CHAPTER 8 AN INTRODUCTION TO METABOLISM The totality of an organism’s chemical reactions is called _______________. A cell’s ______________ is an elaborate road map of the chemical reaction. 1. The chemistry of life is organized into _______________________ Fig. 6.1

Enzymes selectively _____________ each step. _____________ pathways __________ energy by breaking down complex molecules to simpler compounds. _________________ pathways __________ energy to build complicated molecules from simpler compounds. _________________- the study of how organisms manage their energy resources. Some terms

Energy - the capacity to do ________ ( to move or rearrange matter). __________ energy is the energy of _________. Objects in motion, photons, and heat are examples. ___________ energy is the energy that matter ______________because of its location or structure. Chemical energy is a form of potential energy in molecules because of the arrangement of atoms. 2. Organisms transform _________ Cellular respiration and other catabolic pathways unleash energy stored in ________ and other complex molecules.

_________________ is the study of energy transformations. A_________ system- isolated from its surroundings Example- liquid in a thermos An _____ system - energy (and often matter) can be transferred between the system and _______________. 3. The energy transformations of life are subject to two laws of __________________ Organisms are ______ systems. They _________ energy - light or chemical energy in organic molecules - and _________ heat and metabolic waste products.

The first law of ____________________ -energy cannot be created or destroyed. It can be transferred and transformed Plants transform light to __________ energy; they do not __________ energy. The second law of ______________________ - every energy transformation must make the universe more ________________. __________ - a measure of _______, or randomness. Increased randomness = increased ___________ Living cells convert organized energy to heat. Organisms are__________ of low entropy in an increasingly random universe.

4. Organisms live at the expense of _____ ___________ _________________ (G) - portions of a system’s energy that is able to perform work (temperature constant) Fig. 8.5 Diffusion Chemical Reactions Examples High G Low G Work

4. Organisms live at the expense of _____ __________ ____________ (G) - portions of a system’s energy that is able to perform work (temperature constant) Fig. 8.5 Diffusion Chemical Reactions Examples High G Low G Work Gravity

______________reaction - ___________ of free energy and  G is ___________ Fig. 8.6a Cellular respiration: C 6 H 12 O 6 + 6O 2 -> 6CO 2 + 6H 2 O  G = ______________ Thus, 686 kcal are available to do ______ Reactants Products Example:

______________ reaction - ___________ free energy from its surroundings. _________ energy,  G is_______________ reactions are non- spontaneous. Fig. 8.6b Photosynthesis Delta G = _______ kcal / mol. A cell that has reached metabolic ________________ has a  G = 0 and is dead! Reactants Products Example:

5. Cellular work is powered by ____ - couples __________ and ___________ reactions ATP (adenosine triphosphate) is a ___________ consisting of: Fig. 6.8a

ATP is converted to ADP via hydrolysis  G = -7.3 kcal/mol. This energy is “captured” by transferring the phosphate group to another molecule. Fig Fig. 8.9 Result = overall  G  is ______, reaction is ___________

________________, an endergonic process, requires an investment of energy:  G = _________ Fig Over 10 million ATPs are consumed and regenerated per second per cell.

A _________ changes the rate of a reaction without being ____________ by the reaction. An ____________ is a catalytic protein. Enzymes regulate the movement of molecules through ________________________. 6. Enzymes ___________ metabolic reactions by ___________ energy barriers

______________________ is the amount of energy necessary to push the reactants over an energy barrier. This difference is the  G. This is the the energy of activation (E A ) Fig. 8.14

Enzymes _______ the E A. Fig Enzymes do not ________  G. It hastens reactions that would occur eventually.

A ________ is a reactant which binds to an enzyme. Example: Sucrase - enzyme that binds to sucrose and breaks the disaccharide into fructose and glucose. 7. Enzymes are ___________ specific Substrate EnzymeProducts The specificity of an enzyme is due to the fit between the ___________ and that of the substrate. Fig. 8.16

What holds a substrate in the active site? Answer- _________ ______________ ______. What catalyzes the substrate to a product? Answer- __________ of a few amino acids on the _________ 8. The active site is an enzyme’s ________ __________ Fig. 8.17

A single enzyme molecule can catalyze __________ of reactions a second. Enzymes are ____________ by the reaction and are reusable. Most metabolic enzymes can catalyze a reaction in both the __________ and __________ direction. Some enzyme factoids- What affects the rate of reaction?

1.___________ concentration. At low substrate concentrations: There is a limit to how fast a reaction can occur. At high substrate concentrations, the active sites on all enzymes are engaged, called __________________. What affects the rate of reaction? [S] = Rate

2. Temperature (T). at some point heat ______________ protein Each enzyme has an _______________ temperature. Fig. 8.18a What affects the rate of reaction? T = Rate Reaction rate Temperature ( o C) Most enzymes Thermophilic enzyme

3.pH influences _______ and therefore reaction rate each enzyme has an optimal pH. This falls between pH _____ for most enzymes. Exceptions include digestive enzymes in the stomach: these are most active at _____ Fig. 8.18b What affects the rate of reaction?

4. ____________ Non-protein _________ for enzyme activity. Includes _________ molecules (e.g. zinc, iron, and copper). Organic cofactors, ____________, include vitamins or molecules derived from vitamins. 5. ____________ covalent interaction (often irreversible) or ionic (reversible) with enzymes.. If the inhibitor binds to the same site as the substrate, then it _______ substrate binding via _________________________. If the inhibitor binds somewhere other than the active site, it blocks substrate binding via _________________________ What affects the rate of reaction? Fig. 8-19

Some molecules bind weakly to a ____________ site ( a specific receptor on the enzyme that is not the active site). 9. Metabolic control often depends on _________________ regulation Can inhibit or stimulate enzyme activity. Most allosterically regulated enzymes contain multiple polypeptide chains. Some allosteric regulators ___________; Other regulators _____________. Fig. 8.20

__________________ - a metabolic pathway is turned off by its end product. Fig In enzymes with multiple _________________, binding by a substrate to one active site stabilizes favorable conformational changes at all other subunits, a process called ___________________.

A team of enzymes for several steps of a metabolic pathway may be assembled together as a ______________________________. The product from the first can then pass quickly to the next enzyme until the final _____________ is released. 10. The _________________ of enzymes within a cell helps order metabolism