Energy movement in plant molecules

The pair of electrons goes through the photosystems I (PSI) and II (PSII). In the latter, energy from the sun is used to split the electrons of water into two; one oxygen atom and one hydrogen atom. The molecule of chlorophyll in the PSII takes in a photon, and it makes the electrons in that molecule acquire a higher energy (Raines 5). This energy increase of the electrons make them unstable. Therefore, they are carried to another molecule chain of a redox reaction call the Electron Transport Chain (ETC). The electrons now flow from the PSII to the cytochrome b6f and finally to the PSI. In the process, the electron experiences energy loss, and needs to be re-energized by the PSI antenna.

The energy is transmitted to P700 center which is oxidized. It then sends high energy electron to reduce NADP+ to NADPH.

B. The electrons on PSI and PSII help to transport a proton gradient that contributes to power production of ATP. They also aid in storage of energy in the reduced coenzyme NADPH.

C. The electrons save the energy required in Calvin cycle in the production of sugar and other carbohydrates.

2. A Calvin cycle can work at night as long as there is an adequate supply of ATP and NADPH to drive the process. The process can take palce for a short time since ATP, and NADPH supply usually gets depleted quickly. With the decline in ATP and NADPH molecules the pathway run out of high molecule energy to drive the Calvin cycle (Raines 6). Therefore, for the process to continue the plant cell must start At that point the cellular respiration to acquire needed energy.

B. The two products of light reactions used in Calvin Cycle are ATP and NADPH

3. A. Rubisco initiate the carbon fixation in Calvin cycle. It helps by combining carbon dioxide with ribulose 1, 5-bisphosphate (RuBP) to produce two 3-phosphoglycerate molecules (3-PG).

B. The problem caused by RuBisCO to plant is the photorespiration that leads to loss of carbon and energy.

C. the C4 plants have another carbon-fixing enzyme in addition to RuBisCO. The enzyme is usually phosphoenolpyruvate carboxylase (PEP carboxylase). The enzyme catalyzes the conversion of 3-carbon phosphoenolpyruvate (PEP) to oxaloacetate by the help of hydrogen carbonate ions. Since oxaloacetate is a four-carbon compound, PEP carboxylase can quickly raise the level of carbon dioxide (Raines 7). CAM are plants that fix the concentration of carbon at night. These plants store carbon dioxide as four carbon malate and release it during the day when light reaction photosynthesis can take place. At night the night, the carbon dioxide enters the leaves through open stomata and is fixed by PEP carboxylase as oxaloacetate. The oxaloacetate is converted to malate, and this accumulates in the cell vacuole thus giving storage for carbon. In the day the stomata closes and light reaction proceeds resulting in ATP and NADPH. The male is eliminated from the cell vacuoles and decarboxylated to produce carbon dioxide that fixes the Rubisco needed in Calvin cycle.

4.Alternation of generations- Terrestrial plants have two alternating multicellular body forms. The haploid form (gametophytes) lead to production and protection of eggs, gametes, and sperms through mitosis while the diploid (sporophytes) result in the making of spores (Usherwood 1473). The existence of two forms allows for reproduction and survival in different environmental conditions. Terrestrial plants also have walled spores that produce sporangia. This is common among the sporophytes. The sporangium has sporopollenin that makes the wall of the spores hard and thus resistance to harsh environmental conditions. The spores are protected by the sporopollenin until they can be released into the air. Furthermore, terrestrial plants especially the gametophytes produces multicellular gametangia. The female gametangium produces egg cell while male produces sperms. The gametes are protected and from dry conditions by not being exposed to air (Usherwood 1470). They also have apical meristems that include well-branched roots that help in transportation of water and nutrients from the soil up to the plant. They also have stomata to allow for absorption of light and carbon dioxide required for photosynthesis. Besides, they have

B. 1.Alternation of generations – bryophytes. 2. Apical meristems – gymnosperms and angiosperms. 3.Multicellular gametangia- bryophytes. 4. Multicellular embryo is reliant on the parent gametophytes – bryophytes. 5.Protected spores- bryophytes

5. A. bryophytes sporophyte depends on photosynthetic gametophytes for nutrients. Even after fertilization, the sporophyte remains attached to the gametophytes. The gametes are produced via mitosis and the sperms carried through the water to the appropriate male gametes. The bryophytes have stalk and root. The gametophytes in bryophytes have a thin cell. In angiosperms such as fern, the sporophytes and gametophytes photosynthesize. The angiosperms have well developed vascular system that is not only suitable support but for transportation of water and nutrients

B. The large surface area and thin cells in bryophytes gametophytes help in faster absorption and transport of water and nutrients. The gametes mainly produce in the form of sporophytes and gametophytes help the plants to survive various environmental conditions. Besides the roots and stalk aid in absorption and transmission of water and nutrients up the bryophytes body. They have short in length. The presence of well-structured vascular system help to in faster transfer of water and nutrients.

6.A. Both angiosperms and gymnosperms produce seed. The seeds can be dispersed without relying on water. In the angiosperm, the seed is enclosed by carpel for quick dispersal and protection from harsh conditions (Niklas 29). In gymnosperms, the seed is nakedly allowing for rapid dispersal. Besides, both angiosperms and gymnosperms produce many pollen grains to allow for pollination. The production of more pollen grain ensures that even if the agents of dispersal lose some reaches the destined female gametes for reproductive purposes.

B. Angiosperms have reproductive structures and processes. They use seeds as primary means of production and dispersal. The seeds are enclosed by closed carpel that prevents it from desiccation and also helps in dispersal. Besides, they have flowers that are attractive to birds, insects, and bats and this help in it dispersal (Niklas 32). They also have double fertilization and this lead to the production of endosperm a source of nutrient to the embryo. Furthermore, Angiosperms have leaves that help in absorption of sunlight and gasses from photosynthesis. The leaves are capable of preventing water loss during hot seasons by folding or dropping off and also allow water loss during cold season by opening of stomata

Work Cited

Niklas, Karl J., and Ulrich Kutschera. "The evolution of the land plant life cycle." New Phytologist 185.1 (2010): 27-41.

Raines, Christine A. "The Calvin cycle revisited." Photosynthesis Research 75.1 (2003): 1-10.

Usherwood, J. R., A. R. Ennis, and D. J. Ball. "Mechanical and anatomical adaptations in terrestrial and aquatic buttercups to their respective environments." Journal of Experimental Botany 48.7 (1997): 1469-1475.