Photosynthesis Flashcards
What is the photosynthesis equation
6CO2 + 6H2O —-> C6H12O6 + 6O2
Light + plant
Where is the site of photosynthesis
Chloroplast
Outline the structure of the chloroplasts
Has 3 membranes - outer, inner, thylakoid
Has 3 compartments - intermembrane space, stroma, thylakoid space
Where do the light reactions and carbon fixation occur
Light reactions take place on the thylakoid membrane
Carbon fixation occurs in the stroma
What is the light reaction phase
It captures light energy and converts it to chemical energy using pigment and protein complexes embedded in the thylakoid membrane
Elaborate on how photosystems capture light energy
Photosystems are protein complexes that contain the chlorophyll molecule
Chlorophyll absorbs light energy
Light energy absorbed by chlorophyll produces high energy electrons (from water)
High energy electrons then travel through the photosynthetic electron transport chain
Outline the process of the electron transport chain
Photosystems 2 hydrolyses water, spitting it into 1/2 O2 and 2H+. 2 free high energy electrons are produced
2 high energy electrons power cytochrome complex in electron transport chain, active transport of H+ into the thylakoid space
Photosystems 1 uses light energy to reenergise electrons
High energy electrons are then used in the reduction reaction where NADP+ is reduced to NADPH (NADP+ reductase)
Flow of H+ from high to low conc (thylakoid space to stroma) through ATP synthase powers phosphorylation of APD + Pi into ATP
What occurs in the light reaction
Water is split. O2 is produced. ATP and NADPH are produced
What is the relation between the light reactions and the Calvin cycle
The ATP and NADPH produced in the light reactions are used to fix low energy CO2 and produce high energy sugar molecules
What are the 3 steps to the Calvin cycle
Fixation, Reduction, and Regeneration
Where does the Calvin cycle occur
In the stroma
What is fixation
5 carbon molecule + CO2 —> 2 x 3 carbon low energy molecules
Occurs 3 times. Totalling 6 x 3 carbon low energy molecules
What is reduction
The low energy 3 carbon molecules are converted into high energy 3 carbon molecules using 6 ATP and 6NADPH
Yields 6 x 3 carbon high energy molecules
One high energy carbon molecule is taken out, and further used to produce glucose (high energy 6 carbon sugar)
What is regeneration
Converting the remaining 3 carbon molecules back into original 5 carbon molecule
Uses 3ATP
What is the output of the Calvin cycle, and how many CO2 must it fix to produce glucose
Output is a high energy 3 carbon sugar which goes on to make high energy 6 carbon glucose
Must fix 6 CO2 molecules to produce one glucose molecule
Outline the similarities and differences between the glucose energy supply in plants and animals
Both plants and animals breakdown glucose in cellular respiration to generate ATP
Animals must have an external source of glucoses, whereas plants produce glucose during photosynthesis
Outline the similarities and differences between the ATP energy supply of plants and animals
ATP is generated in both respiration and photosynthesis
ATP synthase is responsible for ATP phosphorylation in both processes
ATP synthase requires proton gradient across membrane in both chloroplast and mitochondrion
Outline the H+ concentration gradients in both chloroplasts and mitochondrion
In mitochondrion, H+ pumped from matrix into inter membrane space. H+ then diffuses through ATP Synthase, powering the phosphorylation of ATP.
In chloroplast, H+ pumped from stroma into into thylakoid space. H+ then diffuses through ATP Synthase, powering phosphorylation of ATP.
Outline the symbiotic theory
Explains how eukaryotic cells evolved from prokaryotic cells.
Mitochondria and chloroplasts are descendants of specialised bacteria that somehow survived endocytosis by another species of prokaryote or some other cell type, and became incorporated into the cytoplasm (instead of digested by the cell).
Ancestral prokaryote ingested aerobic bacterium, then photosynthetic bacterium.
Most likely mitochondria engulfed first as almost all eukaryote cells have mitochondria, and chloroplasts would be largely useless without mitochondria (chloroplasts produce glucose for cellular respiration in mitochondria)
