Biology 1001-Chp.6

Which of these is an example of negative feedback?
– The end product of a reaction sequence speeds up the reaction sequence.
– The end product of a reaction sequence shuts down the reaction sequence.
– The first enzyme in a reaction sequence makes the free energy change of the reaction more negative.
– The end product of a reaction sequence has no effect on the reaction sequence.
– The first enzyme in a reaction sequence lowers the activation energy of the reaction.

The end product of a reaction sequence shuts down the reaction sequence. This is an example of negative feedback, or feedback inhibition.

A ball is sitting on top of a shelf. What kind of energy is represented by its height above the ground?
– potential energy
– kinetic energy
– heat energy
– chemical energy
– gravitational energy

potential energy Positional energy is a type of potential energy. If the ball fell, the potential energy would be converted to kinetic energy.

Outside the body, sugar can catch fire and burn in an exergonic reaction. Inside the body, we also talk about burning sugar in an exergonic reaction, but it never catches fire. Why not?
– When sugar is lit on fire, all of the bonds are broken at once. When the body breaks down sugar, enzymes break down one bond at a time.
– When sugar is lit on fire, it is dry so it can continue burning. When the body burns sugar, it does so in the presence of water, which prevents a fire.
– When sugar is lit on fire, it converts all of the chemical energy into heat energy. When the body burns sugar, it converts all of the chemical energy into chemical energy in ATP.
– When sugar is lit on fire, it releases more energy than when the body breaks down sugar.
– When sugar is lit on fire, there is nothing nearby to capture the energy, so it all becomes heat.
– When the body burns sugar, it captures all of the energy in ATP.

When sugar is lit on fire, all of the bonds are broken at once. When the body breaks down sugar, enzymes break down one bond at a time. Enzymes control the speed and order of a reaction.

You place a pot on the stove and turn the stove on. What kind of energy are you giving to the pot?
– electrical energy
– kinetic energy
– positional energy
– potential energy
– chemical energy

kinetic energy Heat energy is a form of kinetic energy.

Why is the first law of thermodynamics called "the law of conservation of energy?"
– because the first law states that energy stays in its current form
– because the first law states that energy can’t be created or destroyed
– Because the first law states that no energy is wasted in converting one form into another.
– because the first law states that all energy can be converted from one form to another
– because the first law states that all energy is converted from one useable form into another

because the first law states that energy can’t be created or destroyed The law also states that energy can change form.

Most enzymes are _____.
– carbohydrates
– lipids
– nucleic acids
– proteins
– minerals

proteins Most enzymes are proteins.

Enzymes work by _____.
– reducing activation energy
– adding energy to a reaction
– adding a phosphate group to a reactant
– increasing the potential energy difference between reactant and product
– decreasing the potential energy difference between reactant and product

reducing activation energy Enzymes work by reducing the energy of activation.

An enzyme _____.
– is an organic catalyst
– is a inorganic catalyst
– can bind to nearly any molecule
– is a source of energy for endergonic reactions
– increases the activation energy of a reaction

is an organic catalyst Enzymes are proteins that behave as catalysts.

What name is given to the reactants in an enzymatically catalyzed reaction?
– substrate
– products
– reactors
– active sites

substrate This is the name given to the reactants in an enzymatically catalyzed reaction.

As a result of its involvement in a reaction, an enzyme _____.
– loses energy
– loses a phosphate group
– permanently alters its shape.
– is unchanged
– is used up

is unchanged Enzymes are not changed as a result of their participation in a reaction.

Which of the following is true about the reaction of ADP and phosphate to form ATP?
– The reaction combines two products to form a reactant.
– The reaction is endergonic.
– The reaction requires activation energy.
– The reaction combines two unstable reactants into a stable product.
– The reaction releases energy.

The reaction is endergonic. Connecting ADP and P is endergonic, breaking ATP apart into ADP and P is exergonic.

Where does the energy that life uses to combat entropy come from?
– from the circle of life
– from the earth
– from the sun
– from food
– from plants

from the sun The majority of living things get their energy from the sun, either directly through photosynthesis or through eating other life that benefited from photosynthesis.

