BIOl 1441 1st Edition Lecture 9 Outline of Last Lecture I. Proteins a. Side groupsb. Levels of protein structureII. Nucleic acidsa. StructureOutline of Current Lecture I. MicroscopyII. Cell classificationIII. Cell sizeIV. Cell organellesCurrent LectureThe Importance of Cells- All organisms are made of cells.- The cell is the simplest unit of life.- Cell structure is correlated to cellular function.- All cells are related by their descent from earlier cells.Fundamental themes in biology1. Structure = Function2. Cells respond to their environmentThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.I. Microscopya. Discovery of microscope in 16th century enabled us to study cells & their componentsb. Light microscope - visible light to magnify an imagei. Passes light through a specimen & then through glass lensesii. Lenses refract (bend) light, magnifying the imagec. Light Microscopyi. Magnification- ratio of an object’s image size to its real size1. Multiple objective lens (4x) times ocular lens (10x) = 40xii. Resolution- measure of the clarity of the image1. Minimum distance 2 points can be separated and still be distinguished as 2 points2. Shorter wavelength – better resolutioniii. Minimum resolution ~200 nanometers (nm)iv. Magnify effectively to ~1,000 times the size of the actual specimenv. Various techniques enhance contrast and enable cell components to be stainedvi. Most cellular organelles too small to be resolvedd. Electron Microscopyi. Scanning electron microscopes (SEMs)- focus a beam of electrons onto the surface of a specimen1. Provides 3D imageii. Transmission electron microscopes (TEMs)- focus a beam of electrons through a specimen 1. Mainly to study the internal ultrastructure of cellsiii. Electrons shorter wavelength than visible light- better resolution (clarity)1. Resolution 2 nm (much smaller)II. Prokaryotic & Eukaryotic Cells-classify by whether or not they have a nucleusa. Basic features of all cells: i. Plasma membraneii. Cytosol- fluid inside celliii. Genetic informationiv. Ribosomes- make proteinsv. Cytoplasm- interior of cell1. Used interchangeable with cytosol III. Prokaryotes vs EukaryotesNo nucleus NucleusCell wall No cell wall No membrane bound organelles Membrane boundSmaller LargerSimple Complex*bacteria *plants, animals, fungi, protistsIV. Cell Size- plasma membrane limitsa. Logistics of carrying out cellular metabolism sets limits on the size of cellsb. Needs a certain level of metabolic ability to support all reactions taking place inside i. Large cell- high level of metabolismii. Small cell- lower level of metabolismc. Cell can only grow to the extent that it can support itselfd. Increase size ® increase volume & surface areae. Volume increases MORE than the surface area- not proportional- surface area only increases a littlei. Smaller object has a greater surface-to-volume ratio than a larger objectii. High surface-to-volume, facilitate exchange of materials between cell and its environmentf. Area calculated in square units (l x w)g. Volume calculated in cubic units (l x w x h)V. Cell Organellesa. Plasma Membrane: Selective barrier that allows sufficient passage of oxygen, nutrients, waste to service the volume of the celli. Surface area must be sufficiently large to accommodate volume- explains microscopic sizeii. Larger organisms do not have larger cells, they have MORE cellsiii. Function- exchange material with surroundings, need a lot of surface area1. Intestinal epithelial cell- microvilli2. Long thin projections3. Increase surface area, not volumeb. Nucleusi. Nucleus contains DNA (only genomic)1. Some genes mitochondria & chloroplastii. Nuclear envelope encloses the nucleus, separating it from the cytoplasm1. Double membrane (phospholipid bilayer)iii. Nuclear lamina- lines inside of the nuclear membrane1. Netlike array of protein filaments maintains the shapeiv. Nuclear matrix- framework of fibers extends throughout the nuclear interior v. Chromosomes- DNA in discrete units (coiled super tight only right before division)vi. Chromatin- complex of proteins and DNA1. Human Cell- 46 Chromosomes2. BOTH CHROMOSOMES AND CHROMATIN HAVE PROTEIN AND DNA-CLASSIFIED ON HOW TIGHTLY THEY ARE COILEDvii. Nucleolus1. Ribosomal RNA (rRNA) is synthesized2. rRNA is assembled into large & small subunits 3. DNA ® mRNA ® Proteinc. Ribosomesi. Make proteins using DNA as “directions”1. Makes all the same proteins but in different locations depending on what type of proteinii. Made of rRNA and proteiniii. Ribosomes carry out protein synthesis in two locations:1. In the cytosol- free ribosomes2. On the outside of the endoplasmic reticulum (ER)- bound ribosomesd. Endomembrane Systemi. Components of the endomembrane system:1. Nuclear envelope2. Endoplasmic reticulum3. Golgi apparatus4. Lysosomes5. Vacuoles6. Plasma membraneii. Components are either continuous or connected via transfer by vesiclesiii. Endomembrane System Functions1. Synthesize proteins2. Transport proteins into membranes/organelles3. Transport proteins out of cell4. Metabolism & movement of lipids5. Detoxification of poisonse. Endoplasmic Reticulum (ER)i. Accounts for more than 1/2 the total membrane in many eukaryotic cellsii. Consists of tubules and sacs- cisternaeiii. There are two distinct regions of ER:1. Smooth ER, which lacks ribosomes2. Rough ER, with ribosomesiv. ER membrane is continuous with the nuclear envelopev. ER lumen (cisternal space)vi. Smooth ER- lacks ribosomes1. Synthesizes lipids2. Phospholipids3. Steroids- sex hormonesa. Testes/ovaries- lots of smooth ERb. Most important steroid=cholesterol4. Metabolizes carbohydrates5. Stores calcium- muscles6. Detoxifies drugs-livera. Make more soluble- secretei. Add a hydroxyl groupvii. Rough ER- bound ribosomes1. Produces secreted proteinsa. Hormone insulin from pancreas cells 2. Polypeptide chain goes into ER lumen through a pore in ER membranea. Folded into native conformation- PROTEIN FOLDINGb. Secreted proteins- glycoproteinsc. Protein covalently bonded to a carbohydrate3. Secretory proteins distributed by transport vesiclesa. Depart ER wrapped in membranes from transitional ERb. Transport vesicles- vesicles moving from one area of cell toanother4. Makes membranes5. Polypeptide grows from ribosome, inserted into ER membranea. Anchored by hydrophobic portionsb.