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

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. 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. Chemical Energy and ATP
The three phosphate groups are the key to ATP's ability to store and release energy.
ATP consists of:
adenine
ribose (a 5-carbon sugar)
3 phosphate groups
Adenine
Ribose
3 Phosphate groups
ATP is used by all types of cells as their basic energy source.
ATP

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.
ATP
ADP
Energy +
Energy
Adenosine Triphosphate (ATP)
Adenosine Diphosphate (ADP) + Phosphate
Partially charged battery
Fully charged battery

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

7. Chemical Energy and ATP
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.

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. The Photosynthesis Equation
The equation for photosynthesis is:
6CO2 + 6H2O C6H12O6 + 6O2
carbon dioxide + water sugars + oxygen
Light
Light

10. The Photosynthesis Equation
Light energy
H2O
Light-Dependent Reactions (thylakoids) O2
ADP NADP+
ATP NADPH
Photosynthesis is a series of reactions that uses light energy from the sun to convert water and carbon dioxide into sugars and oxygen.
CO2 + H20
Sugar
Calvin Cycle (stroma)

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. Light and Pigments
Chlorophyll absorbs light well in the blue-violet and red regions of the visible spectrum.
100 80 60 40 20
Chlorophyll b
Estimated Absorption (%)
Chlorophyll a
Photosynthesis requires light and chlorophyll. In the graph above, notice how chlorophyll a absorbs light mostly in the blue-violet and red regions of the visible spectrum, whereas chlorophyll b absorbs light in the blue and red regions of the visible spectrum.
Wavelength (nm)
Wavelength (nm)

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.
100 80 60 40 20
Chlorophyll b
Estimated Absorption (%)
Chlorophyll a
Photosynthesis requires light and chlorophyll. In the graph above, notice how chlorophyll a absorbs light mostly in the blue-violet and red regions of the visible spectrum, whereas chlorophyll b absorbs light in the blue and red regions of the visible spectrum.
Wavelength (nm)

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. Pop Quiz Word Bank ADP Ribose Phosphate groups Bonds ATP
Adenine
Adenosine
This molecule is called _____.
Energy in this molecule is stored in the _____. 3. 5. 4.

16. 8-3 Inside a Chloroplast Inside a Chloroplast
In plants, photosynthesis takes place inside chloroplasts.
Plant
Chloroplast
Plant cells

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

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
Stroma
Chloroplast

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.
Photosystems
Chloroplast

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. 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. Light- dependent reactions
Inside a Chloroplast
H2O
CO2
Light
NADP+
ADP + P
Light- dependent reactions
Calvin Cycle
Calvin cycle
The process of photosynthesis includes the light-dependent reactions as well as the Calvin cycle.
Chloroplast O2
Sugars

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

25. 9-1 Chemical Pathways
Food serves as a source of raw materials for the cells in the body and as a source of energy.
Animal Cells
Animal
Mitochondrion
Plant
Photo Credits: left: ©Bob Gurr/DRK Photo; middle bottom: ©John Durham/Science Photo Library/Photo Researchers, Inc. ; middle top: ©Ron Boardman/Stone; right: ©Keith Porter/Photo Researchers, Inc.
Plant Cells

26. Both plant and animal cells carry out the final stages of cellular respiration in the mitochondria.
Outer membrane
Intermembrane space
Mitochondrion
Animal Cells
Inner membrane
Photo Credits: left: ©Bob Gurr/DRK Photo; middle bottom: ©John Durham/Science Photo Library/Photo Researchers, Inc. ; middle top: ©Ron Boardman/Stone; right: ©Keith Porter/Photo Researchers, Inc.
Plant Cells
Matrix

27. Chemical Energy and Food
One gram of the sugar glucose (C6H12O6), 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. 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:
6O2 + C6H12O6 → 6CO2 + 6H2O + Energy
oxygen + glucose → carbon dioxide + water + Energy

29. Overview of Cellular Respiration
Electrons carried in NADH
Electrons carried
in NADH and
FADH2
Pyruvic acid
Glucose
Glycolysis
Cytoplasm
Cellular respiration is the process that releases energy by breaking down food molecules in the presence of oxygen. Glycolysis takes place in the cytoplasm. The Krebs cycle and electron transport take place inside the mitochondria.
Mitochondrion

30. Overview of Cellular Respiration
Glycolysis – cytoplasm
Krebs cycle and electron transport - mitochondria
Glycolysis
Cellular respiration is the process that releases energy by breaking down food molecules in the presence of oxygen. Glycolysis takes place in the cytoplasm. The Krebs cycle and electron transport take place inside the mitochondria.
Cytoplasm
Mitochondrion

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

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. Glycolysis 2 ATP 2 ADP 4 ADP 4 ATP Glucose 2 Pyruvic acid
Glycolysis is the first stage in cellular respiration. During glycolysis, glucose is broken down into 2 molecules of pyruvic acid.
Glucose
2 Pyruvic
acid

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

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

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

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

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

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

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. Fermentation Alcoholic Fermentation equation:
Yeasts and a few other microorganisms use alcoholic fermentation
Forms ethyl alcohol and carbon dioxide as wastes
equation:
pyruvic acid + NADH → alcohol + CO2 + NAD+

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. Fermentation The first part of the equation is glycolysis.
Lactic acid fermentation converts glucose into lactic acid. The first part of the equation is glycolysis. The second part shows the conversion of pyruvic acid to lactic acid.

44. Fermentation
The second part shows the conversion of pyruvic acid to lactic acid.
Lactic acid fermentation converts glucose into lactic acid. The first part of the equation is glycolysis. The second part shows the conversion of pyruvic acid to lactic acid.

45. The Totals
The complete breakdown of glucose through cellular respiration, including glycolysis, results in the production of 36 molecules of ATP.

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

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.