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Photosynthesis
Photosynthesis and ATP synthesis
| Question | Answer |
|---|---|
| T or F. In order to live, organisms require a source of energy and a source of carbon. | T |
| Organisms that gain their energy energy by absorbing light are called | phototrophs |
| Organisms that gain their energy not from light but rather from chemical reactions are called | chemotrophs |
| What is the simplest form of carbon that can be used by organisms? | carbon dioxide (CO2) |
| Describe the role of autotrophs. | They use simple inorganic compounds to make complex organic compounds. Most use light energy to drive the anabolic reactions in which they make biological molecules. |
| Describe the role of heterotrophs. | They use complex organic compounds to obtain the energy and biological molecules that they need. |
| List 6 uses of energy in organisms. | 1) Active transport 2) Movement 3) Biosynthesis - production of biomolecules 4) Provide suitable temp. for metabolic reactions 5) Growth and reproduction 6) Maintenance of body temp. in endotherms |
| Name the energy transfer molecule within all cells. | ATP (adenosine triphosphate) |
| Give 3 ways in which ATP is suited to its function. | 1) It is small and soluble so diffuses through a cell easily. 2) It is unstable, has low activation energy and transfers 1-2 phosphate groups easily. 3) The hydrolysis of an ATP molecule supplies packets of energy. |
| Name the two ways in which ATP can be produced. | 1) Substrate-linked phosphorylation : direct synthesis 2) Chemiosmotic phosphorylation (a part of oxidative phosphorylation) : a proton gradient and ATP synthase are responsible for this synthesis |
| Why do most plants appear green? | Plant pigment chlorophyll absorbs red(650 nm) and blue-violet(460 nm) light while green(550 nm) light is reflected thus the plant appears green. |
| What wavelength of light is absorbed by the chlorophyll a in photosystem I ? | 700 nm PS I is also known as P700 |
| What wavelength of light is absorbed by the chlorophyll a in photosystem II? | 680 nm PS II is also known as P680 |
| State the function of ribosomes in the stroma of chloroplasts. | Synthesis of enzymes such as ribulose bisphosphate carboxylase. |
| State the function of starch grains in chloroplasts. | They act as an insoluble food store for the sugars in photosynthesis. This is beneficial as soluble sugars cannot be stored. |
| State the function of grana in chloroplasts. | They create a large surface area for chlorophyll so that a lot of light can be absorbed. |
| State the function of thylakoid membranes in chloroplasts. | They create compartments and enable different enzyme-driven reactions to occur within the chloroplasts at the same time. |
| State the function of DNA in chloroplasts. | They code for some of the chloroplast proteins. |
| Give the simple formula for the process of photosynthesis. | 6CO2 + 6H2O --> (light) C6H12O6 + 6O2 |
| Where does the light dependent reaction of photosynthesis occur? | Thylakoid of chloroplast. |
| State the products of the light dependent stage of photosynthesis and their fate. | ATP, NADPH and O2 ATP and NADPH are passed into the stroma to participate in the light independent reactions. O2 is released to the atmosphere as a by-product. |
| T or F. The light-independent reaction does not need light directly. It can therefore occur day and night. | T |
| Where do the light independent reactions take place? | Stroma of chloroplast |
| State the product of the light independent reaction. | Sugar |
| What is an absorption spectrum? | A graph that shows which wavelengths of light are absorbed by a pigment. |
| What is a an action spectrum? | A graph which shows the wavelengths of light that are actually used in photosynthesis. |
| Chlorophyll a, chlorophyll b and carotenoids are different plant pigments which absorb in different parts of the visible spectrum of light. What is the advantage of plants having more than one pigment? | Each type of pigment absorbs different parts of the visible spectrum. More light can be absorbed by accessory pigments and passed on the primary pigment molecules. |
| Give the route taken, photosystem(s) involved and product(s) of cyclic photophosphorylation in the light dependent stage of photosynthesis. | Route: PSI -> ECs -> PSI ->ECs Only involves PSI Product: ATP |
| Give the route taken, photosystem(s) involved and product(s) of non-cyclic photophosphorylation in the light dependent stage of photosynthesis. | Route : PSII -> ECs -> PSI -> NADP Involves both PS I and PSII Products: ATP, reduced NADP (NADPH) and oxygen |
