Exploring Photosynthesis in Plants

1. Photosynthesis GEP Science P5

2. Source: http://www.botany.org/bsa/misc/carn.html Look at this special plant… What do you see in the Venus Fly Trap? Click on http://www.youtube.com/watch?v=Wdr4aAz7pP8&NR=1 to watch the video.

3. Look at the Panda … Source: Microsoft Clip Art What are the Pandas doing?

4. Look at this bird… Source: http://www.birdpark.com.sg/ What is the bird doing?

5. Look at this bee… Source: http://commons.wikimedia.org/wiki/File:European_honey_bee_extracts_nectar.jpg What is this bee doing?

6. Humans What are these people doing? Source: Microsoft Clip Art

7. Why is eating so important? • Can we survive without eating? • Food gives energy! • Energy is required for all life processes.

8. Question • So where does all that energy from our food come from? • Energy cannot be created or destroyed, so it must have been converted from a source…

9. Look at this plant… Is it doing anything?

10. Why photosynthesis? Photosynthesis is the process by which plants make food in the presence of sunlight. What do the plants need when carrying out photosynthesis? Sunlight, water, carbon dioxide… and? How do we draw the equation for this?

11. Photosynthesis Equation

12. Where does photosynthesis take place? ???

13. Plant nutrition Method of nutrition used by plants is: photosynthesis. • Raw materials needed: • CO2 and H2O • Conditions present: • chlorophyll and sunlight~

14. Leaf Structure

15. To show presence of stomata

16. Section of leaf

17. Structure of Stomata

18. Stomata: open and close close open

19. Photosynthesis • Summary equation: • CO2 + H2O C6H12O6 + O2 Products of photosynthesis: 1 sugar (built up to starch for storage) 2 oxygen. Light, chlorophyll

20. How to show that plant is photosynthesising • Test for presence ofstarch. Photosynthesis is the only way a plant can produce this. • How to test for starch? Use iodine solution.

21. To test a leaf for starch • Boil leaf in water. • Boil leaf in alcohol to remove chlorophyll • Wash in water . • Why must the leaf be boiled in water? To allow I2 solution to penetrate cells. • Why must the leaf be decolorised? To allow blue black colour to show up. • Why must the leaf be washed in water? To soften it.

22. To show thatchlorophyllis needed 1 Destarch a potted plant with variegated leaf by: 2 placing the plant in the light for 48 hrs. 3 Remove a leaf & test for starch. 4 Only the green parts of the leaf give a dark blue (blue- black) colour with I2 solution.

23. To show that light is needed • Destarch 2 potted plants. • Leave 1 in the dark (experimental). • Put one in the light (control). • All other conditions must be the same. • Leave the 2 plants for 48 hrs. • Take a leaf from each plant to test for starch In which plant will starch be present?

24. To show that CO2 is needed for photosynthesis • Destarch 2 potted plants. • Place 1 plant in a bell jar with a dish of soda lime to absorb CO2. • Place the other in a bell jar without CO2 (Which plant is the control?) • All other conditions should be the same for both plants. • Leave the plants for 48 hrs, then test the leaf for starch (with I2 solution). In which plant will starch be present?

25. To show that O2is given off duringphotosynthesis • Place some water plants eg hydrilla under an inverted filter funnel in a beaker of H2O. • Dissolve some NaHCO3 in the H2O ( to provide CO2 to the plant. • Place the apparatus in sunlight for 6 hrs. • Set up a control in the same way, but left in the dark. • Gas bubbles will only be released from the plant placed in sunlight. • This gas rekindles a glowing splint.

26. What happens to sugar formed in photosynthesis 1 Broken down inrespiration. 2 Built up into starch for storage. 3 Turned into fats for storage & other uses. 4 Combined with N2 to form proteins. 5 Moved to other parts of the plant.

27. photosynthesis

28. To testfor presence of starch using I2 solution

29. To show that CO2 is needed for photosynthesis

30. To show thatchlorophyllis needed.Use variegated leaf.

31. To show thatO2 is given off

32. To show thatO2is given off.Glowingsplint rekindles.

33. Where does photosynthesis take place? • Anywhere that contains chlorophyll / chloroplasts! • Do chloroplasts have to be green?

34. Respiration

35. WHERE DOES CELLULAR RESPIRATION TAKE PLACE? • Cellular Respiration takes place in the m_____________ of plant and animal cells. • It is well suited for the process because

36. WHAT ESSENTIAL HAPPENS IN CELLULAR RESPIRATION? • Let’s work it out. • What is needed for respiration? • We know that the ‘main ingredient’ for this process is _________________. • For the chemical bonds in the glucose to break, we need to add ____________ to oxidise the glucose. • What are the outputs of respiration? • The essential output we need is _______. • The ‘waste’ products of the process are ___________ and ____________.

37. Equation for Respiration • Inputs Outputs • Oxygen + Glucose Carbon Dioxide + Water • releasing Energy • Try writing out the chemical equation since you know that glucose is ____________, oxygen is _______ , carbon dioxide is _________ and water is ________. • PAUSE FOR PAIR WORK • However, carbon dioxide and water need not be wasted. • e.g. plants, desert animals, snails and corals etc.

38. TYPES OF RESPIRATION • Cellular respiration can occur in two ways. • Aerobic respiration occurs in the presence of oxygen. • This process releases large amounts of energy. • Most plants and animals respire aerobically. • Anaerobic respiration occurs in the absence of oxygen. • Glucose is broken down without the help of oxygen. • Happens in simple organisms e.g. yeast (a fungus) and certain bacteria. • This process does not release as much energy so it is not as efficient as aerobic respiration. However, enough energy is released for the simple organisms.

