B2.2 Organelles and compartmentalisation
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what are not organelles because they don’t have a membrane
cell wall cytoskeleton cytoplasm
examples of Eukaryotic cells that have a number of compartmentalised organelles
The nucleus Vesicles Ribosomes The plasma membrane
what is the outer membrane of organelles
lysosomes - it encloses their contents and creates a compartment that separates it from the surrounding cytoplasm
what does the compartmentalisation of cell allow for
allows for enzymes and substrates to be localised so are available at higher conc Damaging substances to be kept separated, Optimal conditions to be maintained for certain processes
how can we study organelles
cell fractionation
how does cell fractionation happen
sample broken up in blender- in a homogeniser it is filtered through a gauze filtrate placed in tube and placed in centrifuge centrifuge spins material- speed can be altered
why does gene transcription and translation occur separately in eukaryotes
due to the compartmentalisation of the nucleus
what happens during transcription
mRNA is formed using a template strand of DNA; the mRNA needs some modification before it can be used for translation
advantages of compartmentalisation
small volume - enzymes can be concentrated so speeds up their activity ph can be kept at ideal level incompatible biochemical processes can be kept separate
adaptations of mitochondria
outer membrane smooth and permeable to small molecules inner membrane is folded and less permeable(site of ATP synthase) intermembrane space has low ph due to high conc of protons matrix
what does the cristae allow for
a high surface area so membrane can hold many electron transport chain carriers and ATP synthase enzymes
matrix
has high conc of enzymes and substrates for krebs cycle
thykaloid membrane in chloroplasts
has pigments, enzymes and electron carriers
how are grana adapted for photosynthesis
The granal stacks create a large surface area for the presence of many photosystems which allows for the maximum absorption of light provides more membrane space for electron carriers and ATP synthase enzymes
how are stroma adapted for photosynthesis
they contain enzymes that catalyse the reactions of light independent stage they are compartmentalises for calvin cycle reactions surrounds grana so transport is quick
how is DNA adapted for photosynthesis
contains genes that code for some of the proteins and enzymes used in photosynthesis
how are ribosomes adapted for photosynthesis
allows for the translation of proteins coded by the chloroplast DNA
what are nuclear pores
important channels that allow mRNA and ribosomes to travel out of nucleus
where are ribosomes found in cells
freely in the cytoplasm Or bound to the endoplasmic reticulum (ER) to form rough ER (only in eukaryotic cells)
role of golgi apparatus
modify proteins and lipids before packaging them into Golgi vesicles which then transport them to their required destination
what does the cis side of the golgi apparatus do
receive protein or lipid filled vesicles from the endoplasmic reticulum
what does the trans side of the golgi apparatus do
Once the received proteins or lipids have been modified the final products are sent out via the trans side
what are vesicles
membrane-bound sacs used for transport and storage
types of vesicles
peroxisomes lysosomes transport vesicles secretory vesicles