Bio principles Exam 2 – Brooks Latest Update Graded A+

Bio principles Exam 2 – Brooks Latest Update Graded A+ Cytology the study of cells Robert Hooke - observed cork could float - discovered a honeycomb-like structure in a cork slice using a primitive compound microscope - only saw cell walls as this was dead tissue - coined the term "cell" for these individual compartments he saw Two types of microscopes: 1. Light Microscope 2. Electron Microscope Light Microscope - light is focused on specimen by a glass condenser lens - the image is magnified by an objective lens and an ocular lens - projection on photographic film Electron Microscope - a beam of electrons is used instead of light - bombards object with electrons to see small, precise images - electromagnets are used instead of glass lenses - the electron beam is focused on the specimen by a condenser lens - the image is magnified by an objective lens and projector lens - projection on a screen or on photographic film Two Types: 1. Transmission Electron Microscope 2. Scanning Electron Microscope Transmission Electron Microscope (TEM) - magnet lens focus on electron beam - the image can be viewed through a viewing lens - cuts thin slices with a microtome made of diamonds - displays different colors depending on electrons absorbed Scanning Electron Microscope (SEM) - a scanning coil moves the beam back and forth - electrons reflected from the specimen are analyzed by a computer to reconstruct a 3D image Are electrons visible using the electron microscopes? - No, does not take actual pictures of electrons because electrons are too small, too fast - can only see protons and neutrons Which sequence represents the correct order of levels of organization found in a complex organism? organelles → cells → tissues → organs → organ systems Cell Theory all living things are composed of cells and come from cells Cell Size: Why are most cells small? - to maximize the ratio of surface area to volume for regulating the internal cell environment - small cell = large cell surface area - large cell surface area allows for transport (in & out) of cell - small cells have bigger membranes Cell (Plasma) Membrane composed of fluid like phospholipid bilayer, proteins, cholesterol and glycoprotein Cell Wall - outside of the cell membrane in some organisms - composed of carbohydrates (cellulose = plants, chitin = fungi) or carbohydrate derivative (peptidoglycan = bacteria)