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B4.3 - Photosynthesi
Photosynthesis - OCR A2 Biology
| Question | Answer |
|---|---|
| Define Autotrophic nutrition: | This is where organisms can use external sources of energy in the synthesis of their organic food materials. (e.g. photosynthesis) |
| Define Heterotrophic nutrition: | This is where the organism breaks down organic food materials into soluble molecules so they can be absorbed. |
| Define photosynthesis: | The process by which carbohydrates are synthesised from co2 and h20 using light as an energy source. |
| Give some characteristics of a Palisade Mesophyll cell: | Long. Chloroplast filled. Orientated at right angles to the epidermal cells. Large vacuoles to push chloroplasts near the outside, optimising light absorption. Thin cell walls for rapid gas diffusion. |
| Give some characteristics of a chloroplast: | Only found in plant cells. Made of 2 membranes separated by a fluid filled space. Inner membrane is the Thylakoid membrane. |
| What is the Primary Pigment in a chloroplast? | Chlorophyll A. Either P680 or P700. |
| What is the centre of a photosytem called? And what is located there? | The reaction centre. The primary pigment is found there. |
| What pigment does PSI & PSII have? | PSI = P700, PSII = P680 |
| What do accessory pigments do? | They surround the primary pigments, absorbing wavelengths of light they do not, and passing this energy on to them. |
| What is cyclic photophosphorylation? | The use of light energy to phosphorylate ADP into ATP. It only involves PSI. |
| What happens in cyclic photophosphorylation? | P700 absorbs light energy and emits election. This passes along a series of carriers (in thylakoid membrane). It loses energy, and ATP is produced via chemiosmosis. |
| What is NADP? | A coenzyme used in photosynthesis to pick up Hydrogen. |
| What happens in non-cyclic photophosphorylation? | Involves PSI and PSII. P680 absorbs light energy and emits electrons. Passes along a series of carriers (chemiosmosis occurs) reaching PSI. The electron along with a H ion from the photolysis of water, reduces NADP. |
| What happens to water in non-cyclic photophosphorylation? | PSII has an enzyme that catalyses the photolysis of water. This produces oxygen and a Hydrogen Ion (which is used later on in the production of reduced NADP) |
| The light independent stage does not directly require light, however, it does require what? | The products from the light-dependent stage. The light independent stage is also known as the Calvin Cycle. |
| In the calvin cycle, Carbon dioxide combines with what, to produce what, with this reaction being catalysed by what enzyme? | Carbon dioxide combines with a 5C compound RuBP, to produce an unstable 6C compound. This reaction is catalysed by Rubisco (Ribulose bisphosphate) |
| What is the next 2 steps of the Calvin cycle? | The unstable 6C compound immediately splits into Glycerate-3-phosphate (GP). This is reduced and phosphorylated to produce Triose phosphate. |
| What happens to the TP in the Calvin cycle? | 5 out of 6 molecules of TP are recoiled using ATP, to form 3 molecules of RuBP, to be re-used in the cycle. |
| How does light intensity affect photosynthesis? | Stimulates the stomata to open, allowing co2 to enter. Chlorophyll pigment absorbs it. Splits water (photolysis). |
| How does Temperature affect photosynthesis? | Affects the enzymes in the calvin cycle. (Optimum rate, denaturing of enzymes) |
| What happens to the levels of RuBp and TP in light? | They are higher than the levels of GP as the Calvin cycle can go ahead, turning the GP into TP and RuBp. |
| What happens to the levels of RuBp and TP in dim light? | The levels decrease, as the products of the light dependent reaction are not as readily available. Levels of GP increase. |
| What happens to the levels of RuBp and TP at a low temperature? | The Calvin cycle is enzyme controlled, therefore it will work slower at a lower temperature. So the levels of RuBp, TP and GP will fall. |
| What happens to the levels of RuBp, Tp and GP at a low carbon dioxide concentration? | The levels of RuBp will rise, and the levels of GP and TP will fall, as the conversion from RuBp to GP is slower as there is less carbon dioxide to combine. |
| What does it mean when a graph showing the rate of photosynthesis against an environmental factor, plateaus? | The environmental factor shown is no longer the limiting factor, it is now something else. The point where it begins to level out is known as the saturation point. |
Created by:
Sparksy
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