Bio1332 Biochemistry - Lecture Twenty - Photosynthesis
By the end of the lecture you will; understand the light dependent and light independent reactions of photosynthesis. understand how light absorption by chlorophyll induces electron transfer. understand how two photosystems (PS I and PS II) generate a proton gradient and NADPH. understand how the proton gradient across the thylakoid membrane drives ATP synthesis. understand how the NADPH and ATP produced by the light reactions is used to fix CO2
- 1.
Name the organelle where photosynthesis takes place.
Explanation
Photosynthesis is the process by which plants convert sunlight, water, and carbon dioxide into glucose and oxygen. This process occurs in the chloroplasts, which are specialized organelles found in plant cells. Chloroplasts contain a pigment called chlorophyll, which captures sunlight and uses its energy to drive the chemical reactions of photosynthesis. Therefore, the correct answer is "Chloroplast," "Chloroplast," or "Chloroplasts."Rate this question:
- 2.
Name the two most common carbohydrates produced during photosynthesis. Separate your two answers with a comma and a space.
Explanation
Sucrose and starch are the two most common carbohydrates produced during photosynthesis. They are both energy-storage molecules in plants. Sucrose is a disaccharide made up of glucose and fructose, and it is transported through the plant for immediate energy use or storage. Starch, on the other hand, is a polysaccharide made up of many glucose molecules and is used for long-term energy storage in plants.Rate this question:
- 3.
Please fill answer below: The energy of light captured by pigment molecules, called _________, in chloroplasts is used to excite electrons giving them great reducing potential
Explanation
The energy of light captured by pigment molecules, called chlorophylls, in chloroplasts is used to excite electrons giving them great reducing potential. Chlorophylls are the specific pigment molecules found in chloroplasts that are responsible for capturing light energy during photosynthesis. They absorb light of various wavelengths and transfer the energy to the electrons, which then become highly energized and have the ability to reduce other molecules.Rate this question:
- 4.
If a suitable electron acceptor is nearby, the excited electron can move from the initial molecule to the acceptor molecule. This results in the formation of...
- A.
A positively charged initial molecule and a negatively charged acceptor molecule
- B.
A neutrally charged initial molecule and a negatively charged acceptor molecule
- C.
A negatively charged initial molecule and a positively charged acceptor molecule
- D.
A positively charged initial molecule and a neutrally charged acceptor molecule
Correct Answer
A. A positively charged initial molecule and a negatively charged acceptor moleculeExplanation
When a suitable electron acceptor is nearby, the excited electron can move from the initial molecule to the acceptor molecule. This movement of electrons results in the transfer of a negative charge from the initial molecule to the acceptor molecule, making the initial molecule positively charged and the acceptor molecule negatively charged. Therefore, the correct answer is "A positively charged initial molecule and a negatively charged acceptor molecule."Rate this question:
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- 5.
The site where the photo-induced charge separation occurs is called the special pair of chlorophylls in the ______________.
Correct Answer
Reaction centreExplanation
The photo-induced charge separation occurs in the reaction centre, specifically in the special pair of chlorophylls. This is where the initial step of photosynthesis takes place, where light energy is absorbed by the chlorophyll molecules and converted into chemical energy. The special pair of chlorophylls is responsible for capturing and transferring the energy to other molecules in the reaction centre, initiating the electron transport chain and ultimately leading to the production of ATP and NADPH.Rate this question:
- 6.
Which of the following is true?
- A.
Electrons flow first through Photo System II, then cytochrome bf, then through Photo System I
- B.
Electrons flow first through Photo System I, then cytochrome bf, then through Photo System II
- C.
Electrons flow first through cytochrome bf, then Photo System II, then through Photo System I
- D.
Electrons flow first through cytochrome bf, then Photo System I, then through Photo System II
Correct Answer
A. Electrons flow first through Photo System II, then cytochrome bf, then through Photo System I -
- 7.
Which of the following is true?The Calvin cycle requires __________ per CO2 fixed.
- A.
2 NADPH and 3 ATP
- B.
3 NADPH and 2ATP
- C.
2 NADPH and 2 ATP
- D.
3 NADPH and 3 ATP
Correct Answer
A. 2 NADPH and 3 ATPExplanation
The Calvin cycle requires 2 NADPH and 3 ATP per CO2 fixed. This is because during the Calvin cycle, CO2 is converted into glucose through a series of reactions. These reactions require energy in the form of ATP and reducing power in the form of NADPH. The ATP is used to provide the energy necessary for the reactions, while the NADPH is used as a source of electrons to reduce CO2 and form glucose. Therefore, 2 NADPH and 3 ATP are needed for each CO2 molecule fixed during the Calvin cycle.Rate this question:
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- 8.
Please fill answer below:
- CO2 is fixed by the enzyme _______, which reacts CO2 with ribulose bisphosphate to produce two molecules of 3-phosphoglycerate
Correct Answer
RubiscoExplanation
Rubisco is the correct answer because it is the enzyme responsible for fixing carbon dioxide (CO2) during photosynthesis. It catalyzes the reaction between CO2 and ribulose bisphosphate (RuBP) to produce two molecules of 3-phosphoglycerate, which is an important step in the Calvin cycle. Rubisco is considered one of the most abundant enzymes on Earth and plays a crucial role in carbon fixation, making it essential for the production of organic compounds by plants and other photosynthetic organisms.Rate this question:
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