BIOENERGETICS

Bioenergetics

- transfer and utilization of energy

- Changes in free energy (ΔG)

ENTHALPY, ΔH

- change in heat content

ENTROPY, ΔS

- change in randomness or disorder

1 mol/L, pH = 7

Standard conditions: reactants and products are at a concentration of

CHANGE IN GIBBS FREE ENERGY (ΔG)

predicts the direction of a reaction at constant temperature and pressure

(-) ΔG

: net loss of energy, rxns proceeds spontaneously (A is converted to B), exergonic

 Pdt has a lower free E than the substrate

(+) ΔG

net gain of energy, not spontaneous, endergonic

 Pdt has a higher free E than the substrate

ΔG= 0:

reactions are in equilibrium

additive

The ΔGs are ______ in any sequence of consecutive reactions (same with ΔGo)

METABOLISM

Energy-rich molecules (e.g. glucose) are metabolized by aseries of oxidation rxns ultimately yielding CO2 and H2O

o Metabolic intermediates of these rxns donate e-s to specific coenzymes – NAD+ and FAD to form energyrich reduced coenzymes – NADH and FADH2

 E-rich coenzymes donate a pair of e-s to a specialized set of e- carriers → ETC

o As e-s are passed down the electron transport chain, they lose much of their free energy

OXIDATIVE PHOSPHORYLATION

Is the process by which cells use enzymes to oxidize nutrients, releasing energy to produce ATP (adenosine triphosphate).

MITOCHONDRION

Electron transport and ATP synthesis by OP proceed continuously in all tissues that contain mitochondria

 E-rich coenzymes donate a pair of e-s to a specialized set of e- carriers → ETC

Electron transport chain

present in the inner mitochondrial membrane

o Matrix of the Mitochondrion

 Gel-like solution in the interior of the mitochondria

 50% protein

Is a series of protein complexes embedded in the inner mitochondrial membrane that transfer electrons from electron donors to electron acceptors via redox reactions. This process releases energy, which is used to create a proton gradient across the membrane, ultimately driving ATP synthesis.

NAD+ and FAD

oxidized forms of the coenzymes that are required as H acceptors

ADP and Pi

used to produce ATP

Complex V

catalyzes ATP synthesis hence it is also called ATP Synthase. It also contains

 domain (Fo): spans the inner MM

 domain (F1): appears as a sphere

Coenzyme Q (CoQ)

Quinone derivative → also called ubiquinone because it is ubiquitous in biologic systems

also known as ubiquinone, is a naturally occurring, lipid-soluble antioxidant found in all cells, particularly abundant in mitochondria. It plays a crucial role in the electron transport chain, where it acts as a key component in the process of generating energy (ATP). also functions as an antioxidant, protecting cells from damage caused by free radicals.

Cytochromes

 Each contain a heme group (porphyrin ring + iron)

 Cytochrome C: associated with the outer face of the inner membrane; mobile carrier of e-s

are redox-active proteins containing a heme group with a central iron atom, crucial for electron transport in cellular respiration and photosynthesis. They act as electron carriers, transferring electrons in redox reactions.

Cytochrome a + a3

 Only electron carrier wherein the heme iron has an available coordination site that can act directly with O2 → CYTOCHROME OXIDASE

Site-specific inhibitors

 prevent the passage of electrons by binding to a component of the chain, blocking the oxidation/reduction reaction

Free energy

is released as electrons are transferred from an electron donor (reducing agent or reductant) to an electron acceptor (oxidizing agent or oxidant)

Chemiosmotic Hypothesis

 explains how the free energy generated by the transport of electrons by the electron transport chain is used to produce ATP from ADP + P

Chemiosmosis

 driven by the flow of electrons down

Electron transport

is coupled to the phosphorylation of ADP by the transport (“pumping”) of protons (H+) across the inner mitochondrial membrane → creates:

 ELECTRICAL GRADIENT (More positive charges on the outside)

 pH GRADIENT (Outside of the membrane has a lower pH)

PHOSPHATE CARRIER

 Transports Pi (cytosol → mitochondria)

ADENINE NUCLEOTIDE CARRIER

 Imports 1 ADP (cytosol → mitochondria)

 Exports 1 ATP (matrix → cytosol)

2.5 ATPs

1 NADH =

1.5 ATPs

1 FADH2 =

30-32 ATP per glucose

: max ATP yield estimated by most current sources

 Accounts for the necessary transport of ADP (into the mitochondria) and ATP (out of the mtc)

38 ATP

: assumes that every single proton pumped in the ETC goes towards ATP synthesis

2 ATP = 2 ATP

2 NADH = 3-5 ATP

GLYCOLYSIS

2 NADH = 5 ATP

PYRUVATE OXIDATION

2 ATP = 2 ATP

6 NADH = 15 ATP

2 FADH = 3 ATP

CITRIC ACID CYCLE