The Energy of Life and Cellular Transport

Biological vocabulary covering cellular energy usage, thermodynamics, enzymatic functions, and membrane transport mechanisms.

Metabolism

The sum total of all the chemical reactions within organisms.

Anabolic Reactions

Chemical reactions that consume energy to build complex molecules.

Catabolic Reactions

Chemical reactions that release energy to breakdown complex molecules.

Chemical Work

A type of cellular work involving the driving of endergonic reactions that do not occur spontaneously.

Transport Work

A type of cellular work involving the pumping of substances across membranes against their concentration gradient.

Mechanical Work

Cells performing tasks such as the beating of cilia, contraction of muscle cells, and movement of chromosomes during mitosis.

First Law of Thermodynamics

Principle stating that energy cannot be created or destroyed, only transformed or transferred.

Second Law of Thermodynamics

Principle stating that every energy transfer increases the entropy (disorder) of the universe, with much of this energy lost as heat.

Gibbs Free Energy ($\Delta G$)

The portion of a system's energy that can perform work when temperature and pressure are uniform.

Exergonic Reactions

Spontaneous chemical reactions that release energy where $\Delta G < 0$ and the reactants have more energy than the products.

Endergonic Reactions

Non-spontaneous chemical reactions that absorb energy where $\Delta G > 0$ and the products have more energy than the reactants.

Adenosine Triphosphate (ATP)

The primary energy shuttle of the cell, composed of an adenine nitrogenous base, a ribose sugar, and a chain of three phosphate groups.

ATP Hydrolysis

The process of breaking the terminal phosphate bond by adding water, which releases a significant amount of energy.

Phosphorylation

Attaching a phosphate group $[(PO_{4})^{3-}]$ to an ion or molecule, often creating a highly reactive intermediate.

Enzymes

Biological catalysts, mostly proteins, that speed up chemical reactions without being consumed.

Activation Energy ($E_{a}$)

The energy required to start a chemical reaction; enzymes work by lowering this value.

Active Site

The specific region on an enzyme where the substrate binds to undergo a reaction.

Induced Fit

The phenomenon where an enzyme changes shape slightly upon substrate binding to grip the substrate more snugly.

Denaturation

The unraveling of a protein structure, such as an enzyme, caused by deviations from the optimal temperature or pH range.

Competitive Inhibitors

Molecules that mimic the substrate and bind directly to the active site to block enzymatic action.

Non-competitive (Allosteric) Inhibitors

Inhibitors that bind to an allosteric site rather than the active site, altering the enzyme's shape so it no longer functions effectively.

Feedback Inhibition

A metabolic control mechanism where the end product of a pathway acts as an inhibitor to an enzyme early in that same pathway.

Selectively Permeable

A property of the plasma membrane that allows only certain materials to enter or exit the cell.

Glycolipids

According to the transcript, these are cholesterols scattered around the plasma membrane.

Glycoproteins

Proteins that are either attached or embedded to the plasma membrane.

Fluid-Mosaic Model

Developed in 1972 by S. Jonathan Singer and Garth Nicolson, describing the membrane as a fluid double-layer of protein and phospholipids.

Simple Diffusion

The random spreading of molecules from areas of higher concentration to lower concentration until dynamic equilibrium is reached, requiring no energy.

Osmosis

The diffusion of water molecules across selectively permeable membranes from an area of higher concentration to an area of lower concentration.

Facilitated Diffusion

A passive transport mechanism where carrier or transport proteins help molecules move across the membrane.

Primary Active Transport

The direct use of $ATP$ to pump ions against a concentration gradient, such as the Sodium-Potassium Pump.

Secondary Active Transport (Cotransport)

The movement of molecules driven by the electrochemical gradient generated by primary active transport.

Pinocytosis

A type of endocytosis where the plasma membrane encloses small amounts of fluid droplets to take into the cell.

Phagocytosis

A type of endocytosis where the plasma membrane forms a vesicle around a solid particle or another cell.

Receptor-Mediated Endocytosis

A process where extracellular molecules bind with specific receptor proteins, causing the membrane to invaginate and draw molecules into the cell.

Caveolae

Small, flask-shaped invaginations of the plasma membrane that play roles in signaling, endocytosis, and mechanoprotection.

Exocytosis

A form of active transport requiring $ATP$ used to move molecules like proteins, hormones, or waste from the inside of the cell to the extracellular environment.