Chapter 3: Energy, Catalysis and Biosynthesis

Vocabulary flashcards covering energy, catalysis, enzymes, thermodynamics, redox reactions, and activated carrier molecules from Chapter 3.

Primary Research Article Sections

The standard components of a primary scientific publication, typically including the Abstract, Introduction, Materials and Methods, Results, Discussion, and References.

Second Law of Thermodynamics

The physical law stating that the overall entropy (disorder) of the universe must increase over time; cells obey this law by releasing heat into their surroundings during metabolic reactions.

First Law of Thermodynamics

The principle of conservation of energy, which states that energy can be converted from one form to another but cannot be created or destroyed.

Free-Energy Change ($\Delta G$)

The change in free energy for a chemical reaction; it must be less than zero ($\Delta G < 0$) for a reaction to occur spontaneously or favorably.

Activation Energy

The threshold energy required to initiate a chemical reaction by enabling reactants to reach their transition state.

Transition State

The unstable, high-energy molecular conformation of a substrate during a reaction, which catalysts stabilize to reduce the reaction's activation energy.

Enzyme

A protein or ribozyme catalyst that increases the rate of a chemical reaction by lowering its activation energy without altering the reaction's overall $\Delta G$.

Reaction Coupling

The process in which an enzyme links an energetically favorable reaction ($\Delta G < 0$) with an energetically unfavorable reaction ($\Delta G > 0$) to drive the unfavorable reaction forward.

Activated Carrier Molecules

Small molecules such as $ATP$, $NADH$, and $NADPH$ that store energy in easily transferable chemical bonds or high-energy electrons to power biosynthetic processes.

ATP (Adenosine Triphosphate)

An activated carrier molecule possessing high phosphoryl group transfer potential that releases energy upon breaking the bond between its second ($\beta$) and third ($\gamma$) phosphate groups to yield $ADP$.

NADH

An activated carrier molecule functioning as an electron donor that carries a proton ($H$) and two high-energy electrons, releasing them when oxidized to $NAD^+$.

NADPH

An activated carrier molecule that supplies energy and high-energy electrons in electron transfer reactions during biosynthetic processes when converted to $NADP^+$.

Catabolic Reactions

Metabolic processes that break down complex food molecules, releasing usable chemical energy in the cell.

Anabolic Reactions

Metabolic processes that require an input of energy to build larger, more complex molecules from simpler building blocks.

Photosynthesis Energy Conversion

The biological process wherein plants, algae, and photosynthetic bacteria harvest solar energy from the sun to convert $CO_2$ into organic molecules.

Endergonic Reactions vs. Exergonic Reactions

Endergonic reactions require energy input ($\Delta G > 0$) and build stored energy in products, whereas exergonic reactions spontaneously release energy ($\Delta G < 0$) as reactants transition to lower energy products.

Oxidation-Reduction (Redox) Reaction

A chemical reaction involving electron transfer; oxidation refers to the loss of electrons or hydrogen atoms, while reduction refers to the gain of electrons or hydrogen atoms.

Hydrogenation Reactions

Reactions in which hydrogen atoms are added to a molecule, representing reduction processes (whereas dehydrogenation reactions are oxidations).

Metabolic Pathway Inhibition Analysis

An experimental approach used to determine the order of enzyme action in a pathway ($A \rightarrow B \rightarrow C \rightarrow D$) by inhibiting specific enzymes and identifying which metabolite accumulates prior to the blocked step.

Mass Action Driving Forces

Methods used to promote product formation in reactions with a positive standard free-energy change ($\Delta G^\circ > 0$), such as increasing reactant concentration or continually removing products.