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Biology 1021a Midterm Study Notes.docx

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Western University
Biology 1201A

Biology 1021a Midterm Study Notes 10/25/2011 8:55:00 AM Early Microscope Anthony van Leeuwenhoek Father of microbiology first to observe and describe single celled organisms single lens 1673 Robert Hooke Investigated refraction o Wave theory of light First person to coin the word cell to describe the tiniest components of living systems 1635-1703 The Electron Microscope Resolution limit = 0.2 microns (size of small bacterium) o one micron = 0.001mm magnification limit = 1000x introduced in 1950s enabled organelles, viruses, proteins, etc. to be imaged Uses electrons rather than light = better resolution 2 types: o Transmission Electron Microscope (TEM) Looks THROUGH a cell Vacuum o Scanning Electron Microscope (SEM) Looks at SURFACE of cell Three dimensional Light Microscopes Minimum resolution = 0.2microns (size of small bacterium) Can magnify effectively to about 1000x size of actual specimen o At higher magnifications specimen blurs *electron microscopes are used to view smaller objects s/a cell membrane, DNA double helix, hydrogen atom, etc. but can also be used to view many of the same objects as light microscopes s/a plant/animal cells, mitochondrion/chloroplast and bacteria Cell Fractionation take cells apart to study their components centrifuge o used to fractionate cells and separate their major organelles o spins object around a fixed axis o sedimentation principle the motion will cause more dense substances to separate towards bottom of tube, lighter objects will move to the top ultracentrifuges o capable of speeds as fast as 150,000 rpm applying forces over 1 million times the force of gravity The Cell Simplest collection of matter which has all the properties of life 1. Lowest hierarchical level which is alive 2. Cell is basic unit of life 3. Cell performs all functions necessary to live and reproduce Virus Occur in virtually every kind of organism Some wreck havoc, other cause no disease or outward sign of their presence Highly specific to host Can reproduce only when they enter a cell Prokaryotic Cells Pro before, karyote nucleus Examples: bacteria, mycoplasmas No nucleus o Genetic info NUCLEOID (area in cell) Visible components o Plasma membrane o Ribosomes o Nucleoid o Cytoplasm o Cell wall o Pili /Flagella o Mesosomes o Photosynthetic membranes Eukaryotic Cells Found in four kingdoms o Protista o Fungi o Animalia o Planta True nucleus surrounded with nuclear membrane, contains DNA Visible components o Plasma membrane o Cytoplasm o Nucleus o Ribosomes o Organelles o Endomembrane system o Cytoskeleton o Cell wall o Cell matrix o Flagella (in some) The Nucleus genetic library contains most genes in a eukaryotic cell o some are located in mitochondria/chloroplasts about 5 microns in diameter double membrane o fused in some areas = pores that allow large macromolecules and particles to pass through nuclear lamina o lines nuclear envelope o network of intermediate filaments that maintain the shape of the nucleus chromatin = DNA wrapped in certain proteins o appear as diffuse mass o when cell prepares to divide, chromatin fibers coil up to be seen as separate structures chromosomes each species has a characteristic number of chromosomes nucleolus o ribosomal RNA (rRNA) is synthesized and assembled with proteins from cytoplasm to form ribosomal subunits nucleus directs protein synthesis by synthesizing messenger RNA (mRNA) Cytoplasm Material between plasma membrane and nuclear envelope Variable viscosity Main chem. Constituents: o Water (about 80%) o Nucleic acids o Proteins o Lipids o Carbohydrates o Pigments Ribosomes Contain rRNA and protein Composed of two subunits that combine to carry out protein synthesis Cells that synthesize large quantities of proteins (ex. pancreas) have large numbers of ribosomes FREE ribosomes o Suspended in cytosol and synthesize proteins that function WITHIN the cytosol BOUND ribosomes o Attached to outside of endoplasmic reticulum Can shift between roles Endomembrane System Many internal membranes in a cell are part of this system Membranes are connected in one of two ways: o Direct contact o Via transfer of vesicles (sacs of membrane)
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