1. Energy in the Cell

2. Section 9.1 Summary – pages 221-224
Cell Energy
All living organisms must be able to obtain energy from the environment in which they live.
The sun is the ultimate source of energy.
Plants & other green organisms (Autotrophs) are able to trap the light energy in sunlight and store it in chemical energy for later use.
Other organisms (heterotrophs) cannot use sunlight directly.
They eat green plants. In that way, they obtain the energy stored in plants.
Section 9.1 Summary – pages

3. Section 9.1 Summary – pages 221-224
Work and the need for energy
Some process require cells to use energy. Examples: cell division, movement of flagella or cilia, and the production, transport, and storage of proteins.
There is a molecule in your cells that is a quick source of energy for any organelle in the cell that needs it.
The name of this energy molecule is adenosine triphosphate or ATP for short.
ATP is composed of an adenosine molecule with three phosphate groups attached.
Section 9.1 Summary – pages

4. Section 9.1 Summary – pages 221-224
Forming and Breaking Down ATP
The charged phosphate groups act like the positive poles of two magnets.
Bonding three phosphate groups to form ATP requires considerable energy.
When only one phosphate group bonds, a small amount of energy is required and the chemical bond does not store much energy. This molecule is called adenosine monophosphate (AMP).
When a second phosphate group is added, more energy is required to force the two groups together. This molecule is called adenosine diphosphate, or ADP.
Section 9.1 Summary – pages

5. Section 9.1 Summary – pages 221-224
Forming and Breaking Down ATP
An even greater amount of energy is required to force a third charged phosphate group close enough to the other two to form a bond. When this bond is broken, energy is released. P P P
The energy of ATP becomes available to a cell when the molecule is broken down.
Adenosine
Adenosine triphosphate (ATP) P P
Adenosine diphosphate (ADP) P P
Adenosine
Section 9.1 Summary – pages

6. Section 9.1 Summary – pages 221-224
How cells tap into the energy stored in ATP
When ATP is broken down and the energy is released, the energy must be captured and used efficiently by cells.
Many proteins have a specific site where ATP can bind.
Section 9.1 Summary – pages

7. Section 9.1 Summary – pages 221-224
How cells tap into the energy stored in ATP
Then, when the phosphate bond is broken and the energy released, the cell can use the energy for activities such as making a protein or transporting molecules through the plasma membrane.
ATP
Protein P
Energy
ADP
ADP
Section 9.1 Summary – pages

8. Section 9.1 Summary – pages 221-224
How cells tap into the energy stored in ATP
When ATP has been broken down to ADP, the ADP is released from the binding site in the protein and the binding site may then be filled by another ATP molecule.
Section 9.1 Summary – pages

9. Question
A molecule of adenosine that has one phosphate group bonded to it is _____.
A. AMP
B. ADP
C. ATP
D. ACP
Section 1 Check

10. Adenosine triphosphate (ATP) Adenosine diphosphate (ADP)
The answer is A. AMP is adenosine monophosphate. P P P
Adenosine
The addition and release of a phosphate group on adenosine diphosphate creates a cycle of ATP formation and breakdown.
Adenosine triphosphate (ATP) P P
Adenosine diphosphate (ADP) P P
Adenosine
Section 1 Check

11. Question
What is the function of the protein molecule shown in this diagram?
ATP
Protein P
Energy
ADP
ADP
Section 1 Check

12. This protein molecule has a specific binding site for ATP
This protein molecule has a specific binding site for ATP. In order to access the energy stored ATP, the protein molecule binds the ATP and uncouples one phosphate group. This action releases energy that is then available to the cell.
ATP
Protein P
Energy
ADP
ADP
Section 1 Check

13. Section 9.2 Summary – pages 225-230
Trapping Energy from Sunlight
The process that uses the sun’s energy to make simple organic sugars is called photosynthesis.
These simple sugars are converted into carbohydrates like starch or cellulose.
Section 9.2 Summary – pages

14. Section 9.2 Summary – pages 225-230
Trapping Energy from Sunlight
Photosynthesis happens in two phases.
The light-dependent reactions (Light Reactions) convert light energy into chemical energy.
2. The molecules of ATP produced in the light-dependent reactions are then used to fuel the light-independent reactions (Dark Reactions) that produce simple sugars.
The general equation for photosynthesis is written as
6CO2 + 6H2O→C6H12O6 + 6O2
Section 9.2 Summary – pages

15. Light and Chlorophyll
Light travels in waves. The visible spectrum are the colors we can see.
ROY G BIV – red, orange, yellow, green, blue, indigo, violet are the colors of the visible spectrum.
Various colors of the spectrum are either absorbed or reflected by pigments.
A pigment is a compound that absorbs light.
The only reason we see color is due to light that reflects off the pigment in the object.