Entropy is a tendency toward _____.
– an increase in complexity
– a decrease in energy
– a decrease in life
– an increase in energy
– a decrease in order

a decrease in order Entropy is the tendency for orderly things to become more disorderly.

Which of the following is true about catalysts?
– Catalysts provide the activation energy for an exergonic reaction.
– Catalysts convert exergonic reactions into endergonic reactions.
– Catalysts lower the activation energy of an exergonic reaction.
– Catalysts convert endergonic reactions into exergonic reactions.
– Catalysts provide energy for an endergonic reaction.
– Catalysts raise the activation energy of an endergonic reaction.

Catalysts lower the activation energy of an exergonic reaction. This is the primary definition of a catalyst

How is an intermediate best defined?
– An intermediate is the reactant for a multi-step chemical reaction.
– An intermediate is a reactant that will be used in the middle of a multi-step chemical reaction.
– An intermediate is a product of one reaction that will serve as a reactant in another reaction.
– An intermediate is the product of a multi-step chemical reaction.

An intermediate is a product of one reaction that will serve as a reactant in another reaction. An intermediate is a product that is not finalized.

Hydrogen gas (H2), methane gas (CH4), and a liquid called hexane (C6H14) all burn when lit with a match. They all combine with oxygen to produce carbon dioxide gas (CO2) and water (H2O) when they burn. Looking at these molecules, what conclusion can you draw about exergonic reactions?
– During exergonic reactions, complex chemicals are converted into simple chemicals.
– During exergonic reactions, more energy is released than is put in as activation energy.
– During exergonic reactions, useful energy is lost in the form of heat.
– During exergonic reactions, organic compounds are converted into inorganic compounds.
– During exergonic reactions, nonpolar bonds are broken and polar bonds are created.

During exergonic reactions, nonpolar bonds are broken and polar bonds are created. High-energy bonds are almost always nonpolar. Hydrogen, methane, and hexane are made entirely of nonpolar bonds. Carbon dioxide and water are made entirely from polar bonds.

You fill two balloons with gas, one with hydrogen and one with carbon dioxide. You hold a match to each balloon. The hydrogen balloon explodes in a small fireball. The carbon dioxide balloon pops where the match burns it, but nothing else happens. How can you explain this?
– Hydrogen contains chemical energy and carbon dioxide does not.
– Hydrogen is a reactant and carbon dioxide is a product.
– The carbon dioxide smothered the match before it could start a fire.
– The match did not have enough activation energy to light the carbon dioxide.
– Hydrogen was able to participate in an exergonic reaction and carbon dioxide couldn’t.

Hydrogen was able to participate in an exergonic reaction and carbon dioxide couldn’t. Substances that are flammable or explosive easily participate as reactants in an exergonic reaction. Stable substances such as carbon dioxide don’t.

Which of the scenarios below is most like irreversible, allosteric inhibition?
– Girl A is fighting with Girl B over a doll. During the fight, they rip the doll in half
– Company B makes more cars than company A, so customers buy cars from company B more often.
– A husband is watching a football game on the television. His wife turns off the television and begins a discussion about finances.
– Boy A is playing a video game system. Boy B trips over the cords, pulling the game system off the shelf and breaking it.
– A cat is chasing a bird. A dog begins barking and scares the cat off.

Boy A is playing a video game system. Boy B trips over the cords, pulling the game system off the shelf and breaking it. Boy B is not trying to play the same game, so it is like allosteric inhibition, and the system is broken so the effect is irreversible.

Plants use sunlight to convert carbon dioxide and water into sugar and oxygen. What is the sunlight providing to the equation?
– a reactant
– activation energy
– potential energy
– heat
– kinetic energy

kinetic energy The plant needs to convert kinetic energy from the sunlight into potential energy in a chemical bond.

What type of reaction breaks the bonds that join the phosphate groups in an ATP molecule?
– dehydration decomposition
– anabolism
– hydrolysis
– entropic
– dehydration synthesis

hydrolysis Hydrolysis involves breaking bonds with the addition of water.

