1. PHOTOSYNTHESIS

2. Autotroph Heterotroph (Producers) (Consumers) Make their own food
Photosynthesis
Chemosynthesis
- Plants
- Some bacteria & protists
Heterotroph
(Consumers)
Energy obtained by eating

3. Cellular Energy: ATP
An important compound that cells use to store and release energy is Adenosine Triphosphate (ATP)
ATP is used by all cells as their basic energy source
Adenine
3 Phosphate groups
Ribose

4. Releasing Energy From ATP
Energy stored in ATP is released by breaking the chemical bond between the second and third phosphates.
The energy from ATP is needed for many cellular activities, including active transport across cell membranes, protein synthesis and muscle contraction.

5. Photosynthesis
6H CO  C6H12O6 + 6O2

6. How can plants do it?
Plants contain the green pigment chlorophyll, which takes in sunlight and captures it’s energy, in the chloroplasts.
There are two main types of chlorophyll, “chlorophyll a” and “chlorophyll b”
When chlorophyll absorbs light, energy is transferred to electrons in the chlorophyll molecule, raising their energy level.
These high-energy electrons make photosynthesis work.

7. Interpreting Diagrams
Which wavelengths/ color(s) are absorbed best?
Which wavelengths/ color(s) are reflected?
What is the relationship between reflection of light and the perception of color?

8. Not all plants have green leaves…
They still have chlorophyll!!
It is just hidden by other pigments.

9. Why do leaves change colors?
Chlorophyll breaks down in cold weather as the strength of the sun’s rays weakens.
The other colors, that were always there, show through.

10. How do we know? Chromatography Method of separating pigments
The solvent moves past the spot that was applied
The pigments will differ in solubility and in the strength of their adsorption to the adsorbent
Some will be carried farther up the plate than others.

11. Location of Photosynthesis

12. The Chloroplast

13. Process Overview Two steps: Light Dependent (Light Reactions)
-> thylakoid
Light Independent (Calvin Cycle)
-> stroma

14. Light- dependent reactions
A closer look…….
H2O
CO2
Light
NADP+
ADP + P
Light- dependent reactions
Calvin cycle O2
Sugars

15. Light-Dependent Reactions
Light is absorbed by chlorophyll in clusters called photosystems
A flow of e- starts
This provides energy to make ATP & NADPH
Water is split to replace e- and allow the flow to continue & O2 is released
ATP & NADPH go to the stroma to fuel the Calvin Cycle

16. NADPH When water is split to replace e- in PS-II, H+ are left over
As free e- reach PS-I, two are picked up by NADP+, resulting in NADP-
This negative charge attracts H+ ions resulting in NADPH
NADP+ + 2e-  NADP-
NADP- + H+  NADPH
NADPH carries electrons (energy source) as well as hydrogen (to build sugars) to the stroma for the Calvin Cycle.

17. Chemiosmosis Mechanism that generates ATP
Uses potential energy of an H+ concentration gradient
H+ flow across the thylakoid membrane into the stroma through an enzyme membrane protein called ATP synthase
This drives the (photo) phosphorylation of ATP

18. Self-Assessment – L.D. Reactions
Where in the chloroplast do the light dependent reactions take place?
What happens when a molecule of chlorophyll absorbs light?
How is water used during the light dependent reactions? (2 uses) What is the bi-product of using water?
What two things does NADPH supply for the Calvin Cycle?
What is chemiosmosis? What enzyme is involved in this process? What supplies the energy for this process?

19. Calvin Cycle 1. CO2 enters the stroma 2. It combines with a
5-C sugar RuBP using the enzyme Rubisco to form a 3-C acid (carbon fixation)
Using energy from ATP & NADPH high energy sugars (G3P) are made for the plant
ADP & NADP+ go back to the thylakoid to be “recharged”
In order for the “cycle” to continue, RuBP must be regenerated. 3 “turns” of the Calvin Cycle are needed to generate one G3P molecule. In other words, 3 CO2 molecules are used to make 1 G3P and remake RuBP.