16. Section 9.2 Summary – pages 225-230
The chloroplast and pigments
The pigment chlorophyll is found in the chloroplasts of the cells.
The chloroplast contain stacks of membranes called thylakoid membranes used to trap the energy in the sun’s light.
Clusters of these membranes are called photosystems. Although a photosystem contains several kinds of pigments, the most common is chlorophyll.
Chlorophyll absorbs most wavelengths of light except green.
Section 9.2 Summary – pages

17. Light Reaction Must occur in the light
Begins with the absorption of light in the chloroplast by the chlorophyll (a & b)
Mainly absorbs red and blue light from the spectrum.
Other pigments are known as carotenoids. These are accessory pigments like red, yellow, orange, and purple that you mainly see in the fall.

18. Section 9.2 Summary – pages 225-230
Light-Dependent Reactions
As sunlight strikes the chlorophyll molecules in a photosystem of the thylakoid membrane, the energy in the light is transferred to electrons.
These highly energized, or excited, electrons are passed from chlorophyll to an electron transport chain, a series of proteins embedded in the thylakoid membrane.
Section 9.2 Summary – pages

19. Section 9.2 Summary – pages 225-230
Light-Dependent Reactions
Sun
Light energy transfers to chlorophyll.
At each step along the transport chain, the electrons lose energy.
Chlorophyll passes energy down through the electron transport chain.
This “lost” energy can be used to form ATP from ADP, or to pump hydrogen ions into the center of the thylakoid disc.
Energized electrons provide energy that
splits
H2O
bonds P
to ADP
forming ATP H+
oxygen
released
NADP+
NADPH
for the use in light-independent reactions
Section 9.2 Summary – pages

20. Section 9.2 Summary – pages 225-230
Restoring electrons
To replace the lost electrons, molecules of water are split in the first photosystem. This reaction is called photolysis.
Sun _ 1
Chlorophyll
O2 + 2H+ 2 _
2e- 1
H2O →2Η+ +
O2 + 2e-
H2O 2
Section 9.2 Summary – pages

21. Section 9.2 Summary – pages 225-230
Restoring electrons
The oxygen produced by photolysis is released into the air and supplies the oxygen we breathe.
The electrons are returned to chlorophyll.
The hydrogen ions are pumped into the thylakoid, where they accumulate in high concentration.
Section 9.2 Summary – pages

22. Section 9.2 Summary – pages 225-230
Light-Dependent Reactions
Electrons are re-energized in a second photosystem and passed down a second electron transport chain.
The electrons are transferred to the stroma of the chloroplast. To do this, an electron carrier molecule called NADP is used.
NADP can combine with two excited electrons and a hydrogen ion (H+) to become NADPH.
NADPH will play an important role in the light-independent reactions.
Section 9.2 Summary – pages

23. Section 9.2 Summary – pages 225-230
The Calvin Cycle
(CO2)
(Unstable intermediate)
(RuPB)
ADP +
ATP
ATP
ADP +
NADPH
NADP+
(PGAL)
(PGAL)
(PGAL)
(Sugars and other carbohydrates)
Pg. 229 in textbook
Section 9.2 Summary – pages

24. The Calvin Cycle AKA - Dark reactions Named after Melvin Calvin.
Provides raw materials to produce almost everything for the cell.
Most common pathway for carbon fixation-the incorporation of Carbon dioxide into an organic compound.
Can occur in the dark or in the light.

25. Section 9.2 Summary – pages 225-230
The Calvin Cycle
Carbon fixation The carbon atom from CO2 bonds with a five-carbon sugar called ribulose diphosphate (RDP or RuBP) to form an unstable six-carbon sugar.
(CO2)
The stroma in chloroplasts hosts the Calvin cycle.
(RuBP)
Section 9.2 Summary – pages

26. Section 9.2 Summary – pages 225-230
The Calvin Cycle
Formation of 3-carbon molecules:
The six-carbon sugar formed in Step A immediately splits to form two three-carbon molecules.
(Unstable intermediate)
Section 9.2 Summary – pages

