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Higher Biology 3.1
Food Supply
| Question | Answer |
|---|---|
| What is the definition of food security? | The ability of human populations to access food of sufficient quality and quantity |
| Why are there concerns about food security? | Increase in human population leads to a demand for increased food production |
| What are the two most important features of food production? | That it is sustainable and does not degrade the natural resources on which agriculture depends |
| Name the two factors that agricultural production depends on. | Plant growth and photosynthesis |
| Name the common plant crops. | Cereals, legumes, roots and potatoes |
| Explain why plant crops yield more food per unit area than livestock. | Livestock production includes more trophic levels and there is loss of energy between trophic levels so a greater loss of energy overall |
| What is a key benefit of livestock production compared to planting crops? | Livestock production is often possible in habitats unsuitable for growing crops |
| Name the three fates of light when it hits a leaf. | Absorbed, reflected or transmitted (ART) |
| Name the two stages of photosynthesis. | Light reactions and the Carbon Fixation (Calvin cycle) |
| What type of energy does photosynthesis use to produce carbohydrates? | Light energy |
| Name the three photosynthetic pigments found in a leaf. | Chlorophyll A, Chlorophyll B and carotenoids |
| Explain why plants have a range of pigments in their leaves? | To extend the range of wavelengths of light absorbed by photosynthesis and pass this energy onto chlorophyll |
| Explain what happens to light that is not absorbed by photosynthetic pigments in plants. | The light is reflected or transmitted |
| What does the absorption spectrum show? | Absorption of light by different pigments over the range of visible wavelengths of light |
| Name the main photosynthetic pigment in plants. | Chlorophyll |
| What does the action spectrum show? | Rate of photosynthesis over the range of visible wavelengths of light. |
| Name the first stage in photosynthesis. | Light-dependent reactions |
| What type of energy excites the electrons in the pigment molecules in the first stage of photosynthesis? | Light energy |
| Name the enzyme that generates ATP during photosynthesis. | ATP synthase |
| Name the coenzyme which carries hydrogen to the second stage of photosynthesis. | NADP |
| Which two substances are transferred from the light reactions to the Calvin Cycle? | NADPH and ATP |
| Increased food production depends on factors that control plant growth. List these factors. | Breeding of higher yielding cultivars, use of fertiliser, protecting crops from pests, diseases and competition. |
| List the characteristics that breeders seek to develop in crops. | Higher nutritional values, resistance to pests and diseases, physical characteristics suited to rearing and harvesting as well as those that can thrive in particular environmental conditions. |
| Why are carotenoid pigments important? | Extend range of wavelengths of light absorbed and pass the energy to chlorophyll for photosynthesis. |
| Do all pigments absorb the same range of wavelengths of light? | No, each pigment absorbs a different range of wavelengths of light. |
| Where does absorbed energy excite electrons? | In the pigment molecule |
| Excited electrons are transferred through which structure? | The electron transport chain |
| Transfer of electrons through the electron transport chain in photosynthesis releases energy which is used to generate which molecule? | ATP |
| Describe what happens during photolysis. | Energy is used to split water into oxygen and hydrogen |
| What happens to the oxygen produced during photolysis? | It is evolved (diffuses out of plant cells) |
| What happens to the hydrogen ions produced during photolysis? | They are transferred to the coenzyme NADP (and then passed to stage 2) |
| Name the coenzyme involved in photosynthesis. | NADP |
| What is the carbon fixation stage also known as? | The Calvin cycle |
| What is the Calvin cycle also known as? | Carbon fixation |
| Which enzyme is involved in the Calvin cycle? | RuBisCO |
| What is the purpose of the enzyme RuBisCO? | Fixes carbon dioxide by attaching it to ribulose bisphosphate (RuBP) |
| What does RuBP stand for? (extra info!) | Ribulose bisphosphate |
| What does 3PG stand for? (extra info!) | 3-phosphoglycerate |
| What does G3P stand for? (extra info!) | glyceraldehyde-3-phosphate |
| When RuBisCO fixes carbon dioxide to RuBP which molecule does this produce? | 3-phosphoglycerate (3PG) |
| What two things happen to 3PG during the Calvin cycle? | Phosphorylated by ATP; combined with hydrogen ions from NADPH |
| The phosphorylation and reduction of 3PG is used to form which molecule? | glyceraldehyde-3-phosphate (G3P) |
| Describe the two fates of G3P. | Used to regenerate RuBP and for the synthesis of glucose |
| Describe the different uses of glucose produced by photosynthesis. | Used as a respiratory substrate, synthesised into starch/cellulose or passed to other biosynthetic pathways. |
| Glucose can be passed to other biosynthetic pathways. Name the substances these biosynthetic pathways form. | Variety of metabolites such as DNA, protein and fat |
| What is RuBisCO? | An enzyme |
| Describe the effect of absorbed light energy on the pigment molecules in photosynthesis. | Excites electrons in the pigment molecule |
| Describe the role of NADPH in the Calvin cycle (carbon fixation). | Passes hydrogen to/ reduces 3PG |
| Which compound combines with hydrogen during carbon fixation? | 3-phosphoglycerate (3PG) |
| Pigment molecules absorbing energy results in what happening during the light dependent reactions of photosynthesis? | A transfer of electrons down the electron transport chain |
| Explain the importance of producing glucose in the final stage of the Calvin cycle. | For respiration, cellulose formation, starch formation or other biosynthetic pathways |
| Explain the importance of producing RuBP in the final stage of the Calvin cycle. | For continuation of the cycle/ to allow the cycle to occur or repeat OR to make G3P |
Created by:
MsKerrBiology
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