20. Self-Assessment – Calvin Cycle
What is “waiting” in the stroma to combine with CO2? What enzyme catalyzes this combination?
What is the direct result of this combination?
What is the general name to describe this conversion of inorganic CO2 into a molecule plants can use for biosynthesis?
Why is the Calvin Cycle called a “cycle”? How many “turns” are needed to provide the plants with a molecule of sugar?

21. Process Recap
The two sets of photosynthetic reactions work together.
The light-dependent reactions trap sunlight energy in chemical form (ATP and NADPH).
The light-independent reactions use that chemical energy to produce stable, high-energy sugars.

22. Global Impact of Photosynthesis
Carbon cycle
Greenhouse effect
Greenhouses gases in atm. prevent some heat from the sun from escaping
CO2, methane, H2O vapor are the main GH gases
Global warming
Excessive levels of GH gases result in more heat being trapped
This is not the same thing as ozone depletion

24. Food & Energy
Food serves as a source of raw materials, or building blocks, for the cells in the body and also as a source of energy.
Animal Cells
Animal
Mitochondrion
Plant
Plant Cells

25. Chemical Energy & Food
Cells don't literally “burn” glucose. They release energy by breaking bonds of food molecules.
Cellular (aerobic) respiration is the process of breaking down food to release energy.
This process occurs in the mitochondria.

26. Structure of the Mitochondria

27. Cellular Respiration
Oxygen + Glucose  Carbon Dioxide + Water + ATP
(6O2 + C6H12O6  6CO H2O + ATP)
Cellular respiration is an aerobic process because it requires oxygen (aerobic respiration)
There are three steps in cellular respiration
Glycolysis
Krebs Cycle (a.k.a. “Citric Acid Cycle”)
Electron Transport Chain (ETC)
In the absence of oxygen, glycolysis is followed by fermentation. This is called anaerobic respiration.

28. Overview of Cellular Respiration
Mitochondrion
Cytoplasm

29. Glycolysis Occurs in the cytoplasm
One molecule of glucose (6-C) is split, producing two molecules of pyruvic acid (3-C)
The cell uses two molecules of ATP to start the process and when glycolysis is complete 4 gross or 2 net ATP and 2 NADH are produced.
2 ATP
2 ADP
4 ADP
4 ATP

30. Fermentation Alcoholic Fermentation: Lactic Acid Fermentation:
Performed by yeasts and a few other microorganisms
pyruvic acid + NADH → alcohol + CO2 + NAD+
Lactic Acid Fermentation:
- in cells, such as muscle cells, the pyruvic acid from
glycolysis is converted to lactic acid
- pyruvic acid + NADH → lactic acid + NAD+
**Fermentation regenerates NAD+ so that glycolysis can continue

31. Kreb’s Cycle Occurs in the matrix of the mitochondria
In the presence of oxygen, pyruvate (pyruvic acid) enters the Kreb cycle and broken down, releasing carbon dioxide.
As a result NADH, FADH2 and ATP are generated.
The ATP is used for cellular energy and the electron carriers, NADH and FADH2 go to the E.T.C.

32. Electron Transport Chain (ETC)
Occurs in the cristae (inner membrane) of the mitochondria.
ATP is generated through chemiosmosis in a series reactions involving high energy electrons moving through the electron transport chain.
Oxygen serves as the final electron acceptor, allowing energy to be released to cells.
Each oxygen picks up 2e- and then binds with two H+ to form water.

33. Energy Totals
Glycolysis produces just 2 net ATP molecules per molecule of glucose.
Krebs Cycle & ETC produce 34 ATP.
The complete breakdown of glucose through cellular respiration, including glycolysis, results in the production of 36 molecules of ATP.

34. Photosynthesis v. Cellular Respiration
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