What is bioenergetics
Quantitative study of energy transduction occurring in living cells. Study of the nature and function of the chemical processes that are responsible for these energy transduction
What is the first law of thermodynamics
energy cannot be created or destroyed, but it can be converted from one form to another
What is gibbs free energy
the amount of energy in a system available to do work.
What does free energy change derive from
- Changes in heat content (DH) = enthalpy change
- Changes in the state of order (DS) = entropy change
What doe sit mean if delta G is negative
energy is liberated and the reaction is said to be exergonic and can occur spontaneously
What does it mean if delta G is positive
reaction is endergenic and requires energy input
What biological processes do we require energy for
- Mechanical work e.g., muscle contraction
- Active transport
- Synthesis of complex biomolecules from simple precursors
- Also signal transduction (environmental responses), generation of light (fire flies) and electricity (eels)
How is energy obtained
- Phototrophs – obtain energy by trapping light e.g., photosynthesis
- Chemotrophs – obtain energy by oxidation of food stuffs e.g., catabolism
Where do chemoorganotrophs ge4t their energy from
organic compounds by oxidation (e.g., respiration)
Calories in food groups
- Fats – 9kcal/g
- Carbohydrates – 4kcal/g
- Proteins – 4kcal/g
- Alcohol – 7kcal/g
Why do we control the extraction of energy from food
so we don’t release all the energy at once and increase body temperature excessively
Extraction of energy from food
- Large molecules broken down into smaller units. No useful energy captured
- Small molecules degraded into a few simple units that play a role in central metabolism. Some ATP generated
- ATP produced from the complete oxidation of simple units by the final common pathways for oxidation of fuel
Reduction reactions as an organic compound is degraded
electrons flow through intermediates to oxygen (the final electron acceptor) or are used to reduce other cellular components
Biological redox reaction
1) 1. Direct electron transfer e.g. Fe2+ + Cu2+ ——> Fe3+ + Cu+
- Direct transfer of hydrogen ions e.g.AH2 + B ——-> A + BH2
- Direct combination with oxygen as with mono-oxygenase reactions e.g.R-CH3 + ½O2 ——–> R-CH2OH
What do dehydrogenases do
oxidise organic compounds by abstracting 2H+ and 2 e- and passing them to a mobile carrier in biodegradation and energy abstraction (I.e., respiration)
How can dehydrogenases reduce
can reduce organic compounds by adding 2H+ and 2 e- from a mobile electron carrier typically in biosynthetic pathways
Synthesis and use of NADH
produced in catabolic reactions and by TCA cycle. Used in the generation of ATP by OxPhos. Usually found inside the mitochondria
Use and synthesis of NADPH
produced by PPP. Used primarily for reductive biosynthesis (e.g., FA synthesis). Usually found in the cytoplasm
Use and synthesis of FADH2
produced in catabolic reactions and by TCA cycle. Used in the generation of ATP by OxPhos (generates less energy than NADH)
What bonds does ATP contain
2 phosphoanhydride bonds on its triphosphate unit
ATP equations
ATP + H2O ——> ADP + Pi + energy. ATP + H2O ——–> AMP + PPi + energy
Stability of free energy
free energy is negative and therefore thermodynamically unstable but is kinetically stable.
Use of ATP
principal immediate donor of free energy in biological systems rather than long-term storage form. Consumed within minutes of formation, very high turnover. Around 50kg of ATP consumed in 24h period
How is ATP produced - substrate level phosphorylation
Transfer of phosphoryl group from metabolites with high – phosphoryl transfer potential to ADP producing ATP
