Energy transfer occurs in all cellular activities. For three of the following five processes involving energy transfer, explain how each function in the cell and give an example. Explain how ATP is involved in each example you choose.
· Cellular movement
· Active transport
· Synthesis of molecules
· Chemiosmosis
· Fermentation
Energy transfer is a process that occurs in all cellular activities. Cellular movement is a function towards muscle contraction, cytoplasmic streaming, and locomotion. Muscle contraction is embodied with sliding filaments. It is also composed of contractile proteins such as thick filament, thin filament, sarcomere, myofibril, and myofiber that use ATP hydrolysis to contract. Cytoplasmic streaming is the movement of the living substance (cytoplasm) within a plant or animal cell. The motion transports nutrients, enzymes, and, in plants, large virus particles within the cells. Locomotion incorporates cilia, flagella, and pseudopodia into creatures. These are means of locomotion powered by ATP hydrolysis for some unicellular organisms with 9 + 2 microtubules such as protists, archeozoans, and bacteria. The activities in cell membrane components are synthesized in the endoplasmic reticulum (ER), transported as vesicles to the Golgi apparatus where they are modified, and then are transported to the cell surface where they deliver their contents to the cells exterior and become a part of the cell membrane in a process called exocytosis. The reverse of this process, bringing nutrient containing particles from out side to the inside of the cell is called endocytosis. In addition, in the cell, dynein binds to the microtubule and uses the energy in ATP molecules to power their motor molecules to move from the positive end of the microtubule toward the negative end of the microtubule. Each small step, requires the hydrolysis of one ATP molecule. Dynein pulls subcellular materials toward the center of the cell. A closely related protein, kinesin, also pulls subcellular materials in the opposite direction. In general, ATP is used for all energy transfer processes in cellular activities.
Chemiosmosis occurs in the mitochondrion and chloroplasts. In the mitochondrion, chemiosmosis is used to form an electrochemical proton gradient after the first four stages of aerobic respiration. The general process is the formation of ATP during the electron transport system of aerobic respiration as the result of a gradient across the membrane of the cristae. H+ ions from the matrix are pumped into space between the cristae and the outer membrane, so the H+ gradient develops between the inside and outside of the cristae. This pH differential creates the free energy and the H+ ions pass back across the membrane through the F1complex. Oxygen then is the final Hydrogen electron acceptor producing water. In the chloroplast, protons from the stroma are pumped into the thylakoid sac. A pH gradient develops between the inside and the outside of the thylakoid sac, having an inside high H+ concentration. This pH gradient creates free energy, which then H+ crosses back across the membrane through the CF complex. CF uses H+ to make one ATP from water. In this series of photosynthesis reactions, NADP is the final electron acceptor producing NADPH. ATP is formed through a proton pump and/or gradient with ATP synthase in both situations.
Fermentation is a process included in anaerobic respiration, a less effective energy output than aerobic respiration. Fermentation starts with the process of glycolysis first, and uses substrate-level phosphorylation with enzymes to use two ATP and produce four ATP. It soon breaks down into C3 pyruvic acids. Fermentation can also be used for the breakdown of organic compounds to continue synthesizing ATP and for regenerating oxidized NAD. The reduction of pyruvic acid results in the formation of lactic acid in animal cells (muscles) or ethanol (plants). The net two ATP produced every turn in fermentation is the result of NAD shuttling back and forth and reducing to NADH to once again go through the process of glycolysis. ATP is the minor but important product to power many anaerobic creatures even today.
For Each Part:
1 pt function of process
1 pt example 1 pt additional for detail
1 pt ATP involvement
4 pts = MAX/process
