B2.2 - organelles and compartmentalisation Flashcards
what are organelles?
organelles are discrete subunits of cells that are adapted to perform specific functions
- most organelles are surrounded by a membrane
what are examples of organelles?
examples: nuclei, vesicles, and ribosomes
what are non-examples of organelles?
non-examples: cell wall, plasma membrane, cytoskeleton and cytoplasm
when did the study of the function of individual organelles become possible?
when ultra-centrifuges had been invented and methods of using them for cell fractionation had been developed
what is fractenation?
fractenation involves breaking down a membrane and spinning the sample at high speeds so the heavier components move further down the tube
what were the results from fractenation?
allowed different sizes of ribosomes to be detected as the smaller, less dense 70S was found higher in the fraction than the larger, more dense 80S
what is an advantage of separation of the nucleus and cytoplasm into separate components?
allows separation of the activities of gene transcription and translation
- post-transcriptional modification of mRNA can occur before it meets ribosomes in the cytoplasm
- not possible in prokaryotes
what are advantages of compartmentalisation in the cytoplasm of cells?
- allows accumulation of metabolites and enzymes at high concentrations
- separates incompatible biochemical processes
what are 2 examples of compartmentalisation?
lyosomes - contain hydrolytic enzymes and free radicals which digest biological molecules
- prevents useful molecules being digested and cell damage
phagocytic vacuoles - contain pathogen engulfed by endocytosis
- protects cellular contents from damage by the pathogen
