EXAM 2 CHAPTER 6- METABOLISM, ENZYMES AND ENERGY

kenetic energy

energy in motion

what does pH doe to enzymes?

- Each enzyme has an optional pH at which its activity is the highest - Enzyme structure is also pH dependent - Extremes of pH can denature an enzyme by altering its structure

Law of thermodynamics

- Energy cannot be created or destroyed, but it can be changed from one form to another - Energy cannot be changes from one form to another without a stable loss of usable energy

mechanical energy

- Movement - Chemical--> kinetic

Potential

- Stored energy

what is a factor that affects enzyme speed

- Substrate concentration

Catabolism

- breaks down molecules

Exergonic reactions

- energy is RELEASED - products have less free energy than reactants

what are Coupled reactions

- energy released by an exergonic reaction is used to drive an endergonic reaction - EXORGENIC drives ENDORGENIC reactions

Energy activation

- enzymes speed up chemical reactions - energy of activation is less when enzyme is present

what is ATP

- made from ADP and phosphate molecule - Glucose catabolism provides energy to build up ATP

Endergonic reactions

- require energy - products have more free energy than reactants

Metabolic pathway

- series of linked reactions - Enzymes speed up chemical reactions - A= reactant, B=product - B becomes reactant for reaction 2 - One enzyme per reaction

How enzymes function

- substrate binds to active site on the enzyme - Induced fit model: enzyme goes under slight change for optimum for to substrate - Reaction takes place - Product released and active site return to original shape

what is Metabolism

- sum of all chemical reactions in a cell - catabolism and anabolism

Which is true about energy of activation? The energy of activation is always lower than the energy of the reactant. Energy of activation is measured as the energy that is released after a reaction occurs. Energy of activation is the difference between the energy of the reactant and the energy of the product. Adding the correct enzyme can lower the energy of activation.

Adding the correct enzyme can lower the energy of activation.

Which of the following statements is not true concerning enzymatic activity? Enzyme activity increases as substrate concentration increases until the maximum rate is achieved. Above a certain temperature, an enzyme will become denatured. Each enzyme has a preferred pH at which the enzyme reaction rate is highest. As the temperature increases, most enzymatic reactions will still proceed at the same rate.

As the temperature increases, most enzymatic reactions will still proceed at the same rate.

Which of the following is NOT a correct statement about the second law of thermodynamics and entropy? To maintain organization of a cell, a continual input of energy is required. The amount of disorder in the universe is always increasing. Living cells without energy would become less organized. Carbon dioxide and water form glucose without the input of energy.

Carbon dioxide and water form glucose without the input of energy.

Which of the following statements most accurately describes the first law of thermodynamics? One usable form of energy cannot be completely converted into another usable form. One usable form of energy can be completely converted into another usable form. Energy cannot be created or destroyed. Energy can be neither created nor destroyed but it can be changed from one form to another.

Energy can be neither created nor destroyed but it can be changed from one form to another.

what do high temps do to enzymes?

Higher temps cause a larger number of effective collisions between enzymes and substrates

Which of the following statements is true about enzymes? Boiling temperatures do not affect their activity. They can associate with a wide variety of substrates. Their 3D shape can vary and still be active. They are unaffected by changes in pH. They catalyze only one specific type of reaction.

They catalyze only one specific type of reaction.

If A -> B -> C -> D -> E represents a metabolic pathway, then letter E would be

a product

The location in which the enzyme and substrate complexes is called the... receptor site. active site. enzyme-substrate complex. inhibitor site.

active site.

ATP contains... an adenine base, a ribose sugar, and three phosphate groups. an adenine base, a ribose sugar, and two phosphate groups. an adenine base and three phosphate groups. an adenine base and two phosphate groups.

an adenine base, a ribose sugar, and three phosphate groups.

If an enzymatic reaction was controlled by feedback inhibition, we would expect it to stop... only if the substrate was exhausted. as soon as a critical level of end product builds up. when the cofactors are exhausted. when the product changed the pH.

as soon as a critical level of end product builds up.

Anabolism

building up molecules (synthesis)

The main reason that ATP is considered the energy currency in cells is because it... contains an adenine base. contains accessible energy in phosphate bonds. contains a sugar ring. carries a positive charge.

contains accessible energy in phosphate bonds.

If you wished to increase enzyme activity, you would do all of the following except... increase the concentration of substrate. change to optimum pH for the reaction. decrease the temperature. increase the temperature moderately.

decrease the temperature.

Each enzyme has a particular substrate because enzymes... have active sites complementary in shape to their substrates. increase the energy of activation. decrease the productivity of the cell. are named for their substrate.

have active sites complementary in shape to their substrates.

The function of an enzyme is to... increase the rate of a metabolic reaction. provide the energy for metabolic reactions. raise the energy of activation for a reaction. change the direction of metabolic reactions.

increase the rate of a metabolic reaction.

what is Energy of activation (Ea)

o Energy that must be added to cause reaction Need a match to start wood burning o Enzymes lower the energy of activation Increase the reaction rate

feedback inhibition

o Products binds to active site or another site that change the shape of active site o Poisons are often enzyme inhibitors Cyanide inhibits an essential respiratory enzyme Penicillin blocks the active site on a bacterial enzyme

folic acid

required in growing cells (it is an enzyme cofactor)

In feedback inhibition of a metabolic pathway, where does the inhibitor bind? to the substrate of the first reaction to the product of the first reaction to the enzyme of the first reaction to a substrate or the product of the last reaction

to the enzyme of the first reaction