How do energy carriers participate in coupled reactions?
– Energy carriers can be assembled to power an endergonic reaction.
– Energy carriers can be broken apart to power an exergonic reaction.
– Energy carriers can be broken apart to power an exergonic reaction or assembled using energy from an endergonic reaction.
– Energy carriers can be assembled using the power from an exergonic reaction.
– Energy carriers can be broken apart to power an endergonic reaction or assembled using energy from an exergonic reaction.
– Energy carriers can be broken apart to power an endergonic reaction.

Energy carriers can be broken apart to power an endergonic reaction or assembled using energy from an exergonic reaction. Energy carriers are charged when they are assembled and release their energy when they are broken apart.

Which of these is exhibiting kinetic energy?
– a rock on a mountain ledge
– a space station orbiting Earth
– the high-energy phosphate bonds of a molecule of ATP
– a person sitting on a couch while watching TV
– an archer with a flexed bow

a space station orbiting Earth Kinetic energy is energy of motion.

"Conservation of energy" refers to the fact that _____.
– the net amount of disorder is always increasing
– no chemical reaction is 100 percent efficient
– energy cannot be created or destroyed but can be converted from one form to another
– the entropy of the universe is always increasing
– if you conserve energy you will not be as tired

energy cannot be created or destroyed but can be converted from one form to another This is what is meant by conservation of energy.

Chemical energy is a form of _____ energy.
– motion
– potential
– heat
– kinetic
– entropic

potential Chemical energy is a form of stored energy.

In your body, what process converts the chemical energy found in glucose into the chemical energy found in ATP?
– cellular respiration
– digestion
– potentiation
– anabolism
– redox

cellular respiration This is the name given to the process by which the body converts food energy to energy stored in ATP.

Which of these are by-products of cellular respiration?
– carbon dioxide and water
– glucose, carbon dioxide, and water
– ATP and carbon dioxide
– heat, carbon dioxide, and water
– ATP, carbon dioxide, and water

heat, carbon dioxide, and water

The reaction A –> B + C + heat is released in a(n) _____ reaction.
– exergonic
– dehydration synthesis
– exchange
– anabolic
– endergonic

exergonic Energy has been released.

A(n) _____ reaction occurs spontaneously.
– exergonic
– chemical
– endergonic
– kinetic
– anabolic

exergonic In exergonic reactions the products have less potential energy than the reactants.

Which of these reactions requires a net input of energy from its surroundings?
– hydrolysis
– exergonic
– endergonic
– catabolic
– ATP –> ADP + P

endergonic The products of endergonic reactions have more potential energy than the reactants.

In cells, what is usually the immediate source of energy for an endergonic reaction?
– ADP
– ATP
– sugar
– glucose
– as spontaneous reactions, endergonic reactions do not need an addition of energy

ATP The hydrolysis of ATP provides the energy needed for an endergonic reaction.

The reaction ADP + P –> ATP is a(n) _____ reaction.
– chemical
– endergonic
– spontaneous
– hydrolysis
– exergonic

endergonic Energy has been acquired from the surroundings.

The energy for an endergonic reaction comes from a(n) _____ reaction.
– ADP + P –> ATP
– glucose + glucose –> maltose
– exergonic
– anabolic
– synthesis

exergonic The energy released by an exergonic reaction can be used to drive an endergonic reaction.

What is the fate of the phosphate group that is removed when ATP is converted to ADP?
– It is acquired by a reactant in an exergonic reaction.
– It is acquired by a reactant in a spontaneous reaction.
– It is broken down into one phosphorus and four oxygen atoms.
– It is acquired by a reactant in an endergonic reaction.
– It is used to convert an ATP into an AQP.

It is acquired by a reactant in an endergonic reaction. By acquiring the phosphate group the reactant acquires energy.

Select the INCORRECT association.
– kinetic energy … motion
– potential energy … positional energy
– exergonic … spontaneous
– enzyme … protein
– exergonic … uphill

exergonic … uphill Exergonic reactions release energy.

What is energy coupling?
– the hydrolysis of ATP to ADP + P
– the use of an enzyme to reduce EA
– a description of the energetic relationship between the reactants and products in an exergonic reaction
– the use of energy released from an exergonic reaction to drive an endergonic reaction
– a barrier to the initiation of a reaction

the use of energy released from an exergonic reaction to drive an endergonic reaction This is energy coupling.

