Cell Structure and Function Cell Theory Based upon

Cell Structure and Function

Cell Theory Based upon work of Theodor Schwann, Matthais Schleiden and Rudolph Virchow. ¡ All organisms are composed of cells ¡ Cells are the basic units of structure and function in organisms ¡ Cells come only from preexisting cells because cells are selfreproducing. ¡

Why are most cells microscopic? Cells need a large surface area to adequately exchange nutrients and wastes ¡ surface-area-to-volume ratio ¡ Total surface area (Hx. Wx. Sx. C) divided by total volume (Hx. Wx. Lx. C) ¡ Some organelles have microvilli, villi and rugae to increase surface area ¡

Microscopes 17 th century – Leewenhooke ¡ Compound Light Microscope ¡ Uses light rays and glass lenses to focus ¡

Transmission Electron Microscope ¡ ¡ ¡ Electrons pass through the specimen Focus by magnetic lenses Image projected on fluorescent screen

Scanning electron microscope ¡ ¡ ¡ Narrow beam of electrons scan surface of specimen Specimen is coated with metal layer Secondary electrons given off by metal produce an image on a screen

Magnification and Resolution ¡ ¡ ¡ Light microscope = approx. 1000 x TEM = hundreds of thousands Difference is in illumination – wavelength of electrons is shorter than wavelength of light. Greater resolution=greater detail Resolution – minimum distance between 2 objects at which they can still be seen as two separate objects. If humans eyes are set at 1. 0, LM=500, EM = 100, 000 resolving power.

Viewing advancements To increase the contrast of a specimen, different types of light, staining and optical methods can be used. ¡ Confocal microscopy – 3 -D using laser beam. ¡ Video enhanced contrast microscopy ¡

Prokaryotic Cells Lack nucleus and membrane bound organelles ¡ Can cause disease, decompose and help to make foods/chemicals ¡ Classified into 2 Domains ¡

Structure Bacillus – rod shaped ¡ Coccus – sphere shaped ¡ Spirilla – rigid twisted rods ¡ l (called spirochetes if flexible)

Cell envelope ¡ Plasma membrane – phospholipid bilayer embedded with proteins Regulates materials into and out of the cytoplasm l Internal pouches – mesosomes – increase surface area for enzymes Cell wall – contains peptidoglycan – maintains shape Glycocalyx – layer of polysaccharides outside of cell wall, aids in protection from immune system and attachment capsule – if organized and hard to remove slime layer – if unorganized and easy to remove l

Cytoplasm Nucleoid region – houses the single circular strand of DNA ¡ Plasmid – extrachromosomal piece of circular DNA used as vector in GE ¡ Ribosomes ¡ Inclusion body – stored nutrients ¡

Cyanobacteria Photosynthetic bacteria ¡ Contain thylakoids in cytoplasm that contain chlorophyll that absorb solar energy to produce carbs. ¡ Release oxygen ¡

Appendages – made of protein Flagella – locomotion, made of filament, hook and basal body ¡ Fimbriae – small, bristlelike fibers on surface of cell, attachment ¡ Sex Pili – rigid tubular structures, exchanging DNA - conjugation ¡

Domain: Archaea No peptidoglycan in cell wall ¡ More diverse in shape ¡ May be more closely related to eukaryotes because of biochemical make-up. ¡ Live in extreme habitats, like those of long ago… ¡