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Bioenergetics And Transformation > Bioenergetics and ATP synthesis > Flashcards

Bioenergetics and ATP synthesis Flashcards

1
Q

What is bioenergetics ?

A

The quantitative study of energy transduction occurring in living cells

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2
Q

What is the first law of thermodynamics ?

A

It states that energy cannot be created or destroyed but it can be converted from one form to another

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3
Q

What is an exergonic reaction ?

A
  • if ΔG is negative this means energy is liberated and the reaction is energetically favourable and so it is exergonic
  • exergonic reactions can occur spontaneously
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4
Q

What is an endergonic reaction ?

A
  • if ΔG is positive the reaction will require an energy input in order to occur and it is said to be endergonic
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5
Q

What does it mean if ΔG is 0 ?

A
  • the system is at equilibrium
  • no net change can take place
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6
Q

Describe ΔG in relation to reaction pathways and rates of reaction

A
  • the ΔG of a reaction is the same no matter the pathway that the reaction takes
  • ΔG doesn’t provide any information on the rate of reaction
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7
Q

Why do living organisms need energy ?

A
  • living organisms require continual input of free energy because many biological processes are endergonic
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8
Q

Give some examples of biological processes which are endergonic

A
  • muscle contraction
  • active transport
  • biosynthesis
  • signal transduction
  • generation of light and electricity
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9
Q

How do phototrophs obtain energy ?

A
  • obtain energy by trapping light
    e.g. photosynthesis
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10
Q

How do chemotrophs obtain energy ?

A
  • obtain energy by oxidation of food
    e.g. through catabolism
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11
Q

What is metabolism ?

A

anabolism + catabolism

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12
Q

How do chemoorganotrophs obtain energy ?

A
  • obtain energy from organic compounds by oxidation
    e.g. C6H12O6 + 6O2 → 6CO2 + 6H2O
  • this will yield ~ 30-32 ATP
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13
Q

What are the main energy sources for chemoorganotrophs specifically humans ?

A
  • fats : 9 kcal/g
  • carbohydrates : 4 kcal/g
  • proteins : 4 kcal/g
  • alcohol : 7 kcal/g
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14
Q

Why is it important that humans have controlled extraction of energy from food ?

A
  • don’t want to release all the energy at once
  • don’t want to increase body temperature excessively
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15
Q

How is energy extracted from food ?

A

Stage 1 - Large molecules broken down into smaller units. No useful energy is captured

Stage 2 - Small molecules are degraded into a few simple units that play a role in central metabolism. Some ATP is generated ~ 5-10%

Stage 3 - ATP (~90-95%) is produced from the complete oxidation of simple units by the final common pathways for oxidation of fuel. ~90-95%

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16
Q

What happens when an organic compound is degraded ?

A

when an organic compound is degraded (oxidised) :
- electrons flow through intermediates to oxygen (the final electron acceptor)
- or they are used to reduce other cellular components

17
Q

What happens in a redox reaction ?

A
  • the electron donor is the reducing agent and is oxidised
  • the electron acceptor is the oxidising agent and is reduced
18
Q

Give the different types of biological redox reactions with examples

A
  1. Direct electron transfer
    e.g. Fe2+ + Cu2+ <> Fe3+ + Cu+
  2. Direct transfer of hydrogen ions e.g. AH2 + B <> A + BH2
  3. Direct combination with oxygen e.g. R-CH3 + ½O2 > R-CH2OH
  4. The most common involve dehydrogenation
19
Q

How do dehydrogenase enzymes work ?

A
  • oxidise organic compounds by abstracting 2H+ & 2 electrons and passing them to a mobile carrier in biodegradation and energy abstraction ( i.e. respiration)
  • reduce organic compounds by adding 2 H+ & 2 electrons from a mobile electron carrier typically in biosynthetic pathways
20
Q

Describe NADH

A
  • produced in catabolic reactions and by the Krebs cycle
  • used in the generation of ATP by oxidative phosphorylation
  • usually found inside the mitochondria
21
Q

Describe NADPH

A
  • produced by PPP
  • used primarily for reductive biosynthesis (e.g. FA synthesis)
  • usually found in the cytoplasm
22
Q

Describe FADH2

A
  • produced in catabolic reactions and by the Krebs cycle
  • used in the generation of ATP by oxidative phosphorylation
  • usually found inside the mitochondria
23
Q

Give some examples of electron carriers

A
  • NADH
  • NADPH
  • FADH2
24
Q

What is the energy currency of a cell ?

A

ATP

25
Q

Describe the structure of ATP

A
  • it is an energy rich molecule with high phosphoryl transfer potential
  • it contains 2 phosphoanhydride bonds on its triphosphate unit
26
Q

How does ATP release energy ?

A

the hydrolysis of bonds will yield energy which is used in endergonic processes

27
Q

Describe the stability of ATP

A
  • it is thermodynamically unstable because ΔG is negative
  • it is kinetically stable because in the absence of a catalyst the breakdown is very slow
28
Q

Describe the ATP-ADP cycle

A
  • it is the fundamental mode of energy exchange in biological systems
  • ATP is the principal immediate donor of free energy in biological systems rather than long-term storage form
  • it is consumed within minutes of formation but it has a very high turnover
  • around 50Kg of ATP is consumed in a 24h period
29
Q

How is ATP produced ?

A
  • substrate level phosphorylation : the transfer of a phosphoryl group from metabolites with high phosphoryl transfer potential to ADP which produces ATP
  • oxidative phosphorylation : electrons are transferred from fuels via electron carriers to the final electron acceptor (oxygen)
30
Q

Where does oxidative phosphorylation happen ?

A
  • in the mitochondria
  • in animals over 90% of ATP is formed by this method
31
Q

What are the 4 main functions of metabolism ?

A
  • obtaining energy e.g. ATP
  • converting nutrients into own characteristic molecules
  • polymerising monomeric precursors e.g. polysaccharides
  • synthesising and degrading molecules required for special cellular functions e.g. intracellular messengers
32
Q

What are the 2 classes of metabolic pathways ?

A
  • catabolic reactions : transform fuels into usable cellular energy (breakdown)
  • anabolic reactions : utilise the useful energy formed by catabolism to generate complex structures from simple ones (synthesis)
33
Q

Give some differences between catabolic and anabolic reactions

A
  • degradative v synthetic
  • produces ATP v requires ATP
  • exergonic v endergonic
  • produces electrons v needs electrons
  • generates NADH and FADH2 v uses NADPH

Bioenergetics And Transformation (10 decks)

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