B1.4 Photoshynthesis

Question 1

<p>Define photosynthesis</p>

Answer 1

<p>The process by which plants harness the energy from the sun and transfer this energy into a useable food source in the form of glucose that can be stored as starch</p>

Question 2

<p>State the reactants of photosynthesis</p>

Answer 2

<p>Carbon dioxide & water</p>

Question 3

<p>State the products of photosynthesis</p>

Answer 3

<p>glucose + oxgygen</p>

Question 4

<p>Photosynthesis is an '........'thermic reaction.</p>

Answer 4

<p>Endothermic</p>

Question 5

<p>Endothermic means</p>

Answer 5

<p>a chemical reaction in which energy is transferred from the surrounding to the reacting mixture</p>

Question 6

<p>State the word equation for photosynthesis?</p>

Answer 6

<p>carbon dioxide + water (+ light) ------> oxgyen + glucose</p>

Question 7

<p>State the chemical equation for photosynthesis?</p>

Answer 7

<p>6CO₂ + 6H₂0 ( + light) ---------> C₆H₁₂O₂ + 6O₂</p>

Question 8

<p>Why are plants and some algae termed 'producers'?</p>

Answer 8

<p>They are organisms that make their own food through the process of photosynthesis</p>

Question 9

<p>Name the two main stages of photosynthesis?</p>

Answer 9

<ol> <li>Light dependent</li> <li>Light independent</li></ol>

Question 10

<p>State what happens in the first stage of photosynthesis?</p>

Answer 10

<p>The first stage is the light dependent stage of photosynthesis where energy transferred from light is used to split water molecules into oxygen gas and hydrogen ions</p>

Question 11

<p>State what happens in the second stage of photosynthesis?</p>

Answer 11

<p>The second stage isthe light independent stage of photosynthesis where carbon dioxide gas combines with the hydrogen ions produced in stage 1 of photosynthesis to make glucose</p>

Question 12

<p>What happens to the glucose produced in photosynthesis?</p>

Answer 12

<ol> <li>Stored as starch - food store</li> <li>Used for respiration</li> <li>Stored in fruit as sucrose</li> <li>Used to build cellulose cell walls</li> <li>Combined with nitrogen to build protiens for grow and repair</li> <li>Biosynthesis into fats and oils for food and growth</li></ol>

Question 13

<p>How can you test for starch to prove photosynthesis has taken place?</p>

Answer 13

<ol> <li>Place leaf in boiling water for 1 minute to kill it</li> <li>Place in boiling tube with ethanol</li> <li>Place boiling tube in a water bath an boil until white (chlorophyll removed)</li> <li>Wash leaf with water to remove ethanol and soften</li> <li>Place on white tile and add 1-2 iodine drops</li> <li>Watch for colour change in iodine.</li></ol>

Question 14

<p>How can a leaf be 'destarched' before a photosynthesis experiement?</p>

Answer 14

<p>Keep it in the dark for a minimum of 24 hours - starch present will be used up in respiration and without light no further glucose can be produced by photosynthesis to be converted to starch.</p>

Question 15

<p>How do you prove chlorophyll is needed for photosynthesis?</p>

Answer 15

<ol> <li>Take a variagated plant and destarch</li> <li>Place the destarched plant in sunlight for several hours</li> <li>Test oneof the leave with iodine for the presence of starch</li></ol>

Question 16

<p>How do you prove light is needed for photosynthesis?</p>

Answer 16

<ul> <li>Take a destarched plant and cover part of one of its leaves with black card or tin foil</li> <li>Place the destarched plant in sunlight for several hours</li> <li>Remove and uncover thepartially covered leaf</li> <li>Test the leaf that was partially covered with iodine for the presence of starch</li></ul>

Question 17

<p>How do you prove carbon dioxideis needed for photosynthesis?</p>

Answer 17

<ul> <li>Take a destarched plant cover part of one of its leaves/stems with a conical flask or polythene bag containing soda lime</li> <li>Place the destarched plant in sunlight for several hours</li> <li>Remove one of the covered leaves and testwith iodine for the presence of starch</li></ul>

