Sub-cellular Organelles Flashcards
Features of eukaryotic cells
Int. membrane bound compartments (organelles), chromosomes in nucleus
Nucleus
Largest organelle, surround by nuclear envelope
Contain genetic info - DNA arranged as chromosomes
Mitochondria
Site of cellular respiration
No. in cell - highly variable
Inner/outer - differentially permeable, diff. functions
Outer membrane = relatively permeable, allow free passage small molecules, contains pore forming protein (porin)
Inner membrane = thinner than outer, fold into cristae, e- transport chain embedded
Contains mitochondrial DNA - synthesise own proteins and self replicate
Rough endoplasmic reticulum
Interconnecting network - membranous tubules, vesicles, flattened sacs (cisternae)
Ribosomes attached
Translation begins on ribosome, set off signalling sequence, finish translation in rER (fold to tertiary structure, disulphide bonds, glycosylation)
Synthesis of intramembranous, export and lysosomal proteins
Ribosome
Part of rER membrane or secrete out
Site of translation
2 subunits of unequal size, made or ribosomal RNA associated w/ ribosomal proteins
Smooth endoplasmic reticulum
No ribosomes
Functions = lipid biosynthesis (cholesterol, phospholipids), membrane synthesis and repair Storage/release calcium ions - cell signalling
Liver - metabolism glycogen, detoxification metabolic by-products/drugs/alcohol
Muscle cells - sarcoplasmic reticulum release/re-uptake calcium ions activates contractile mechanism
Cells w/ many sER = liver, steroid-hormone secreting (adrenal glands, gonads)
Golgi apparatus
Protein modification/maturation
Site protein/lipid glycosylation, synthesis glycosaminoglycans (ECM)
Proteolysis - remove groups to activate
Membrane bound cisternae form network of tubules
Proteins synthesised in rER transported to GA in coated vesicles
Secretory products packaged into membrane bound vesicles (package into diff. vesicles depending on final location)
Cis face - receiving (vesicles fuse)
Trans face - release (modified molecules packaged into vesicles)
Lysosomes
Membrane-bound vesicles containing hydrolytic enzymes
Site of degradation of materials (pathogens/waste), taken up by phagocytosis/endocytosis
Peroxisome
Membrane-bound vesicle containing oxidases/catalase
Site of fatty acid breakdown
Produce hydrogen peroxide - kill pathogens
Detoxification
Protect cell from reactive oxygen species - byproduct of normal metabolism
Cytoskeleton
Movement - cell motility
Cellular organisation - move organelles, vesicle transport (secretion)
Structure - mechanical strength, maintain shape and polarity of cell
Microfilaments (cytoskeleton)
Actin filaments
Diameter = 5-7nm
Actin = 2 strand helical polymer
2 actin protofilaments (many globular actin monomers) twisted into helix
Filaments have structural polarity (+ve end grows/shrinks fast, -ve end grows/shrinks slowly)
Determine cell shape
Allow cell movement - rapid interchange small soluble units and large filament polymers, allow move towards chemo-attractant (e.g. nutrient source, antigen)
Microtubules (cytoskeleton)
Diameter = 25nm
Globular tubulin protein sub-units: long, hollow cylinders, alpha/beta, rigid and straight
Position organelles, chromosomes, vesicles
Direct movement of intracellular transport
Quick breakdown/assemble - change cell shape, organelle position
Motor proteins move along microtubules
Microtubule organising centre (MTOC): radiate from fixed point, dynamic +ve end free in cytoplasm (growth/shrinkage)
Dynamic instability - convert between shrinking/growing
Organisation diff. depend on cell type:
Fibroblasts - all attach to MTOC
Neuron axon - +ve end at synapse, -ve in cell body
Microtubules associate proteins (MAP) - bind to/stabilise microtubules
Motility - flagella/cilia
Intermediate filaments (cytoskeleton)
Diameter = 10-12nm
Intermediate filament proteins w/ spec. roles
Keratin - support epithelial cells
Destine
Neurofilament - neuron structure
Nuclear latin proteins - nuclear structure (shape/pores)
Mechanical strength/structure
