Chapter 5.1: ATP and Reduced Coenzymes Are the Energy Currency for Biosynthesis

Flashcards from Chapter 5.1 of Principles of Life, 3rd Edition.

Metabolic pathway

A series of reactions that converts molecules from one form to another via controllable enzymes

• Often compartmentalized in certain cytoplasmic regions, organelles (eukaryotes), or microcompartments (prokaryotes)

Organelles

Regions where certain metabolic pathways are performed, in eukaryotes

Microcompartments

Regions where certain metabolic pathways are formed, in prokaryotes

Energy

What is needed for many of a cell’s processes, often obtained through organic molecule breakdown, photosynthesis, or inorganic compounds

Endergonic reactions

Reactions that require energy to proceed, often obtained from coupled exergonic reactions or stored energy from ATP or NADH; these include active transport, cell movements, and anabolism

Exergonic reactions

Reactions that release energy; these include cell respiration and metabolism

ATP and NADH

The two most common energy-storing coenzymes used to power endergonic reactions; these couple to each other through oxidative phosphorylation in order to provide energy for the cell

Adenosine triphosphate (ATP)

The main energy currency of the cell that stores energy in a phosphate bond (P_i) linked to ADP, used to power endergonic reactions like active transport, molecule synthesis, and cell movement after hydrolysis

Weak bond

A bond that is less stable and stores high levels of energy for later use, seen in ATP, decreasing free energy after hydrolysis

Pyrophosphate (PP_i)

An ion that can be released from ATP through the breaking apart of two phosphate groups; this can release more energy if further broken down into P_i

Substrate-level phosphorylation

The transfer of a phosphate group to another molecule via enzymes; used with ADP to form ATP

Oxidative phosphorylation

How most ATP is produced outside of substrate-level phosphorylation, coupling the oxidation of NADH to the synthesis of ATP from ADP and P_i

Redox reaction

A reaction where electrons are transferred from an oxidized atom to a reduced atom

Oxidation

The loss of one or more electrons; this is associated with less energy storage as electrons are transferred away from the unit in the bond for the release of energy

Reduction

The gain of one or more electrons; this is associated with more energy storage as electrons are transferred towards the unit in the bond

Electronegativity

The ability to attract electrons

Nicotinamide adenine dinucleotide (NAD)

An electron carrier in redox reactions that exists in oxidized (NAD⁺) and high-energy reduced (NADH) forms, achieved through the transfer of hydrogen and two electrons from an oxidized molecule

• This then transfers electrons to O₂, releasing high levels of energy

Flavin adenine dinucleotide (FAD)

An electron carrier that acts similarly to NAD during glucose metabolism

Nicotinamide adenine dinucleotide phosphate (NADP)

An electron carrier that acts similarly to NAD during photosynthesis