1. Chapter 10: Photosynthesis
Chassey Lock and Shiyenne Earley

2. The Process That Feeds The Biosphere
Photosynthesis- Plants use the sun's energy to convert water and carbon dioxide into sugars.
Autotrophs- organism capable of producing their own food through photosynthesis or other processes.
Heterotrophs- An organism that obtains organic food molecules by eating other organisms or their by-products.

3. *The Process That Feeds The Biosphere
Life on Earth is solar powered; photosynthesis gives life to all living things.
Everything consumes energy by one of two methods: autotrophic or heterotrophic nutrition.
Nearly all plants are autotrophs, specifically photoautotrophs.
Heterotrophs are typically animals that consume plants, or other animals-that consumed plants- and so on.

4. Which process is most directly driven by light energy?
removal of electrons from chlorophyll molecules

5. Which of the following statements is a correct distinction between autotrophs and heterotrophs?
Autotrophs, but not heterotrophs, can nourish themselves beginning with CO2 and other nutrients that are inorganic.

6. Converting light to chemical energy
Photosynthetic enzymes and other molecules are grouped together to carry out the process of photosynthesis.
The process of the grouping originated from bacteria containing such regions of molecules.
These regions work similar to the chloroplast, which are believed to have developed from these regions in a prokaryote living in a eukaryote.

7. Chloroplasts: The Sites of Photosynthesis
Chlorophyll- A green pigment found in the chloroplasts of plants, algae, and some bacteria.
Mesophyll- The ground tissue of a leaf, sandwiched between the upper and lower epidermis and specialized for photosynthesis.
Stomata- A microscopic pore surrounded by guard cells in the epidermis of leaves and stems that allows gas exchange between the environment and the interior of the plant.
Stroma- Fluid inside chloroplasts.
Thylakoids- A flattened membrane sac inside the chloroplast, used to convert light energy to chemical energy. (the stacked sacs inside are called grana)

8. *Chloroplasts
All green plants have a chloroplast, though leaves are the major site; the color comes from chlorophyll.
The tissue of the leaf, the mesophyll, is the main site for chloroplasts.
CO2 and O are transferred through the stomata (stoma).
Normal mesophylls have about chloroplasts in each.
Thylakoids separate the stroma from inner compartments.
Chlorophyll is found in the thylakoid membranes.

9. The chloroplasts were first made acidic by soaking them in a solution at pH 4. After the thylakoid space reached pH 4, the chloroplasts were transferred to a basic solution at pH 8. The chloroplasts then made ATP in the dark. Explain this result.
Photosynthesis requires light and the experiment was done in the dark =, therefore there is nit an electron for the reduction of NADP+. The Calvin cycle requires NADPH.

10. Tracking Atoms Through Photosynthesis
6CO2 + 12H2O + Light Energy -> C6H12O6 + 6O2 + 6H2O
We summarize photosynthesis into the above formula.
It can be simplified to:
6CO2 + 6H20 + Light Energy -> C6H12O6 + 6O2 to give the net consumption of water.

11. Which of the following sequences correctly represents the flow of electrons during photosynthesis?
H2O -> NADPH -> Calvin cycle

12. The Splitting of Water
Plants split H2O as a source of electrons from H atoms, and release O2 as a by-product.
This theory was given by C. B. Van Niel.

13. The Two Stages of Photosynthesis
Light Reactions- First stage of photosynthesis. Named Because it requires light to happen. Begins with the absorption of light in the Chloroplasts.
Calvin Cycle- A biochemical pathway of photosynthesis in which carbon dioxide is converted into glucose using ATP and NADPH.
NADP+ - (nicotinamide adenine dinucleotide phosphate) carrier molecule that transfers high-energy electrons from chlorophyll to other molecules.
Photophosphorylation- The process of generating ATP from ADP and phosphate by means of a proton-motive force generated by the thylakoid membrane of the chloroplast during the light reactions of photosynthesis.
Carbon Fixation- The incorporation of carbon from carbon dioxide into an organic compound by an autotrophic organism.

14. *The Two Stages
Photosynthesis takes place in two stages: light reactions and the Calvin cycle.
The light reactions are the steps that change solar to chemical energy.
The light reactions use solar power to reduce NADP+ to NADPH by adding a pair of electrons with a hydrogen ion.
Calvin cycle begins with carbon fixation, then reduces carbon to carbohydrates by adding electrons.
The Calvin cycle produces sugar.

15. In its mechanism, photophosphorylation is most similar to _____.
oxidative phosphorylation in cellular respiration

16. Which of the following does not occur during the Calvin cycle?
release of oxygen

17. The Nature of Sunlight
Wavelength- The distance between crests of waves, such as those of the electromagnetic spectrum.
Electromagnetic Spectrum- All of the frequencies or wavelengths of electromagnetic radiation.
Photons- All of the frequencies or wavelengths of electromagnetic radiation.

18. *The Nature of Sunlight
Light is known as electromagnetic energy that travel in rhythmic patterns.
The light band between 380 nm to 750 nm in wavelength is visible light.
The shorter a wavelength is- the greater energy of that photon.

