biology EXAM #3 pt.2

Question 1

The living cell is a

Cellular respiration extracts

Cells apply this energy to

Some organisms even convert

Answer 1

miniature chemical factory where thousands of reactions occur

energy stored in sugars and other fuels

perform work

energy to light, as in bioluminescence

Question 2

An organism’s metabolism transforms ¡

Metabolism
Is the totality of an

Arises from

Answer 2

matter and energy, subject to the laws of thermodynamics

organism’s chemical reactions

interactions between molecules

Question 3

A metabolic pathway has many steps

That begin with a ___________ and end with a ________

That are each catalyzed by a

Answer 3

specific molecule; product

specific enzyme

Question 4

Change of free energy ΔG => free energy indicates

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

Answer 4

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

exergonic
endergonic

Question 5

Catabolic pathways:

-Break down

-Release

• example of a pathway of catabolism?

Answer 5

complex molecules into simpler compounds

energy

Cellular respiration

Question 6

Anabolic pathways:

consume energy to

For example, the synthesis of

Bioenergetics is the study of

Answer 6

build complex molecules from simpler ones

protein from amino acids is an anabolic pathway

how energy flows through living organisms

Question 7

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

Answer 7

-capacity to cause change

-solar energy; associated with motion

-chemical energy, food: location of matter
molecular structure

Question 8

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

Answer 8

energy transformations

conservation

-transferred and transformed
-created or destroyed

Question 9

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 ____

Answer 9

energy transfer or transformation increases the entropy of the universe

the entropy, or disorder, of the universe.

heat

Question 10

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 :

Answer 10

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

Question 11

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

Answer 11

less organized forms of energy and matter

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

Question 12

Living systems: increase the…

Use energy to :

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

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

Answer 12

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

Question 13

Advantages of ATP as energy carrier:

Provides a

Breakdown of ATP to ADP+P releases

ATP breakdown is coupled to

Answer 13

-common energy currency for many reactions

-sufficient energy for biological processes- little wasted

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

Question 14

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

Answer 14

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)

Question 15

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

Answer 15

spontaneous processes; spontaneous

Question 16

Spontaneous processes can be harnessed to

Organisms live at the expense of

During a spontaneous change free energy …

Answer 16

perform work

free energy

decreases and the stability of a system increases

Question 17

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

Answer 17

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

Question 18

Reactions in a closed system eventually reach

The concept of free energy can be applied to

Answer 18

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

the chemistry of life’s processes

Question 19

Cells are not in __________; they are:

A defining feature of life is that

A catabolic pathway in a cell releases

Answer 19

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

metabolism is never at equilibrium

free energy in a series of reactions

Question 20

An exergonic reaction :

An endergonic reaction is one that :

Answer 20

net release of free energy and is spontaneous

absorbs free energy from its surroundings and is nonspontaneous

Question 21

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

Answer 21

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

Question 22

ATP powers

A cell does three main kinds of work:

Answer 22

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

Question 23

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

Answer 23

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

Question 24

The three types of cellular work are powered by:

In the cell, the energy from the exergonic reaction of

Overall, the coupled reactions are

Answer 24

the hydrolysis of ATP

ATP hydrolysis can be used to drive an endergonic reaction

exergonic

Question 25

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 :

Answer 25

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

Question 26

A catalyst is a

An enzyme is a

Enzymes do not affect the change in ___________; instead, they:

Answer 26

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

Question 27

Induced fit of a substrate
The active site is the region on the enzyme where

Brings chemical groups of the active site into __________ that :

Answer 27

the substrate binds

positions that enhance their ability to catalyze the chemical reaction

Question 28

Every chemical reaction between molecules involves:

An example of a chemical reaction is the

Answer 28

both bond breaking and bond forming

hydrolysis of sucrose

Question 29

The activation energy
Is the:

Is often supplied

An enzyme catalyzes reactions by

Answer 29

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

Question 30

The enzyme binds to __ ________, forming an ____________

The active site can lower an EA barrier by:

(4)

Answer 30

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

Question 31

In an enzymatic reaction, the substrate binds to the

Enzymes are extremely

Very small amounts of enzyme can have

Answer 31

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

Question 32

The catalytic cycle of an enzyme

Answer 32

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.

Question 33

The activity of an enzyme is affected by

Each enzyme has an

Has an optimal ____ in which it can function

Answer 33

general environmental factors

optimal temperature in which it can function

pH

Question 34

Cofactors - molecule which
-Are…
-_____ such as zinc, iron and copper in ionic and vitamins

Organic nonprotein cofactors are called

Answer 34

helps enzyme function
-nonprotein enzyme helpers
-Inorganic

coenzymes

Question 35

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,

Answer 35

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

Question 36

Competitive inhibitors bind to the

Noncompetitive inhibitors bind to…., causing:

Some examples of inhibitors are:

Answer 36

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

Question 37

Competitive inhibitors like:

Bind to the

Answer 37

morphine

active site of an enzyme, competing with the substrate

Question 38

Noncompetitive inhibitors bind to

A noncompetitive inhibitor binds to the
enzyme __________________, altering
the….. so that:

Answer 38

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.

Question 39

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.

Answer 39

regulators of enzyme activity

Question 40

Enzymes are

Changes (mutations) in genes lead to

Altered amino acids, particularly at the active site, can result in

Answer 40

proteins encoded by genes

changes 
in amino acid composition of an enzyme

novel enzyme activity or altered substrate specificity

Question 41

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

Question 42

Regulation of enzyme activity helps

A cell’s metabolic pathways must be ________, for example with:

Answer 42

control metabolism

tightly regulated, allosteric regulation and feedback mechanisms

Question 43

Allosteric regulation is the term used to describe

Many enzymes are

Answer 43

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

allosterically regulated

Question 44

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

Answer 44

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

Question 45

Cooperativity is a form of

One substrate molecule primes

Cooperativity is allosteric because

Answer 45

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

Question 46

In feedback inhibition
:

The end product of a metabolic pathway:

Feedback inhibition prevents

Answer 46

shuts down the pathway

a cell from wasting chemical resources by synthesizing more product than is needed

Question 47

Within the cell, enzymes may be: (3)

Answer 47

Grouped into complexes
Incorporated into membranes
Contained inside organelles

Question 48

Enthalpy =

Answer 48

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

H = E + p * V