39. A BIT MORE ABOUT ANAEROBIC RESPIRATION • Anaerobic respiration occurs in the absence of oxygen. • E.g. Yeast breaks down glucose to alcohol and carbon dioxide during anaerobic respiration and energy is given out. • This is known as alcoholic fermentation. This is how alcohol in wines and beers are produced. • This process is also required for the making of bread. • Yeast mixed with a dough mixture anaerobically to produce carbon dioxide which causes the dough to rise.

40. A BIT MORE ABOUT ANAEROBIC RESPIRATION • Anaerobic respiration can also happen in animals. • Anaerobic respiration in muscles produces lactic acid which is toxic and can cause cramp. • Essentially, this happens when not enough oxygen is delivered to the muscle tissue esp. in vigorous exercise. • An oxygen debt is built up in the muscles. • Water and lactic acid is produced. • Lactic acid will cause fatigue and also energy released in this type of respiration is not enough. • One will have to stop exercising. • Oxygen debt is then paid back and the lactic acid is converted back to glucose for use again.

41. Before Exercise During Exercise 1 min after exercise Time to return to normal Lupus 70 beats/min 140 beats/min 130 beats/min 5 min Janus 60 beats/min 120 beats/min 100 beats/min 3 min A BIT MORE ABOUT ANAEROBIC RESPIRATION • Anaerobic respiration can also happen in animals. • Anaerobic respiration in muscles produces lactic acid which is toxic and can cause cramp. • e.g. Look at the following table. • A pair of identical twins decided to measure their pulse rates before, during and after exercise. Lupus has a sedentary job in an office and enjoys watching TV. Janus has a physically demanding job on a building site and likes to play footbal and tennis. They each did two minutes jogging on the spot.

42. Before Exercise During Exercise 1 min after exercise Time to return to normal Lupus 70 beats/min 140 beats/min 130 beats/min 5 min Janus 60 beats/min 120 beats/min 100 beats/min 3 min A BIT MORE ABOUT ANAEROBIC RESPIRATION • Think about the following questions. • Why does the heart beat faster during exercise? • Why does Lupus take a longer time to return to normal? • Who would be more likely to feel a cramp? Why? • PAUSE FOR PAIR WORK

43. Several systems work together to enable respiration to take place. Let’s find out which ones they are. • What is the word equation for respiration? • Glucose + oxygen water + carbon dioxide releasing energy • We know that respiration happens in the mitochondria of the cells. How does glucose and oxygen reach the cells for respiration to take place? • PAUSE FOR DISCUSSION

44. RESPIRATION IN ANIMALS • The path of glucose e.g. potato: • The potato is taken into the mouth and the _______ help to break it up into smaller pieces while the ________ helps to soften and digest the food slightly. • The partially digested potato travels down the gullet to the stomach. • In the stomach, further digestion takes place when the potato is mixed with digestive juices. • The potato moves to the small intestine where it is fully digested to become glucose.Glucose is absorbed into the bloodstream in the small intestine. • So, respiration requires the • DIGESTIVE SYSTEM

45. RESPIRATION IN ANIMALS • The path of oxygen : • We require the process of breathing to take in oxygen. The oxygen is then absorbed into the bloodstream in the lungs. • So, respiration also requires the • RESPIRATORY SYSTEM • So is breathing respiration?

46. RESPIRATION IN ANIMALS • Finally for the oxygen to get from the lungs to the cells in all parts of the body and for the glucose to get from the small intestines to the cells in all parts of the body, we need the • CIRCULATORY SYSTEM

47. RESPIRATION IN PLANTS • How does glucose get to all cells in plants? • How does oxygen get to all cells in plants? • PAUSE FOR DISCUSSION • For glucose, • It gets transported from the leaves to the rest of the plant through special tubes, phloem. • For oxygen, • Plants carry out simple diffusion of gases. Leaves of course do so through stomata but for the rest of the plant, it is through diffusion. It happens even in roots.

48. Gaseous Exchange in Plants • We seldom find leaves giving off carbon dioxide in bright sunlight. Does that mean plants do not respire in the day? • During photosynthesis, oxygen is set free. Some of it is retained for tissue respiration. • But in bright sunlight the rate of photosynthesis is much greater than the rate of respiration, hence more oxygen is set free than the cells can retain for respiration. • Similarly, since the amount of carbon dioxide produced during tissue respiration is not sufficient for food-making, more carbon dioxide has to diffuse into the leaf from the outside atmosphere. • Respiration occurs continuously, day and night, in all living cells.

49. RESPIRATION Energy is liberated Oxygen is consumed and carbon dioxide and water given off Breakdown of glucose molecules Occurs at all times Not dependent on sunlight or chlorophyll PHOTOSYNTHESIS Energy is stored in glucose molecules Oxygen is given off and carbon dioxide and water are consumed. Build up of glucose molecules Occurs only in cells containing chlorophyll and in the presence of sunlight. Let’s compare respiration and photosynthesis.

50. RESPIRATION Controlled process Energy released mainly in the form of chemical energy Energy released step by step in small quantities No sudden rise in temperature Need enzymes BURNING Uncontrolled process Energy released entirely in the form of heat and light Sudden release of stored energy Sudden rise in temperature No need catalyst Let’s compare respiration and burning (combustion). In what ways are the two processes similar? Both release stored energy through oxidation. However, they can be quite different.