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Phosphate-buffered saline (PBS) is a buffer solution (pH ~ 7.4) commonly used in biological research. It is a water-based salt solution containing disodium hydrogen phosphate, sodium chloride and, in some formulations, potassium chloride and potassium dihydrogen phosphate. The buffer helps to maintain a constant pH.
27 wrz 2021 · 4.1: Energy and Metabolism. Scientists use the term bioenergetics to describe the concept of energy flow (Figure \ (\PageIndex {1}\)) through living systems, such as cells. Cellular processes such as the building and breaking down of complex molecules occur through stepwise chemical reactions.
Muscular contraction, synthesis of molecules, neurotransmission, signaling, thermoregulation, and subcellular movements are all energy-requiring processes. Where does this energy come from? The currencies of energy are generally phosphate-containing molecules.
ATP synthase (Figure 1) is a classic example of energy conversion by biomolecules, with two connected rotary motors powered by two different forms of energy. Chemical energy is perhaps the most common form of energy used by cells, given the intrinsically chemical nature of biomolecules.
The energy is used to do work by the cell, usually by the released phosphate binding to another molecule, activating it. For example, in the mechanical work of muscle contraction, ATP supplies the energy to move the contractile muscle proteins.
All living organisms require energy to perform their life processes. Energy, as you learned earlier in the chapter about enzymes, is the ability to do work or to create some kind of change. You are familiar with or have learned about many processes that can require energy: Movement; Reproduction; Maintaining homeostasis of many different conditions
Plants perform one of the most biologically useful energy transformations on earth: that of converting the energy of sunlight to chemical energy stored within organic molecules . Some examples of energy transformations are shown in Figure 4.4 .
