Biochemistry Lecture - Biochemical Energy Production

Reviewer for Biochemical Energy Production

Nutritional Requirements

macronutrients and micronutrients

Macronutrients

Nutrients needed by the body in relatively large amounts, i.e. carbohydrates, lipids, and proteins (measured in gram quantity daily)

Micronutrients

Nutrients needed by the body in only small amounts, i.e. vitamins and minerals (measured in milligrams and micrograms daily)

Reference Daily Intakes (RDIs)

A set of standards for PROTEINS, VITAMINS, and MINERALS used on food labels as part of daily values.

Daily Reference Values (DRVs)

A set of standards for NUTRIENTS and FOOD COMPONENTS (such as fats and fibers) that have important relationships with health. It is used on food labels as a part of the Daily Values.

Daily Values (DVs)

Reference values developed by the FDA specifically for use on the food labels. Represents both RDIs and DRVs.

Carbohydrates

The most ideal and primary energy source.

Lipids

More concentrated source of energy; contain some fat-soluble vitamins; source of essential fatty acids.

Proteins

Responsible for the maintenance and repair of cells; synthesis of N- containing compounds of the body.

RDI for Protein in Pregnant Women

60g

RDI for Protein in Nursing Mothers

65g

RDI for Protein in Infants Under 1

14g

RDI for Protein in Children Ages 1 to 14

16g

RDI for Protein in Adults

50g

Vitamins

Organic substances that are generally classified as either fat-soluble or water soluble.

Minerals

Metals or nonmetals used in the body in the form of ion or compounds. Can be toxic in great amounts.

Major Minerals

Minerals found in the body in quantities greater than 5g, e.g. Ca, P, K, S, Na, Cl, Mg.

Trace Minerals

Minerals found in the body in quantities smaller than 5g, e.g. Fe, Mn, Cu, I.

Metabolism

Is the sum of all chemical reactions that occur in a living organism. Provides the source of energy needed by an organism.

Catabolism

All metabolic reactions in which large biomolecules are broken down to smaller ones. Energy is released in this process.

Anabolism

All metabolic reactions in which small biochemical molecules are joined together to form larger ones. Energy is used in this process.

Metabolic Pathway

A sequence of reactions used to produce one product or accomplish one process.

Linear Pathway

Continuous series of reactions in which the product of one reaction is the reactant in the next.

Circular Pathway

The final product is one of the reactants used to begin the series again.

Spiral Pathway

A series of repeated reactions is used to break down or build up a molecules.

Adenosine Phosphate

AMP, ATP, ADP. Functions as both a source of phosphate group and a source of energy.

Uridine Triphosphate (UTP)

Involved in carbohydrate metabolism.

Guanosine Triphosphate (GTP)

Involved in protein and carbohydrate metabolism.

Cytidine Triphosphate (CTP)

Involved in lipid metabolism.

Flavin Adenine Dinucleotide (FAD)

A coenzyme required in numerous metabolic redox reactions. The flavin subunit is the active form (accepts and donates electrons)

Nicotinamide Adenine Dinucleotide (NAD)

A coenzyme that acts as a proton (H+) and electron carrier in cellular respiration. It can cycle between its + and -H forms, depending on the reaction it takes part in

Coenzyme A

A derivative of vitamin B, it is an enzyme in respiration that helps form acetyl- CoA.

ATP-ADP Cycle

Motion active transport biosynthesis, ADP, Oxidation of fuel molecules, ATP

Biochemical Energy Production

Process of converting food into usable energy.

Stage 1

Digestion. Large molecules are chemically broken down through hydrolysis. Begins in mouth, continues in the stomach, and is completed in small intestine. Carbohydrates are broken down into glucose and monosaccharides, proteins into amino acids, and fats and oils into fatty acids and glycerol.

Protease

Enzymes that hydrolyze proteins into amino acids.

Carbohydrase

Enzyme that breaks down disaccharides and polysaccharides into monosaccharides.

Lipases

Enzymes that break down lipids into fatty acids and glycerols.

Stage 2

Acetyl Group Formation. Monosaccharides, fatty acids, and certain amino acids are further oxidized into Acetyl CoA. Occurs in cytosol (glucose metabolism) as well as mitochondria (fatty acid metabolism).

Stage 3

Citric Acid Cycle. Also known as Tricarboxylic Acid Cycle (TCA cycle), and Krebs Cycle. It is the series of biochemical reactions in which the acetyl portion of acetyl CoA is oxidized to carbon dioxide and the reduced coenzymes FADH2 and NADH are produced.

Hans Adolf Krebs

Credited with mapping out the citric acid cycle of cellular respiration.

