Welcome to Chapter 6 Dr. Joseph Silver

major topics are -what is energy -what is thermodynamics -how do enzymes work - how does ATP work -multienzyme complexes -what is metabolism -the role of feedback

thermodynamics is that branch of chemistry which deals with changes of energy

why is this important to biology because you cannot live without a constant input of energy

where does our energy come from from the sun which allows for the production of the plant and animal food we eat

energy is described as kinetic (motion) or potential(position)

energy can be mechanical, chemical, sound, electrical, light, radioactive and all forms of energy can generate heat

heat is usually described as a calorie one calorie is the amount of heat needed to raise the temperature of one gram of water one degree Celsius at one atmosphere of pressure

since the source of all energy on our earth is from the sun then the energy chemically locked in the ionic and covalent bonds of all plants and animals comes from heat from the sun

when we break down the food we eat we release the heat locked into the chemical bonds of our food

when an atom releases or loses an electron it is said to be oxidized (more positive) when an atom gains an electron it is said to be reduced (more negative) these reactions are very important in the movement of energy through biological systems

anabolic = use energy to build up catabolic = use energy to breakdown heat = energy moves from one item to another chemical energy = potential energy available from chemical reactions pathways = steps from raw material to finished product metabolism = chemical reactions of an organism

entropy The idea of entropy comes from a principle of thermodynamics dealing with energy. It usually refers to the idea that everything in the universe eventually moves from order to disorder, and entropy is the measurement of that change. The word entropy finds its roots in the Greek entropia, which means "a turning toward" or "transformation." The word was used to describe the measurement of disorder by the German physicist Rudolph Clausius and appeared in English in A common example of entropy is that of ice melting in water. The resulting change from formed to free, from ordered to disordered increases the entropy.

Enthalpy A partial measure of the internal energy of a system. Enthalpy cannot be directly measured, but changes in it can be. If an outside pressure on a system is held constant, a change in enthalpy entails a change in the system's internal energy, plus a change in the system's volume (meaning the system exchanges energy with the outside world). For example, in endothermic chemical reactions, the change in enthalpy is the amount of energy absorbed by the reaction; in exothermic reactions, it is the amount given off.

1 st law of thermodynamics known as conservation of energy energy cannot be created or destroyed it can only change from one form to another and during each change some energy is lost as heat

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what is heat energy caused by the random movement of molecules or caused by the kinetic energy of atoms the faster the atoms move the more heat is generated

2 nd law of thermodynamics sates that disorder in the universe (entropy) is increasing the universe is becoming more disorganized (less order) every energy transfer increases the entropy of the universe

spontaneous = increases entropy nonspontaneous = decreases entropy

in order to do work energy must be available where does it come form in biological systems it comes from breaking chemical bonds

the energy available to do work is called free energy and it comes from breaking chemical bonds

free energy = energy in - (abs temp x change in entropy) available for a chemical work bond (enthalpy)  G =  H - T  S

-  G = spontaneous +  G or zero  G = nonspontaneous every spontaneous process decreases the systems free energy

endergonic = needs energy to proceed (+G) exergonic = reaction gives off energy (-G)

endergonic reactions require an input of energy to start the chemical reaction this is known as the energy of activation

enzymes biological catalysts lower the energy of activation (fig 8.14) an enzyme makes 1 biological chemical reaction proceed millions of times faster and a cell makes 1,000s or 1,000,000 of the same enzyme

where does the energy come from to do biological work from ATP adenosine tri phosphate and also from GMP

ATP has 3 phosphate bonds each is a positive functional group to keep a 2 nd group in place requires some energy but to keep a 3rd positive bond attached requires a large amount of energy when the energy of the 3 rd bond (high energy bond) is released it is used to do work

enzymes are not destroyed when they are used to do work they are used over and over until they are not needed then they are recycled

enzymes have an active site with the correct shape substrates (chemicals) fit into the enzyme causing changes which activate a chemical reaction which changes the substrate

most biological chemical reactions are part of a series of steps leading to the breakdown or building up of various chemicals

in order to make the chemistry of cells more efficient enzymes needed to accomplish a specific task are part of a multienzyme complex all of the enzymes needed for one job are right next to each other so that the individual steps needed to form a product take place right next to each other

it was once believed that all enzymes were proteins but scientists have now identified RNA enzymes (ribozymes) there are thousands of different RNAs in our cells and for most we have yet to determine their function

many enzymes are activated by molecules called activators activators can activate an enzyme or they can inhibit an enzyme

an enzyme can be inhibited by binding to the activation site and not allowing the substrate access to the enzyme competitive inhibition or a chemical can bind to the enzyme changing the shape of the activation site noncompetitive inhibition see fig. 8.18

the chemical reactions of an organism is known as metabolism anabolism = use of energy to build up molecules catabolism = getting energy by breaking up molecules

our bodies do 1000s of chemical reactions production of a product usually involves multiple steps the sequence of steps are known as a biochemical pathway

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when a cell no longer needs to keep making a product the cell must stop making the product how does this happen?

by allosteric regulation a molecule binds to an enzyme and changes it’s shape to activate or inhibit the enzyme

It happens by feedback inhibition the end product of a biochemical pathway acts on the first step of the pathway to stop the pathway

the opposite also happens when the end product level drops to a low amount then the pathway begins to make more end product