Section of Organic Chemistry by John McMurry by the whole-book author John McMurry. OpenStax publishes and hosts the book. Whole-book publication: 20 September 2023; no separate section author or revision date is established.

Online text: openstax.org/books/organic-chemistry/pages/27-2-soap

Cited passages: §27.2 opening chemical definition and fat hydrolysis equation; §27.2 paragraphs on ionic carboxylate heads, hydrocarbon tails and grease removal; Publisher citation information.

Section of Organic Chemistry by John McMurry by the whole-book author John McMurry. OpenStax publishes and hosts the book. Whole-book publication: 20 September 2023; no separate section author or revision date is established.

Online text: openstax.org/books/organic-chemistry/pages/21-6-chemistry-of-esters

Cited passages: §21.6 Conversion of Esters into Carboxylic Acids: Hydrolysis, paragraphs surrounding Figure 21.8; Publisher citation information: author, book title, publisher and publication date.

Section of Organic Chemistry by John McMurry. John McMurry is the whole-book author; no separate chapter byline is established. OpenStax publishes and hosts the book. The publication date is 20 September 2023; no separate section revision date is established.

Official text: openstax.org/books/organic-chemistry/pages/25-5-cyclic-structures-of-monosaccharides-anomers

Inspected locators: §25.5, intramolecular hemiacetal formation, anomers and final mutarotation discussion; publisher citation information.

Section of Organic Chemistry by John McMurry. John McMurry is the whole-book author; no separate chapter byline is established. OpenStax publishes and hosts the book. The publication date is 20 September 2023; no separate section revision date is established.

Official text: openstax.org/books/organic-chemistry/pages/25-1-classification-of-carbohydrates

Inspected locators: §25.1, simple and complex carbohydrates; aldose, ketose and carbon-count classification; publisher citation information.

An endosome is a membrane-enclosed sorting compartment in the endocytosis pathway. Cargo may return to the cell membrane or proceed toward lysosomes; entry therefore does not by itself establish a digestive fate.^[ref]

A lysosome is an acidic digestive and recycling organelle: one surrounding lipid bilayer encloses a lysosomal lumen containing acid hydrolases. These enzymes break down proteins, nucleic acids, carbohydrates and lipids by hydrolysis. Cargo can originate outside the biological cell, entering through endocytosis, or within its own cytoplasm, delivered through autophagy. Digestion therefore serves both disposal and reuse.^[ref]

An endosome sorts endocytosed cargo: some returns to the cell membrane, while some proceeds toward lysosomes. An autophagosome instead encloses material already in the cytoplasm. Both routes bring cargo into contact with digestive enzymes; neither implies that every internalized molecule is destroyed.^[ref]

Enzyme supply is a different itinerary from cargo disposal. Secretory protein routing and protein targeting deliver newly made digestive enzymes through the endoplasmic reticulum, Golgi apparatus and trans-Golgi network toward lysosomes.^[ref] The existing membrane transport and differential centrifugation articles explain the boundary-crossing and separation principles used below.

A proteasome is a different digestive machine: a protein complex without a surrounding lipid bilayer, acting on individual proteins in the cytosol and cell nucleus. Many targets carry ubiquitin chains. A lysosome accepts a much broader range of cargo, including material delivered inside an autophagosome. Thus an unwanted soluble protein and an unwanted mitochondrion pose different disposal problems; a proteasome does not swallow an intact mitochondrion.^[ref]

A transport vesicle is a membrane-bounded carrier that moves cargo between cellular compartments. Budding and fusion preserve the distinction between lumen-facing and cytosol-facing membrane surfaces.

The Golgi apparatus modifies and sorts cargo arriving from the endoplasmic reticulum for delivery to other cellular destinations. The eponym refers to Camillo Golgi.

Its usual stacked organization is polarized: cargo enters on the cis side, encounters medial processing regions, and leaves through the trans side and trans-Golgi network. Golgi cisternae enclose a Golgi lumen separated from the surrounding cytosol. Processing changes cargo; sorting selects its destination.^[ref]

This division of labor explains why reaching the Golgi apparatus does not imply being secreted: cargo can take different onward routes, while resident enzymes continue working there. The conventional route discussed here is part of secretory protein routing; many cytosol proteins never enter it.

