mbb201 topic 1

organelles, cells and microscopes

whats a cell

the structural and functional units of all living organisms

whats an organ

a fully differentiated structural and functional unit in an animal that is specialized for some particulary function

tissue - cells that aggregate to form a specific function

four characteristics of cells

1.cells can vary enormously in appearance 2.cells function but have the same basic chemistry 3. cells have evolved from the same ancestral cell 4. genes provide the insturctions for cell form, function and complex

what does it mean to say that cells have the same basic chemistyr

1.genetic info is carried in the form of genes which provide the necessary information for a cell to function 2. genes are encoded by dna 3. central dogma of molecular biology dna→rna→protein

what do genes do

1. genes provide the instructions for cell form, function and complex behavior 2. genome provide the genetic info program that instructs the cell how to behave 3. different cells in the same organism have the same DNA but express different genes and produce diff proteins depending on their state, cues

what are the 3 fundamental features of all cells

1.nucleus in eukaryotic or nucleoid in prokaryotic 2.plasma membrane 3. cytoplasm

prokaryotic vs eukaryotic cell

prokaryotic: no membrane bound organelles, smaller, nucleoid, single circular chromosome, cytoplasm boudn by plasma membrane. eukaryotic cell: membrane boudn organelles, larger, nucleus, multiple linear chromosomes, plasma membrane bound by plasma membrane

nucleus/nucleoid function

nucleus: membrane enclosed organelle containing the cell’s genetic material, contains nuclear pores, nucleoid: region of cell which contains most of the cells gneetic material , not surrounded by membrane

mitochondira

generate usable energy from food to power the cell, contains some of their own dna and reproduce by division, contains an inner and outer membrane, contribute to celllular respiration, generates atp,

chloroplasts

eukaryotic plant cells use cholorplasts to capture energy from sunlight

whats the endosympbiont theory

both mitochondria evolve from ancient bacteria - they both have theri own ddna and ribosomes and can produce some of their own proteins, early eukaryotes may have ingested bacteria by phagocytosis without then digesting them, allowing a symbiotic relationship to develop

cytosol vys cytoplasm

cytosol is the aqueous fluid portion of the cytoplasm, cytoplasm includes the aqueous portion, the suspeded particles and the organelles

ER

major site of protein, membrane lipid and oligosaccharides synthesis, contiuous with the outer membrane of the nuclear envelope

rough er

ribosomes attached to the ER translate rna into proteins,

smooth er

synthesis of lipids and steroids, drug detox

golgi apparatus

processing station, stacks of flattened membrane-enclosed sacs that modifies and packages molecules mad in the ER destined to be secreted or sent to another compartment, exchange of material is mediated by transport vesicles, membranae vesicles that transfer material to and from compartments

lysosomes

acidic organelles that are the principal site of intracellular digestion, hydrolytic enzymes are activated by the acidic lysosomal environment maintainted by an ATP drive h+ pump, hydrolases delivered from the ER via the golgi apapratus (secretory vesicles containting these enzymes often become lysosomes)

perioxisomes

carry out oxidation reactions leading to the production of hydrogen peroxide, prominent in the liver and kidney cells of animals, detoxify other harmful compounds, and catavolize unusual substances, generate harmful highly reactive oxygen species to detoxify harmful compounds but also detoxifies using catalase, used in the breakdown of fatty acids into acetyl coa

secretory vesicles

not an organelle but an important part of teh endomembrane system - the er, golgi and secretory vesicles and lysosomes make up the endomembrane system of the cell responsible for trafficking substances through the cell - once processed by the golgi coplex, materials to be exported from the cell are packaged into secretory vesicles, these move to the plasma membrane and fuse with it, releasing their contents outside the cell through exocytosis

what does the cytoskeleton do?

-provides spatial and mechanical framework for cells to function, network of protein filaments in the cytoplams involved in strength, organization, movement, shape, cell division, each type of cytoskeletal filament is constructed from smaller subunits: actin(thin, mostly in muscle), microtubule(thickest, forms mitotic spindle during cell division), intermediate filaments(provide structure and support)

function of cell membranes

1.define boudnaries of a cell and organelles and act as permeability barriers 2. serve as sites for biological functions (e- transport, protein sorting) 3.possess transport proteins that regulate the movement of substances into and out of cells and organelles 4.contain protein molecules that act as receptors to detect external signals 5.provdie mechanisms for cel to cell contact adhesion and communication

whats resolving power(resolution)

the ability of an imaging device to distinguish adjacent objects as separate from each other

light microscopy staining

light passing through an unstained, living cell endergoes very little change in amplitude but the phase of light is changed and small phase difference can be made visible by using special lenses, specialized light microscopy techniques that have been developed for observing living and fixed cells

whats fluorexcence microscipy

can be used to localize and quantify specific molecules in fixed and live cells, light is absorbed at one wavelength and emitted at a longer wavelength, ex: DAPI has an absorption max of 358nm and an emission max of 461nm

two fluorexcence microscope filters

1. filters light before hitting the specimen, allowing only the wavelength of light that excites the fluorexcent dye, 2. blocks all light except the wavelength of light emitted by the excited fluorexcent dye

properties of fluorexcence microscopy

-some fluorescent dyes can be added directly to live or fixed samples, fluorochromes can be conjugated to antibodies to specifically target protein of interest, its selective

whats confocal fluorexcence

allows one to distinguish structures in the middle of a cell from those at the top or bottom

what are the two types of electron microscopy

transmission EM and scanning EM, the main difference is the location of the specimen and detector during analysis, both reveal the strucure of a cell

why can’t we see atoms with electron microscopes

-hydrogen atoms have a radius of 53pm - theoretical limit of 300keV electron microscope is 100pm, but biological samples are fragile and won’t survive high energy electron beams