27. Section 9.2 Summary – pages 225-230
The Calvin Cycle
Use of ATP and NADPH:
A series of reactions involving ATP and NADPH from the light-dependent reactions converts the three-carbon molecules into phosphoglyceraldehyde (PGAL), three-carbon sugars with higher energy bonds.
ATP
ADP +
NADPH
NADP+
(PGAL)
Section 9.2 Summary – pages

28. Section 9.2 Summary – pages 225-230
The Calvin Cycle
Sugar production:
One out of every six molecules of PGAL is transferred to the cytoplasm and used in the synthesis of sugars and other carbohydrates. After three rounds of the cycle, six molecules of PGAL are produced.
(PGAL)
(Sugars and other carbohydrates)
Section 9.2 Summary – pages

29. Section 9.2 Summary – pages 225-230
The Calvin Cycle
RuBP is replenished:
Five molecules of PGAL, each with three carbon atoms, produce three molecules of the five-carbon RuBP. This replenishes the RuBP that was used up, and the cycle can continue.
ADP+ P
ATP
(PGAL)
Section 9.2 Summary – pages

30. Question 1
The process that uses the sun’s energy to make simple sugars is ________.
A. cellular respiration
B. glycolysis
C. photosynthesis
D. photolysis
Section 2 Check

31. The answer is C. Photosynthesis happens in two phases to make simple sugars and convert the sugars into complex carbohydrates for energy storage.
Section 2 Check

32. Question 2
The function accomplished by the light-dependent reactions is ________.
A. energy storage
B. sugar production
C. carbon fixation
D. conversion of sugar to PGAL
Section 2 Check

33. Sun
The answer is A. The light-dependent reactions transfer energy from the sun to chlorophyll, and pass energized electrons to proteins embedded in the thylakoid membrane for storage in ATP and NADPH molecules.
Light energy transfers to chlorophyll.
Chlorophyll passes energy down through the electron transport chain.
Energized electrons provide energy that
splits
H2O
bonds P
to ADP
forming ATP H+
oxygen
released
NADP+
NADPH
for the use in light-independent reactions
Section 2 Check

34. Question 3 The first step in the Calvin cycle is the ________.
A. replenishing of ribulose biphosphate
B. production of phosphoglyceraldehyde
C. Splitting of six-carbon sugar into two three-carbon molecules
D. Bonding of carbon to ribulose biphosphate
Section 2 Check

35. The answer is D. The carbon atom from CO2 bonds with a five-carbon sugar to form an unstable six-carbon sugar. This molecule then splits to form two three-carbon molecules.
Section 2 Check

36. Question 4
How many rounds of the Calvin cycle must occur in order for one molecule of PGAL to be transferred to the cell’s cytoplasm?
A. 1
B. 2
C. 3
D. 4
Section 2 Check

37. The answer is C. Each round of the Calvin cycle produces two molecules of PGAL.
Section 2 Check

38. Section 9.3 Summary – pages 231-237
Cellular Respiration
The process by which mitochondria break down food molecules to produce ATP is called cellular respiration.
There are two phases of cellular respiration: Anaerobic and aerobic.
The first phase, anaerobic—no oxygen is required, has two parts Glycolysis and Fermentation
The last phase is aerobic and requires oxygen to be completed.
Section 9.3 Summary – pages

39. Cellular Respiration
The complex process in which cells make ATP by breaking down organic compounds
The reverse of photosynthesis.
C6H12O6 + 6O2 → 6CO2 + 6H2O
Both photosynthesis and cellular respiration are used by autotrophs and heterotrophs just use cellular respiration.

40. Section 9.3 Summary – pages 231-237
Glycolysis
Glycolysis is a series of chemical reactions in the cytoplasm of a cell that break down glucose, a six-carbon compound, into two molecules of pyruvic acid, a three-carbon compound.
4ATP
2ADP
2 Pyruvic acid
2ATP
4ADP + 4P
Glucose
2PGAL
2NAD+
2NADH + 2H+
Section 9.3 Summary – pages

41. Section 9.3 Summary – pages 231-237
Glycolysis
Glycolysis is not very effective, producing only two ATP molecules for each glucose molecule broken down.
The efficiency of Glycolysis is only 3.5%
4ATP
2ADP
2 Pyruvic acid
2ATP
4ADP + 4P
Glucose
2PGAL
2NAD+
2NADH + 2H+
Section 9.3 Summary – pages