19. Photosynthetic Pigments: The Light Receptors
Spectrophotometer- An instrument that measures the proportions of light of different wavelengths absorbed and transmitted by a pigment solution.
Absorption Spectrum- A graph plotting a pigment's light absorption versus wavelength.
Chlorophyll a- A type of blue-green photosynthetic pigment that participates directly in the light reactions.
Action Spectrum- A profile of the relative performance of different wavelengths of light.
Chlorophyll b- A type of yellow-green accessory photosynthetic pigment that transfers energy to chlorophyll a.
Carotenoids- An accessory pigment, either yellow or orange, in the chloroplasts of plants. By absorbing wavelengths of light that chlorophyll cannot, carotenoids broaden the spectrum of colors that can drive photosynthesis.

20. *Photosynthetic Pigments
Different pigments, or colors, absorb light of different wavelengths.
A spectrophotometer measures the amount of color in something.
An action spectrum is prepared by illuminating chloroplasts and then plotting wavelengths.
Carotenoids may broaden the spectrum of colors used in photosynthesis.

21. A Photosystem Photosystem- Light-collecting units of the chloroplast.
Reaction-Center Complex-A complex of proteins associated with a special pair of chlorophyll a molecules and a primary electron acceptor. Located centrally in a photosystem, this complex triggers the light reactions of photosynthesis. Excited by light energy, the pair of chlorophylls donates an electron to the primary electron acceptor, which passes an electron to an electron transport chain.
Light Harvesting Complex- Pigment molecules bound to proteins.
Primary Electron Acceptor -A specialized molecule sharing the reaction center with the chlorophyll a molecule; it accepts an electron from the chlorophyll a molecule

22. *A Photosystem
The reaction center complex includes a pair of chlorophyll a molecules.
The number and variety of pigments in a molecule enables them to take up a greater space.

23. Linear Electron Flow
Linear Electron Flow- A route of electron flow during the light reactions of photosynthesis that involves both photosystems (I and II) and produces ATP, NADPH, and O2. The net electron flow is from H2O to NADP+.

24. *Linear Electron Flow
Light drives the synthesis of ATP and NADPH by supplying energy to the embedded thylakoid membranes.
Linear electron flow occurs during the light reactions of photosynthesis.

25. Cyclic Electron Flow
Cyclic Electron Flow- A route of electron flow during the light reactions of photosynthesis that involves only photosystem I and that produces ATP but not NADPH or oxygen.

26. *Cyclic Electron Flow
This is another option to linear electron flow, using photosystem I.
Cyclic is basically a short circuit, it circles around and around.
Though, they both use the same mechanisms.

27. The Calvin cycle uses ATP and NADPH to convert CO2 to sugar
The Calvin cycle is anabolic, meaning it builds carbohydrates from smaller molecules.
Takes place in 3 phases: Carbon fixation, reduction, and regeneration of the CO2 acceptor.
In phase 1 carboxylase, or rubisco, catalyzes the first step. (This is the most abundant protein in chloroplasts.)
In phase 2 an additional phosphate is added to ATP.
In phase 3 ATP is taken away so that CO2 may be added again.

28. 1) The light reactions of photosynthesis supply the Calvin cycle with
ATP & NADPH

29. Photorespiration: An Evolutionary Relic?
Photorespiration- A metabolic pathway that consumes oxygen, releases carbon dioxide, generates no ATP, and decreases photosynthetic output; generally occurs on hot, dry, bright days, when stomata close and the oxygen concentration in the leaf exceeds that of carbon dioxide.

30. *Photorespiration
C3 plants use photorespiration in order to rearrange oxygen molecules to survive in arid climates.
They produce 3-carbon compounds.

31. Photorespiration can decrease soybean’s photosynthetic output by about 50%. Would you expect this figure to be higher or lower in wild relatives of soybeans? Why?
Lower, they are able to reproduce offspring with less photorespiration because it makes off spring that are subject to natural selection, driving the species towards not having photorespiration.

32. C4 Plants
C3 Plants-A plant that uses the Calvin cycle for the initial steps that incorporate CO2 into organic material, forming a three-carbon compound as the first stable intermediate.
C4 Plants-A plant that prefaces the Calvin cycle with reactions that incorporate CO2 into four-carbon compounds, the end product of which supplies CO2 for the Calvin cycle.

33. C4 Plants
Bundle-Sheath Cells- A type of photosynthetic cell arranged into tightly packed sheaths around the veins of a leaf.
Mesophyll Cells-A loosely arranged photosynthetic cell located between the bundle sheath and the leaf surface.

34. *C4 Plants They produce a four-carbon compound as their first product.
PEP carboxylase adds CO2 to phosphoenolpyruvate (PEP), forming oxaloacetate; fixes carbon efficiently.

35. CAM Plants
Crassulacean Acid Metabolism or CAM-The CO2 taken in at night is stored as organic acids in the vacuoles of mesophyll cells until daybreak when the stomata close. The Calvin cycle is able to proceed during the day because the stored CO2 is released from the organic acids to be incorporated into the sugar product of the Calvin cycle.
CAM Plants-A plant that uses crassulacean acid metabolism, an adaptation for photosynthesis in arid conditions, first discovered in the family Crassulaceae. Carbon dioxide entering open stomata during the night is converted into organic acids, which release CO2 for the Calvin cycle during the day, when stomata are closed.

36. *CAM Plants
CAM plants behave opposite to normal plants, as they open their stoma at night, conserving water.
Similar to the processes of C4 plants.

37. How is photosynthesis similar in C4 plants and CAM plants?
In both cases, rubisco is not used to fix carbon initially.