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Biology 241 > 6.4 Chemical Reactions > Flashcards

6.4 Chemical Reactions Flashcards

1
Q

what is a chemical reaction?

A

the process by which molecules, called reactants, are transformed into other molecules, called products

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2
Q

what changes during a chemical reaction?

A

the bonds linking the atoms

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3
Q

most chemical reactions in the cell are readily reversible, what does that mean?

A

the products can react to form the reactants

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4
Q

the way the reaction is written defines forward and reverse reactions:

A

a forward reaction proceeds from left to right, a reverse reaction proceeds from right to left

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5
Q

the direction of a reaction can be influenced by:

A

the concentrations of reactants and products

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6
Q

how to favour the forward reaction?

A

increase the concentration of the reactants or decrease the concentration of the products

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7
Q

the effect of favouring the forward reaction can be found in the reactions of many metabolic pathways, how does that work?

A

the products of many reactions are quickly consumed by the next reaction, helping to drive the first reaction forward

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8
Q

Gibbs free energy (G)

A

the amount of energy available to do work

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9
Q

how does one determine whether the reaction releases energy that is available to do work?

A

you can compare the free energy of the reactants and products

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10
Q

what is delta G (change in G)

A

the free energy of the products minus the free energy of the reactants

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11
Q

if change in G is positive:

A

the products of a reaction have more free energy than reactants and a net input of energy is required to drive the reaction forward

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12
Q

if change in G is negative:

A

the products of a reaction have less energy than reactants and energy is released and available to do work

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13
Q

exergonic

A

describes reactions with a negative change in G that release energy and proceed spontaneously

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14
Q

endergonic

A

describes reactions with a positive change in G that are not spontaneous and so require an input of energy

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15
Q

spontaneous in the context of free energy means that:

A

a reaction releases energy

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16
Q

non-spontaneous in the context of free energy means that:

A

a reaction requires a sustained input of energy

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17
Q

the total amount of energy is equal to:

A

the energy available to do work plus the energy that is not available to do work because of the increase in entropy

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18
Q

enthalpy (H)

A

the total amount of energy in a system

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19
Q

entropy (S)

A

the degree of disorder in a system

20
Q

absolute temperature (T)

A

temperature measured on the kelvin scale

21
Q

the formula for the total amount of energy (H) is:

A

energy available to do work (G) + energy lost to entropy (TS)

22
Q

the formula to determine energy available to do work (G) is:

A

H - TS

total amount of energy - energy lost to entropy

23
Q

the value of change in G depends on BOTH the:

A

change in enthalpy and the change in disorder

24
Q

catabolic reactions are those in which the products have :

A

less chemical energy (lower enthalpy) in their bonds than reactants have, the products are more disordered (higher entropy) than the reactants are-have a negative value of change in H and a positive value for change in S (releases energy-spontaneous)

25
Q

anabolic reactions are the opposite of catabolic reactions so:

A

increasing chemical energy (positive delta H) and decreasing disorder (negative delta S0, synthesis of macromolecules, positive value of delta G, requires a net input of energy

26
Q

if the change in enthalpy and entropy are both positive or both negative, whether or not the reaction is spontaneous is determined by:

A

the absolute value of these parameters which then determines whether delta G is positive or negative

27
Q

what effect does increasing temperature have on the free energy (delta G) of a chemical reaction?

A

increasing the temperature increases the value of (TS) which decrease G (G=H-TS)

28
Q

hydrolysis reactions consist of a chemical reaction in which a water molecule is split into:

A

a proton (H+) and a hydroxyl group (OH-), hydrolysis reactions often break down polymers into their subunits and in the process one product gains a proton and the other gains a hydroxyl group

29
Q

the reaction of ATP with water is an exergonic reaction because:

A

there is less free energy in the products compared to the reactants

30
Q

why is the reaction of ATP an exergonic reaction?

A

ADP is more stable than ATP, contains less chemical energy in its bonds (negative H), and because there is two molecules (ADP and P), there is increased entropy (H), so G is negative and the reaction is spontaneous and releases energy

31
Q

the free energy difference for ATP hydrolysis is approximately: (under lab conditions)

A

-7.3 kcal per mole of ATP

32
Q

the value of the free energy difference for ATP hydrolysis is influenced by several factors including:

A

the concentration of reactants and products, the pH of the solution, and the temperature and pressure

33
Q

in cell conditions, the free energy difference is approximately:

A

-12 kcal per mole of ATP

34
Q

the release of free energy during ATP hydrolysis comes from:

A

breaking weaker bonds (with more chemical energy) in the reactants and forming more stable bonds (with less chemical energy in the products)

35
Q

the change in G for the forward and reverse reactions have the same:

A

absolute value but opposite signs

36
Q

energetic coupling

A

the driving of a non-spontaneous reaction by a spontaneous reaction

37
Q

energetic coupling requires that the net change in G of the two reactions be:

A

negative and the two reactions must occur together or share an intermediate

38
Q

the synthesis of ATP from ADP and inorganic P is an:

A

endergonic reaction with a positive change in G requiring an input of energy

39
Q

in some cases, the synthesis of ATP can be driven by:

A

exergonic reactions through energetic coupling

40
Q

hydrolysis reactions can be ranked by:

A

their free energy differences (change in G)

41
Q

ADP is an energy:

A

ACCEPTOR

42
Q

ATP is an energy:

A

DONOR

43
Q

reactions with a free energy difference more negative than that of ATP hydrolysis transfer:

A

a phosphate group to ADP by energetic coupling (helping to drive ATP synthesis because it is more exergonic)

44
Q

reactions with a free energy differences less negative than that of ATP hydrolysis receive:

A

a phosphate group from ATP by energetic coupling (because it is less exergonic compared to ATP hydrolysis)

45
Q

the free energy difference for ATP hydrolysis compared to hydrolysis of common phosphorylated molecules is:

A

intermediate which allows ATP to drive reactions as well as be replenished

Biology 241 (31 decks)

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