42. Section 9.3 Summary – pages 231-237
Fermentation
The process used when no oxygen is available for further respiration. This doesn’t produce any further energy but changes pyruvic acid into other substances.
During heavy exercise, when your cells are without oxygen for a short period of time, an anaerobic process called fermentation follows Glycolysis and provides a means to continue producing ATP until oxygen is available again.
Section 9.3 Summary – pages

43. Section 9.3 Summary – pages 231-237
Lactic acid fermentation
Lactic acid fermentation is one of the processes that supplies energy when oxygen is scarce.
In this process, the reactions that produced pyruvic acid are reversed.
Two molecules of pyruvic acid use NADH to form two molecules of lactic acid.
This releases NAD+ to be used in Glycolysis, allowing two ATP molecules to be formed for each glucose molecule.
Section 9.3 Summary – pages

44. Section 9.3 Summary – pages 231-237
Lactic acid fermentation
The lactic acid is transferred from muscle cells, to the liver that converts it back to pyruvic acid.
Useful in manufacturing cheese & yogurt.
Occurs in muscle during rapid exercise causing extreme soreness.
Section 9.3 Summary – pages

45. Section 9.3 Summary – pages 231-237
Alcoholic fermentation
Another type of fermentation, alcoholic fermentation, is used by yeast cells and some bacteria to produce CO2 and ethyl alcohol.
Occurs in plant cells and micro-organisms as waste products.
The CO2 is what makes bread to rise and beer to bubble.
Section 9.3 Summary – pages

46. Aerobic Respiration
The second major phase of cellular respiration is Aerobic respiration which requires oxygen.
Aerobic respiration takes place in the mitochondria. This phase consist of two parts called the Citric Acid or Krebs Cycle and the Electron Transport Chain (ETC). During the Citric Acid cycle the pyruvic acid breaks down into citric acid and carbon dioxide. The energy released during the process forms 2 ATP not counting the 2 formed in Glycolysis.

47. Section 9.3 Summary – pages 231-237
Glycolysis
Before citric acid cycle and electron transport chain can begin, pyruvic acid undergoes a series of reactions in which it gives off a molecule of CO2 and combines with a molecule called coenzyme A to form acetyl-CoA.
Mitochondrial membrane
CO2
Outside the mitochondrion
Inside the mitochondrion
Coenzyme A
- CoA
Pyruvic acid
Pyruvic acid
Intermediate by-product
Acetyl-CoA
NAD+
NADH + H+
Section 9.3 Summary – pages

48. Section 9.3 Summary – pages 231-237
The citric acid cycle
IF there is oxygen available the following steps will take place.
The citric acid cycle, also called the Krebs cycle, is a series of chemical reactions similar to the Calvin cycle in that the molecule used in the first reaction is also one of the end products.
For every turn of the cycle, one molecule of ATP and two molecules of carbon dioxide are produced.
The mitochondria host the citric acid cycle.
Section 9.3 Summary – pages

49. Section 9.3 Summary – pages 231-237
The Citric Acid Cycle
(Acetyl-CoA)
NAD+
Oxaloacetic acid
Citric acid
NADH + H+
NADH + H+ O= =O
Citric Acid Cycle
NAD+
(CO2)
NAD+
NADH + H+ O= =O
(CO2)
ADP +
ATP
FADH2
FAD
Section 9.3 Summary – pages

50. Section 9.3 Summary – pages 231-237
The citric acid cycle
Citric acid:
The two-carbon compound acetyl-CoA reacts with a four-carbon compound called oxaloacetic acid to form citric acid, a six-carbon molecule.
Acetyl-CoA
Citric acid
Oxaloacetic acid
Section 9.3 Summary – pages

51. Section 9.3 Summary – pages 231-237
The citric acid cycle
Formation of CO2:
A molecule of CO2 is formed, reducing the eventual product to a five-carbon compound. In the process, a molecule of NADH and H+ is produced.
NAD+
NADH + H+ O= =O
(CO2)
Section 9.3 Summary – pages

52. Section 9.3 Summary – pages 231-237
The citric acid cycle
Formation of the second CO2:
Another molecule of CO2 is released, forming a four-carbon compound. One molecule of ATP and a molecule of NADH are also produced.
NAD+
NADH + H+ O= =O
ADP +
(CO2)
ATP
Section 9.3 Summary – pages

53. Section 9.3 Summary – pages 231-237
Recycling of oxaloacetic acid:
The four-carbon molecule goes through a series of reactions in which FADH2, NADH, and H+ are formed. The carbon chain is rearranged, and oxaloacetic acid is again made available for the cycle.
The citric acid cycle
NADH + H+
NAD+
FAD
FADH2
Section 9.3 Summary – pages