| Loss of electrons from PSII makes it unstable. How does it become stable again? | PSII stimulates the splitting/photolysis of water. H2O -> 2H+ + 1/2 O2 + 2e- The electrons then pass to PSII making it stable again. The H+ along with electrons from PSI are used to reduced NADP. |
| State the three main processes which occur in the light independent stage (Calvin cycle) of photosynthesis. | 1) Fixation of carbon dioxide - carboxylation 2) Reduction to form carbohydrates 3) Regeneration of RuBP |
| Give the full name of the enzyme rubisco. | Ribulose bisphosphate carboxylase/oxygenase |
| Triose phosphate (TP) may undergo a number of different metabolic pathways. List 4 possible fates of TP in the chloroplast. | 1) Recycled to RuBP 2) Converted into hexose phosphates and then into starch 3) Converted into fatty acids 4) Converted into amino acids |
| T or F. Rubisco is the most abundant and important enzyme on Earth. It is active in the light but less active in the dark. Oxygen acts as a competitive inhibitor. | T |
| List 3 environmental conditions which can influence the rate at which the Calvin cycle can proceed. | 1) Carbon dioxide concentration 2) Temperature 3) Oxygen concentration |
| Describe the effect of carbon dioxide concentration on the Calvin cycle. | If the carbon dioxide concentration is low, then the rate of carboxylation catalyzed by rubisco will be slower than if the concentration was higher. |
| Describe the effect of temperature on the Calvin cycle. | The enzymes of the Calvin cycle are temperature dependent, so at low temperatures the rate of the light-independent stage is slow. At high temperatures, the enzymes are denatured so the Calvin cycle stops. |
| Describe the effect of oxygen concentration on the Calvin cycle. | Oxygen competes with carbon dioxide for the active site of rubisco. The enzymes acts as an oxygenase instead of a carboxylase in the presence of high O2 concentration. At low CO2 conc, this reduces the rate at which CO2 is fixed and TP produced. |
| T or F. The enzymes of the Calvin cycle are influenced by temperature, so reactions will be fasted at the optimum temperature. | T |
| T or F. The Calvin cycle is dependent on supplies of ATP and reduced NADP; in turn the supply of these is determined by light intensity and the energy available for the light-dependent stage. | T |
| List 3 ways in which the rate of photosynthesis may be investigated. | 1) Carbon dioxide uptake 2) Oxygen production - simplest method 3) Dry mass production |
| Give a simple formula for calculating light intensity if distance is varied in an experiment. | Light intensity = 1/d^2 where d=distance |
| State one limitation of the gas collection method for determining the rate of photosynthesis. | The gas that is collected is not pure oxygen from photosynthesis. It contains other gases, such as carbon dioxide, that come out of solution. |
| State three precautions which should be taken when conducting an experiment investigating the effect of light intensity on rate of photosynthesis. | 1) Exclude light from other sources. 2) Use a freshly cut piece of the plant and only take readings when the volume of gas given off has become constant. 3) Take repeat readings and calculate the mean value. |
| Define limiting factor. | A limiting factor is any rate determining factor which influences the rate of photosynthesis when it is in short supply. The rate of photosynthesis increases with increase in that factor until a saturation/maximum point is reached. |
| List 5 ways in which automated greenhouses are suited to supplying optimum conditions for photosynthesis. | 1) Control light intensity 2) Control temperature with heaters and ventilation 3) Enrich CO2 concentration by burning hydrocarbons 4) Supply water direct to the roots 5) Supply mineral nutrients direct to roots at the optimum concentration |
| List 3 actions which can be taken by Caribbean farmers to ensure optimum conditions for plant growth. | 1) Use plastic and mesh greenhouses to reduce heavy rainfall on plants and extreme light intensities. 2) Drip irrigation and proper drainage 3) Apply fertilizers to ensure minerals do not limit growth 4) Sow crops at optimum density |
| Define phosphorylation | Chemical process in which phosphate is added to a compound, e.g. ADP to form ATP. |
| Define photophosphorylation | Process that takes place in photosynthesis to use light energy to drive formation of ATP. Takes place in the grana of chloroplasts during photosynthesis. |
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CAPE Biology Unit 2
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