Most enzymes do not work if the temperature is raised too much. Why is this?
– Enzymes cannot make temporary bonds with substrates at higher temperatures.
– Reactions require more activation energy at higher temperatures.
– Substrates change shape at higher temperatures.
– The substrate molecules are moving too quickly at high temperature for the reaction to occur.
– Enzymes denature at higher temperatures.

Enzymes denature at higher temperatures. Incorrect temperature, pH, and salt concentrations cause an enzyme to change shape.

Which of the following reactions could be coupled with the synthesis of ATP from ADP and phosphate?
– the breakdown of ATP into ADP and phosphate
– the assembly of sugar from water and carbon dioxide
– the assembly of amino acids into a protein
– the breakdown of sugar into water and carbon dioxide

the breakdown of sugar into water and carbon dioxide This exergonic reaction is used to power the endergonic assembly of ATP.

Why does feedback inhibition occur at the beginning of a metabolic pathway instead of in the middle?
– because all of the initial substrates would still be used up if the pathway were stopped in the middle
– because the final product does not fit the allosteric site of any other enzymes
– because the pathway cannot be stopped in the middle if the first reaction takes place
– because the final product can only fit in the active site of the first enzyme in the pathway

because all of the initial substrates would still be used up if the pathway were stopped in the middle. The benefit of stopping a metabolic reaction at the beginning is it allows you to keep the reactants or use them in a different pathway.

A man wants to build a windmill to generate electricity. What type of energy is the man trying to take from the wind?
– electrical energy
– positional energy
– heat energy
– movement energy
– potential energy
– chemical energy

movement energy wind is moving air

What is the definition of an endergonic reaction?
– a reaction where the reactants have more energy than the products
– a reaction where the products give off energy
– a reaction where reactants are combined to make products
– a reaction where the products have more energy than the reactants
– a reaction where products are combined to form reactants

a reaction where the products have more energy than the reactants Endergonic reactions require an input of energy, so the products have more energy than the reactants used to create them.

How do competitive inhibitors stop a chemical reaction?
– Competitive inhibitors bind to the substrate.
– Competitive inhibitors alter the substrate into a different chemical.
– Competitive inhibitors break the hydrogen bonds of the enzyme, causing it to unfold.
– Competitive inhibitors bind in the active site of an enzyme.
– Competitive inhibitors bind to the enzyme, changing its shape.

Competitive inhibitors bind in the active site of an enzyme. This prevents the desired substrate from making use of the enzyme.

Which of the following represents an increase in entropy?
– smashing a drinking glass
– rearranging the books on a shelf
– sorting coins into like groups
– turning off an oven
– flattening a lump of dough
– putting trash in a trashcan

smashing a drinking glass A broken glass has more pieces than a whole glass. A broken glass is more disordered.

Which trait below is a characteristic of energy carriers?
– able to break down endergonically
– able to capture heat energy
– able to release energy easily
– able to store energy for a long time
– able to create energy where needed

able to release energy easily Energy carriers are used directly at the site where energy is needed. If they were stable, they would require their own source of activation energy to function.

E. coli bacteria can use the enzyme lactase to digest lactose and use it as an energy source. However, it is more efficient for bacteria to use glucose as an energy source if it is present. Which of the methods of regulating enzyme activity would be most energy efficient for a bacterium that has plenty of glucose?
– The bacterium should produce an irreversible, allosteric inhibitor of lactase.
– The bacterium should stop production of lactase.
– The bacterium should produce an irreversible, competitive inhibitor of lactase.
– The bacterium should produce a reversible, allosteric inhibitor of lactase.
– The bacterium should produce a reversible, competitive inhibitor of lactase.
– The bacterium should use feedback inhibition to stop the metabolic pathway that lactase starts.

the bacterium should stop production of lactase. Producing lactase enzyme costs energy, which would be wasted if there was plenty of glucose around.

