chapter 6 hw

energy

capacity to cause change; neither created or destroyed but can move from one form to another (law of conservation of energy)

Chemical reactions occur when molecules collide. Determine how changes in temperature affect collisions.

change in temperature affects how often the molecules collide and change in temperature affects the energy with which molecules collide.

where do muscles get energy to perform work?

chemical energy from food

Which of these reactions requires a net input of energy from its surroundings?

endergonic

for any reaction to occur

energy is needed to break bonds in reaction molecules

What is energy coupling?

the use of energy released from an exergonic reaction to drive an endergonic reaction

noncompetitive inhibitor

- A substance that reduces the activity of an enzyme by binding to a location remote from the active site, changing its conformation so that it no longer binds to the substrate. - has reversible effect; enzyme activity is restored when the noncompetitive inhibitor is removed from the enzyme. - distorts the enzyme's shape when it binds to the enzyme.

In general, enzymes are what kinds of molecules?

proteins (Enzymes are proteins.)

competitive inhibitor

- A substance that reduces the activity of an enzyme by entering the active site in place of the substrate whose structure it mimics. - competes with the substrate for the active site of the enzyme. - structure of it is very similar to that of the substrate. - At sufficient concentration, it reduces enzyme activity; enzyme activity can be regained by increasing the substrate concentration.

Irreversible inhibitors

- chemically and covalently binds to active site; rendering it permanently inactive - alters the enzyme's chemical structure - cannot be removed easily. - usually forms covalent bonds within the active site, preventing the substrate from entering the active site or preventing catalytic activity. - include nerve gases and insecticides, which act on acetylcholinesterase - some drugs, including the antibiotic penicillin (which inhibits an enzyme involved in bacterial cell-wall synthesis) and aspirin (which inhibits cyclooxygenase-2, the enzyme involved in the inflammatory reaction)

unsaturated fat

A fat that is liquid at room temperature because the tails contain double bonds, so they are bent and don't easily line up; found in vegetable oils, nuts, and seeds; some fish, such as salmon; has double bonds in the tails, decreasing the amount of H; safer

endergonic reaction

A non-spontaneous chemical reaction in which free energy is absorbed from the surroundings; potential energy increases from products to reactants; uphill; harder change for cell because needs additional energy input; energy coupling-obtains energy(phosphate group) from exergonic reaction (ATP->ADP) in cell

exergonic reaction

A spontaneous (without net addition of energy) chemical reaction in which there is a net release of free energy; potential energy decreases from products to reactants; heat has been released to the environment; disorder increased?entropy increased?; downhill; easier change for cell

In cells, what is usually the immediate source of energy for an endergonic reaction?

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

You have an enzymatic reaction proceeding at the optimum pH and optimum temperature. You add a competitive inhibitor to the reaction and notice that the reaction slows down. What can you do to speed the reaction up again?

Add more substrate; it will outcompete the inhibitor and increase the reaction rate. Many drugs used to treat different medical conditions, including hypertension, are competitive inhibitors. It is fairly easy to make a molecule that is similar in structure to a particular substrate because the known enzyme's shape can be used as a model of what the molecule needs to look like. It is more difficult to make a noncompetitive inhibitor because it is less obvious what the noncompetitive inhibitor's shape and structure should be.

What will happen to the rates of the forward and reverse reactions when a catalyst is added?

Both forward and reverse rates increase.

A(n) _____ reaction occurs spontaneously.

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

Consider a situation in which the enzyme is operating at optimum temperature and pH, and has been saturated with substrate. What is your best option for increasing the rate of the reaction?

Increase the enzyme concentration. If an enzyme is saturated with substrate, and it is operating at optimum pH and optimum temperature, there is very little that can be done except to increase the enzyme concentration. Some enzymes can be activated further by allosteric activators, in which case one might add some activator to the reaction. But otherwise, increasing the enzyme concentration is the only option.

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 endergonic reaction. By acquiring the phosphate group the reactant acquires energy.

When butter melts, does it gain double bonds?

No, melted butter is still saturated. It turns to liquid because heat energy breaks the weak nonpolar attractions that bind the fat molecules to one another.

cofactor

Non-protein helpers that may be bound tightly to the enzyme as a permanent resident, or may bind loosely and reversibly along with the substrate. binds to an enzyme and plays a role in catalysis; ex: a vitamin; inorganic ion

Why does water reject the tails of fats?

Polar water molecules attract one another and approach as close as possible. The attractions squeeze out the nonpolar fat tails, which are neutral and offer little attraction. The part of the fat where the tails join is more compatible with water; it's slightly polar.

Why do saturated fats cause heart disease?

Saturated fats inhibit the excretion of cholesterol and stimulate synthesis of cholesterol in the liver. The resulting increase in cholesterol raises the risk of heart disease. Unsaturated fats have an opposite effect, stimulating the breakdown and secretion of cholesterol.

energy of activation (Ea)

The amount of energy that reactants must absorb before a chemical reaction will start

Which of the following statements about the role of ATP in cell metabolism is true?

The energy from the hydrolysis of ATP may be directly coupled to endergonic processes by the transfer of the phosphate group to another molecule. A key feature in the way cells manage their energy resources to do this work is energy coupling, the use of an exergonic process to drive an endergonic one. ATP is responsible for mediating most energy coupling in cells, and in most cases it acts as the immediate source of energy that powers cellular work.

You have added an irreversible inhibitor to a sample of enzyme and substrate. At this point, the reaction has stopped completely. What can you do to regain the activity of the enzyme?

The enzyme is inactive at this point. New enzyme must be added to regain enzyme activity.

Which of the following is the most logical way to regulate an enzymatic pathway if you are trying to keep a constant level of product around?

The final product inhibits the first enzyme (and deactivates it?)

if the reactants are gases... Imagine the gas molecules bouncing around inside a container. Three conditions must be met for two molecules to react with one another:

The molecules must collide. The molecules must align properly during the collision. The collision must occur with enough energy. The minimum energy is called activation energy.

Hydrogenation

The process of converting unsaturated fats to saturated fats by adding hydrogen at the double bonds ex: to make margarine, salad oil is converted to a solid by adding h to double bond

What would happen to the rate of the forward reaction if the concentration of a reactant were decreased?

The reaction rate would decrease because collisions between reactants would decrease

Which statement about the binding of enzymes and substrates is correct?

When substrate molecules bind to the active site of the enzyme, the enzyme undergoes a slight change in shape (NOT LOCK AND KEY) As the substrate enters the active site, the enzyme changes shape slightly due to interactions between the substrate's chemical groups and chemical groups on the side chains of the amino acids that form the active site. This shape change makes the active site fit even more snugly around the substrate. This induced fit is like a clasping handshake.

Does tail length of fats matter?

Yes; even a saturated fat can be liquid at room temperature if its tails are short. Weak nonpolar attractions occur between the tails, and tend to keep the tails lined up. Long tails can interact with one another at more locations, leading to stronger forces so the molecules keep their alignment better.

A substrate binds to an enzyme at the ___, where the reaction occurs

active site

When properly aligned, the enzyme and substrate form ___

an enzyme-substrate (ES)complex

In your body, what process converts the chemical energy found in glucose into the chemical energy found in ATP?

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

rate of reaction

change in concentration of a product over change in time

The reaction ADP + P --> ATP is a(n) _____ reaction.

endergonic Energy has been acquired from the surroundings.

"Conservation of energy" refers to the fact that _____.

energy cannot be created or destroyed but can be converted from one form to another

action energy

energy needed to start chemical reaction; represents barrier that prevents reaction occcurign without added energy

The following reaction A --> B + C + heat is a(n) _____ reaction.

exergonic

The energy for an endergonic reaction comes from a(n) _____ reaction.

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

saturated fat

fat in which all three fatty acid chains contain the maximum possible number of hydrogen atoms; has 2 or 3 H atoms on every C atom in the tails; can lead to heart disease; solid at room temperature because the tails tend to be straight, and the molecules can line up to make a solid; most animal fats (found in butter and fatty meat); margarine (consists of artificially saturated plant fats)

Which of these are by-products of cellular respiration?

heat, carbon dioxide, and water While ATP is produced by cellular respiration, it is not considered a by-product of the process.

breakdown of fat

hydrolysis

What type of reaction breaks the bonds that join the phosphate groups in an ATP molecule?

hydrolysis Hydrolysis involves breaking bonds with the addition of water.

Fats

include butter, lard, margarine, and salad oil; don't mix with water because they have a long, nonpolar hydrocarbon tail. Water, being polar, rejects the tail. That makes it hard to transport fats through the body. However, cells use fats for energy storage because the tail hold more potential energy than other biological molecules; have up to three fatty acid tails that join by ester linkages to a glycerol backbone; triacylglycerols/triglycerides; vary in the lengths of the hydrocarbon tails (from 4 to 26 C's in a tail), and the number and location of double bonds in each tail (from 0 to 4 double bonds)

an increase in temperature, an increase in reactant concentration, or the presence of a catalyst will all...

increase the rate of the reaction. Most reactions double in rate for each 10∘C increase in temperature.

An enzyme _____.

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

As a result of its involvement in a reaction, an enzyme _____.

is unchanged Enzymes are not changed as a result of their participation in a reaction. An enzyme's shape is not permanently altered as a result of its participation in a reaction

an enzyme is denatured (change its shape and lose its biological activity) when

it loses its native conformation and its biological activity; at too high a temperature or at a pH outside the enzyme's optimal range.

An enzyme is considered a catalyst because

it speeds up chemical reactions without being used up

An enzyme is considered specific because

its ability to recognize the shape of a particular molecule.

shorter tail length of fats...

more likely to be liquid - long tails can interact with each other at more locations = stronger forces to keep the molecule in line

catalyzed reaction (with enzyme) is ____ to proceed than an uncatalyzed reaction, and it forms products _____ than an uncatalyzed reaction (aka higher reaction rate)

more likely; more rapidly

adenine group

nitrogenous base attached to the ribose sugar.

beta-phosphate

phosphate group attached to the alpha-phosphate.

alpha-phosphate

phosphate group closest to the ribose sugar.

Chemical energy is a form of _____ energy.

potential

Chemical energy is a form of _____ energy.

potential Chemical energy is a form of stored energy.

ATP

powers nearly all forms of cellular work by providing energy stored in chemical bonds; five carbon sugar molecule (ribose), adenine, string of phosphate groups; during cellular respiration, glucose releases energy and this energy is stored when phosphate group is added to ADP and forms ATP; ATP releases energy when covalent bond btwn phosphate groups breaks during hydrolysis, and the energy is used to drive other chemical reactions

Enzymes work by _____.

reducing the energy of activation.

ribose sugar

scaffold that provides the backbone for the entire adenosine triphosphate molecule.

enzyme

special kind of protein that serves as a biological catalyst that increases rate of reaction without being changed into different molecule; doesn't add energy to reaction; lowers energy barrier; very selective, its 3D shape only allows it to work on specific molecules - enzyme substrates; as substrates bind to enzymes active site, they are held in position that facilities reaction, this takes less EA than unaided reaction; because specific enzyme-substrate fit, each enzyme can catalyze only ONE kind of reaction involving specific substrates

potenetial energy

stored energy; pulling back string in bow

body breaks down food molecules

stored potential energy from food can be converted into KE; cellular respiration (converts chem energy from food, to ATP, H20 and CO2)

In a catalyzed reaction a reactant is often called a ___

substrate

What name is given to the reactants in an enzymatically catalyzed reaction?

substrate

Three major factors will affect the rate of the reaction:

temperature, concentration, and catalysts

the higher the activation energy,

the LESS product formed per unit time. Activation energy is sometimes called the energy barrier because it hinders reaction progress.

"saturation"

the amount of hydrogen (H) in the tails

catabolism

the breaking down of high-energy molecules into simple molecules; generate energy

anabolism

the building of complex molecules from simple ones; require energy

kinetic energy

the energy an object has due to its motion; bowstring is released (stored PE converts to KE for work and heat of moving arrow)

Adenosine triphosphate (ATP) is made up of three main structural parts:

the nitrogenous base adenine, the ribose sugar, and the three phosphate groups bonded together by phosphodiester bonds.

Why are fat tails rich in energy?

their numerous C-C and C-H bonds have electrons that will move to oxygen if the opportunity arises. When O2 attacks, oxygen atoms pull electrons from C and H to make C-O and H-O bonds. This oxidation happens because oxygen attracts electrons more strongly than C and H; it's more electronegative.

gamma-phosphate

third phosphate group and is attached to the beta-phosphate, farthest from the ribose sugar, where it is most likely to participate in energy-releasing reactions.

structure of fats

three fatty acid tails that join by ester linkages to a glycerol backbone

heat

type of KE; random motion of atoms and molecules; heat generated by friction between arrow and air molecules in bow and arrow example, when hits target all energy becomes heat energy (which rapidly transfers to air and spreads out; heat energy has highest amount of entropy/disorder of any kind of energy; heat energy not used to do work)

where does the energy for anabolism and catabolism (involved in biological processes) come from?

usually stored in intermediate energy-carrying molecules such as adenosine triphosphate (ATP).

Which part of the adenosine triphosphate molecule is released when it is hydrolyzed to provide energy for biological reactions?

γ-phosphate it is the primary phosphate group on the ATP molecule that is hydrolyzed when energy is needed to drive anabolic reactions. Located the farthest from the ribose sugar, it has a higher energy than either the α- or β-phosphate.