The Living Cell

Pregunta	Respuesta
Archaea	Enzymes form extremophiles e.g. thermostable DNA polymerase
Cell Membrane	Maintain chemical integrity by separation - amphipathic bilayer. Best in liquid crystallised state. Selective permeability
Cell wall	Fully permeable. Cellulose in plants - most abundant polysaccharide Peptidoglycan Chitin
Gram Bacteria	POSITIVE -> thick pepdioglycan and membrane under. Purple NEGATIVE -> membrane, thin peptidoglycan then membrane. Pink. Bacteria won't work - cannot active peptidoglycan
Information Storage requirements	Molecule must be stable and accessible - rapid replication without error
DNA	Major and minor grooves allow access to information. Genome = total DNA in organism
Genes	Not all encode proteins and some may encode multiple (alternative splicing)
Plasmids	Readily transferred, antibiotic resistance. Horizontal gene transmission - rapid spread
DNA packaging	2m in cells. Octomer form nucleosome and further folding. Chromatin packing regulates gene expression
Nucleus	Contains pores, regulated bu NPC above 60,000 Da. Mammals 3-4000 pores
Central Dogma	DNA replication -> transcription -> translation One way system
DNA -> protein	Transcription and translation Spontaneous 3D folding
Ribosomes	2 main chain rRNA and over 50 proteins. Small and large subunit 70s -> (50s large/ 30s small) 80s -> (60s large/ 40s small) rRNA made in nucleolus Smaller subunit = protein assembly framework, large = catalyst for amino acids into polypeptide
ER	Makes 10% cell volume Signal peptide recognised by translator proteins to allow them to move through ER
Proteomics	Large scale protein analysis 80,000 proteins in human cell
Metabolism	Chemical reaction release energy from catabolism, or use energy in anabolism
Metabolomics	Study of cellular metabolites. Changes can occur from stress/ environment. Use to diagnose/ treat disease/ test drug retention times
Specific environments	Enabled through membranes Different pH Proteins organised in arrays
Peroxisome	Oxidative reactions (e.g. breakdown fatty acids). Make myelin sheath hence issue could cause neurological disease
Glyoxysome	In plants Convert fats to sugar via glyoxylate cycle
ATP	High energy final bonds due to phosphate repulsion being overcome Terminal phosphorylate other molecules to drive anabolic reactions Chemiosmosis and substrate level phosphorylation
ATP synthase	100 ATP per second. Rotation action Chemiomosis
Mitochondria	Outer membrane smooth and permeable Inner very impermeable, but rich to proteins for energy transduction Membrane potential 160mV across inner membrane drives ATP synthesis 0.001% of nuclear DNA
Chloroplast	Phototransduction Thylakoid membrane of flattened vesicles forming grand. 3pH difference drives chemiosmosis Not made denovo - arise by division of different ones
Transport of proteins	Requires transit across membranes via transporters Fate depends on amino acid sequence - no signal remains in cytosol Others have sorting signals recognised by complementary membrane translators Sorting signal 15-60 amino acids. Removed by peptidases
Entrance/ exit from cell	Enter through endocytosis Leave through exocytosis
Vesicle Movement	flow along organised routes. Budd off from donor Polarised Golgi cistern - material enters from cis end and leaves via trans. Small vesicles transfer between cistern - each has different enzyme and environments. Chemically modified e.g. ogliosaccharide
Cytoskeleton	Dynamic. More refined in eukaryotes 3 filament types - microtubules, intermediate filaments, actin filaments
Microtubules	Set position of organelles and direct transport
Intermediate filaments	Mechanical strength
Actin filaments	Shape and movement of cell
Interactions and assembly	All interact with accessory proteins to control assembly and structure and regulate interactions e.g. motor proteins heir structures - non-covalent hence rapid assembly/ disassembly
Microtubule	25nm, hollow cylinder. Heterodimer of alpha and beta tubular. Bind head to tail into protofilaments and assemble side to side into cylinder of 13 protofilaments. Polar - alpha minus end, beta positive. New subunits added more readily to + end Used in plants in cell shape
Kinesin and Dyenin	Kinesin to + end and dyeing to - end. Hydrolyse ATP and bind to microtubules and cargo. Cycle of bind and release moves 1 step at a time Kinesis 2-3um/sec, dyenin 14um/sec
Use motors	Able to move vesicles and mRNA to make more efficient processes ER binds to kinesin/ Golgi binds to dyenin
Actin filaments	7nm 2 parallel chains of actin in helix. More rapid growth at + end High concentration in cell membrane Used by bacteria to move in cytoplasm
Myosin	Close relation to kinesin + end directed motors, move material along actin Regulate cell shape
Intermediate filaments	10-12nm Elongated subunits Cross linked in strong arrays for mechanical stability. Keratins stabilise outer layers of skin/hair/nails Nuclear laming - meshwork outside nuclear envelope
Bacteria tublin	forms Z ring in bacteria and chloroplasts for cell division
Cilia	metachronal waves over long sheets. beat then relax. 6-10u, dyenin bridges produce sliding
Flagella	sperm and protists undulating wave from base to tip. 50-200um Prokaryote thinner, each attached by hook to protein discs in wall - miniature turbine
Ciliary and flagella	Rooted in cortex by basal bodies inconvertible to centriole in centriole doublets of microtubules in 9+2 configuration, linked by accessory proteins
Defects in cilliary dyenin	Kartagener's syndrome Lung infections, sperm immotile, opposite body axis
Generation of daughter cells	Mitosis (prophase, metaphase, anaphase, telophase, cytokinesis-contractile ring and myosin pinches)
Adhesive junctions	Most fundamental in cell communication, Adhesion to each other for common extracellular material secretion. Transmembrane junction protein links - actin intermediate associated
Channel forming junctions	Direct passage between adjacent cells - animal gap junctions for passage of inorganic ions and small polar molecules. Formed my hexametric complexes Coordination of cell activities regulated by small molecules Permeability regulated by Ca2+ or pH
Plasmodesmata	Plant cell channel forming junctions Bridge cell wall with cytoplasmic channels Form as cell divides - cytokinesis incomplete to form
Other junctions	Occluding (tight) Signal -relaying

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	Creado por Alice Hathaway hace casi 6 años