Step 1: Condensation

The acetyl group from acetyl CoA is removed by the enzyme citrate synthase and is attaches it to oxaloacetate to form CITRATE. CoA is discarded.

Step 2: Isomerization

Aconitase removes a water molecule from the citrate transforming it into cis-aconitate. Water is added to form an isomer of citrate called ISOCITRATE.

Step 3: Oxidation and Decarboxylation

Isocitrate is oxidized by NAD+ using the enzyme isocitrate dehydrogenase, it then decarboxylates to form a-KETOGLUTARATE. CO2 and H+ are also released.

Step 4: Oxidation and Decarboxylation

a-Ketoglutarate is further oxidized by another NAD+ using the enzyme ketoglutarate dehydrogenase. The resulting molecules joins with CoA to form SUCCINYL-CoA. CO2, NADH, and H+ are also released.

Step 5: Phosphorilation

The CoA from Succinyl-CoA is displaced by a phosphate group to form SUCCINATE using succinyl-CoA synthase. A GDP also reacts forming one GTP.

Step 6: Oxidation

Succinate is oxidized by FAD using succinate dehydrogenase to form FUMARATE and FADH2.

Step 7: Hydration

Fumarate is catalyzed by fumarase through hydration (adding of H2O) and produces MALATE.

Step 8: Oxidation

Malate is oxidized using malate dehydrogenase, reacts with NAD+, and produces OXALOACETATE, NADH, and H+

Total NADH Produced in Citric Acid Cyle per 1 Acetyl-CoA

3

Total FADH2 Produced in Citric Acid Cyle per 1 Acetyl-CoA

1

Total ATP Produced in Citric Acid Cycle per 1 Acetyl-CoA

1 GTP

ATP High

ATP inhibits the activity of citrate synthase.

ATP Low, ADP High

ADP activates citrate synthase, cycle proceeds.

Isocitrate Dehydrogenase Regulation

NADH acts as an inhibitor while ADP as an activator.

Acetyl-CoA

Fuels the citric acid cycle. Is obtained from the breakdown of carbohydrates, lipids, and proteins.

C=O

NAD is the oxidizing agent.

C=C

FAD is the oxidizing agent.

Riboflavin B2

Electron carrier for succinate dehydrogenase.

Niacin (Nicotinamide) B3

Electron carrier for isocitrate dehydrogenase, a-ketoglutarate dehydrogenase, and malate dehydrogenase.

Pantothenic Acid B5

Forms Acetyl CoA

Thiamine B1

Coenzyme for pyruvate dehydrogenase and a-ketoglutarate dehydrogenase.

Stage 4

Electron Transport Chain and Oxidative Phosphorylation.

Electron Transport Chain (ETC)

Facilitates the passage of electrons trapped in FADH2 and NADH during citric cycle. It is a series of biochemical reactions in which intermediate carriers (protein and non-protein) aid in the transfer of electrons and hydrogen ions from NADH and FADH2.

Molecular Oxygen O2

Receiver of electrons in ETC

Overall ETC Reaction

2 hydrogen + 2 electrons + 1/2 molecular oxygen (O2) -> H2O + Energy

Complex 1

NADH-coenzyme Q reductase. NADH from citric acid cycle is the source of electrons for this complex. It contains >40 subunits including flavin mononucleotide (FMN) and several iron-sulfur protein clusters (FeSP).

Complex 2

Succinate-coenzyme Q reductase. It is smaller than complex 1, and contains only four subunits including two iron-sulfur protein clusters (FeSP). It generates FADH2. CoQ is the final recipient of the electrons from FADH2.

Complex 3

Coenzyme Q - cytochrome C reductase. It contains 11 different subunits, several iron-sulfur proteins and cytochromes are electron carriers in this complex.

Cytochrome

A heme iron protein in which reversible oxidation of an iron atom occurs.

Complex 4

Cytochrome C oxidase. It contains 13 subunits including two cytochromes. The electrons flow from cyt c to cyt a to cyt a3.

Final Stage of ETC

molecular oxygen + 4 hydrogen + 4 electrons - > water.

Coenzyme Q

Brings electrons from complex I to complex III.

Cytochrome C

Brings electrons from complex III to complex IV.

Oxidative Phosphorylation

Process by which ATP is synthesized from ADP and a Phosphate Group using the energy released in the electron transport chain.

Coupled Reactions

Are pairs of biochemical reactions that occur concurrently in which energy released by one reaction is used by the other reaction.

Proton Pumps in ETC

Complex I, III, and IV. Transfers protons from the matrix side to the intermembrane space.

For Every Two Electrons Passed Through ETC

4 protons cross through complex I, 4 through complex III, and 2 through complex IV.

1 M FADH2 Oxidized in ETC

1.5 M ATP is Formed

1 M GTP

! M ATP is formed