Bioenergetics Flashcards
What is Photosynthesis
-Plants use light as their source of energy. To trap the light, plants carry out the process of photosynthesis.
-Because this takes in light energy, it is an endothermic reaction.
-Photosynthesis takes place in the leaves of the plant. These contain chlorophyll which can absorb light energy.
What is the Equation for Photosynthesis
Carbon Dioxide + Water 🡢 Glucose + Oxygen
Explain what is Meant by the Term Limiting Factor
A limiting factor is any factor which limits the rate of photosynthesis.
Describe what Happens to the rate of Photosynthesis as Light Intensity Increases
-As light intensity increases, the rate of photosynthesis increases steadily but only up to a certain point.
-Beyond that, it won’t make any difference- as light intensity increases, the rate will no longer increase.
-This is because it’ll either be carbon dioxide levels or temperature which is now the limiting factor, not light.
Describe how Greenhouses can Prevent Light from Becoming the Limiting Factor
-Use greenhouses constructed from glass or alternative materials that enable maximum transmission of light.
-Position plants for maximum light absorption.
Artificial lighting systems can be used:
-with increased light intensities
-that provide optimum wavelengths of light for photosynthesis
-that lengthen a plant’s growing season so that crops can be grown in more months of the year
Describe what Happens to the rate of Photosynthesis as Carbon Dioxide Levels Increases
-As carbon dioxide levels increase, the rate of photosynthesis increases steadily but only up to a certain point.
-Beyond that, it won’t make any difference- as carbon dioxide levels increase, the rate will no longer increase.
-This is because it’ll either be light intensity or temperature which is now the limiting factor, not light.
Describe how Greenhouses can Prevent Carbon Dioxide from Becoming the Limiting Factor
-Use paraffin heaters on a small scale
-On a larger scale, use carbon dioxide wastes from industrial processes that has been cleaned up before use
-Can use liquid carbon dioxide, applied through pipes, though this can be expensive
-Sometimes use fungi, grown as a mycelium in bags around the greenhouse, that add carbon dioxide through their respiration
Describe how Temperature Affects the Rate of Photosynthesis
-Often, if temperature is the limiting reactant, it is because it is too low. The enzymes needed for photosynthesis work more slowly at low temperatures.
-However, if the plant gets too hot, the enzymes needed for photosynthesis will become denatured.
Describe how Greenhouses can Prevent Temperature from Becoming the Limiting Factor
-Greenhouses help to trap the sun’s heat, and make sure that the temperature doesn’t become limiting.
-In winter, a farmer might use a heater as well to keep the temperature at the ideal level.
-In summer, it might get too hot so shades or a ventilation system might be installed to cool things down.
Describe the Benefit of Using Oil Burners in Greenhouses
-Burning oil generates heat and also releases carbon dioxide.
-Both temperature and carbon dioxide concentration can be limiting factors so by using oil burners, we ensure that the rate of photosynthesis is very high.
-Light intensity can also be a limiting factor but in practise, during the day, the light intensity in a greenhouse is very high.
Describe how Chlorophyll Levels Affect the Rate of Photosynthesis
-Variegated plants have a lower level of chlorophyll than non-variegated plants.
-This means that variegated plants can trap less light energy and will have a lower rate of photosynthesis.
Describe how Glucose is Used in Respiration
-Glucose produced by photosynthesis can be used for respiration.
-Glucose is broken down with oxygen to provide energy to the cells. Energy is released in a chemical reaction which takes place in the mitochondria.
-Carbon dioxide and water are the waste products.
What does it Mean that Burning Oil in Greenhouses has Economic Benefits
-Burning oil is expensive so this adds to a gardener’s costs.
-However, burning oil should increase the yield of crops.
-If the increased yield offsets the increased cost, then the gardener will make money. This is an economic argument.
Describe how Glucose is Used for Cellulose
-Energy transferred in respiration may be sued to build smaller molecules into bigger molecules.
-Glucose is converted into complex carbohydrates such as cellulose which is used to strengthen cell walls.
Describe how Glucose is Used to Build Proteins
-Some glucose from photosynthesis is used to make amino acids.
-To do so, glucose combines with nitrate ions and other minerals from the soil.
-The acids are built into proteins to be used as enzymes and other things for the plants survival.
-The creation of these proteins uses energy transferred from respiration
Describe the Use of Glucose as Starch
-Some glucose from photosynthesis is converted into starch to be stored.
-Starch is insoluble in water (unlike glucose) so has no effect on how water moves in and out of the plant. Because of this, plants can store a lot of starch- it is the plant’s main energy store.
-Starch is stored in the cells of leaves which provides an energy store. for when it is dark. It is also stored in tubers to help the plant survive winter.
