, so it H-bonds with itself in a hairpin model. This formation is exergonic. Proteins  Made by ribosomes, then pushed into bilyaers for energy generation, transport etc.  Transport proteins have three classes  Channel: uses facilitated diffusion. Examples are aquaporin(moves water ten times faster than normal), gated proteins(change shape using ATP)…these are also called ion channels. Transport ions and water  Carrier: also called transporters or permeases since their reactions with substrates seem like enzymes’  Pumps: use ATP or an electrochemical gradient. However, transport is ONE-WAY ONLY(unidirectional). An example is the sodium-potassium pump. Pumps allow cells to uptake nutrients despite the concentration gradient, remove waste and maintain constant/non-equilibrium concentrations of inorganic ions. Transporting Osmosis  Depends on hypertonic(outside more concentrated) or hypotonic(inside more concentrated) concentration. Happens when a large concentration of cells want to go through the membrane but can’t. If unprotected, cell bursts.  Movement is spontaneous and continues until equilibrium due to entropy. Diffusion  Particles spreading out in a solvent to minimize entropy. No membrane involved.  One of the 3 mechanisms for crossing the cell membrane. They are 1. Simple diffusion: this 2. Facilitated/passive diffusion: involves a channel or carrier protein and a membrane. 3. Active transport: pumps are involved.  Requires kinetic energy and a medium(solutions or empty spaces for gases) Bonds  Bond energies are listed from strongest to weakest o Covalent(polar/non-polar)……share electrons o Ionic(ions)……………………..transfer electrons o Permanent dipole-permanent dipole(PDPD)…..H-bond
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