Dark Reactions of Photosynthesis:
Carbon dioxide into sugars. Rubisco catalyze the transfer of CO2 into ribulose, a 5C sugar, then using
rubisco catalyze into 1,5 bisphosphate ribulose to form 2 3phosphogycerate molecules. This catalyst is
inefficient, and is thus made in huge quantities to counter its inefficiency.
6 5C sugar + 6 CO2 -> 12 3PG. 2 3PG is then used in gluconeogenesis into glucose. The remaining 10 3PG
into 6 5C sugars. The cycle then continues.
Net reaction: 6co2 + 12h2o + 18atp + 12 nadph -> glucose + 18adp + 18 pi + 12nadp + 6h
Most proteins in a cell localize to particular sites of the cell. The Golgi complex targets proteins towards
the ER. Vesicles are then used to target proteins to parts of the cell.
The cisternae is the ER lumen, found inbetween the folds of the ER. The synthesis of all secreted
proteins take place on the rough ER, where ribosomes are attached to the membranes of the ER. When
the cell is disrupted (homogenized), a soup of the cell parts, the rough ER forms vesicles, or rough
microsomes, with the ribosomes on the outside.
B and D treated microsomes with EDDA, which strips the microsomes of their ribosomes. When a
translated mRNA for secretory protein is used in a cell free system, the translated product was larger
than the actual secreted form. When tested with microsomes present, they found that the desired
protein was produced. It is also found that the N-terminus was removed in the final desired form. The N-
terminus must then be the signal sequence. These sequences are found to be positively charged amino
acids adjacent to 6 or more hydrophobic amino acids.
The signal sequence is associated immediately upon synthesis with the signal recognition particle (SRP),
which is also bound to the large subunit of the ribosome. SRP is then associated with a receptor, which
is an integral membrane protein, with one side protruding onto the cytosol side. SRP is GTP bound
when activated. When the growing chain associates with the translocon, the SRP and the receptor
bound GTP, and then