Photosynthesis & Cellular Respiration

1. Photosynthesis & Cellular Respiration

2. Energy • Energy: • The ability to perform work. • Life depends on energy, but where does this energy come from? • Thermal • Electromagnetic • Chemical  • Nuclear • Light • The form of energy that we are most interested in is chemical energy.

3. Energy • Energy for life’s activities is stored in the chemical bonds of energy-storing compounds. • These compounds release energy when certain chemical bonds are broken. • Compounds that store energy include: • ATP: Adenosine triphosphate • NAD+: Nicotinamide adenine dinucleotide • NADPH: Nicotinamide adenine dinucleotide phosphate • FADH2: Flavin adenine dinucleotide

4. Energy • When we convert energy from one form to another we release the energy stored in the chemical bonds. • The energy storage molecule that is used by all organisms and in all processes is ATP. • ATP consists of three parts: • Adenine • Ribose • Phosphate Groups

5. Energy: ATP • Ribose and adenine are chemically bonded to form a molecule called adenosine. • A chain of three phosphate groups (Tri = 3) is bonded to adenosine. Unit 2: Maintenance in Living Things

6. Energy: ATP • An ATP molecule releases energy whenever a bond holding a phosphate group to the molecule is broken. • This chemical reaction – the release of the end phosphate group from ATP – creates a new molecule: ADP. (adenosine diphosphate) • The chemical energy released by the breaking of a phosphate bond in ATP can be used by a cell to do work.

7. Energy • What does a cell need energy for? • Growth • Repair • Reproduction • Active Transport • Movement • Cells are constantly at work so they need a constant supply of ATP. • So they must continuously generate ATP by attaching a phosphate group to ADP.

8. Energy • Forming this chemical bond requires energy. • Where does this energy come from? • FOOD! • The chemical energy stored in the bonds of food.

9. Energy This cycle occurs very rapidly– 10 million ATP molecules are made in each cell every SECOND!

10. Autotrophs • Autotrophic Nutrition: • The organism makes organic compounds from inorganic raw materials. • Exp. Sunlight, Carbon Dioxide, Water, Iron, & Sulfur • Most plants and some monerans and protists (including all algae) are autotrophs. • There are two types of autotrophic nutrition: • Photosynthesis • Chemosynthesis

11. Autotrophs • Photosynthesis is the most common type of autotrophic nutrition. • Photosynthesis: process by which organic nutrients are synthesized from inorganic compounds in the presence of light in autrotrophic nutrition. • These inorganic compounds include CO2 & H2O. • Examples of organisms that use photosynthesis: • Plants • Algae

12. Autotrophs

13. Autotrophs Light Energy Unit 2: Maintenance in Living Things

14. Autotrophs • Another less common type of autotrophic nutrition is chemosynthesis. • Chemosynthesis: process by which organisms obtain energy by the oxidation of sulfur, iron, or other simple materials. • Examples of organisms that use chemosynthesis: • Bacteria • Deep Sea Worms Unit 2: Maintenance in Living Things

15. Autotrophs Unit 2: Maintenance in Living Things

16. Autotrophs • Why do you think photosynthesis is the most common type of autotrophic nutrition? • HINT: Think about the available resources.

17. Chloroplasts • Chloroplasts: • The location where photosynthesis occurs. • This organelle contains chlorophyll and other pigments. • A photosynthetic cell contains anywhere from one to several thousand chloroplasts.

18. Chloroplast Structure • A chloroplast is surrounded by two membranes. • The inner membrane is folded into many layers, in some areas this inner membrane layers fuse to form thylakoids. • Thylakoids: • Disk shaped structures that contain photosynthetic pigments. • The thylakoids are surrounded by a gel-like matrix called the stroma.

19. Chloroplast Structure • A stack of thylakoids is called the grana. • Each chloroplast may contain a hundred or moregrana. • Hundreds of chlorophyll molecules and other pigments in the grana are organized into photosytems. • Photosytem: • Light collecting units of the chloroplast.

20. Chloroplast Structure

21. Electron Carriers • When the sunlight excites electrons in chlorophyll, the electrons gain a great deal of energy. • These high energy electrons require a special carrier. • A carrier molecule is a compound that can accept a pair of high-energy electrons and transfer them along with most of their energy to another molecule.

22. Electron Carriers • This process is called electron transport, and the electron carriers are known as the electron transport chain. • One of these carrier molecules is NAD+. • NAD+ accepts and hold two high-energy electrons along with a hydrogen ion (H+). • This converts NAD+ into NADPH.

23. Electron Carriers • This conversion is how some of the energy of the sunlight is trapped in chemical form. • These electron carriers are carried elsewhere in the cell to where they are needed to make other chemical reaction happen.

24. Photosynthesis • Photosynthesis consists of two types of reactions: • Light-Dependent Reaction (Light Reaction): • Converts light energy to the chemical energy of ATP. • Occurs in the thylakoid membranes. • Light-Independent Reaction (Dark Reaction): • Use the products of the light-dependent reactions to convert carbon dioxide and water to sugars. • Occurs in the stroma.

25. Photosynthesis: Light Reaction • The light reaction produces oxygen gas and converts ADP & NAD+into the energy carriers ATP & NADPH. • The reactions starts in Photosystem II. • In Photosystem II light is absorbed and used to split water, releasing O2, H+ ions, and energized electrons. • Then in Photosystem I the electrons released by Photosystem II are energized again in Photosystem I.

