Biochemistry PMY-3 > Bioenergetics > Flashcards

Bioenergetics Flashcards

(58 cards)

Study These Flashcards
1
Q

What are bioenergetics?

A

The study the transfer and utilization of energy in living systems

Predicts if a reaction is possible or not

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is energy?

A

The ability to do work or cause changes ?

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

How is energy measured?

A

Measured in joules or calories

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

State the first law of thermodynamics

A

Energy cannot be created nor destroyed only converted/transformed from one form to the next

Energy of the universe is constant

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

State the second law of thermodynamics

A

Every energy transfer or spontaneous process increases the entropy of the universe

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

How is the first law of thermodynamics applied to chemistry?

A
  • metabolic reactions obey this law as they release/take heat from surroundings
  • enthalpy change🔼H= change in bond energy that occurs during a chemical reaction under constant temperature and pressure
  • this is also the max heat released or absorbed during a chemical reaction under constant pressure in a cell
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Explain enthalpy change

A
  • enthalpy change🔼H= change in bond energy that occurs during a chemical reaction under constant temperature and pressure
  • this is also the max heat released or absorbed during a chemical reaction under constant pressure in a cell

Reactions with a negative value of 🔼H realest heat to surroundings(exothermic)

Reactions with a positive value of 🔼H, remove heat from surroundings (endothermic )

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

How does the second law of thermodynamics apply to chemistry?

A
  • Entropy measures the degree of randomness (disorder).
  • Cells maintain highly ordered structures and obey this law by releasing some energy as heat to the surroundings during metabolism
  • heat transferred increases entropy of surroundings
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Explain entropy

A

Entropy measures the degree of randomness(disorder)

Reactions with a negative value of 🔼S have decreased disorder

Reactions with a positive value 🔼S means increased disorder

🔼S of a reaction cannot by itself predict whether a reaction is spontaneous

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is Gibbs Free energy?

A

The maximum amount of useful energy that is available to do work in a cell

-Predicts the direction of a spontaneous reaction at constant temperature and pressure

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Explain the Gibbs free energy formula and it’s interpretations

A

🔼G = 🔼H- T 🔼S

🔼G= free energy change

🔼H= enthalpy change

🔼S= entropy change

Spontaneous reactions, 🔼G is negative EXERGONIC

Non-spontaneous reactions, 🔼G is positive ENDERGONIC

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Predict 🔼G when enthalpy change is negative and. Entropy is positive

A

When 🔼H is-ve and 🔼S is +ve the 🔼G is -ve and reaction is ALWAYS spontaneous

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Predict 🔼G when enthalpy change is negative and Entropy is negative

A

When 🔼H and 🔼S are negative

🔼G is spontaneous at low temperatures

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Predict 🔼G when both 🔼H and 🔼S are both positive

A

🔼G can be + or -

Spontaneous at high temperature

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Predict 🔼G when enthalpy change is positive and entropy change is negative

A

🔼G is never spontaneous

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What are 3xergonic reactions?

A

🔼G is negative

  • Reactions proceeds spontaneously in the direction written A —> B with net release of free energy
  • Proceeds toward a state of lower free energy
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is an endergonic reaction?

A
  • 🔼G is positive
  • Energy must be added to proceed in the direction written (B—> A)
  • Conversion of B —> A is non-spontaneous
  • Proceeds toward a state of higher free energy
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Contrast exergonic and endergonic reactions

A

Exergonic - spontaneous, negative 🔼G, releases free energy, increases entropy of universe

Endergonic - non-spontaneous, 🔼G is positive, free energy must be added, decreases entropy of universe

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What is 🔼G at equilibrium?

A

🔼G is zero

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Describe spontaneousity achieving equilibrium

A

-Reactions will proceed spontaneously with a net release of free energy until equilibrium has been established

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Describe spontaniety of equilibrium reactions

A

At equilibrium the reaction is at its lowest state of free energy and has no tendency to change

At equilibrium the free energy change is zero and the net reaction ceases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What does 🔼G depend on?

A

The initial concentration of reactants and products

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What are the symbols in the reaction formula:

🔼G= 🔼G^o + RTln[B]/[A]

A

🔼G^o= the standard free energy change

R= is the gas constant

T is the absolute temperature (K)

[A] and [B] are the actual concentrations of reactants and products

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What does Gibbs free energy change predict?

Study These Flashcards
A

The direction of a reaction toward equilibrium starting at any concentration of reactants and products

