biology EXAM #3 pt.2 Flashcards by vjhvbh ghcghcv

The living cell is a

Cellular respiration extracts

Cells apply this energy to

Some organisms even convert

miniature chemical factory where thousands of reactions occur

energy stored in sugars and other fuels

perform work

energy to light, as in bioluminescence

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An organism’s metabolism transforms ¡

Metabolism
Is the totality of an

Arises from

matter and energy, subject to the laws of thermodynamics

organism’s chemical reactions

interactions between molecules

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A metabolic pathway has many steps

That begin with a ___________ and end with a ________

That are each catalyzed by a

specific molecule; product

specific enzyme

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Change of free energy ΔG => free energy indicates

-ΔG then = ___________ reaction
+ ΔG then = __________ reaction

the portion of the system’s energy that can perform work when To and pressure are uniform throughout the system.

exergonic
endergonic

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Catabolic pathways:

-Break down

-Release

example of a pathway of catabolism?

complex molecules into simpler compounds

energy

Cellular respiration

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Anabolic pathways:

consume energy to

For example, the synthesis of

Bioenergetics is the study of

build complex molecules from simpler ones

protein from amino acids is an anabolic pathway

how energy flows through living organisms

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Energy:
Is the

Exists in various forms, of which some can perform work
Kinetic energy is _____ energy: is the energy associated with ________

Potential energy is _______ energy: is stored in the…
Includes energy stored in

-capacity to cause change

-solar energy; associated with motion

-chemical energy, food: location of matter
molecular structure

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Thermodynamics:
Is the study of

According to the first law of thermodynamics – the principle of

Energy can be
Energy cannot be

*hacer flashcards de los law of thermodynamics

energy transformations

conservation

-transferred and transformed
-created or destroyed

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According to the second law of thermodynamics – every…

Spontaneous changes that do not require outside energy increase

There is loss of usable energy in the form of ____

energy transfer or transformation increases the entropy of the universe

the entropy, or disorder, of the universe.

heat

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Living cells unavoidably convert

Spontaneous processes occur without ____ _____; they can happen :

For a process to occur spontaneously, it must:

Processes that decrease entropy are _____________; they will occur only if :

organized  forms of energy to heat, a more disordered form of energy

energy input; they can happen quickly or slowly

increase the entropy of the universe

nonspontaneous; they will occur only if energy is provided

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Organisms create ordered structures from

Organisms also replace…with…

For example, animals consume complex molecules in their food and release smaller, lower energy molecules and heat into the surroundings

less organized forms of energy and matter

ordered forms of matter and energy in their surroundings with less ordered forms

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Living systems: increase the…

Use energy to :

ATP- energy for … (meaning of the abvr)
Generated from:

ATP structure:
“_____ ______” compound because :
Releases:

entropy of the universe

maintain order

cells; Adenosine triphosphate; ADP + P

Modified adenine, ribose,  and 3 phosphates
“high energy” compound because  the terminal phosphate group is  easily removed

7.3 kcal per mole

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Advantages of ATP as energy carrier:

Provides a

Breakdown of ATP to ADP+P releases

ATP breakdown is coupled to

-common energy currency for many reactions

-sufficient energy for biological processes- little wasted

-endergonic reactions in such a way that it minimizes energy loss

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The free-energy change of a reaction tells us whether

A living system’s free energy is energy that

The change in free energy, ∆G during a biological process is related directly to the

the reaction occurs spontaneously

can do work under cellular conditions, when temperature and pressure are uniform, as in a living cell

system’s enthalpy change or total energy (∆H) and the change in system’s entropy (∆S)

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ΔG is negative for all ___________ ___________; processes with zero or positive ΔG are never __________

spontaneous processes; spontaneous

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Spontaneous processes can be harnessed to

Organisms live at the expense of

During a spontaneous change free energy …

perform work

free energy

decreases and the stability of a system increases

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Free energy is a measure of

During a spontaneous change, free energy

Equilibrium is a

A process is spontaneous and can perform work only when

a system’s instability, its tendency to change to a more stable state

decreases and the stability of a system increases

state of maximum stability

it is moving toward equilibrium

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Reactions in a closed system eventually reach

The concept of free energy can be applied to

equilibrium which is considered maximum stability and can then do no work

the chemistry of life’s processes

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Cells are not in __________; they are:

A defining feature of life is that

A catabolic pathway in a cell releases

equilibrium; they are open systems experiencing a constant flow of materials

metabolism is never at equilibrium

free energy in a series of reactions

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An exergonic reaction :

An endergonic reaction is one that :

net release of free energy and is spontaneous

absorbs free energy from its surroundings and is nonspontaneous

Cells in our body experience a constant flow of….., preventing :

flow of materials in and out, preventing metabolic pathways from reaching equilibrium

ATP powers

A cell does three main kinds of work:

cellular work by coupling exergonic reactions to endergonic reactions

Mechanical —such as contraction of muscle cells
Chemical —pushing endergonic reactions
Transport —pumping substances against the direction of spontaneous movement

To do work, cells manage energy resources by

ATP drives _________ reactions by ____________, which is:

The recipient molecule is now called a

Most energy coupling in cells is mediated by

by energy coupling, the use of an exergonic rxn to drive an endergonic rxn

endergonic reactions by phosphorylation, which is transferring a phosphate to other molecules

phosphorylated intermediate

ATP

The three types of cellular work are powered by:

