Chapter 6: A Tour of The Cell 1 Flashcards
Light Microscope
Visible light is passed through a specimen. Glass lenses refract light to magnify it.
Magnification
Ratio of image size to real size
Resolution
Clarity. The minimum distance two points can be separated and still be distinguished as two points. Inversely related to wavelength of radiation that microscope uses.
Contrast
accentuates differences in parts of sample
Electron microscope
focuses beam of electrons through specimen. electron beams have very short wavelengths.
Scanning Electron Microscope
Used for topography. The sample is coated with a thin film of gold. The electron beam excites electrons on the surface which are converted to a pattern on the screen.
Transmission Electron Microscope
Used for internal structure of cells. Aims electron beam through thin section of specimen, which is stained with heavy metals that attach to cellular structures and enhance electron density. Electromagnets are used as lenses to focus image of transmitted electrons.
Brightfield
Light passes directly through specimen. sometimes stained with dyes for contrast (needs preserved cells).
Phase-contrast
Variations in density are amplified to enhance contrast in unstained cells (can be living).
Differential-interference-contrast (Nomarski)
Exaggerate differences in density (3D)
Fluorescence
label molecules with fluorescent dyes. reveals locations of molecules
Confocal
uses laser to eliminate out-of-focus light from thick sample. captures sharp images at many different planes to make 3D reconstruction.
Deconvolution
Digitally removes out of focus light and reassigns it to the source.
Super resolution
Lights up individual fluorescent molecules and record position.
Artifacts
structural features seen in micrographs that do not exist in living cell
Cell fractionation
Technique that isolates cell components based on size and density.
Cell fractionation steps
- Centrifuged at 1000g for 10 minutes (pellet rich in nuclei and cellular debris)
- 20,000 g for 10 minutes. Pellet rich in mitochondria (and/or chloroplasts)
- 80,000 g for 60 minutes. Pellet rich in microsomes (pieces of plasma membranes and cells’ internal membranes)
- 150,000 g for 3 hours. Pellet rich in ribosomes
Supernatant
Liquid from centrifuge that is poured into another tube and centrifuged at a higher speed
Cytosol
Semifluid, jelly-like substance inside cells where subcellular components are suspended
Eukaryotic Cell
Most of the DNA is inside the nucleus. Larger than prokaryotic cells. (10-100 um)
Prokaryotic Cell
DNA inside nucleoid. Has ribosomes
Nucleoid
Region where cell’s DNA is located (not enclosed by a membrane)
Cytoplasm
Region between nucleus and plasma membrane
Organelles
Membrane-bound structures of specialized form and function. Absent in prokaryotic cells
Plasma membrane
Boundary of every cell that functions as selective barrier
Surface area/volume ratio
Cells need large surface area/volume ratio for more exchange with environment
Nucleus
Contains most of the genes in eukaryotic cell. 5 um in diameter.
Nuclear envelope
encloses the nucleus and separates it from cytoplasm. It is a double membrane of lipid bilayers 20-40 nm apart. Perforated by 100nm pores structures (where the inner and outer membranes are continuous)
Nuclear lamina
Netlike array of protein filaments that maintains shape of nucleus by mechanically supporting the nuclear envelope
Pore complex
protein structure outlining each pore and regulates entry/exit of proteins, RNA, and other macromolecules.
Nuclear matrix
framework of protein fibers extending throughout nuclear interior
chromosomes
The structures that carry DNA. One long DNA molecule with many proteins.Each eukaryotic species has specific number of chromosomes
chromatin
complex of DNA and proteins making up a chromosome. condenses as cells prepare to divide.
Nucleolus
located inside nucleus. It’s where rRNA is formed and where proteins from cytoplasm are assembled with the rRNA into large and small ribosome subunits (exit through nuclear pores). nucleus can have 2+ nucleoli.
Ribosomes
made of rRNA and protein. carries out protein synthesis.
Bound ribosomes
attached to outside of ER or bound to nucleus. Makes proteins for insertion into membranes, packaging within certain organelles, or secretion.
Free ribosomes
Suspended in cytosol. Function within the cytosol
Endomembrane system
Nuclear envelope, ER, Golgi apparatus, lysosomes, vesicles/vacuoles, plasma membrane. Carries out synthesis of proteins, transport of proteins into membranes/organelles or secretion, metabolism and movement of lipids, detoxification of poisons. Physically connected or connected by vesicles.
Vesicles
tiny sacs made of membrane
Endoplasmic reticulum
Extensive network of membranes (over 50% of the cell’s membranes). Has two connected regions, smooth ER and rough ER.
Smooth ER
Outer surface lacks ribosomes
- synthesis of lipids (oils, phospholipids, steroids)
- detoxification (adds hydroxyl groups). smooth ER proliferation causes tolerance
- storage of calcium ions
- carbohydrate metabolism
Rough ER
Makes secretory proteins and makes membranes for the cell (transferred through transport vesicles)
Glycoproteins
Proteins with carbohydrates covalently bonded. Form most ER secretory proteins.
Transport vesicles
vesicles that move to different parts of cell
Golgi apparatus
made of cisternae. It is polar (cis/trans face). Modifies/stores ER proteins and makes many polysaccharides (pectins, other noncellulose). Adds molecular identification tags (like ZIP codes)
Cisternae
flattened membranous stacks
Cis face
located near ER. Recieves vesicles that fuses with it.
Trans face
gives rise to vesicles that pinch off.
Cisternal maturation model
cisternae of Golgi progress forward from cis to trans face while carrying/modifying cargo
Lysosome
membranous sac of hydrolytic enzymes used by animal cell to digest (hydrolyze) macromolecules. Very acidic (shape of inner proteins protect it from destruction). Made in ER -> Golgi.
Phagocytosis
engulfing smaller organisms/food particles. forms a food vacuole that fuses with lysosome. digestion products pass into cytosol.
autophagy
when lysosomes use hydrolytic enzymes to recycle the cell’s own organic material. damaged organelle/part of cytosol enclosed by double membrane and lysosome fuses with outer membrane. enzymes dismantle inner material.
Vacuoles
large vesicles from endoplasmic reticulum and Golgi apparatus. vacuolar membrane is selective.
Contractile vacuoles
pump excess water out of freshwater protists
plant vacuoles
stores important organic compounds (seed), store poisonous compounds to protect against animals, store pigments
central vacuole
large vacuole in plant cells that developed through coalescence of smaller vacuoles. Contains cell sap (stores inorganic ions). enlarges as vacuole absorbs water.
