the eukaryotic cell part 2 Flashcards
what are lysosomes
organelles found in animal cells which contain digestive enzymes and are responsible for degrading worn out or obsolete components of the cell, as well as destroying invading bacteria and programmed cell death
what are the three primary transport routes to the lysosomes
1) endocytosis
2) phagocytosis
3) autophagy
what is endocytosis
invaginations of the cell membrane form vesicles that bud off and transport objects through the cell to the lysosome
what is phagocytosis
a form of endocytosis where whole cells and other large insoluble particles move from the cell surface to the lysosomes
what is autophagy
where worn out organelles and bulk cytoplasm are surrounded by a membrane and delivered to the lysosomes
what happens in the lysosome
the lumen of the lysosome is acidic and contains hydrolytic enzymes which degrade polymers into their monomeric subunits
- pump H+ and Cl- ions from the cytosol across the membrane acidifying the lumen
what enzymes are included in the lysosome
1) nucleases- degrade RNA and DNA
2) proteases- degrade proteins and peptides
3) phosphatases - remove phosphate groups
what are primary lysosomes
roughly spherical and do not contain obvious particulate or membrane debris
it is formed by the fusion of the Golgi vesicles with late endosomes
what are secondary lysosomes
larger and more irregular shaped, result from fusion of primary lysosomes with other membrane bound organelles and vesicles
what are residual bodies
where indigestible materials pass outwardly and fuse with the plasma membrane
what are autophagic vacuoles
a fusion of a primary lysosome with a autophagosome
what are the main types of vacuole
1) storage
2) lytic
what is a storage vacuole
where the vacuole membrane contains a variety of transport proteins which allow plant cells to accumulate and store water, ions and nutrients
what is a lytic vacuole
the lumen of a vacuole has an acidic PH and contains degradative enzymes
how does the vacuole keep its shape
the membrane is permable to water but not to small molecules stored within it. the solute conc therefore is much higher inside than outside so water moves into the vacuole by osmosis which increases turgor
what is a peroxiosome
organelles which play a key role in lipid metabolism and control of reactive oxygen species
in the liver and kidney cells they degrade toxic molecules.
THEY OXIDISE ORGANIC SUBSTANCES LIKE FATTY ACIDS AND AMINOACIDS
what is the endoplasmic reticulum
an extensive network of closed, flattened membrane bound sacs called cisternae which is important in the synthesis of lipids, membrane proteins and secreted proteins
what are the two regions the ER is divided into
1) smooth which lacks ribosomes
2) rough which is studded with ribosomes
what is the smooth ER
a subset of the endomembrane system which synthesises lipids, fatty acids, phospholipids, steroid hormones and involved in the detoxification of harmful metabolic by-products
what do enzymes in the SER do in the liver
modify or detoxify hydrophobic chemicals by chemically converting them into water soluble products that can be excreted from the body
what does the RER do
synthesis of proteins
outline how proteins are transported from the ER to their destination
1) membranes and secreted proteins have signal sequences
2) signal sequences direct ribosomes to the ER membrane where they dock on the transposon protein complex
3) polypeptide synthesis starts and the signal peptide is cleaved
4) completed polypeptides leave the ribosomes and folds into final conformation
what is the golgi complex
the main sorting hub of the secretory pathway which recives proteins and membrane lipids first synthesised in the ER.
it completes the chemical modifications and then packages and transports to appropriate destinations
outline the structure of the golgi complex
a series of flattened membrane vesicles or sacs surrounded by a number of spherical vesicles
what are the three defined regions
1) the cis region which accepts things from the ER
2) the medical region where final modifications are done
3) the trans medium where everything is sorted and sent off
outline transport through the golgi complex
1) vesicles from the RER fuse with the cis membranes of the golgi complex
2) proteins in the vesicles move to the cis region to the medial region and finally to the trans region
3) vesicles bud off the trans golgi membranes
4) vesicles containing proteins move to the cell surface and others move to the lysosome
what are the major sites of protein sorting in cells
ER
golgi complex
vesicles
outline the secretory pathway
1) transport vesicles bud off and carry secreted proteins to the golgi complex
2) proteins are concentrated and packaged into immature secretory vesicles
3) vesicles then coalesce to form larger mature secretory vesicles
4) they accumulate under the apical surface of the cell and fuse with membrane releasing content
what happens to proteins lacking the ER signal sequence in non-secretory pathways
1) released into the cytosol and remain their
2) proteins with organelle specific targeting sequence first released into the cytosl but then imported into other organelles
