1. Energy in a Cell – Chapter 9
Dr. Bill Stafford
2015

2. KEY CONCEPT All cells need chemical energy.

3. ATP – Chapter 9.1
Energy is essential for life of the cell and the organism
Energy must be obtained from the environment for use by organisms.
Energy must be transformed into a form the cell can use – ATP
Organisms must be able to store energy for future use
Organisms must use energy in a controlled way

4. ATP – Chapter 9.1 The cell and organisms use energy in many ways
Active transport of substances into and out of the cell through the plasma membrane
Replicating (making a copy of) its DNA
Movement of cilia or flagella
Synthesis (making) of proteins
Movement of substances and organelles within the cell
Muscle movement
Thinking – try it you might like it

5. ATP – Chapter 9.1
ATP – adenosine triphosphate – the form of energy a cell uses for its processes and activities
Structure
Adenosine molecule
Three phosphate groups attached to the adenosine molecule
These phosphate groups are each negatively charged and do not like to be side-by-side close to each other
This makes the bond between the second and third phosphate group energized like a compressed spring

6. ATP – Chapter 9.1 Three forms of the adenosine – phosphate molecule
1. AMP – adenosine with one phosphate attached
“Mono means one” – adenosine monophosphate
Low energy bond between adenosine and phosphate
2. ADP – adenosine with two phosphates attached to the adenosine
“di means two” – adenosine diphosphate
Higher energy bond between the two phosphates
3. ATP – adenosine with three phosphates attached to the adenosine
“Tri means three” – adenosine triphosphate
Highest energy bond between the 2nd and 3rd phosphate

7. ATP – Chapter 9.1 ADP (add energy) ATP (release energy) ADP
ATP formation and breakdown is a way for the cell to recycle energy
The cell adds a phosphate group to ADP forming a usable energy source in the form of ATP
When the third phosphate group is released to make ADP again, that energy that is released can be used by the cell to do its activity
All the cell has to do is put one phosphate group on ADP to form ATP and take one phosphate group off ATP to release the energy stored in the bond between the 2nd and 3rd phosphate for use by the cell.

8. ATP

9. ATP – Chapter 9.1
The energy stored in ATP is actually stored in the chemical bond between the 2nd and 3rd phosphate group
Sometimes if a cell activity requires less energy, it removes the second phosphate group from ADP and captures that energy which is less than from ATP. Then AMP is formed.

10. ATP – Chapter 9.1
How cells capture the energy stored in the chemical bond between the 2nd and 3rd phosphate group
Proteins in the cell have a specific location where the ATP binds to it. Then when the protein does its work, the phosphate bond is broken and the energy released is used by the protein to do work.

11. ATP – Chapter 9.1 Uses of energy (ATP) by the cell
Making macromolecules
Making enzymes (proteins)
Build membranes and organelles for the cell
Maintain homeostasis
Many, many other cellular activities

12. ATP – Chapter9.1
Draw ADP and ATP molecules showing the difference between the two molecules.
Which molecule has the most energy stored in it and where is the energy stored in the molecule?

13. Photosynthesis – Chap. 9.2
Definition – process plants use to trap the energy from sunlight and change it into ATP or store it as a carbohydrate called glucose.
Plants can make ATP directly from sunlight, but the sun doesn’t shine 24 hrs a day
So, the plant can build a glucose molecule that has the energy from sunlight stored in it.

14. Photosynthesis

15. Photosynthesis – Chap. 9.2
The capturing of energy from sunlight and the storing of energy in the glucose molecule happens in an organelle called the chloroplast.
The release of the sun’s energy stored in the glucose molecule and the capturing of that energy to make ATP occurs in the organelle called the mitochondria.

16. Photosynthesis

17. Photosynthesis – Chap. 9.2
What organelle is involved in photosynthesis?

18. Photosynthesis – Chap. 9.2 Two phases of photosynthesis
Light-dependent reactions – converts light energy into chemical energy – ATP and NADPH
Light-independent reactions – Calvin cycle produces glucose (sugar)

19. Photosynthesis

20. Photosynthesis
List the two phases of photosynthesis and briefly describe what happens in each phase.

21. Photosynthesis – Chap. 9.2 General equation for photosynthesis
6CO2 + 6H2O + energy (sunlight)  C6H12O6 + 6O2
reactants products

22. Photosynthesis

23. Photosynthesis – Chap. 9.2
Write the general balanced equation for photosynthesis.

24. Photosynthesis – Chap. 9.2 Site of Photosynthesis – Chloroplast
Light-dependent reactions – happens in thylakoid of chloroplasts
Chlorophyll a and other pigments found in grana in thylakoid
Electron transport systems built into inner membranes of the thylakoid
Light-independent reactions – stroma – space in the chloroplast

25. Photosynthesis

26. Photosynthesis
Where in the chloroplast does the light- dependent reaction occur?
Where in the chloroplast does the light- independent reaction occur?

