sub cellular organelles Flashcards
what are the precursors of lysosomes
- endosomes
what enzymes do lysosomes contain
- hydrolytic enzymes coming from the Golgi complex which degrade proteins and other large molecules
major job of lysosomes
- eliminate unwanted cellular material and recycle their components
- destroy bacteria and yeast (in immune cell)
name 4 digestive enzymes that lysosomes contain
- nucleases - breakdown of DNA/RNA
- phosphatases - removes phosphate
- glycosidases - breakdown of sugar
- proteases - breakdown of protein
what does peroxisome do
- degrades long chain fatty acids and cholesterol
- converts cholesterol to bile
- these reactions produce toxic hydrogen peroxide - this is degraded by catalase
- synthesise plasmalogens - which is a component of myelin
what three processes do lysosomes process materials brought to the cell by
- phagocytosis
- pinocytosis
- autophagy
- receptor - mediated endocytosis
what is autophagy
- self breakdown
- breakdown unwanted cellular components eg organelles
- takes place in autophagosome initially
- then fuses with lysosome
- can be macro or micro autophagy
what is p gingivalis
- anaerobic bacteria, which produce proteins called gingipains and cause gum damage
where are peroxisomes founds
- in liver cells and are specialised lysosomes
how are peroxisomal disorders caused
- caused by mutations in the peroxisomal enzymes
- or faults in peroxisome assembly
- cause toxic long chain fatty acids to accumulate
what is the process called when things exit from a cell
- exocytosis
what are the two ways things may be secreted
- constitutive secretion
- regulated secretion
- vesicles are sometimes processed through the endosomal pathway
explain endosomal pathway
- membranous ‘bubbles’ released by cells
- different classes; exosomes (released from endosomes)
; microvesicles (‘bud away’ from plasma membrane)
how are extracellular vesicles formed
- exosomes formed through endocytosis
- multi vesicular body
- processed through Golgi body
- cell surface
- vesicles released from the cell and bind or interact with other cells
what is the ER connected to and what does it consist of
- the nuclear membrane is connected to the ER
- it is a network of membranous tubules
- consists of smooth and rough ER
what is smooth er involved with
- contains enzymes for
; lipid synthesis
; steroid hormone synthesis
; metabolising toxins eg alcohol - stores calcium and contains no ribosomes
what is rough er involved with
- studded with ribosomes
- involved in production and processing of proteins in collaboration with the Golgi complex
- can also modify proteins; initiate adding of carbohydrates and adding membrane anchors
how are diseases caused in ER
- usually due to mutation in amino acid sequence causing misfolding
- proteins not processed properly and not taken from ER to Golgi
- diseases caused by proteins being retained in the ER
; CF
; diabetes
function of Golgi apparatus
- proteins synthesised in the rough ER are transported to Golgi complex in vesicles
- modifies the proteins made in the rough ER
- distributes the modified proteins to lysosomes, plasma membrane or secretory vesicles
structure of Golgi apparatus
- sack of flattened vesicles with a cis network, facing nucleus
- and a trans network, facing plasma membrane
- proteins are transported to and from Golgi in vesicles
vesicles in Golgi
- vesicles are coated in different proteins depending on their destination
- proteins travel from ER to cis face of Golgi in COP11 coated vesicles
- when processed in golgi, proteins travel to membrane in clathrin coated vesicles
- vesicles are recycled - coated in COP 1 and transported back to the ER
how is cholera caused
- cholera toxin binds to a component of COP1 and is processed and activated in ER
- the cholera toxin activated the CFTR channel, disrupting Cl- transport in guts
- this causes secretion of water, dehydration and diaheria
what does mitochondria do
- power station of cell
- oxidise fuel in their inner matrix and generate ATP across their inner membrane via the ETC
what is the purpose of the inner membrane of the mitochondria being folded
- maximises the surface area for generating ATP
- these folds are called cristae
how is the mitochondria different from other organelles
- they are able to divide independently and they have its own DNA, which encodes some of the protein required to make new mitochondria
- still require proteins from mitochondria
how are mitochondrial diseases caused
- mutation in mitochondrial DNA cause disease
- symptoms are caused by a lack of ATP in affected organs
- particularly affect organs with high energy demand eg. muscles
what is mitophagy
- specifically degrades and recycles mitochondria
- known to contribute to development of Parkinson’s and dementia
3 features of prokaryotes
- have no membrane bound organelles
- have a nucleoid
- have a peptidoglycan cell wall as a cell membrane
- aerobic bacteria have no mitochondria but generate ATP across cell membrane
what are cilia and flagella composed of and purpose
- specialised structure
- structure extends from plasma membrane
- present in multi cellular and uni cellular organelles
- composed of bundles of microfilaments
- used for propelling liquids and other material along surfaces
what is cytoskeleton composed of and purpose
- composed of tubules and filaments
- dictates structure and shape of cell
what is organelle biogenesis
- new organelles are formed by expansion of existing ones
- the new phospholipids are synthesised in the smooth ER
- move to organelles - in vesicles (golgi, lysosomes) or by transport proteins (mitochondria)
- proteins are synthesised in mitochondria or er