25
What is the difference in Gibbs free energy in reversible reactions?
In reversible reactions, 🔼G for the forward reaction is equal in magnitude but opposite in sign to the reverse reaction
26
What is standard free energy change (🔼G^o)?
The free energy change of a reaction under standard conditions when initial reactant and product concentrations are 1M
27
Standard conditions are _____ concentrations, ______K (______degrees Celsius) and ______ atm
1 298 25 1
28
What is 🔼G’?
The value of 🔼G^o at pH=7.0, [H2O]= 55M
29
Why can’t 🔼G^o predict the direction of physiological reactions?
Cannot predict the direction of a reaction under physiological conditions because it is not altered by concentrations of substrates and reactants
30
🔼G is composed solely of...
The constants R, T and K eq 🔼G^o= -RTlnKeq
31
What are the chemical conditions of standard Gibbs free energy ?
- under standard conditions - [B]= [A]= 1M - 🔼G^o is positive - Reaction is non spontaneous in the written direction A —> B - formation of A is favoured
32
What are conditions of standard free energy and equilibrium?
- Reaction is allowed to establish equilibrium - At equilibrium more A than B I.e. K eq< 1 - Equilibrium lies to the left - formation of reactants (A) was favoured
33
Describe standard free energy change and reaction direction if Keq is above 1
🔼G^o is negative and reaction is forward A —> B
34
Describe the standard free and direction of the reaction when Keq is below 1
🔼G^o’ is positive Reverse reaction B—> A
35
Describe the standard free energy change and direction of the reaction when Keq=1
Reaction at equilibrium 🔼G^o’ =0
36
How can a reaction with 🔼G^o - 0 proceed spontaneously in the cell?
Under non-standard conditions -Non-spontaneous reaction made spontaneous by altering concentrations of reactants and products Apply Le Chatelier’s principle -[B]
37
What is the additive property of 🔼G and 🔼G^o’
🔼G and 🔼G^o’ of consecutive reactions are additive - This additive property of free energy changes is very important in biochemical pathways - As long as the sum of the 🔼Gs is negative, the pathway can proceed as written. Glucose +ATP —> glucose 6-p + ADP 🔼G^o’= -4kcal/mol Glucose-6-p —> fructose 6-p 🔼G^o’= +0.4 kcal/mol Net: glucose-6-p +ATP —> fructose 6-p + ADP 🔼G^o’=-3.6 kcal/mol
38
What is thermodynamic coupling?
The free energy released by exergonic reactions is used to drive endergonic (unfavorable) processes in the cell Coupling occurs through common intermediates which can transfer chemical energy between the two reactions A+B —> C +D D +X —> Y + Z - 🔼G^o’ values for the coupled reactions are additive - The overall process is exergonic with a 🔼G^o’< 0(-ve)
39
Coupling favorable reactions with an unfavorable reaction might...
Yield an overall favorable reaction
40
Where is the energy stores in ATP?
In the high energy phosphoanhydride bonds
41
What is the 🔼G^o’ of ATP hydrolysis?
🔼G^o’= -7.3 kcal/mol ATP+H2O —> adp+p
42
What is the 🔼G^o’of ADP hydrolysis?
🔼G^o’= 7.3 kcal/mol ADP+ H2O—> AMP + P
43
Why is ATP hydrolysis exergonic?
Hydrolysis of ATP is exergonic because ADP | and P are more stable with less free energy than ATP
44
Why is ATP unstable?
Instability and high bond energy of the phospho-anhydride bond of ATP arises from repulsion between the negatively charged phosphate groups Also the free phosphate anion is more stable than it is in ATP due to an increase in resonance and solubility(increased entropy)
45
Energy released as heat cannot be _______ into energy ________ processes such as biosynthetic reactions or maintenance of ion gradients
Transferred Requiring
46
Energy transfer is facilitated by....
Transferring the phosphate group to a reactant or protein generating a common intermediate that is part of the energy requiring process
47
What are high energy compounds?
Compounds with a free energy of hydrolysis equal to or higher than ATP Are mainly phosphate or thioester compounds
48
What is the phosphorylation transfer potential?
🔼G^o’ if hydrolysis
49
Compounds with higher 🔼G^o’ of hydrolysis than AaTP can...
Be used to make ATP
50
ATP can be used to form compounds with...
Lower 🔼G^o’ of hydrolysis
51
The high energy bonds of UTP, CTP and GTP are...
Equivalent to ATP and are synthesized from ATP by nucleoside phosphokinases
52
Give some examples of substrate phosphorylation
- Succinate thiokinase in TCA cycle | - PFK-1, Glucokinase, Pyruvate kinase, phospoglycerate kinase in glycolysis
53
What is substrate level phosphorylation?
An enzyme catalyzed reaction where a phosphate group is transferred from a compound with a higher phosphoryl group potential to another compound having a lower phosphoryl group potential Catalyzed by kinases
54
What is a low energy state for a cell?
Cells with a low [ATP]/[ADP] ratio is said to be in a low energy state
55
What is a high energy state for a cell?
Cells with a high [ATP]/ [ADP] is said to be in a high energy state
56
The free energy change of ATP hydrolysis depends greatly om...
The concentrations of ATP, ADP and P
57
Describe ATP and energy balance in the cell
In the cell the ATP hydrolysis reaction is kept far from equilibrium by maintaining the [ATP] higher [ADP] Cells maintain ATP homeostasis using the [ATP]/ [ADP] ratio as a signal to regulate the rate of ATP generation to match its utilization
58
What processes might use energy utilization?
Muscle contraction Active transport Biosynthesis Detoxification Thermogenesis
Biochemistry PMY-3
flashcards
Decks in class (37)
# Cards
Brainscape helps you reach your goals faster, through stronger study habits.
© 2026 Bold Learning Solutions. Terms and Conditions