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foundations of medicine 1 > life at the cellular level (4) - energy (thermodynamics) > Flashcards

life at the cellular level (4) - energy (thermodynamics) Flashcards

1
Q

Give examples of types of energy

A

Heat
Light
Mechanical
Electrical

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2
Q

What is the first law of thermodynamics

A

Energy can be converted from one form to another but the total energy of the universe remains constant

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3
Q

What is the second law of thermodynamics

A

All energy transformations ultimately lead to more disorder in the universe, i.e. increase the entropy

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4
Q

What is entropy

A 
The degree of disorder
 As usable energy decreases
unusable energy increases,
entropy increases
 Entropy is also a gauge of randomness or chaos within a closed system. As usable energy is irretrievably lost, disorganization, randomness and chaos increase.
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5
Q

How do cells maintain order

A

By performing lots of chemical reactions which require energy

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6
Q

What do cells use energy for

A

To grow and form complex molecules and systems

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7
Q

Do cells live in isolation

A

No, they are open systems, taking energy from the sun and food molecules to generate the order required for life

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8
Q

How do cells apply the 2nd law of thermodynamics

A

The chemical reactions that generate the cell’s order produce heat, which is discharged into the surrounding environment and disorders it, so the total entropy increases

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9
Q

What is Gibbs free energy

A

“useful”, or Free energy in a closed system can be defined by 3 quantities:
– Enthalpy, H – heat released to surroundings (reflects number/kind of bonds formed/broken)
– Entropy, S – randomness/disorder – Absolute temperature, T
G = H - TS

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10
Q

What can free energy change be used to define

A

The spontaneity of a reaction

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11
Q

When can spontaneous reactions occur

A

If a system:
– Gives up energy (water runs downhill spontaneously, giving up potential energy as it goes)
And/or
– Becomes more random and increases in entropy (complex structures decay spontaneously giving up potential energy)

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12
Q

What must a spontaneous process do to enthalpy and entropy

A

Decrease enthalpy (H) and/or increase entropy (S)

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13
Q

spontaneous reactions only occur if ΔG is

A

negative

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14
Q

what is the free energy change equation

A

ΔG = ΔH - TΔS

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15
Q

what does it mean if ΔG is -ve

A

the reaction releases energy

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16
Q

how much order do biological processes require

A

more rather than less, so reactions to generate proteins, DNA, cells, organs, etc, etc require reactions that have +ve ΔG

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17
Q

why do cells use a process called “energy coupling”

A

to carry out thermodynamically unfavourable reactions

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18
Q

what does ΔG = 0 mean

A

it is incompatible with life

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19
Q

do reactions reach equilibreium

A

no, as energy passes from the environment to the organism and back to the environment
This works because organisms use pathways of reactions: e.g. food molecules to excretory products
spontaneous reactions move towards equilibrium but do not reach equilibrium

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20
Q

what does life do to maintain a steady state

A

utilises series of reactions

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21
Q

what does free energy flow between

A

catabolic processes and anabolic processes allowing them to occur

22
Q

what is each step in metabolic pathways catalysed by

A

enzymes

23
Q

what do enzymes do

A

function to selectively alter the rate of particular parts of metabolic pathways

24
Q

what are intermediate metabolites

A

tend to be compartments of several pathways

there aren’t many of them compared to the number of reactions that exist in the cells of our bodies

25
Q

how much potential energy does glucose have and what does that mean

A

has a high potential energy and is used as a food molecule by many organisms

26
Q

how can glucose be degraded

A

by heating in air, releasing its potential energy as heat

starts off with high potential energy and ends with low potential energy

glucose+6O2 -> 6CO2+H2O
and releases heat

The same reaction occurs in cells but in a series of small chemical reactions facilitated by enzymes

27
Q

what do small reactions allow

A

the potential energy to be used or stored at a particular point along the pathway

28
Q

what happens when ATP is converted into ADP

A

Free Energy is released, which is harnessed from this catabolic process to drive thermodynamically unfavourable reactions (+ΔG)

29
Q

what is an exergonic reaction

A

a reaction that have a negative ∆G and release free energy

30
Q

what is an endergonic reaction

A

Reactions that have a positive ∆G and require input of free energy

31
Q

give an example of an exergonic reation

A

catabolic pathways

32
Q

give an example of an endergonic reaction

A

anabolic pathways

33
Q

why is a catabolic reaction exergonic

A

as it “saves” Free Energy within a system by forming ATP

catabolic reactions are thermodynamically favourable reactions

34
Q

why is an anabolic pathway endergonic

A

as it is “supplies” with Free Energy within a system by forming ADP through the conversion of ATP to ADP

anabolic reactions are thermodynamically unfavourable reactions

35
Q

what type of reaction is

ATP+H2O -> ADP+Pi

A

hydrolysis

36
Q

what type of reaction is

ADP+Pi -> ATP+H2O

A

condensation

37
Q

what has a higher potential energy ATP or ADP+Pi

A

ATP, so hydrolysis occurs with a decrease in Free Energy (exergonic)
ADP to ATP condensation reaction requires Free Energy input (endergonic)

38
Q

is a hydrolysis reaction endergonic or exergonic

A

exergonic

39
Q

is a condensation reaction endergonic or exergonic

A

endergonic

40
Q

ATP allows anabolic, thermodynamically unfavourable reactions, to

A

proceed through coupling of catabolic thermodynamically favourable reactions

41
Q

what is phosphoenolypyruvate (PEP)

A

produced in an intermediate step during the process of glucose releasing its potential energy when degraded

acts as an intermediate for a reaction that goes on to produce ATP during PEP to pyruvate conversion
potential energy released from PEP to pyruvate conversion is “stored” in the form of ATP

42
Q

what is the ΔG for the reaction PEP→pyruvate

A

-31.4kJ/mol

43
Q

when is the potential energy of PEP “released”

A

it is converted into pyruvate

44
Q

when is the potential energy of PEP “saved”

A

it is “saved” as potential energy in an ATP molecule

45
Q

why is ATP called the “universal currency” of Free Energy

A

because energy flows through many biological pathways by utilising phosphoryl group transfer between molecules

46
Q

why does potential energy in food molecules arise

A

because they contain large numbers of H atoms

47
Q

give examples of molecules containing large numbers of H atoms

A

carbohydrates, glucose
fatty acids, palmitate (palmitate has lots of H atoms making it similar to petroleum – another molecule that is rich in energy)

48
Q

what will the oxidation of glucose release

A

electrons that spontaneously flow through a series of intermediate steps to another chemical species, such as O2
this can be described as an electron motive force (emf)

49
Q

what is enf

A

describes that electrons can accomplish work as they pass through chemical intermediates

50
Q

from the thousands of metabolic reactions that occur within the cell, how many activated carriers of energy are used

A

a small number
this hints as the evolutionary background of metabolic processes
these activated carriers act as coenzymes in biochemical pathways to facilitate fuel oxidation and biosynthesis reactions

foundations of medicine 1 (7 decks)

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