Question 18

<p>How do you prove oxygen is given of during photosynthesis?</p>

Answer 18

<ol> <li>Place an upturned funnel and test tube over an aquatic plant in a beaker of water</li> <li>Put the apparatus in the light for maximum photosynthesis</li> <li>Collect a full test tube of gas</li> <li>Place a glowing splint into the test tube to test for oxygen</li> <li>Relights = oxygen present</li></ol>

Question 19

<p>What is meant by a 'limiting factor'?</p>

Answer 19

<p>Factors which can prevent an increase in the rate of photosynthesis</p>

Question 20

<p>State the main limiting factors which affect the rate of photosynthesis?</p>

Answer 20

<ul> <li>Light intensity</li> <li>Carbon dioxide availability</li> <li>Temperature</li></ul>

Question 21

<p>Which of the following is NOT a limiting factor of photosynthesis:</p>

<ol> <li>Temperature</li> <li>Light intensity</li> <li>Amount of chlorophyll</li> <li>Carbon dioxide concentration</li> <li>volume of rain</li></ol>

Answer 21

<p>volume of rain</p>

Question 22

<p>Describes the effect of light intensity on the rate of photosynthesis</p>

Answer 22

<p>As light intensity increases, the rate of photosynthesis increases until another limiting factor has an effect.</p>

Question 23

<p>Describes the effect of temperature on the rate of photosynthesis?</p>

Answer 23

<p>As temperature increases, the rate of photosynthesis increases, up to a point and then any further increase in temperature decreases the rate of photosynthesis</p>

Question 24

<p>Why does the rate of photosynthesis drop if the temperature gets too high?</p>

Answer 24

<p>The enzymes involved in photosynthesis have denatured</p>

Question 25

<p>Describethe effect of carbon dioxide concentration on the rate of photosynthesis</p>

Answer 25

<p>As carbon dioxide concentration increases, the rate of photosynthesis increases until another limiting factor has an effect</p>

Question 26

<p>What is happening at point B on the graph?</p>

Answer 26

<p>Another limiting factor is preventing an increase in rate of photosynthesis.</p>

Question 27

<p>Based on the graph, predict where the rate of photosynthesis would plateau if the temperature was 10 degrees Celcius and the carbon dioxide concentration was 0.04%.</p>

Answer 27

<p>Below the 0.04% line</p>

Question 28

<p>Why should a farmer keep careful control of the limiting factors for photosynthesis in their greenhouse? Choose the best answer</p>

<ul> <li>To maximise the rate photosynthesis to get the biggest plants</li> <li>To maximise the rate of photosynthesis in the most efficient way possible</li> <li>To maximise the light intensity for photosynthesis</li> <li>To keep the greenhouse warm for their plants</li></ul>

Answer 28

<p>To maximise the rate of photosynthesis in the most efficient way possible</p>

Question 29

<p>Explain why commercial growers increase the carbon dioxide concentration in a greenhouse?</p>

Answer 29

<p>A Greenhouse is warm and light so temperatureand light intensityare therefore not limiting factors.</p>

<p>As CO₂ concentration is the limiting factor in this situation therefore increasingCO₂ concentration with increase photosynthesis and therefore plant growth/yield</p>

Question 30

<p>State the inverse square law</p>

Answer 30

<p>relative light intensity =<u> 1 </u></p>

<p> (distance from light source)²</p>

<p></p>

<p>The law states that when you double the distance from the light source, the light intensity fall by a factor of four.</p>

Question 31

<p>State the limiting factor for line B</p>

Answer 31

<p>Temperature</p>

Question 32

<p>Explain why, for line A, increasing the temperature does not increase the rate of photosynthesis.</p>

Answer 32

<p>The carbon dioxide concentration has limited the rate of photosynthesis.</p>