Topic Membrane Essay - Key Points!

Q) Discuss the functional significance of membranes in photosynthesis and respiration

Main points
Key idea:	Increase surface area for attachment of electron carriers + stalked particles
· Due to infolding of inner mitochondrial membranes (IMM)(to form cristae) + thylakoid membr of chloroplast · Ref to electron transport chain (ETC) · Ref to stalked particles – consist of hydrophilic protein channels embedded in membr + ATP synthase at tip of struc
Key idea:	Flow of energized e throu ETC
· Energized e flow throu ETC + ref to down an energy gradient · Energy released during transfer of e, used to pump H+ (protons) · Ref to fr mitochondrial matrix to intermembrane space · Ref to fr chloroplast stroma to thylakoid space
Key idea:	Establish proton gradient
· Ref to membr being impermeable to H+ · Results: H+ (proton) conc gradient a/x IMM and thylakoid membrane · H+ flow back into matrix or stroma throu stalked particles by facilitated diffusion, where ATP synthase catalyzes phosphorylation of ADP to form ATP
Key idea:	Membranes compartmentalize enzymes
· Enz involved in : i) link rx + Krebs cycle w/n matrix of mito ii) light indep rx (i.e. Calvin cycle) w/n stroma of chloroplast
Key idea:	Membranes facilitate reactions
· Maintain optimal cond for various rx w/n organelles · Membranes - in close proximity to mitochondrial matrix and chloroplast stroma, for oxidative phosphorylation and photophosphorylation, to occur efficiently
Key idea:	Outer and inner mitochondrial membranes create intermembrane space
· Ref to H+ entering intermembrane space fr matrix – required for H+ (proton) conc gradient, then syn of ATP (as described)
Key idea:	Attachment of photosynthetic pigments on thylakoid membrane
· Ref to photosynthetic pigments (e.g. chlorophyll) functionally grouped into  photosystem I or II · Ref to maximizing absorption of light + photoactivation of chlorophyll - excitation, subsequent displacement of energized e fr rx centres of photosystems · Energized e flow throu ETC, leads to syn of ATP (as described)
Key idea:	Permeability of membranes
· Ref to both outer and inner membr of organelles being permeable substrates or products of cellular respiration and photosyn · E.g. O2, CO2, H2O, ADP, inorganic phosphate and ATP · Ref to mitochondrial membr being permeable to pyruvate fr glycolysis + pyruvate = substrate for link rx in matrix of mitochondrion
Comments: (i) Visualize the answer with the aid of a labelled diagram. (ii) Verbalize the answer + write down the main points w/o referring to the answer (use abbreviations) (iii) Read again within the next 24h & once more within 72h (do not spend more than 10min) (iv) The proton gradient gives rise to the proton motive force which is the source of potential energy for the synthesis of ATP.