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Biochemistry > Energy > Flashcards

Energy Flashcards

1
Q

The energy associated with any system can be described by

A
  1. H = G + TS

H = Enthalpy (total heat energy of system)

G = (Gibb’s) Free energy

S = Entropy (level of randomness in system)

T = Temperature

  1. chemical reaction takes place there is a change (represented by Triangle) in energy in the system

DH = DG + TDS

(D For delta)

DG is amount of energy available to use

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2
Q

Thermodynamically favourable reactions:

A

DG is -ve, described as exergonic [gives out energy]

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3
Q

Thermodynamically unfavourable reactions:

A

DG is +ve, described as endergonic

[require energy. Not spontaneous]

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4
Q

DGº

A

is a constant equal to DG under specific conditions (reactants and products at 1M; pH 7.0)

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5
Q

Coupled reactions

A

Can link an endergonic reaction with an exergonic reaction so that both take place

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6
Q

Biological Energy

A
  1. Biological systems store energy in chemical form
  2. Major form in which energy is stored is ATP (adenosine triphosphate)
  3. Made of three components

Adenine, Ribose, 3 phosphates

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7
Q

ATP with 3, 2 and 1 phosphate

A

Adenosine triphosphate (ATP)

Adenosine diphosphate (ADP)

Adenosine monophosphate (AMP)

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8
Q

ATP

A
  1. part of a family of nucleotides
  2. Can release energy to drive energetically less favourable reactions
  3. Hydrolysis of bonds between phosphate groups releases high amount of energy
  4. high energy compounds can drive ATP synthesis e.g. phosphocreatine -> creatine + ATP
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9
Q

2 Mechanisms of ATP synthesis from ADP

A
  1. Substrate level Phosphorylation

Oxidative Phosphorylation

  1. ultimately involve addition of a phosphoryl group to ADP replacing the terminal H
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10
Q

Substrate level phosphorylation

(Conversion of ADP to ATP using a phosphate from a phosphorylated immediate, the latter being one of the substrates of the reaction)

4 points

A
  1. Involves phosphoryl group transfer
  2. In slp the phosphoryl group is transferred to ATP from a compound which is hydrolysed
  3. Hydrolysis of compound has a free energy of more negative than 31 kJ/mol
  4. coupled reaction catalysed by kinase

Exogenic
ADP + Pi -> ATP + H2O

Endogenic
?-Phosphate + ADP -> ? + ATP

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11
Q

Substrate level phosphorylation
example
2 points

A
  1. At rest, muscle only has enough ATP to contract for less than a second
  2. Creatine phosphate is major source of phosphoryl groups for ATP regeneration during short intense burst of exercise

Creatine phosphate + ADP <=> ATP + creatine

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12
Q

Oxidative phosphorylation

(Generation of ATP from ADP and inorganic phosphate via the electron transport chain)

4 points

A
  1. The synthesis of ATP that occurs when the energy released by oxidation of NADH and FADH2 through an electron transport chain, with oxygen acting as the terminal electron acceptor, is used to phosphorylate ADP
  2. NADH and FADH2 are coenzymes that function as H-carriers
  3. In eukaryotes the process is associated with the inner mitochondrial membrane
  4. In prokaryotes the process is associated with the cell membrane
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13
Q

Oxidative phosphorylation - Mitochodri

4 points

A
  1. Sub-cellular organelles
  2. Present in cytoplasm of all eukaryotic cells
  3. Variable shape and size - approximately 1-2 mm x 0.1-0.5 mm
  4. Surrounded by a double membrane
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14
Q

Oxidative phosphorylation - Mitochodri outermembrane

A

Smooth, inelastic, freely permeable to small molecules - salts, sugars, short chain carboxylic acids, ATP/ADP, NAD+/NADH

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15
Q

Oxidative phosphorylation - Mitochodri inner membrane

4 points

A
  1. Thrown into folds called cristae
    Inner surface covered in “bumps” called elementary particle
  2. Permeable only to limited range of compounds - urea, glycerol, short chain carboxylic acids
  3. Specific carrier proteins transport other compounds
  4. Enzymes for electron transport embedded in the membrane
  5. Matrix
    Fluid filled

Contains enzymes for TCA
cycle and b-oxidation

Contains mitochondrial DNA and RNA

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16
Q

Oxidation and Reduction

6 points

A
  1. OIL RIG
  2. Oxidation - Loss of H; gain of O; loss of e
  3. Reduction - Gain of H; loss of O; gain of e
  4. Cannot have oxidation without reduction
  5. An oxidation/reduction reaction is made up of two redox couples
  6. A redox couple is made up of an electron acceptor and an electron donor
17
Q

Electrode potential (Eo’)

The tendency to gain or lose electrons. It is measured in volts relative to H.

