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1 Energy Flow Through Living Things: Photosynthesis & Cellular Respiration Chapter 8&9.

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Presentation on theme: "1 Energy Flow Through Living Things: Photosynthesis & Cellular Respiration Chapter 8&9."— Presentation transcript:

1 1 Energy Flow Through Living Things: Photosynthesis & Cellular Respiration Chapter 8&9

2 2 8-1 Energy and Life Living things need energy to survive –comes from food –energy in most food comes from the sun Plants use light energy from the sun to produce food autotrophs organisms that make their own food –Ex - plants heterotrophs organisms that must obtain energy from the foods they consume –animals

3 3 Chemical Energy and ATP Energy – the ability to do work –Forms: light, heat, electricity, chemical compounds chemical compound that cells use to store and release energy is adenosine triphosphate (ATP) –ATP - basic energy source for all cells

4 4 Chemical Energy and ATP ATP consists of: –adenine –ribose (a 5-carbon sugar) –3 phosphate groups Adenine ATP Ribose 3 Phosphate groups The three phosphate groups are the key to ATP's ability to store and release energy.

5 5 Chemical Energy and ATP –Storing Energy ADP has two phosphate groups instead of three. A cell can store small amounts of energy by adding a phosphate group to ADP. ADP ATP Energy Partially charged battery Fully charged battery + Adenosine Diphosphate (ADP) + Phosphate Adenosine Triphosphate (ATP)

6 6 Chemical Energy and ATP –Releasing Energy Energy stored in ATP is released by breaking the chemical bond between the second and third phosphates. P ADP 2 Phosphate groups

7 7 ATP energy uses: -cellular activities: active transport, protein synthesis -muscle contraction Most cells have only a small amount of ATP, because it is not a good way to store large amounts of energy. Cells can regenerate ATP from ADP as needed by using the energy in foods like glucose. Chemical Energy and ATP

8 8 8-2 Photosynthesis Photosynthesis - the process in which green plants use the energy of sunlight to convert water and carbon dioxide into high-energy carbohydrates and oxygen

9 9 The Photosynthesis Equation The equation for photosynthesis is: 6CO 2 + 6H 2 O C 6 H 12 O 6 + 6O 2 carbon dioxide + water sugars + oxygen Light

10 10 The Photosynthesis Equation O2O2 CO 2 + H 2 0 Sugar ADP NADP + Light-Dependent Reactions (thylakoids) H2OH2O ATP NADPH Calvin Cycle (stroma) Light energy

11 11 Light and Pigments photosynthesis requires chlorophyll –pigments - light-absorbing molecules that gather the sun's energy The main pigment in plants is chlorophyll. There are two main types of chlorophyll: –chlorophyll a –chlorophyll b

12 12 Light and Pigments Chlorophyll absorbs light well in the blue-violet and red regions of the visible spectrum. Wavelength (nm) Estimated Absorption (%) Chlorophyll b Chlorophyll a Wavelength (nm)

13 13 Light and Pigments Chlorophyll does not absorb light will in the green region of the spectrum. Green light is reflected by leaves, which is why plants look green. Estimated Absorption (%) Chlorophyll b Chlorophyll a Wavelength (nm)

14 14 Light Energy Light is a form of energy –compound that absorbs light also absorbs energy from that light –chlorophyll absorbs light  the energy is transferred directly to electrons in the chlorophyll molecule  raising the energy levels of these electrons –high-energy electrons are what make photosynthesis work

15 15 Pop Quiz 1.This molecule is called _____. 2.Energy in this molecule is stored in the _____ Word Bank ADP Ribose Phosphate groups Bonds ATP Adenine Adenosine

16 Inside a Chloroplast Inside a Chloroplast In plants, photosynthesis takes place inside chloroplasts. Plant Plant cells Chloroplast

17 17 Inside a Chloroplast Chloroplasts contain thylakoids—saclike photosynthetic membranes. Chloroplast Single thylakoid

18 18 Inside a Chloroplast Thylakoids are arranged in stacks known as grana. A singular stack is called a granum. Stroma – space outside of the thylakoids Granum Chloroplast Stroma

19 19 Inside a Chloroplast Proteins in the thylakoid membrane organize chlorophyll and other pigments into clusters called photosystems, which are the light-collecting units of the chloroplast. Chloroplast Photosystems

20 20 Photosynthesis Reactions reactions of photosystems include: –light-dependent reactions (requires light) take place within the thylakoid membranes uses water, ADP, and NADP + produces oxygen, ATP, and NADPH –light-independent reactions (Calvin cycle) takes place in the stroma ATP and NADPH not stable enough to store the energy they carry for more than a few minutes uses ATP and NADPH energy to build high-energy sugars for long term storage

21 21 Photosynthesis Reactions The two sets of photosynthetic reactions work together. –The light-dependent reactions trap sunlight energy in chemical form. –The light-independent reactions use that chemical energy to produce stable, high- energy sugars from carbon dioxide and water.

