lysosomes, vacuoles, quick flashcards

what is the structure of a lysosome

membranous sac of hydrolytic enzymes that can digest macromolecules

their enzymes work best in acidic environment inside the lysosome

what is the function of a lysosome

fuses with the food vacuole and digests the contents

also use enzymes to recycle the cell’s own contents through autophagy

how do cells protect themselves from self digestion

pH controlled mechanisms → hydrolases only work in acidic pH

bulky protective structure of lysosomal components → protected from cleavage by high level of glyosylation

an H+ATPase in the membrane pumps H+ into the lysosome, maintaining its lumen at an acidic pH

what is phagocytosis

engulfing solid particles

used by unicellular protists and some specialized cells in multicellular eukaryotes (eg macrophages)

what is autophagy

damaged organelles are wrapped in a double membrane autophagosome, which fuses with a lysosome to digest and recycle the contents

what is nonselective autophagy regulated by

by nutrient availabilty

eg degrades cytosolic proteins and organelles

what is selective autophagy regulated by

by receptors that recruit cargo to the autophagosome membrane

eg mitophagy selectively degrades mitochondria

what is tay sachs disease

a lipase is missing

leads to accumulation of lipids in the brain as the lipids cannot be digested

what is inclusion cell disease

almost all lysosomal enzymes are missing due to them being secreted

leads to inclusions of undigested material in the cell

leads to multi organ disfunctions

what are vacuoles

large vesicles derived from the ER and golgi apparatus

what do vacuoles do

food vacuoles - formed by phagocytosis in animal cells

contractile vacuoles - pump excess water out of cells, found in protists

central vacuoles - in plant cells, have sap, is a repository of inorganic ions, major role in growth of plant cells and maintains turgor

digestive vacuoles - are plant lysosomes

how do plant cells grow w/o increasing volume of cytoplasm

storing more water in the vacuole instead of making more cytoplasm

the cytosol is pushed to the edges of the cell, supported by actin filaments

what are peroxisomes

specialized metabolic compartments bounded by a single membrane

have enzymes that remove hydrogen atoms and transfer them to oxygen, forming hydrogen peroxide

also contains catalse which converts this to water

what do peroxisomes do

some use oxygen to break fatty acids into smaller molecules, eventually used for fuel for respiration

in the liver, they detoxify alcohol and other harmful compounds

what are glyoxysomes

are in the fat-storing tissues of plant seeds

convert fatty acids to sugar to feed the emerging seedling

what is X-linked adrenoleukodystrophy (ALD)

defective peroxisomal enzyme = unable to break down very long chain fatty acids

fatty acids accumulate, damaging the myelin sheath in the nervous system. nerves cannot conduct impulses properly

leads to neurological symptoms and paralysis

what is used to treat ALD

mix of rapeseed and olive oil

reduces the levels of very long chain fatty acids

must be used with low fat diet