Photosynthesis Flashcards
Describe the relationship between the function of a chloroplast and its structure
Stroma — colourless to allow light to reach thylakoids / contains water for photolysis / has RuBP or reduced NADP / for light independent reactions or Calvin cycle
Thylakoid / Grana — light dependent reaction / photophosphorylation
Thylakoid membrane / Grana — have electron carriers or ATP synthase / (are many in number / have large surface area) to absorb more light
Starch grains — store glucose or energy
Outline the main features of cyclic photophorylation.
Light excites electrons in PS1;
Electrons passed along electron carriers to electron transfer chain;
H+/ protons pumped into thylakoid space;
H+ / protons diffuse back to stroma through ATP synthase;
ATP produced
Suggest and explain why SOx4 plants have a different mean plant biomass than wild type plants.
Sox4 plants have an extra copy of SBPase gene;
Increased transcription of SBPase gene so more SBPase;
Increased rate of regeneration / production of RubBP;
So increased carbon fixation / Calvin cycles / light independent reaction / TP / GP;
More glucose / sucrose for respiration ATP production; OR more starch / lipid for storage; OR more cellulose for cell walls;
More amino acids / proteins for growth;
More cell division / cell elongation / mitosis
In very dry conditions, CO2 concentration can become the main limiting factor of photosynthesis in plants.
Explain how very dry conditions cause CO2 concentration to become the main limiting factor of photosynthesis in plants.
Decrease in CO2 diffusing to air space / palisade cells / mesophyll cells / chloroplasts / stroma;
Stress response;
Ref to ABA;
Ref to action of Ca2+ as a second messenger;
Stomata close
Suggest how nitrate deficiency could limit the quantity of SBPase made by Sox4 plants.
Nitrogen needed to produce nucleotides for transcription of SBPase gene / expression of SBPase gene / mRNA production;
Amino acids for protein synthesis / SBPase production / enzyme production
Explain why the link reaction only occurs when oxygen is available.
Pyruvate is converted to acetyl group / 2C group / acetyl coA in link reaction;
NAD needed in link reaction;
NAD becomes reduced;
reduced NAD goes to ETC;
ETC / oxidative phosphorylation works if oxygen is present; OR oxygen is final electron acceptor;
So reduced NAD is oxidised / NAD is regenerated
Describe the similarities and the differences between cyclic photophosphorylation and non-cyclic photophosphorylation
Similarities:
Photoactivition in chlorophyll occurs in both;
ETC involved in both;
ATP produced in both;
Differences:
Cyclic
Only PSI;
No photolysis;
No reduced NADP / oxygen produced;
Electrons emitted from PSI returned to PSI;
Non-Cyclic:
Both photosystems;
Photolysis;
Reduced NADP / oxygen produced;
Electrons emitted from PSII are replaced by water
Explain why herbicides that prevent cyclic photophosphorylation and non-cyclic photophosphorylation stop carbohydrate being produced in the chloroplast.
No ATP and reduced NADP made;
No GP / TP made; OR no Calvin cycle / light-independent reaction;
No regeneration of RuBP
Explain the relationship between the absorption spectrum of the main chloroplast pigments in a species of plant and the action spectrum for photosynthesis for that species.
Action spectrum shows rate of photosynthesis for light wavelengths / colours;
Absorption spectrum shows how much each wavelength / colour is absorbed;
Higher absorption gives higher photosynthesis
Explain why temperature can be a limiting factor of photosynthesis.
Higher temperature increases rate;
Temperature affects photophosphorylation / light dependent reaction / Calvin cycle / light independent reaction;
Enzymes denature at too high temperatures
Outline how the light-independent stage of photosynthesis leads to the production of carbohydrates such as starch in plant leaves.
RuBP joins with CO2 to make GP;
GP to TP;
Uses ATP and reduced NADP;
TP —> glucose —> starch;
Condensation / polymerisation / glycosidic bonds
Suggest and explain why the inner membrane of a mitochondrion remains intact when the organelle is placed in pure water.
Cristae let inner membrane expand;
When water enters matrix by osmosis;
Inner membrane impermeable to water;
Water does not enter matrix by osmosis;
Inner membrane moves H+ ions out of matrix;
So less water enters matrix by osmosis
Name 3 molecules other than coenzymes that are found in the mitochondrial matrix and explain their role in aerobic respiration.
Pyruvate for link reaction ;
Oxaloacetate to accept acetyl / make citrate;
Citrate to make reduced NAD;
Enzymes to catalyse link reaction;
Oxygen to accept e-;
Water as a solvent / medium for reactions;
DNA / RNA to make respiratory enzymes
The inner membrane contains a very high proportion of the molecule cardiolipin. Cardiolipin makes the inner membrane impermeable to some ions.
Suggest why the inner membrane contains a very high proportion of cardiolipin.
So H+ cannot move through / must move through ATP synthase;
To maintain proton gradient
Reduced NAD and reduced FAD transfer hydrogen atoms to carriers located in the inner mitochondrial membrane.
Explain how hydrogen atoms form reduced NAD and reduced FAD lead to a membrane potential forming across the inner mitochondrial membrane during oxidative phosphorylation.
H atoms split into protons and electrons;
E- flow down electron transfer chain;
Releases energy used to move H+ to intermembrane space;
More / build up of H+ / positive charge in intermembrane space;
Causes proton / electrochemical gradient
