Chapter 4: Cellular Metabolism

Catalysts

________: Chemical substances that accelerate reaction rates without affecting the products of the reaction and without being altered or destroyed by the reaction.

Troponin

________ requires calcium to perform its function.

Metabolic processes

________ must occur at biologically acceptable temperatures, which are too low for life.

Anaerobes

________: Those that employ another molecule as the final electron acceptor.

Cellular metabolism

________: Refers to the collective chemical processes that occur within living cells to accomplish these activities.

Aerobes

________: Those that use molecular oxygen as the final electron acceptor.

hydrogen atom

A(n) ________ is attached to one subunit and a hydroxyl- (OH) unit is attached to another.

Heterotrophs

________: Organisms that can not synthesize their own food but must obtain nutrients from the environment, including animals, fungi, and many single- celled organisms.

Cellular respiration

________: The oxidation of fuel molecules to produce energy with molecular oxygen as the final electron acceptor.

Hans Krebs

________: A British biochemist who described three stages in the complete oxidation of fuel molecules to carbon dioxide and water.

Second law of thermodynamics

________: States that a closed system moves toward increasing disorder, or entropy, as energy is dissipated from the system.

Aerobic cellular respiration

________: Uses oxygen as the final electron acceptor and releases carbon dioxide and water from the complete oxidation of fuels.

Nicotinamide adenine dinucleotide

________ (NAD) contains the vitamin** nicotinic acid** (niacin)

law of thermodynamics

First ________: States that energy can not be created or destroyed.

Mechanisms

________ exist for critically regulating enzymes in both quantity and activity.

vertebrates

Among ________, amphibians and especially mammals produce mainly urea.

α ketoglutaric

It is highly toxic because it inhibits respiration by reacting with ________ acid to form glutamic acid, and effectively removes ________ from the Krebs cycle.

Triglycerides

________ (neutral fats): Are especially rich depots of metabolic energy because the fatty acids of which they are composed are highly reduced and free of water.

Coenzymes

________: Contain groups derived from vitamins, most of which must be supplied in the diet.

Cytochromes

________ contain iron.

Endergonic

________: Reactions in cells that require the addition of free energy.

Reptiles

________ and birds, as well as many terrestrial invertebrates, produce mainly uric acid.

Enzymes

________: They reduce the amount of activation energy required for a reaction.

Cofactors

________: Small nonprotein groups which perform their enzymatic functions.

Terrestrial animals

________ can not get rid of ammonia so conveniently and must detoxify it by converting it to a relatively nontoxic compound; urea and uric acid.

Deamination

________: the amino group splits to form ammonia and a keto acid.

Condensation

________: Subunits of molecules are linked together by removal of water.

Oxidation reduction redox reaction

________: Involves a transfer of electrons from an electron donor (the reducing agent) to an electron acceptor (the oxidizing agent)

nitrogen atoms

Once ________ are removed, the carbon skeletons of amino acids can be completely oxidized, usually by way of pyruvic acid or acetic acid.

Acetyl CoA

________ is channeled into the Krebs cycle, where the acetyl group is completely oxidized to carbon dioxide.

Stage II

________: Also called glycolysis, most of the glucose is converted into two 3- carbon units (pyruvic acid) in the cell cytoplasm.

Carbonic anhydrase

________ contains zinc.

Transamination

________: the amino group is transferred to a keto acid to yield a new amino acid.

digestive tract

When animals eat proteins, most are digested in the ________, releasing their constituent amino acids, which are then absorbed.

Hydrolysis reaction

________: A molecule is cleaved by the addition of water at the cleavage site.

Feedback inhibition

________: The final end product of a particular metabolic pathway inhibits the first enzyme in the pathway.

Ribosomal RNA

________: A major component of ribosomes, provides the activation energy that enables amino acids to assemble into polypeptide chains during the process of translation.

Hydrolysis

________: Breaking with water.

central purpose of carbohydrate

The ________ and fat metabolism is to provide energy, much of which is needed to construct and maintain cellular structure and metabolic processes.

Stage III

________: The final oxidation of fuel molecules occurs, with a large yield of ATP.

enzyme acts

If a(n) ________ reversibly, either synthesis or degradation may result.

Fatty acids

________: Are degraded by sequential removal of 2- carbon units, which enter the Krebs cycle through acetyl- CoA.

Coenzyme

________ A contains the vitamin pantothenic acid.

Cellular metabolism

Refers to the collective chemical processes that occur within living cells to accomplish these activities

Potential energy

It is stored energy

Kinetic energy

Energy of motion

First law of thermodynamics

States that energy cannot be created or destroyed

Second law of thermodynamics

States that a closed system moves toward increasing disorder, or entropy, as energy is dissipated from the system

Free energy

The energy in a system available for doing work

Exergonic

Reactions in cells release free energy

Endergonic

Reactions in cells that require the addition of free energy

Activation energy

This must be supplied before the bond is stressed enough to break

Catalysts

Chemical substances that accelerate reaction rates without affecting the products of the reaction and without being altered or destroyed by the reaction

Enzymes

They reduce the amount of activation energy required for a reaction

Cofactors

Small nonprotein groups which perform their enzymatic functions

Coenzymes

Contain groups derived from vitamins, most of which must be supplied in the diet

Ribosomal RNA

A major component of ribosomes, provides the activation energy that enables amino acids to assemble into polypeptide chains during the process of translation

Substrate

The molecule whose reaction it catalyzes

Enzyme-substrate complex (ES complex)

Formed during the binding of enzyme to substrate, in which the substrate is secured by covalent bonds to one or more points in the active site of the enzyme

Hydrolysis

Breaking with water

Hydrolysis reaction

A molecule is cleaved by the addition of water at the cleavage site

Condensation

Subunits of molecules are linked together by removal of water

Feedback inhibition

The final end product of a particular metabolic pathway inhibits the first enzyme in the pathway

Oxidation-reduction "redox" reaction

Involves a transfer of electrons from an electron donor (the reducing agent) to an electron acceptor (the oxidizing agent)

Heterotrophs

Organisms that cannot synthesize their own food but must obtain nutrients from the environment, including animals, fungi, and many single-celled organisms

Aerobes

Those that use molecular oxygen as the final electron acceptor

Anaerobes

Those that employ another molecule as the final electron acceptor

Cellular respiration

The oxidation of fuel molecules to produce energy with molecular oxygen as the final electron acceptor

Oxidation of fuel molecules

describes the removal of electrons from fuel molecules and not the direct combination of molecular oxygen with fuel molecules

Aerobic cellular respiration

Uses oxygen as the final electron acceptor and releases carbon dioxide and water from the complete oxidation of fuels

Hans Krebs

A British biochemist who described three stages in the complete oxidation of fuel molecules to carbon dioxide and water

Stage I

Food passing through the intestinal tract is digested into small molecules that can be absorbed into the circulation

Stage II

Also called glycolysis, most of the glucose is converted into two 3-carbon units (pyruvic acid) in the cell cytoplasm

Stage III

The final oxidation of fuel molecules occurs, with a large yield of ATP

Krebs cycle

Also known as citric acid cycle and tricarboxylic acid cycle

Triglycerides (neutral fats)

Are especially rich depots of metabolic energy because the fatty acids of which they are composed are highly reduced and free of water

Fatty acids

Are degraded by sequential removal of 2-carbon units, which enter the Krebs cycle through acetyl-CoA

Deamination

the amino group splits to form ammonia and a keto acid

Transamination

the amino group is transferred to a keto acid to yield a new amino acid