22 22 Inside a Chloroplast Chloroplast Light H2OH2O O2O2 CO 2 Sugars NADP + ADP + P Calvin Cycle Light- dependent reactions Calvin cycle

23 23 Electron Carriers electrons in chlorophyll absorb sunlight  electrons gain energy –Cells use electron carriers to transport these high-energy electrons from chlorophyll to other molecules –One carrier molecule is NADP +. transport electrons NADP + accepts and holds 2 high-energy electrons along with a hydrogen ion (H + ) - NADP +  NADPH energy of sunlight can be trapped in chemical form NADPH carries high-energy electrons to chemical reactions elsewhere in the cell to make carbohydrates

24 24 Factors Affecting Photosynthesis Many factors affect the rate of photosynthesis, including: Water Temperature Intensity of light

25 Chemical Pathways Food serves as a source of raw materials for the cells in the body and as a source of energy. Animal Plant Animal Cells Plant Cells Mitochondrion

26 26 Both plant and animal cells carry out the final stages of cellular respiration in the mitochondria. Animal Cells Plant Cells Mitochondrion Outer membrane Intermembrane space Inner membrane Matrix

27 27 Chemical Energy and Food –One gram of the sugar glucose (C 6 H 12 O 6 ), when burned in the presence of oxygen, releases 3811 calories of heat energy –calorie - the amount of energy needed to raise the temperature of 1 gram of water 1 degree Celsius Cells gradually release the energy from glucose and other food compounds beginning with glycolysis - releases a small amount of energy.

28 28 Overview of Cellular Respiration If oxygen is present: –cellular respiration - the process that releases energy by breaking down glucose and other food molecules in the presence of oxygen –glycolysis  Krebs cycle  electron transport chain equation: –6O 2 + C 6 H 12 O 6 → 6CO 2 + 6H 2 O + Energy –oxygen + glucose → carbon dioxide + water + Energy

29 29 Overview of Cellular Respiration Cytoplasm Pyruvic acid Mitochondrion Electrons carried in NADH Electrons carried in NADH and FADH 2 Glucose Glycolysis

30 30 Overview of Cellular Respiration Glycolysis – cytoplasm Krebs cycle and electron transport - mitochondria Cytoplasm Mitochondrion Glycolysis

31 31 Stretch break You have 2 minutes to talk, stretch, stand up…

32 32 Glycolysis the process in which one molecule of glucose is broken in half, producing two molecules of pyruvic acid, a 3-carbon compound –ATP Production cell uses up 2 molecules of ATP to start the reaction When glycolysis is complete, 4 ATP molecules have been produced  a net gain of 2 ATP molecules –NADH Production removes 4 high-energy electrons  electron carrier called NAD +  becomes an NADH molecule. The NADH molecule holds the electrons until they can be transferred to other molecules.

33 33 Glycolysis 2 ADP 4 ADP 4 ATP 2 Pyruvic acid 2 ATP Glucose

34 34 Glycolysis 2 ADP 4 ADP 4 ATP 2 ATP Glucose 2 Pyruvic acid

35 35 Glycolysis 4 ADP 4 ATP Glucose 2 ADP 2 ATP 2 Pyruvic acid

36 36 Glycolysis Glucose 2 Pyruvic acid 4 ADP 4 ATP 2 ADP 2 ATP 2NAD +

37 37 Glycolysis Glucose 2 Pyruvic acid 4 ADP 4 ATP 2 ADP 2 ATP 2NAD + 2

38 38 Glycolysis To the electron transport chain 2NAD + 2 Pyruvic acid 4 ADP 4 ATP 2 ADP 2 ATP 2

39 39 Glycolysis –The Advantages of Glycolysis very fast - cells can produce thousands of ATP molecules in a few milliseconds does not require oxygen

40 40 Fermentation oxygen is not present  glycolysis is followed by a different pathway - fermentation –Fermentation – release of energy (ATP) from food in the absence of oxygen –cells convert NADH to NAD + by passing high- energy electrons back to pyruvic acid –Anaerobic – does not require oxygen

41 41 Fermentation –Alcoholic Fermentation Yeasts and a few other microorganisms use alcoholic fermentation Forms ethyl alcohol and carbon dioxide as wastes –equation: pyruvic acid + NADH → alcohol + CO 2 + NAD +

42 42 Fermentation –Lactic Acid Fermentation pyruvic acid that accumulates from glycolysis  converted to lactic acid regenerates NAD + so that glycolysis can continue –converts glucose into lactic acid –equation: pyruvic acid + NADH → lactic acid + NAD +

43 43 Fermentation The first part of the equation is glycolysis.

44 44 Fermentation The second part shows the conversion of pyruvic acid to lactic acid.

45 45 The Totals

46 46 Comparing Photosynthesis and Cellular Respiration The energy flows in photosynthesis and cellular respiration take place in opposite directions.

47 47 Comparing Photosynthesis and Cellular Respiration On a global level, photosynthesis and cellular respiration are also opposites. –Photosynthesis removes carbon dioxide from the atmosphere and cellular respiration puts it back. –Photosynthesis releases oxygen into the atmosphere and cellular respiration uses that oxygen to release energy from food.


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