27. Photosynthesis – Chap. 9.2 Pigments
Capture the energy from sunlight to make ATP and NADPH
Chlorophyll a – primary pigment – looks green because it reflects the green wavelength of light – absorbs other colors
Chlorophyll b – secondary pigment
Caratenoid – looks orange
Leaves turn colors in the fall as chlorophyll a is reabsorbed and the other pigments predominate

28. Photosynthesis – Chap. 9.2 Structure of chloroplast
Double membrane organelle
Thylakoid inside inner membrane of chloroplast and is full of grana which look like poker chips – the grana are full of chlorophyll
The chlorophyll in the grana capture energy from the sunlight
The inner membrane is the site of the ETC
The space around the thylakoid is called the stroma and is the site of the light-independent reaction where glucose is made.

29. Photosynthesis – Chap. 9.2
Light-dependent reactions – require sunlight to happen
Sunlight hits the chlorophyll molecule in the thylakoid and excites an electron  excited electron with energy
The excited electron goes down the electron transport chain (ETC) and the ETC captures the energy from the excited electron in a step-wise manner and uses this energy to make ATP

30. Photosynthesis What does sunlight do to the chlorophyll molecule?
What does the ETC do with the electron that was excited by sunlight?

31. Photosynthesis – Chapter 9.2
Light-dependent reaction (cont.)
The sunlight hits another chlorophyll molecule system (photosystem I) and reexcites the electron and sends it to another ETC.
This electron is attached to an electron carrier called NADP+ and forms NADPH
NADPH carries the energized electron to the stroma of the chloroplast to be used to make glucose (sugar)
The electron attached to NADPH still has energy and that energy from that still excited electron will be used to make glucose.

32. Photosynthesis
What two molecules are produced by the light-dependent reaction and used by the light-independent reaction to produce sugar?

33. Photosynthesis – Chap. 9.2 Light-dependent reactions (cont.)
Replacement of electron that was removed from the chlorophyll and left attached to NADPH
The water molecule (H2O) is split and an electron from it is used to replace the electron that was removed from the chlorophyll
2H2O  4H+ O2 + 4e-
This reaction is called photolysis and supplies the oxygen that we breathe
The oxygen produced in photosynthesis is produced from splitting a water molecule
Oxygen is a waste product of photosynthesis

34. Photosynthesis
Where does the oxygen that is produced during the light-dependent reaction come from?

35. Photosynthesis

36. Photosynthesis

37. Photosynthesis – Chap. 9.2 Light – independent reactions
This reaction is called the Calvin cycle and it is a series of reactions that forms glucose (sugar)
This reaction takes place in the stroma of the chloroplast
The sugar (glucose) is made to serve as a storage form of energy for the plant cell to use when there is no sunlight to form ATP
“The sun doesn’t shine all the time”

38. Photosynthesis
Why does the plant produce sugar by the Calvin cycle?

39. Photosynthesis – Chap. 9.2
The Calvin cycle is named after Melvin Calvin.
It is called a cycle because the last molecule formed in this series of reactions starts the next cycle.
It forms a circle that starts over with the end product

40. Photosynthesis – Chap. 9.2 Calvin cycle (cont.)
The NADPH and ATP formed in the light-dependent reaction is used as an electron and energy source to fix CO2 to form sugar – called carbon fixation
It takes 3 ATP and 2 NADPH for each CO2 fixed in each cycle of the Calvin cycle
It takes 6 times through the Calvin cycle to make 1 glucose molecule
So it takes 18 ATP and 12 NADPH to form 1 glucose molecule

41. Photosynthesis What is carbon fixation?
How many times through the Calvin cycle is required to make 1 glucose molecule?
How many ATP and NADPH are needed to make one glucose molecule?

42. Photosynthesis – Chap. 9.2
Photosynthesis is performed by organisms called autotrophs or producers.
They produce their own food from the energy in sunlight and the inorganic molecules of CO2 and H2O
All other organisms that cannot produce their own food are called heterotrophs or consumers.
They get their food for energy from the autotrophs

43. Photosynthesis
What kind of organisms produce their own food and ATP from sunlight and CO2?
What kind of organism cannot produce their own food, but must get energy from food?

44. Photosynthesis – Chap. 9.2
There is a cycle of food from sunlight  autotrophs  heterotrophs
There is a cycle of O2 and CO2 between autotrophs and heterotrophs
Autotrophs  O2  heterotrophs  CO2  autotrophs
This leads to a balance in nature