Concept explainers
Introduction: Photosynthesis is the process in which the chloroplast of plants capture sunlight, and converts it into chemical energy stored as sugar and other molecules. This occurs in two stages known as the light reactions (require light) and, the Calvin cycle (synthesis). During light reactions, water is split to give off oxygen, and produces ATP and NADPH. During Calvin cycle, a carbon dioxide molecule is accepted by a carbon acceptor molecule (ribulose-1, 5-bisphosphate, RuBP) and forms a six-carbon compound. This is converted into three-carbon sugars (glyceraldehyde-3-phosphate, G3P) through the oxidation of NADPH. Next, some of the G3P molecules form sugars and others regenerate to RuBP molecule.
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- A decrease in entropy occurs during the CO2 uptake phase of the Calvin cycle, as freely moving CO2 molecules become fixed into a carbon skeleton. How can this occur without direct participation by NADPH and/or ATP?arrow_forward1. If ATP breakdown (hydrolysis) is inhibited, which of the following types of movement across cell membranes is also inhibited? (A) Movement of oxygen into a cell (B) Movement of water through aquaporins (C) Passage of a solute against its concentration gradient (D) Facilitated diffusion of a permeable substance 2. Which of the following questions is most relevant to understanding the Calvin cycle? (A) How does chlorophyll capture light? (B) How is ATP used in the formation of 3-carbon carbohydrates? (C) How is NADP+ reduced to NADPH? (D) How is ATP produced in chemiosmosis? OXYGEN CONCENTRATION IN THE WATER OF A LAKE Hours of Darkness 06:00 08:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00 24:00 02:00 04:00 06:00 Time of Day 3. What most likely causes the trends in oxygen concentration shown in the graph above? (A) The water becomes colder at night and thus holds more oxygen. (B) Respiration in most organisms increases at night. (C) More organisms are respiring at night than during the…arrow_forwardWhich of the following questions is most relevant to understanding the Calvin cycle? A How does chlorophyll capture light? B How is ATP used in the formation of 3-carbon carbohydrates? C How is NADP+ reduced to NADPH? D How is ATP produced in chemiosmosis?arrow_forward
- If 30 molecules of CO2 enter the Calvin Cycle,a. How many molecules of phosphoglycerate (PGA) will be produced? b. How many molecules of glyceraldehyde phosphate (PGAL) leave the cycle? c. How many molecules of ribulose bisphosphate (RuBP) will be produced? d. How many molecules of ATP will be utilized?arrow_forwardWhich of the four stages of aerobic cellular respiration is most similar to the light-independent reactions oxygenic photosynthesis? Explainarrow_forwardIn mechanism, photophosphorylation is most similar to(A) substrate-level phosphorylation in glycolysis.(B) oxidative phosphorylation in cellular respiration.(C) carbon fixation.(D) reduction of NADP+.arrow_forward
- The Calvin cycle begins when CO2 reacts with (a) phosphoenolpyruvate(b) glyceraldehyde-3-phosphate (c) ribulose bisphosphate (d) oxaloacetate (e) phosphoglyceratearrow_forwardhe Calvin Cycle represents the major pathway by which photosynthetic organisms gain carbon. Which of the following statements about the Calvin Cycle is correct? 1. NADPH is consumed during the reduction phase of the cycle. 2. Each turn of the cycle generates one extra molecule of glyceraldehyde 3-Phosphate (G3P). 3. The cycle would stop if ribulse-1,5-bisphosphate (RuBP) does not get regenerated. 4. The Calvin Cycle is often referred to as the “Dark Reactions” because it operates continually in the dark. A. 1,2 and 3 B. 1 and 3 C. 2 and 4 D. 4 only E. All of 1,2,3 and 4 are correctarrow_forwardIn biochemistry, the exergonic process ofconverting glucose and oxygen to carbon dioxide and water in aerobic metabolism can be considered the reverse of photosynthesis,in which carbon dioxide and water are converted to glucose andoxygen. Do you expect both processes to be exergonic, both endergonic, or one exergonic and one endergonic? Why? Would youexpect both processes to take place in the same way? Why?arrow_forward
- A culture of the single celled organism Chlamydomonas is actively carrying out photosynthesis in the presence of light and CO2. If you turned off the light, how would you expect the amounts of ribulose 1,5-bisphosphate and 3-phosphoglycerate to change over the next minute? How about if you left the light on and removed the CO2? Please answer these questions with specific references to the Calvin cycle.arrow_forwardDaniel Arnon and coworkers carried out experiments with intact, salt- washed chloroplasts to study photophosphorylation. When the chloroplasts were illuminated in the presence of ADP +P, ATP was produced, but oxygen was not produced or nor consumed. ATP formation was not accom- panied by a measurable electron transport involving any external electron donor or acceptor. The overall reaction for this result is: ADP + P -", ATP When NADP+ was included in addition to the ADP + P, ilumination of the intact chloroplats again resulted in resulted in the photophosphorylation of ADP to ATP. In addition, the NADPpt was reduced to NADPH + H* and o, was produced. Moreover, the light-induced reduction of NADP* was greatly decreased if ADP + P; were ommitted. The equation for this reaction is: NADP* + H,0 + ADP + R -", NADPH + H + ATP + }02 Briefly describe the mechanism(s) of these two types of photophosphoryla- tion that explain all of these results.arrow_forwardWhich correctly lists the inputs of the Calvin cycle? a) CO2, H2O, ATP, NADPHb) Glucose, ATPc) H2O, photons d) Glyceraldehyde 3-phosphate, ADP, NADP+e) ATP, NADH, FADH2, CO2arrow_forward