Metabolism & Energy Production

Flashcards for reviewing lecture notes on metabolism, ATP, coenzymes, citric acid cycle, and electron transport chain.

Metabolism

The sum of all chemical reactions that take place in an organism.

Catabolism

The breakdown of large molecules into smaller ones; energy is generally released during this process.

Anabolism

The synthesis of large molecules from smaller ones; energy is generally absorbed during this process.

Metabolic Pathway

A series of consecutive reactions.

Linear Pathway

A series of reactions that generates a final product different from any of the reactants.

Cyclic Pathway

A series of reactions that regenerates the first reaction.

Mitochondria

Organelles within the cytoplasm of a cell where energy production occurs.

Matrix

The area enclosed by the inner membrane of the mitochondria where energy production occurs.

Digestion

The catabolism of food, catalyzed by enzymes in the saliva, stomach, and small intestines.

Carbohydrates

Hydrolyzed into monosaccharides beginning with amylase enzymes in saliva and continuing in the small intestine.

Stomach

The location where Protein digestion begins when stomach acid denatures the protein and pepsin begins to cleave the large protein backbone into smaller peptides.

Triacylglycerols

Emulsified by bile secreted by the liver, then hydrolyzed by lipases in the small intestines into 3 fatty acids and a glycerol backbone.

Monosaccharides, amino acids, and fatty acids

Degraded into acetyl groups, which are then bonded to coenzyme A forming acetyl-CoA.

Citric Acid Cycle

The location where acetyl CoA is oxidized to CO2 and produces energy stored as a nucleoside triphosphate and reduced coenzymes.

ATP (adenosine 5’-triphosphate)

The primary energy-carrying molecule in the body, produced by the electron transport chain and oxidative phosphorylation.

Phosphorylation

The reverse reaction where a phosphate group is added to ADP, forming ATP requiring 7.3 kcal/mol of energy.

Coupled Reactions

Pairs of reactions that occur together; the energy released by one reaction is absorbed by the other reaction.

Creatine

An amino acid byproduct, is taken by athletes as a supplement to boost their performance. It is stored in muscle tissue as creatine phosphate, a high-energy molecule.

Oxidation

A loss of electrons, or a loss of hydrogen, or a gain of oxygen.

Reduction

A gain of electrons, or a gain of hydrogen, or a loss of oxygen.

Oxidizing Agent

Causes an oxidation reaction to occur, so the coenzyme is reduced.

Reducing Agent

Causes a reduction reaction to occur, so the coenzyme is oxidized.

Coenzyme NAD+ (nicotinamide adenine dinucleotide)

An oxidizing agent; after gaining H+ and 2 e−, the reduced form of NAD+ is NADH.

Coenzyme FAD (flavin adenine dinucleotide)

An oxidizing agent. After gaining 2 H+ and 2 e−, the reduced form of FAD is FADH2

FAD

Is synthesized in cells from vitamin riboflavin.

Coenzyme A (HS-CoA)

Neither an oxidizing nor a reducing agent.

Acetyl CoA

A thioester that delivers a two-carbon acetyl group in a variety of metabolic pathways.

Citric Acid Cycle

A cyclic metabolic pathway that begins with the addition of acetyl CoA to a four-carbon substrate; produces high-energy compounds for ATP synthesis.

Citrate synthase

Reacts acetyl CoA with oxaloacetate to form citrate.

Aconitase

Isomerizes the tertiary alcohol in citrate to the secondary alcohol in isocitrate.

Step [3] of Citric Acid Cycle

Isocitrate loses CO2 in a decarboxylation reaction catalyzed by isocitrate dehydrogenase.

Step [4] of Citric Acid Cycle

Releases another CO2 with the oxidation of α-ketoglutarate by NAD+ in the presence of coenzyme A to form succinyl CoA and NADH.

Step [5] of Citric Acid Cycle

The thioester bond of succinyl CoA is hydrolyzed to form succinate, releasing energy that converts GDP to GTP.

Step [6] of Citric Acid Cycle

Succinate is converted to fumarate with FAD and succinate dehydrogenase; FADH2 is formed.

Step [7] of Citric Acid Cycle

Water is added across the double bond; this transforms fumarate into malate, which has asecondary alcohol.

Step [8] of Citric Acid Cycle

The secondary alcohol of malate is oxidized by NAD+ to form the ketone portion of oxaloacetate and NADH.

Electron Transport Chain

A multistep process using 4 enzyme complexes (I, II, III and IV) located along the mitochondrial inner membrane.

Reduced coenzymes (NADH and FADH2)

Are reducing agents, and can donate H+ and e- when oxidized.

ATP synthase

Catalyzes the phosphoryation of ADP into ATP.

Hydrogen cyanide (HCN)

Binds to the Fe portion of the cytochrome oxidase, preventing O2 from being reduced to H2O, halting the electron transport chain and energy production.