26. Photosynthesis: Light Reaction • Enzymes in the membrane use the electrons to form high-energy molecule of NADPH. • NADPH is used to make sugar in the Calvin Cycle (Dark Reaction)

27. Photosynthesis: Dark Reaction • The dark reaction in most plants is called the Calvin Cycle. • The Calvin Cycle takes place in the stroma. • ATP and NADPH made in the light-dependent-reactions are used for chemical energy. • One glucose molecule is produced from every 6 carbon dioxide molecules that enter the cycle.

28. Photosynthesis: Dark Reaction • You start by having three molecules of CO2 enter the cycle. • These three molecules of CO2 combine with three molecules of RuBP to make 6 molecules of PGA. • In two steps energy from ATP and NADPH is used to make 6 high-energy molecules of PGAL, with 3 carbons each.

29. Photosynthesis: Dark Reaction • In the next portion of the cycle two molecules of PGAL are combined to form a glucose molecule. • The remaining PGAL molecules are recycled back into RuBP. • This recycling requires ATP.

30. Photosynthesis: Dark Reaction

31. Review

32. Review • What is the significance of photosynthesis? • Source of oxygen. • Source of most chemical bond energy in organisms.

33. Use of the Products of Photosynthesis • The glucose formed during photosynthesis us used as an energy source by most organisms during cellular respiration. • Glucose may also be used to synthesize other organic compounds, such as fats and proteins, that are needed for the metabolism of the organism.

34. Use of the Products of Photosynthesis • Excess glucose may be converted by dehydration synthesis to storage products for later use. • Storage: Autotrophic organisms store the products of photosynthesis in the form of insoluble materials such as: • Starches • Lipids • Proteins

35. Use of the Products of Photosynthesis • Digestion: To use these stored materials they must be broken down in to soluble materials (by hydrolysis). • Digestion in plants occurs within the cells so a specialized digestive system is not needed. • Transport: The products from digestion may be used in the cell or transported to other cells or tissues of the same organisms for use or further storage.

36. Photosynthesis Summary • The raw materials are CO2 & H2O • The energy is supplied by sunlight. • Chlorophyll acts to trap the light energy. • High-energy molecules are created from low-energy molecules using the sunlight's energy. • Enzymes catalyze reactions that produce a three-carbon compound as the first product. • More enzymes control reactions that lead to the formation of glucose, a six-carbon compound. • Oxygen is produced as a waste product.

37. Review • During photosynthesis, the breakdown of water requires: • Starch • Light • Oxygen-18 • Carbon-14 Answer: B

38. Review • The first step in photosynthesis is the: • Formation of ATP • Synthesis of water • Absorption of light energy by chlorophyll • Fixation of carbon dioxide Answer: C

39. Review • Carbon fixation is a series of chemical reactions which occurs during: • ATP synthesis • Photosynthesis • DNA synthesis • Respiration Answer: B

40. Review • The basic raw materials of photosynthesis are: • Sugar & CO2 • Oxygen & water • Water & CO2 • Oxygen & sugar Answer: C

41. Review • Which factor LEAST influences the rate of photosynthesis? • Atmospheric concentration of CO2 • Time of day • Number of chloroplasts • Concentration of nitrogen in the air Answer: D

42. Review • Most of the food for the animal life of the oceans is obtained from: • Material carried into the oceans by rivers • Underwater plants • Ocean currents • Marine algae Answer: D

43. Respiration • Respiration: • Chemical reactions through which an organism obtains energy from food. • The chemical energy is almost always stored in the bonds of the energy carrier ATP.

44. Respiration • ATP is synthesized from ADP and P (phosphate). • The energy stored in ATP is released by hydrolysis of the ATP into ADP and phosphate. • This reversible process is controlled by an enzyme called ATPase.

45. Respiration • If oxygen is used the process is called aerobic respiration. • Aerobic Respiration: • Respiration carried on in the presence of oxygen, in which glucose is completely oxidized to CO2 & H20. • If oxygen is not used the process is called anaerobic respiration. • Anaerobic Respiration: • Respiration in the absence of oxygen, in which glucose is partially oxidized.

46. Respiration: Gas Exchange • In aerobic respiration, oxygen must be absorbed from the environment and transported to where it is needed and carbon dioxide must be released. • This exchange of gases with the environment occurs by diffusion through moist membranes.

47. Respiration: Chemical Respiration • The chemical reactions that release the energy in food molecules and store it in ATP take place inside the cells of the organism. • In aerobic respiration, most of these reactions occur in the mitochondria, where necessary enzymes are present.

48. Respiration: Chemical Respiration • Chemical respiration in plants is the exact same as it is in animals. • Respiration in plants goes on continuously, whether or not photosynthesis is also occurring.

49. Anaerobic Respiration • Some simple organisms, such as bacteria, cannot carry on aerobic respiration. • They rely on anaerobic respiration for their energy needs. • Other organisms, such as yeasts, make use of aerobic respiration when oxygen is available, but can live by anaerobic respiration when there is no oxygen.

50. Anaerobic Respiration • Anaerobic respiration in these organisms is also called fermentation. • Muscle cells in animals can function for a limited time on the anaerobic phase of cellular respiration. • Most types of anaerobic respiration break down glucose into lactic acid or alcohol. • CO2 is released as a waste product.