Chapter 4: Obtaining Energy

Flashcards covering energy, metabolism, thermodynamics, chemical reactions, enzyme activity, and the stages of cellular respiration and fermentation based on Chapter 4 of Openstax Concepts of Biology.

Bioenergetics

The flow of energy where producers, consumers, and decomposers recycle energy ($E$) continuously between living organisms.

Metabolism

The collection of all metabolic pathways—series of chemical reactions facilitated by enzymes—occurring at once to maintain the balance of energy.

First Law of Thermodynamics

The law stating that energy is neither created nor destroyed, but is instead transferred from one form to another.

Second Law of Thermodynamics

The law stating that energy transformations are inefficient and some energy is always lost as heat with each transfer, increasing disorder or entropy.

Entropy

Disorder that increases within a system as energy loss (usually as heat) increases.

Potential energy ($PE$)

Stored energy associated with an object's structure or location.

Chemical energy

A form of potential energy ($PE$) stored in the chemical bonds of molecules.

Kinetic energy

Energy associated with movement or objects in motion.

Exergonic reaction

A chemical reaction that releases energy, where reactants have more potential energy ($PE$) in their chemical bonds than the products.

Endergonic reaction

A chemical reaction that requires a net input of energy, where products have more potential energy ($PE$) in their chemical bonds than the reactants.

Enzymes

Proteins that increase the rate of chemical reactions without being consumed, generally ending in '-ase' and named for the substrate they bind to.

Activation energy ($E_A$)

The specific amount of energy that all chemical reactions must overcome to initiate the reaction.

Competitive inhibition

A mode of regulation where an inhibitor and a substrate compete to bind to the active site of an enzyme.

Noncompetitive (allosteric) inhibition

A mode of regulation where an inhibitor binds to a site other than the active site, changing the active site's shape and preventing substrate binding.

Feedback Inhibition

A process where a reaction product slows or stops the metabolic pathway to prevent overproduction and conserve resources.

ATP (Adenosine Triphosphate)

The usable form of energy for the cell to power its work; it is made on demand rather than stored.

Hydrolysis

The process of adding water ($H_2O$) to $ATP$ to release a phosphate group and energy, resulting in $ADP$.

Phosphorylation

The binding of a phosphate group to another molecule, which energizes the bound molecule.

Glycolysis

A multistep reaction occurring in the cytoplasm that breaks down a six-carbon Glucose molecule into two three-carbon pyruvate molecules, yielding a net of $2$ ATP and $2$ NADH.

Pyruvate Oxidation (Transition Step)

A step in the cytoplasm where one three-carbon pyruvate is converted into one two-carbon Acetyl-CoA, producing one $NADH$ and losing one $CO_2$.

Citric Acid Cycle

A cycle in the mitochondria involving Acetyl CoA and oxaloacetate that produces $2$ $CO_2$, $1$ ATP, $3$ NADH, and $1$ $FADH_2$ per cycle.

Electron transport chain (ETC)

A process in the mitochondrial or cell plasma membrane where $NADH$ and $FADH_2$ donate electrons to a chain, ending with a final electron acceptor (such as $O_2$ in eukaryotes) to create an $H^+$ gradient.

Chemiosmosis

A process facilitated by ATP synthase that uses the $H^+$ gradient to produce between $34 - 36$ ATP.

Oxidative Phosphorylation

The combined process of the electron transport chain and chemiosmosis to produce ATP.

Fermentation

A process using organic molecules to regenerate $NAD^+$ in the absence of oxygen, allowing glycolysis to continue.

Lactic Acid Fermentation

A type of fermentation occurring in animal cells under low oxygen conditions where pyruvate is converted to lactic acid ($3$-carbon) and $NADH$ is converted back to $NAD^+$.

Alcohol Fermentation

A type of fermentation where pyruvate is converted into $CO_2$ and the two-carbon molecule ethanol to regenerate $NAD^+$ from $NADH$.

Saccharomyces and Lactobacilli

Specific yeast and bacterial species commonly used in food production processes involving fermentation.