tailieunhanh - Plant physiology - Chapter 2 Energy and Enzymes

The force that through the green fuse drives the flower Drives my green age; that blasts the roots of trees Is my destroyer. And I am dumb to tell the crooked rose My youth is bent by the same wintry fever. The force that drives the water through the rocks Drives my red blood; that dries the mouthing streams Turns mine to wax. And I am dumb to mouth unto my veins How at the mountain spring the same mouth sucks. Dylan Thomas, Collected Poems (1952) In these opening stanzas from Dylan Thomas’s famous poem, the poet proclaims the essential unity. | Energy and Enzymes The force that through the green fuse drives the flower Drives my green age that blasts the roots of trees Is my destroyer. And I am dumb to tell the crooked rose My youth is bent by the same wintry fever. The force that drives the water through the rocks Drives my red blood that dries the mouthing streams Turns mine to wax. And I am dumb to mouth unto my veins How at the mountain spring the same mouth sucks. Dylan Thomas Collected Poems 1952 In these opening stanzas from Dylan Thomas s famous poem the poet proclaims the essential unity of the forces that propel animate and inanimate objects alike from their beginnings to their ultimate decay. Scientists call this force energy. Energy transformations play a key role in all the physical and chemical processes that occur in living systems. But energy alone is insufficient to drive the growth and development of organisms. Protein catalysts called enzymes are required to ensure that the rates of biochemical reactions are rapid enough to support life. In this chapter we will examine basic concepts about energy the way in which cells transform energy to perform useful work bioenergetics and the structure and function of enzymes. Energy Flow through Living Systems The flow of matter through individual organisms and biological communities is part of everyday experience the flow of energy is not even though it is central to the very existence of living things. 1 2 CHAPTER 2 What makes concepts such as energy work and order so elusive is their insubstantial nature We find it far easier to visualize the dance of atoms and molecules than the forces and fluxes that determine the direction and extent of natural processes. The branch of physical science that deals with such matters is thermodynamics an abstract and demanding discipline that most biologists are content to skim over lightly. Yet bioenergetics is so shot through with concepts and quantitative relationships derived from thermodynamics that it is .