54. Section 9.3 Summary – pages 231-237
The electron transport chain
In the electron transport chain, the carrier molecules NADH and FADH2 gives up electrons that pass through a series of reactions. Oxygen is the final electron acceptor.
Space between inner and outer membranes
Electron carrier proteins
Enzyme
Inner membrane
Electron pathway
e -
4H+ + O2
H2O
NADH
NAD+
ADP +
ATP
+ 4 electrons
FADH2
FAD
H2O
Center of mitochondrion
Section 9.3 Summary – pages

55. Pyruvic Acid 2 NADH 6 ATP ETC Acetyl CoA 2 ATP directly
Overall, the electron transport chain adds 32 ATP molecules to the four already produced.
Glucose
Glycolysis 2 ATP
2 NADH 6 ATP ETC
Pyruvic Acid 2 NADH 6 ATP ETC
Acetyl CoA
2 ATP directly
Krebs Cycle 6 NADH ATP ETC
2 FADH ATP ETC
38 Total ATP molecules made.

56. Aerobic Respiration The efficiency of Aerobic Respiration is 66%.
Aerobic respiration is about 20 times more efficient than Glycolysis alone.

57. Section 9.3 Summary – pages 231-237
Comparing Photosynthesis and Cellular Respiration
Table 9.1 Comparison of Photosynthesis and Cellular Respiration
Photosynthesis
Cellular Respiration
Food synthesized
Food broken down
Energy from sun stored in glucose
Energy of glucose released
Carbon dioxide taken in
Carbon dioxide given off
Oxygen given off
Oxygen taken in
Produces sugars from PGAL
Produces CO2 and H2O
Requires light
Does not require light
Occurs only in presence of chlorophyll
Occurs in all living cells
Section 9.3 Summary – pages

58. Question 1
What do the Calvin cycle and the Citric acid cycle have in common?
A. The molecule used in the first reaction is also one of the end products.
B. Both require input of ATP molecules.
C. Both generate ADP.
D. From every turn of the cycle, two molecules of carbon dioxide are produced.
Section 3 Check

59. The answer is A. In the Calvin cycle, RuBP bonds to carbon in the first step and is produced in the last step. In the citric acid cycle, oxaloacetic acid reacts in the first step and is recycled in the last step.
Section 3 Check

60. Question 2
The process by which mitochondria break down food molecules to produce ATP is called ________.
A. photosynthesis
B. cellular respiration
C. the light-independent reaction
D. the Calvin cycle
Section 3 Check

61. The answer is B. Photosynthesis, light-independent reactions, and the Calvin cycle all occur in plants.
Section 3 Check

62. Question 3 The three stages of cellular respiration are _____.
A. Glycolysis, the Calvin cycle, and the electron transport chain
B. carbon fixation, the citric acid cycle, and the electron transport chain
C. Glycolysis, the citric acid cycle, and the electron transport chain
D. the light-dependent reactions, the citric acid cycle and the electron transport chain
Section 3 Check

63. The answer is C. The first stage is anaerobic, but the last two stages require oxygen to be completed.
Section 3 Check

64. Question 4 Which of the following yields the greatest net ATP?
A. Lactic acid fermentation
B. Alcoholic fermentation
C. Calvin cycle
D. Cellular respiration
Section 3 Check

65. The answer is D. Cellular respiration is far more efficient in ATP production than the fermentation reactions.
Comparison of Fermentation to Cellular Respiration
Lactic Acid
Alcoholic
Cellular respiration
glucose
glucose
glucose
glycolysis (pyruvic acid)
glycolysis (pyruvic acid)
glycolysis (pyruvic acid)
carbon dioxide
carbon dioxide
lactic acid
alcohol
water
2 ATP
2 ATP
38 ATP
Section 3 Check

66. Question 4
In which of the following structures do the light-dependent reactions of photosynthesis take place? A. C. B. D.
Chapter Assessment

67. The answer is D. The light-dependent reactions of photosynthesis take place in the thylakoid membranes of chloroplasts.
Chapter Assessment

68. Question 6
What component of thylakoid membranes absorbs specific wavelengths of sunlight?
A. electrons
B. pigments
C. chloroplasts
D. mitochondria
Chapter Assessment

69. Question 7
Which of the following is a product of cellular respiration?
A. lactic acid
B. alcohol
C. glucose
D. carbon dioxide
Chapter Assessment