A
  1. Electrons move from most -ve electrode potential to most +ve
  2. The change in electrode potential (DEo´) for an oxidation/reduction reaction is the difference between the electrode potentials for the two redox couples
  3. DEo´ is related to DG°´by the equation
    DG°´ = -nFDEo´
n = number of electrons transferred
F = Faraday’s constant
18
Q

Oxidative phosphorylation

Respiratory (Mitochondrial electron transport chain)

2 points

A
  1. Composed of a number of hydrogen and electron carriers

2. Within the chain each carrier is successively reduced and then oxidised as H or e are passed between them

19
Q

Oxidative phosphorylation

Respiratory (Mitochondrial electron transport chain)

4 coenzymes (hydrogen carriers)

2 points

A
  1. CoQ/CoQH2 (Coenzyme Q)
  2. FAD/FADH2 (Flavin adenine dinucleotide)
  3. FMN/FMNH2 (Flavin mononucleotide)
  4. NAD+/NADH+H+ (Nicotinamide adenine dinucleotide)
20
Q

Oxidative phosphorylation

Respiratory (Mitochondrial electron transport chain)

5 cyochromse (electron carriers)

A 
cyta
cyta3
cytb
cytc
cytc1
21
Q

Oxidative phosphorylation

Respiratory (Mitochondrial electron transport chain)

order of the carriers in the respiratory chain

A
  1. NADH
  2. FMN
  3. CoQ
  4. Cytb
  5. Cytc1
  6. Cytc
  7. cyta+a3
  8. O2
22
Q

Oxidative phosphorylation

Respiratory (Mitochondrial electron transport chain)

Complex 1

7 points

A
  1. NADH passes two electrons to FMN reducing it to FMNH2
  2. Accompanied by uptake of two H+ from mitochondrial matrix
  3. FMNH2 transfers electrons to FeS clusters.
  4. Fe3+ (Ferric) ions reduced to Fe2+(Ferrous)
  5. Fe2+(Ferrous) transfers electrons to CoQ
  6. CoQ reduced to CoQH2 or ubiquinol
  7. Energy used to pump 4 H+ across the inner membrane from the matrix to the inter membrane space

Complex I acts as a proton pump

23
Q

Oxidative phosphorylation

Respiratory (Mitochondrial electron transport chain)

complex III

5 points

A
  1. CoQH2 passes its electrons to heme group of cytb reducing Fe3+ to Fe2+
  2. Cytb Fe2+ transfers its electrons to FeS cluster of complex III
  3. Fe2+ S transfers its electrons to heme group of cytc1
  4. Cytc1 Fe2+ transfers electrons to heme group of cytc
  5. Energy released enough to pump 4 more H+ across the inner membrane
24
Q

Oxidative phosphorylation

Respiratory (Mitochondrial electron transport chain)

Complex IV

6 points

A
  1. Cytc Fe2+ transfers electrons to cyta reducing Cu2+ to Cu+
  2. Cyta transfer electrons via Cu+ to its heme group.
  3. Cyta transfer electrons from its heme group to cyta3 reducing Cu2+ to Cu+
  4. Cyta3 transfer electrons via Cu+ to its heme group
  5. Electrons transferred from Cyta3 heme group to oxygen giving water.
  6. Energy released enough to pump 2 more H+ across the inner membrane
25
Q

Oxidative phosphorylation

Respiratory (Mitochondrial electron transport chain)

Complex II

6 points

A
  1. Succinate is oxidised to fumarate by succinate dehydrogenase.
  2. Two electrons released generate FADH2
  3. FADH2 transfers its electrons to FeS cluster.
  4. Fe2+S transfers electrons to CoQ to reduce it to COQH2
26
Q

Oxidative phosphorylation

Respiratory (Mitochondrial electron transport chain)

4 points

A
  1. Oxidation of NADH+H+ through the respiratory chain (mitochondrial electron transport chain) generates sufficient energy to synthesise 3 ATP/mole
  2. Oxidation of FADH2 through the respiratory chain generates sufficient energy to synthesise 2 ATP/mole
  3. ATP synthesis depends on the action of a reversible ATPase - ATP synthase
  4. The electron transport chain and ATP synthesis are linked through a process described as the chemiosmotic mechanism
27
Q

Chemiosmotic mechanism Depends on

5 points

A
  1. A membrane impermeable to H+ and other inorganic ions
  2. Transfer of H+ across the membrane
  3. In mitochondria H+ move from matrix to intermembrane space associated with electron transport
  4. Dissipation of proton gradient by transport of H+ through the ATP synthase
  5. ATP only synthesised when linked to H+ transport
28
Q

ATP synthase

A
  1. Requires 3 H+ to be transported through ATP synthase for each ATP generated

Equivalent to 3ATP/NADH and 2ATP/FADH2

  1. But
    - H+ used to transport ADP into mitochondrial matrix for phosphorylation
    - Sometimes ATP used to transport NADH from cytoplasm into mitochondrion
    - Now believe 2.5 ATP/NADH and 1.5 ATP/FADH2 represent true net gain of ATP
29
Q

Inhibitors of oxidative

A
  1. Antimycin A – antibiotic. Works by inhibiting etc at complex III. Used as an antibiotic - acts as a poison to bacteria.
  2. Cyanide, carbon monoxide – poisons. Prevents final stage of etc by inhibiting cytochrome oxidase
  3. Oligomycin – antibiotic. Inhibits link between e.t.c. and phosphorylation of ADP to ATP by inhibiting ATP synthase. Used as an antibiotic - acts as a poison to bacteria.

Biochemistry (17 decks)

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