The Cell Flashcards
(42 cards)
The cell theory can be summarized as
All living things are composed of cells.
The cell is the basic functional unit of life.
Cells arise only from pre-existing cells.
Cells carry genetic information in the form of DNA which is passed from parent to daughter cell.
The three primary methods available to study the cell and it’s structures are
Microscopy, autoradiography and centrifugation
The compound light microscope is used in
The observation of non-living specimens.
Contrast is obtained through staining techniques.
Total magnification is equal to the product of the eyepiece magnification and the magnification of the selected objective lense.
Phase contrast microscope
Used to study living specimens.
Differences in refractive index are used to produce contrast between cellular structures.
Electron microscope
Uses a beam of electrons to allow 1000x higher magnification then possible with light microscopy.
Tissues must be fixed and sectioned and sometimes stained with solutions of heavy metals.
Autoradiography
Uses radioactive molecules to trace and identify cell structures and biochemical activity ( such as protein synthesis)
Centrifugation
Can be used to separate cells or mixtures of cells with out destroying them.
At low speeds cell mixtures separate based on cell type.
At high speeds cell components separate based on their densities.
Example: ribosomes on bottom and mitochondria and lysosomes on top.
Prokaryotes
Bacteria and cyanobacteria. Contain cell wall. No nucleus. Ribosomes ( subunits = 30s and 50s) No membrane bound organelles.
Eukaryotes
Protist, fungi, plants and animals.
Cell wall present in fungi and plants only.
Contain a nucleus with DNA organized into chromosomes.
Ribosomes ( subunits = 40s and 60s)
Membrane bound organelles suspended in semi-fluid medium called cytosol.c
Cell membrane
Composed of phospholipid bilayer. Exhibits selective permeability. Smaller non-polar ( hydrophobic) molecules defuse freely. Charged ions ( hydrophilic) and large molecules may requires a carrier protein.
Nucleus
Surrounded by nuclear membrane or envelope.
Nuclear pores allow 2 way exchange of materials between nucleus and cytoplasm.
Contains DNA complexed with his tones to form chromosomes.
Nucleolus
Dense structure in nucleus where ribosomal RNA (rRNA) synthesis occurs.
Ribosomes
Site of protein production.
Synthesized by the nucleolus.
Consists of two subunits.
Each subunit composed of rRNA and proteins.
Free ribosomes - found in cytoplasm
Bound ribosomes - line outer membrane of endoplasmic reticulum
Endoplasmic reticulum
network of membrane enclosed spaces connected at points with the nuclear membrane.
With ribosomes - rough ER
Without ribosomes - smooth ER
Endoplasmic reticulum is involved in
Transport of materials through the cell.
Smooth ER- involved in lipid synthesis and detoxification of drugs and poisons.
Rough ER- involved in protein synthesis
Bound ribosome synthesize proteins which then
cross into cisternae of RER and undergo chemical modification.
Then cross into smooth ER, secreted into cytoplasmic vesicles and transported to Golgi apparatus
Golgi apparatus
Stack of membrane enclosed sacs.
Receives vesicles from smooth ER, modifies them (eg glycosylation) repackages into vesicles and distributes.
Secretory vesicles produced by Golgi release contents into cells exterior via exocytosis.
Vesicles and vacuoles
Membrane-bound sacs involved in transport and storage.
Vacuoles are larger than vesicles and more likely to be found in plants.
Lysosomes
Membrane-bound vesicles that contain hydrolytic enzymes involved in intracellular digestion.
Breaks down materials ingested by cell.
Aids in renewing cells components by breaking down old ones and releasing components for reuse.
Autolysis- rupture of lysosome digesting cellular contents (“suicide”)
Microbodies
Membrane-bound organelles specialized as containers for metabolic reactions.
Two important types are peroxisomes and glyoxysomes.
Peroxisomes
Contain oxidative enzymes that catalyze a class of reactions in which hydrogen peroxide is produced by the transfer of a hydrogen from a substrate to an oxygen. Break fats down into smaller molecules that can be used for fuel. Used ion the liver to detoxify compounds harmful to the body.
Glyoxysomes
Found in fat tissue of germinating seedlings.
Used to convert fats into sugar until seedling is mature enough to produce sugar via photosynthesis.
Mitochondria
Sites of aerobic respiration (energy supply).
Semiautonomous - their own circular DNA and ribosomes, self replicate via binary fission.
Cell wall
Protects cell from external stimuli and desiccation.
Animal cells do not have cell wall.
