Energy and Chemical Reactions Metabolism The totality of an organism’s chemical reactions Arises from interactions between molecules The transformation of matter and energy Subject to the laws of thermodynamics

Energy The ability to move and change matter Life requires energy. Almost all energy for life is derived from the sun. A productive way of viewing life is to see it as a set of coordinated chemical reactions. This leads to an obvious question – What determines what chemical reactions are possible?

Thermodynamics The study of energy transformation First law of thermodynamics: Energy can be transferred or transformed but Neither created nor destroyed. For example, the chemical (potential) energy in food will be converted to the kinetic energy of the cheetah’s movement in (b). (a) Chemical energy The study of energy transformation The first law of thermodynamics Energy can be transferred and transformed Energy cannot be created or destroyed

Thermodynamics The second law of thermodynamics Spontaneous changes that do not require outside energy increase the entropy of the universe Entropy= disorder in the universe entropy is always increasing.   Second law of thermodynamics: Every energy transfer or transformation increases the disorder (entropy) of the universe. For example, disorder is added to the cheetah’s surroundings in the form of heat and the small molecules that are the by-products of metabolism. (b) Heat co2 H2O +

The Direction of Spontaneous Reactions (and what it takes to go the other way)

Energy can be converted from one form to another On the platform, a diver has more potential energy. Diving converts potential energy to kinetic energy. Climbing up converts kinetic energy of muscle movement to potential energy. In the water, a diver has less potential energy.

Flow of energy through life Life is built on chemical reactions transforming energy from one form to another organic molecules  ATP & organic molecules sun organic molecules  ATP & organic molecules solar energy  ATP & organic molecules

Energy (E) Transfer Overview Energy transfer in the environment

Chemical Reactions Reactants are the starting materials for chemical reactions Products are the newly formed substances that result from the chemical reaction. Energy is absorbed or released when chemical bonds are broken and new ones are formed.

Exergonic Reaction release energy reactants exergonic reaction release energy products contain less potential energy than their reactants products

Endergonic Reaction absorb energy products endergonic reaction reactants absorb energy yield products rich in potential energy

The “Nature of Life” – Coupling Favorable to Unfavorable Reactions Energy and Enzymes 2/17/2019 The “Nature of Life” – Coupling Favorable to Unfavorable Reactions Chemical Reactions G. Podgorski, Biol. 1010

Energy content of common chemicals (foods) Energy used in activities

Activation Energy Energy needed to start a chemical reaction

Enzymes Substances that increase the speed of chemical reactions Are not changed in the reaction Essential for life Most are proteins, some are RNA. .

Enzymes Lower Reaction Activation Energy

Enzymes providing Activation Energy

Enzyme Action Substrate = substance reactant) on which the enzyme acts during a chemical reaction Active site = the pocket on an enzyme where the substrate fits during a chemical reaction

Cellular environment affects enzyme activity Enzyme activity is influenced by temperature salt concentration pH Reaction rate is affected by amount of substrate

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