Energy and Cellular Metabolism

Vocabulary flashcards covering the core concepts of energy, thermodynamics, enzymatic reactions, metabolic pathways (glycolysis, citric acid cycle, ETS), and the basics of protein synthesis as presented in Chapter 4.

Energy

The capacity to do work, required for living organisms to thrive, reproduce, and maintain a state of order.

Gradients

Forms of stored energy (concentration, electrical, or electrochemical) that release energy when substances move down them.

Compartmentation

The use of cellular and subcellular divisions to isolate and separate biochemical processes for maximum efficiency.

Chemical work

The making and breaking of chemical bonds.

Transport work

The movement of ions, molecules, and larger particles across membranes, useful for creating concentration gradients.

Mechanical work

The movement of organelles, changes in cell shape, the beating of flagella and cilia, and muscle contraction.

Kinetic energy

The energy of motion.

Potential energy

Stored energy found in concentration gradients and chemical bonds.

First law of thermodynamics

The law of conservation of energy stating that the total amount of energy in the universe is constant.

Second law of thermodynamics

The principle that processes move from a state of order to randomness or disorder, known as entropy.

Bioenergetics

The study of energy flow through biological systems.

Activation energy

The energy required to get a chemical reaction started.

Exergonic reactions

Energy-producing reactions.

Endergonic reactions

Energy-utilizing reactions that will not occur without an input of energy.

Enzymes

Proteins or RNA that act as catalysts to speed up the rate of chemical reactions by lowering activation energy.

Substrates

The reactants that bind to an enzyme in an enzymatic reaction.

Isozymes

Enzymes that catalyze the same reaction but under different conditions or in different tissues.

Proenzymes (Zymogens)

Inactive forms of enzymes that must be activated to function.

Coenzymes

Molecules that act as receptors or carriers for atoms or functional groups; many vitamins are precursors to these.

Oxidation

The removal or loss of electrons from a molecule.

Reduction

The gain of electrons by a molecule.

Hydrolysis

A reaction that splits large molecules by adding a water molecule.

Dehydration

A reaction that removes water to make one large molecule from several smaller ones.

Kinases

Enzymes that add a phosphate group to a molecule.

Deamination

The subtraction or removal of an amino group from a molecule.

Amination

The addition of an amino group to a molecule.

Transamination

The transfer of an amino group from one molecule to another.

Ligation reactions

Reactions where synthetases join two molecules together using energy from ATP.

Metabolism

All chemical reactions that take place in an organism.

Catabolism

Metabolic pathways that involve energy-releasing breakdown of molecules.

Anabolism

Metabolic pathways that involve energy-utilizing synthesis of molecules.

Intermediates

Molecules in metabolic pathways that exist between the initial reactant and the final product.

Feedback inhibition

A control mechanism where the accumulation of an end product inhibits the first step of its pathway.

Glycolysis

A pathway in the cytosol where one 6-carbon glucose is converted into two 3-carbon pyruvate molecules, yielding a net of $2$ ATP and $2$ NADH.

Citric acid cycle

A never-ending circle of mitochondrial reactions that produce ATP, high-energy electrons (NADH and $FADH_2$), and $CO_2$ from acetyl CoA.

Electron transport system

A mitochondrial process where oxygen is the final acceptor of electrons and $H^+$ ions, yielding $26-28$ ATP.

Codon

A sequence of three bases in mRNA encoding one amino acid.

Transcription

The synthesis of mRNA, tRNA, and rRNA from a DNA template strand.

Translation

The assembly of amino acids into a protein chain using an mRNA template and ribosomes.

Exons

Segments of mRNA that encode proteins.

Introns

Noncoding segments of genes that are removed during mRNA processing.

Alternative splicing

The removal of different introns from mRNA to allow a single gene to code for multiple proteins.

Tay-Sachs disease

A recessive genetic disorder caused by a lack of the enzyme hexosaminidase A, leading to the accumulation of gangliosides in nerve cells.