In the last step of extracting energy from sugar, an enzyme called cytochrome c oxidase attaches electrons to oxygen and hydrogen ions, forming water. The electrons are temporarily bound to an iron atom in the enzyme before they are attached to oxygen. Cyanide is a poison that acts by binding near this iron atom, preventing oxygen from getting near enough to accept the electrons. How would you describe the action of cyanide?
– Cyanide is a noncompetitive inhibitor of oxygen.
– Cyanide is regulating cytochrome oxidase c by feedback inhibition.
– Cyanide is a competitive inhibitor of cytochrome c oxidase.
– Cyanide is a noncompetitive inhibitor of cytochrome c oxidase.
– Cyanide is a competitive inhibitor of oxygen.
– Cyanide is an allosteric regulator of cytochrome c oxidase.

Cyanide is a competitive inhibitor of cytochrome c oxidase. The enzyme is inhibited at the active site.

Which of these is a correct description of a coupled reaction?
– In a coupled reaction, one exergonic reaction provides activation energy to power another exergonic reaction.
– In a coupled reaction, one endergonic reaction provides energy to power another endergonic reaction.
– In a coupled reaction, two exergonic reactions are performed simultaneously to lower their activation energy.
– In a coupled reaction, an exergonic reaction provides energy to run an endergonic reaction.
– In a coupled reaction, an endergonic reaction provides energy to run an exergonic reaction.

In a coupled reaction, an exergonic reaction provides energy to run an endergonic reaction. Life uses many coupled reactions to perform endergonic reactions, such as building proteins from amino acids or charging up ATP.

The enzyme amylase in human saliva breaks starch polymers down into smaller sugar units. However, it cannot break down cellulose polymers. Both are made of glucose monomers, but in cellulose the monomers are linked together in a different shape than starch. Why can’t amylase digest cellulose?
– The bonds of cellulose do not fit properly in the active site.
– The bonds of cellulose require more activation energy to break.
– Enzymes only combine substrates into a single product, they do not break substrates apart.
– Cellulose cannot bind properly to the allosteric site.
– Cellulose cannot activate the enzyme.

The bonds of cellulose do not fit properly in the active site. Changing the orientation of a bond often prevents an enzyme from affecting a substrate.

Some people restate the second law of thermodynamics this way: "When energy changes forms, some energy is always lost." Why is this statement incorrect?
– This statement implies that energy conversion is not 100% efficient.
– This statement implies that energy changes forms.
– This statement implies that useful energy is reduced during energy conversions.
– This statement implies that some energy is destroyed.

This statement implies that some energy is destroyed. The first law of thermodynamics says that energy is never destroyed. If you were to say "lost as heat," the statement would be more correct.

When grilling using charcoal, people often wet the charcoal with lighter fluid first. The lighter fluid catches fire first and eventually sets the coals burning. Why does the lighter fluid light faster than the charcoal?
– Setting the lighter fluid on fire is a spontaneous reaction and lighting the charcoal is a stable reaction.
– The lighter fluid is warmer than the charcoal, which makes it easier to burn.
– Burning lighter fluid is a more exergonic reaction than burning charcoal.
– Setting lighter fluid on fire takes less activation energy than setting charcoal on fire.
– Burning lighter fluid is exergonic and burning charcoal is endergonic.

Setting lighter fluid on fire takes less activation energy than setting charcoal on fire. Substances that catch fire quickly, such as matches and lighter fluid, undergo reactions with a low activation energy.

Imagine a candy bar sitting on a table in front of you. Which specific types of energy are present in the candy bar?
– chemical and heat energy
– positional and chemical energy
– positional and heat energy
– heat, chemical, and positional energy
– electrical, positional, heat, and chemical energy
– chemical, movement, and heat energy

heat, chemical, and positional energy The bar has some heat in it, has energy stored in the form of chemical bonds (which is where the Calories come from), and has the potential to fall off the table.

Which of the following is most like an intermediate in a metabolic pathway?
– a tablespoon of nutmeg that will be used in a cake
– a carrot that has been peeled and is waiting to be cut
– a log on fire that has been half burned
– a car up on jacks waiting to have its tires changed
– a person waiting in a line to buy tickets
– a pepperoni pizza coming out of the oven

a carrot that has been peeled and is waiting to be cut This carrot has already been processed some by being peeled and will be processed further by cutting. If these carrots are going to be cooked after cutting, the cut carrots will also represent an intermediate.