Nutrient Role in Bioenergetics

Chapter 4

Bioenergetics

Bioenergetics refers to the flow of energy within a living system.

Energy is the capacity to do work. Aerobic reactions require oxygen. Anaerobic reactions do not require

oxygen.

Bioenergetics

First law – Energy is neither created nor destroyed, but instead, transforms from one state to another without being used up.

Bioenergetics

There are six forms of interchangeable energy states:• Chemical• Light • Electric• Mechanical• Heat • Nuclear

Bioenergetics

The process of photosynthesis is a chemical reaction.

Chlorophyll absorbs radiant energy: To synthesize glucose from carbon

dioxide and water To release oxygen.

Solar energy and photosynthesis provide power to the animal world through food and oxygen.

Bioenergetics

Photosynthesis

What is the equation for the chemical reaction of photosynthesis?

Bioenergetics

Respiration is the reverse of photosynthesis.

C6H12O6 + O2 → 6CO2 + 6H2O

Cellular Respiration

Organism transforms the chemical energy into a form it can use. Cellular Respiration-Step by step process

Glucose Lipids Amino acids

Heat

Bioenergetics

Takes one of three forms:• Mechanical work of muscle contraction• Chemical work for synthesizing cellular

molecules• Transport work that concentrates diverse

substances in body fluids

Bioenergetics

Potential energy Energy associated with a substance’s

structure or position. Kinetic energy

Energy of motion. Potential energy and kinetic energy

The total energy of any system.

Bioenergetics

Adenosine Triphosphate

Bioenergetics

Cellular Oxidation–Reduction Reactions Constitute the mechanism for energy

metabolism Redox reactions power the transfer

process of energy

Bioenergetics

Oxidation–reduction reactions couple:• Oxidation = a substance loses electrons

Transfer oxygen, hydrogen, or electrons

• Reduction = a substance gains electrons Atoms gain an electron-reducing valence

Coupled Reactions

Coupled Reactions

Reduction Reaction 2C3H4O3 + 2H → 2C3H6O3

LDH

Pyruvate (gains 2 e-) → Lactate

Coupled Reactions

Oxidation Reaction 2C3H6O3 - 2H → 2C3H4O3

LDH

Lactate (loses 2 e-) Pyruvate

Bioenergetics

ATP – energy currency Potential energy extracted from food

ATP Chemical energy extracted for biologic

work Cells Muscle contraction

Phosphate Bond

Stored or potential energy High energy bonds ATP – hydrolysis

ATP + H2O → ADP + P – 7.3 kCal/mole ATPase

Bioenergetics

Bioenergetics

Phosphocreatine (PC) is also a high-energy phosphate compound. ATP-PC (phosphagens) Releases energy when bonds between

creatine and phosphate are broken. Sustains all out exercise ~ 5-8 s Resynthesis of ATP used – reservoir Stored in muscle - anaerobic

Bioenergetics

Cells store 4-6 times more PCr than ATP Muscle

Provide a reservoir of high-energy phosphate bonds ATP + H2O ADP + Pi

ATPase

ADP + C~P ATP + C Creatine kinase

Bioenergetics

Phosphorylation Refers to energy transfer through

phosphate bonds Oxidative phosphorylation

Synthesizes ATP by transfer of electrons NADH and FADH2

Cellular Oxidation-Reduction Reactions

Mechanism for energy metabolism Involves transfer of hydrogen atoms

Loss of hydrogen: oxidation Gain of hydrogen: reduction

Cellular Oxidation

Mitochondria NAD and FAD → NADH and FADH2

Cytochromes – Electron Transport Chain (ETC)

Transfer of electrons (H+) Energy conserved – high energy phosphate

bonds Figure 4.11

Bioenergetics

Sources for ATP formation include:• Glucose derived from liver glycogen

Glycogenolysis Triacylglycerol and glycogen stored in muscle

• Free fatty acids - circulating Triacylglycerol in liver, adipocytes Lipoprotein complexes - circulating

• Amino acids Intramuscular and liver-derived carbon skeletons

Bioenergetics