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Transcript
Section 3-1 Cell Size: • Magnification: quality of making an image appear larger than actual size • Resolution: measure of clarity of an image • e- microscopes have ↑ mag/resolution Section 3-1 Light microscopes: •Form an image when light passes through 1 or more lenses to produce an enlarged image of specimen Section 3-1 Types of Microscopes: • Electron microscopes use beam of erather than light to view specimen • Live organisms can’t be viewed w/ emicroscope Section 3-1 Transmission Electron Microscope: • e- beam directed at very thin slice of specimen stained w/metal ions • e- that pass through strike fluorescent screen, forming an image; can’t view live specimen Section 3-1 Scanning Electron Microscope: • e- beam is focused on specimen coated w/ very thin layer of metal • Shows 3D details of surface of specimen; can’t view live specimen Neutrophil (yellow) engulfing anthrax (orange) Section 3-1 Scanning Tunneling Microscope: • Needle-like probe measures differences in voltage caused by e- that leak, or tunnel, from surface of object being viewed • Shows 3D details of surface of specimen • Live specimens can be viewed e- surrounded by 48 iron atoms Section 3-2 Cell Size •Small cells function more efficiently than large cells •If cell’s surface area–to-volume ratio is too low, subs can’t enter/leave cell well enough to meet cell’s needs Section 3-2 Cell Theory has 3 parts: 1. All LT are made of 1 or more cells 2. Cells are basic units of structure/function in organisms 3. All cells arise from existing cells All cells have: • Cell membrane • Cytoplasm • Cytoskeleton • DNA • Ribosome Section 3-2 Prokaryotic cells (bacteria): •Single-celled organisms; no nucleus or internal compartments •Have cell wall, may have cilia/flagella •Have circular molecule of DNA E. coli bacteria cell Section 3-2 Eukaryotic cells (all other LT): •Nucleus contains cell’s DNA •Other internal compartments, organelles Typical animal cell Section 3-2 Cell membrane: • Selectively permeable membrane, determines which substances enter/leave cell • Selective permeability caused by the way phospholipids interact w/ water • Phospholipid made of phosphate group and 2 fatty acids Section 3-2 Proteins are embedded in the phospholipid bilayer to help move substances across cell membrane “Outside of the cell” “Inside of the cell” Section 3-3 Nucleus: •Internal compartment stores cell’s DNA •Nucleus controls cell’s functions •Nuclear envelope is double membrane surrounding the nucleus •Nuclear pores are small openings scattered over surface of nuclear envelope Section 3-3 Ribosome: •Structure where proteins are made Endoplasmic Reticulum (ER): •Extensive network of internal membranes that move proteins and other subs through cell; acts as a highway Section 3-3 Vesicles: •Carry newly made proteins through cytoplasm from ER to Golgi apparatus Golgi apparatus: •Set of flattened, membrane-bound sacs that serve as packaging/distribution center of cell Section 3-3 Lysosome: •Sacs of enzymes that engulf/breakdown large substances into smaller ones Mitochondria: (aka “powerhouse”) •Organelles that convert food energy from organic compounds to make ATP ATP: •Main energy currency of cell; “spendable” Section 3-3 Plants have 3 structures not found in animal cells: 1. Cell Wall: support/maintain shape of cell; protects cells, connect cell to adjacent cells 2. Chloroplasts: uses light energy to make organic compds from CO2/water 3. Large Central Vacuole: stores water, nutrients, wastes Section 3-3 Summary of Organelles: