Metabolism

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UVU College Biology Chapter 8

Catabolism is to anabolism as __________ is to __________.

exergonic; endergonic

When you have a severe fever, what may be a grave consequence if this is not controlled?

change in conformation of enzymes

Which term most precisely describes the cellular process of breaking down large molecules into smaller ones?

catabolism

The mechanism in which the end product of a metabolic pathway inhibits an earlier step in the pathway is known as

feedback inhibition

Living organisms increase in complexity as they grow, resulting in a decrease in the entropy of an organism. How does this relate to the second law of thermodynamics?

As a consequence of growing, organisms create more disorder in their environment than the decrease in entropy associated with their growth.

What is true for all exergonic reactions?

The reaction proceeds with a net release of free energy.

Which types of molecules are the major structural components of the cell membrane?

phospholipids and proteins

Celery stalks that are immersed in fresh water for several hours become stiff and hard. Similar stalks left in a salt solution become limp and soft. From this we can deduce that the cells of the celery stalks are

hypertonic to fresh water but hypotonic to the salt solution

The presence of cholesterol in the plasma membranes of some animals

enables the membrane to stay fluid more easily when cell temperature drops

What kinds of molecules pass through a cell membrane most easily?

small & hydrophobic

How does a noncompetitive inhibitor decrease the rate of an enzyme reaction?

by changing the shape of the reaction

Metabolic pathway

a pathway that begins witha specific molecule, which is then altered in a series of defined steps, resulting in a certain product. Each step of the pathway is catalyzed by a specific enzyme.

Catabolic pathway

a metabolic pathway that releases energy by breaking down complex molecules to simpler compounds (aka breakdown pathways)

A major pathway of catabolism is

cellular respiration

Anabolic pathways

consume energy to build complicated molecules from simpler ones, aka biosynthetic pathways

Energy released from the downhill reactions of catabolic pathways can be stored and then used to drive the _________ .

uphill reaction of anabolic pathways

Bioenergetics

they study of flows through living organisms how energy

Energy

the capacity to cause change

Kinetic energy

energy that can be associated with the relative motion of objects

Thermal energy

kinetic energy associated with the random movement of atoms or molecuels

Potential energy

energy that matter possess because of its location or structure such as water behind a dam.

Chemical energy

the potential energy available for release in chemical reaction

An isolated system is unable to

exhange either energy or matter with its surrounds, such as liquid in a thrermos.

Open systems can

transfer energy and matter between they system and its surroundings

Organisms are ____ systems

open

Because organisms absorb energy and release heat and metabolic waste to their surroundings they are _______.

open systems

1st law of thermodynamics

Energy can be transferred and transformed, but it cannot be created or destroyed.

2nd law of themodynamics

Every energy transfer or transformation increases the entropy of the universe.

For a process to occur on its own, without an input of energy (spontaneously), it must ______.

Increase the entropy of the universe

Spontaneous

a process that can occur without an input of energy

The entropy of a particular system may actually decrease as long as ________.

the total entropy of the universe increases.

Free energy

the portion of a system's energy that can perform work when temperature and pressure are uniform throughout the system

The change in free energy can be calculated for a chemical reaction with this formula

>G = >H-T>S

In >G = >H-T>S what do the letters represent?

>G is the change in free energy
>H is the change in the system's enthalpy or total energy
>T is absolute temperature in Kelvin
>S is the change in the system's entropy

Free energy = the change in the system's ____ minus temp * the change in the system's entropy

enthalpy or total energy

Only processes with a ____ >G are spontaneous.

negative

For a process to occur spontaneously, the system must either give up _____, give up ______ or both.

enthalpy (H must decrease)
give up order (TS must increase)

Every spontaneous process _________.

decreases the system's free energy.

>G represents the difference between

the free energy of the final state and the free energy of the initial state.

We can think of free energy as a measure of a system's ___________.

instability, its tendency to change to a more stable state.

Equilibrium

a state of maximum stability

Any change from the equilibrium position will have a _____ >G and __________ spontaneous.

positive
will not be

Because a system at equilibrium cannot spontaneously change, _____.

It can do no work.

Exergonic reaction

proceeds with a net release of free energy.

Because the chemical mixture loses free energy, >G is ____________ for an exergonic reaction.

negative

Endergonic reaction

one that absorbs fee energy from its surroundings.

Because endergonic reactions essentially store free energy in molecules >G is

positive

The magnitude of >G in exergonic reactions represents __________

the amount of work the reaction can perform.

The magnitude of >G in endergonic reactions represents

the quantity of energy require to drive the reaction.

A series of enzymes catalyze the reaction X Y Z A. Product A binds to the enzyme that converts X to Y at a position remote from its active site. This binding decreases the activity of the enzyme.
What is substance X?

a substrate

The mechanism in which the end product of a metabolic pathway inhibits an earlier step in the pathway is known as

feedback inhibition

Some enzymatic regulation is allosteric. In such cases, what would usually be found?

an enzyme with more than one subunit

Give an example of cooperativity

a molecule binding at one unit of a tetramer allowing faster binding at each of the other three

What is the structure of ATP?

ATP contains the sugar ribose, with the nitrogenous base adenine and a chain of three phosphate groups bonded to it.

The bonds between the phosphate groups of ATP can be broken by _______.

