8/7/2019 FRQ - ATP

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Kim Pham

AP Biology

FRQ: ATP

Energy transfer is a process that occurs in all cellular activities. For example, cellular movements,

including muscle contraction, cytoplasmic streaming, and locomotion, all need the input of ATP in order to be

carry out. For instance, muscle contraction need ATP to slidethe muscle filaments, since muscles filaments are

compose of contractile proteins such as thick filament, thin filament, sarcomere, fibersthat use all ATPhydrolysis to contract (using energy release from ATP to break down water). Cytoplasmic streaming is the

movement of the 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 outside 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 differentialcreates 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.

Source of Info: AP College board, Wikipedia, AP Biology.com