In the cell, the energy from the exergonic reaction of

Overall, the coupled reactions are

the hydrolysis of ATP

ATP hydrolysis can be used to drive an endergonic reaction

exergonic

ATP is a renewable resource that is The energy to phosphorylate ADP comes from The ATP cycle is a revolving door through which energy Catabolic pathways drive the :

renewable resource that is regenerated by addition of a phosphate group to adenosine diphosphate (ADP) catabolic reactions in the cell passes during its transfer from catabolic to anabolic pathways regeneration of ATP from ADP and phosphate

A catalyst is a An enzyme is a Enzymes do not affect the change in ___________; instead, they:

chemical agent that speeds up a reaction without being consumed by the reaction catalytic protein that speed up metabolic reactions by lowering energy barriers without being consumed by the reaction free energy (ΔG); instead, they hasten reactions that would occur eventually

Induced fit of a substrate The active site is the region on the enzyme where Brings chemical groups of the active site into __________ that :

the substrate binds positions that enhance their ability to catalyze the chemical reaction

Every chemical reaction between molecules involves: An example of a chemical reaction is the

both bond breaking and bond forming hydrolysis of sucrose

The activation energy Is the: Is often supplied An enzyme catalyzes reactions by

initial amount of energy needed to start a chemical reaction in the form of thermal energy or heat that the reactant molecule absorbs from the surroundings in a system lowering the EA barrier

The enzyme binds to __ ________, forming an ____________ The active site can lower an EA barrier by: (4)

binds to its substrate, forming an enzyme-substrate complex 1)Orienting substrates correctly 2)Straining substrate bonds 3)Providing a favorable microenvironment 4)Covalently bonding to the substrate

In an enzymatic reaction, the substrate binds to the Enzymes are extremely Very small amounts of enzyme can have

active site of the enzyme fast acting and emerge from reactions in their original form huge metabolic effects because they are used repeatedly in catalytic cycles

The catalytic cycle of an enzyme

1) Substrates enter active site; enzyme changes shape so its active site embraces the substrates (induced fit). 2) Substrates held in active site by weak interactions, such as hydrogen bonds and ionic bonds. 3) Active site (and R groups of its amino acids) can lower EA and speed up a reaction 4) Substrates are Converted into Products. 5) Products are Released. 6) Active site Is available for two new substrate Mole.

The activity of an enzyme is affected by Each enzyme has an Has an optimal ____ in which it can function

general environmental factors optimal temperature in which it can function pH

Cofactors - molecule which -Are... -_____ such as zinc, iron and copper in ionic and vitamins Organic nonprotein cofactors are called

helps enzyme function -nonprotein enzyme helpers -Inorganic coenzymes

Factors affecting enzymatic rate Enzyme inhibition occurs when: Activity of cell enzymes is regulated by Ex: when product is abundant it binds to the enzyme’s active site and blocks further production When product is used up, it is removed from the active site In a more complex type of inhibition,

enzyme cannot bind its substrate feedback inhibition product binds to a site other than the active site, which changes the shape of the active site

Competitive inhibitors bind to the Noncompetitive inhibitors bind to...., causing: Some examples of inhibitors are:

active site  of an enzyme, competing with the substrate another part of an enzyme, causing the enzyme to change shape and making the active site less effective toxins, poisons, pesticides, and antibiotics

Competitive inhibitors like: Bind to the

morphine active site of an enzyme, competing with the substrate

Noncompetitive inhibitors bind to A noncompetitive inhibitor binds to the enzyme __________________, altering the..... so that:

another part of an enzyme, changing the function away from the active site; altering the conformation of the enzyme so that its active site no longer functions.

Inhibitors act as DDT, parathion, nerve gas – inhibitors of enzymes of the nervous system Antibiotics – inhibit specific enzyme´s active site that produce cell walls of bacteria.

regulators of enzyme activity

Enzymes are Changes (mutations) in genes lead to Altered amino acids, particularly at the active site, can result in

proteins encoded by genes changes  in amino acid composition of an enzyme novel enzyme activity or altered substrate specificity

Under environmental conditions where the new function is beneficial, natural selection would favor the mutated allele For example, repeated mutation and selection on the β-galactosidase enzyme in E. coli resulted in a change of sugar substrate under lab conditions

Regulation of enzyme activity helps A cell’s metabolic pathways must be ________, for example with:

control metabolism tightly regulated, allosteric regulation and feedback mechanisms

Allosteric regulation is the term used to describe Many enzymes are

any case in which a protein’s function at one site is affected by binding of a regulatory molecule at another site allosterically regulated

Most allosterically regulated enzymes are made from The enzyme complex has The binding of an activator stabilizes the The binding of an inhibitor stabilizes the They change shape when

polypeptide subunits, each with its own active site active and inactive forms active form of the enzyme inactive form of the enzyme regulatory molecules bind to specific sites, affecting function

Cooperativity is a form of One substrate molecule primes Cooperativity is allosteric because

allosteric regulation that can amplify enzyme activity an enzyme to act on additional substrate molecules more readily binding by a substrate to one active site affects catalysis in a different active site

In feedback inhibition : The end product of a metabolic pathway: Feedback inhibition prevents

shuts down the pathway a cell from wasting chemical resources by synthesizing more product than is needed

Within the cell, enzymes may be: (3)

Grouped into complexes Incorporated into membranes Contained inside organelles

Enthalpy =

(the sum of the internal energy E) + ( pressure p x volume V). Using the symbol H for the enthalpy: H = E + p * V