Hydrolisis

When the terminal phosphate bond in ATP is broken, a molecule of inorganic phosphate leaves the ATP, which becomes

ADP

Activation energy

the initial investment of energy for a starting reaction (the energy required to contort the reactant molecules so the bonds can break)

Transition state

where,at the summit of the progress of the reaction, reactants are in an unstable condition. They are activated and their bonds can be broken.

The absorption of thermal energy _____ the speed of the reactant molecules, so they __________.

increases
collide more often and more forcefully

The reactant an enzyme acts on is referred to as

the enzyme's substrate

While enzyme and substrate are joined, the ________ of the enzyme converts the substrate to the product of the reaction.

catalytic action

Active site

the restricted region of the enzyme molecule that binds with a substrate

What is the formula for ATP reaction

ATP + H2O --> ADP + (P)i

ATP is useful to the cell because ______.

the energy it releases on losing a phosphate group is somewhat greater than the energy most other molecules could deliver.

The triphosphate tail of ATP is the chemical equivalent of _________

a compressed spring.

The cell's proteins harness the energy released during ATP hydrolysis in several ways to perform these three types of cellular work:

chemical, transport, mechanical.

Chemical work

the pushing of endergonic reactions, which would not occur spontaneously

Transport work

the pumping of substances across membranes against the direction of spontaneous movement

Mechanical work

the contraction of muscle cells and the movement of chromosomes during cellular reproduction

Energy coupling

the use of an exergonic process to drive an endergonic one

The shuttling of inorganic phosphate and energy is called

the ATP cycle

Catabolic pathways, especially ______, provide the energy for the endergonic process of making ATP.

cellular respiration

The energy required to contort reactant molecules so that bonds can break is called ____.

Activation energy

Every chemical reaction between molecules involves both ________ & __________.

bond breaking & bond forming

Enzymes catalyse a reaction by ________, enabling the reactant molecules to _______.

lowering the Ea barrier
absorb enough energy to reach the transition state even at moderate temperatures.

The specificity of an enzyme results from ____.

its shape.

The catalytic cycle of an enzyme

1. Substrates enter the active site, enzyme changes shape to enfold the substrate in an induced fit.
2. Substrates are held in active site by weak interactions, such as hydrogen bonds & ionic bonds.
3. Active site can lower Ea and speed up a reaction
4. Substrates are converted to products
5. Products are released
6. Active sit is available for new substrate molecule.

The active site can lower Ea and speed up reaction by:

*acting as a template for substrate orientation
*stressing the substrates and stabilizing the transistion state
*providing a favorable microenvironment
*participating directly in the catlytic reaction

Up to a point, the rate of enzymatic reaction increase with increasing temperature, partly because ______________.

substrates collide with active sites more frequently when the molecules move rapidly.

Thermal agitation of the enzyme molecule disrupts ___________________ that stabilize the active shape of the enzyme and the protein molecule eventually ___________.

hydrogen bonds, ionic bonds, & other weak interactions
denatures

Optimal pH values for most enzymes fall in the range of

pH 6-8

Most human enzymes have optimal temperatures of

35-40 degrees Celsius (close to human body temperature)

Optimal temperature allows

the greatest number of molecular collision and the fastest conversion of the reactants to products molecules without denaturing the enzyme.

Cofactors

nonprotein helpers for catalytic activity that may be bound tightly to the enzyme as permanent residents, or they may bind loosely and reversibly along with the substrates.

Coenzyme

a cofactor that is an organic molecule, such as vitamins

Competitive inhibitors

reversible inhibitors that resemble normal substrate molecules and compete for admission into the active site. They reduce the productivity of enzymes by blocking substrates from entering active sites.

Noncompetitive inhibitors

do not directly compete with the substrate to bind to the enzyme at the active site. Instead they impede enzymatic reactions by binding to another part of the enzyme. This interaction causes the enzyme molecule to change its shape in such a way that the active site becomes less effective at catalyzing the conversion of substrate to product.

Toxins and poisons are often

irreversible enzyme inhibitors

Allosteric regulation

any case in which a proteins' function at one site is affected by the binding of a regulatory molecule to a separate site.

ATP binds several catabolic enzymes allosterically, lowering their affinity for substrate and thus ________.

inhibiting their activity

The binding of an _________ to a regulatory site stabilizes the shape that has functional active site, whereas the binding of an inhibitor __________.

activator
stabilizes the inactive form of the enzyme

Cooperativity

If an enzyme has 2 or more subunits, a substrate molecule causing induced fit in one subunit can trigger the same favorable change in all the other subunits of the enzyme.

How does cooperativity amplify the response of enzymes to substrates?

One substrate molecule primes an enzyme to accept additional substrate molecules more readily.

Feedback inhibition

a common method of metabolic control in which a metabolic pathway is switched off by the inhibitory binding of its end product to an enzyme that acts earlier in the pathway

The addition of starting materials and the removal of end products prevent metabolism from reaching

equilibrium

Hydrolisis at ATP's terminal phosphate group produces ___ & ____ and releases ____.

ADP & phosphate
free energy

ATP hydrolisys drives _________ by phosphorylation, the transfer of a __________, making them more reactive.

endergonic reactions
phosphate group to specific reactants

ATP hydrolysis can cause changes in ___________.

the shape and binding affinities of transport & motor proteins.

________ drive the regeneration of ATP form ADP and phosphate

Catabolic pathways

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