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

ExamplesHigh G

Low GWork

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

ExamplesHigh G

Low GWork

Gravity

• ______________reaction - ___________ of free energy and G is ___________

Fig. 8.6a

Cellular respiration:

•C6H12O6 + 6O2 -> 6CO2 + 6H2O

•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

2..

1.

3.

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. 8.10

Fig. 8.9

Result = overall Gis ______, reaction is ___________

• ________________, an endergonic process, requires an investment of energy: G = _________

Fig. 8.12

•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 (EA)

Fig. 8.14

Enzymes _______ the EA.

Fig. 8.15

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 Enzyme Products

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

Rea

ctio

n r

ate

Temperature (oC)

Most enzymesThermophilic

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. 8.21

•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