Nonlinear optics studies the response of matter to light when the induced electric polarization is not proportional to the driving electric field. An intense laser can make these additional terms observable. The striking consequence is that a material can emit light at a frequency absent from the incident beam: second-harmonic generation doubles it. This extends a s usable optical spectrum without requiring a second lasing transition.

Franken and colleagues frequency-doubling experiment established an optical harmonic in 1961. Nicolaas S theoretical work developed the description of interacting light waves in nonlinear matter. His 1981 lecture connects a nonlinear constitutive relation with Maxwell's equations and explains compensation of optical dispersion by birefringence.^[ref]

A Lippmann plate records colour as a depth-dependent optical structure in a photographic emulsion. A standing wave writes a spacing; wave interference during later illumination selects the reflected wavelengths. This makes a photographic plate a spatial record of an optical spectrum. The striking idea is that information about colour can live in geometry.

Gabriel Lippmann presented his colour process in 1891 and received the 1908 Nobel Prize in Physics. His career belongs principally to physics: he held chairs in mathematical and experimental physics.^{[ref] [ref]}

Phosphorescence is delayed luminescence sustained by long-lived excited states after excitation has ceased. In a common molecular mechanism, population reaches a triplet state and returns to a singlet ground state through a weak, spin-changing transition. Long-lived emission in a solid can also involve trapped charge carriers, so a slow decay alone does not uniquely establish the microscopic mechanism.

A useful experiment shutters the excitation and records emitted intensity versus time with a photodetector. Scattered excitation should disappear with the shutter, whereas delayed emission persists. The measured decay can depend on temperature, quenching and multiple states rather than following one universal lifetime.

Optical nonreciprocity means that exchanging source and detector paths need not restore the corresponding transmission when external conditions, including the magnetic field, are held fixed. The Faraday effect gives a linear polarization rotation with the same laboratory sense on both traversals; see Faraday rotation on a round trip.

A maser uses stimulated emission to amplify microwaves. With population inversion and feedback it can sustain a coherent wave field as an oscillator. The name abbreviates "microwave amplification by stimulated emission of radiation".^[ref]

Why make molecules supply an oscillator? Their energy levels offer a reproducible frequency reference, while stimulated emission lets successive molecules reinforce one coherent wave field. In his 1964 lecture, Charles Hard Townes traced his motivation to microwave spectroscopy: resolving molecular structure required useful coherent sources.^[ref] The interesting balance is between molecular amplification and escaping energy: even a beam with population inversion fails to oscillate if cavity losses win. This is the microwave counterpart of laser threshold.

Additive color produces a color stimulus by superposing light from different sources. For mutually incoherent sources, their spectral intensities add, and the combined optical spectrum drives the observer's receptors. Red and green display primaries can therefore give a yellow appearance without emitting only yellow-wavelength light.

Project two colored beams onto the same diffuse screen and compare their overlap with the separately illuminated regions. Holding the surroundings and adaptation fixed makes the comparison interpretable. The attainable colors depend on the primary optical spectra and their allowed powers, which define a device gamut; merely naming three primaries does not specify every stimulus they can produce.

Light emission from excited matter that is not simply its thermal radiation at the local temperature. Fluorescence is one form of luminescence.

The ability of an imaging or measurement system to distinguish nearby spatial features. A resolution criterion must specify the features and measurement conditions: diffraction, noise and sampling can all limit the distinction. A small pixel spacing alone does not establish high spatial resolution; electron microscope resolution illustrates the role of wavelength and numerical aperture.

Ellipsometry measures the change in polarization of an electromagnetic wave upon specular reflection to infer material properties. For a simple planar sample, the complex reflection-coefficient ratio is written $\rho =r_p/r_s=\tan \Psi e^{i\Delta }$: $\Psi$ describes a relative amplitude and $\Delta$ a relative wave phase between the two incident polarizations.

A source, polarization-control optics, sample at a known incidence angle and analyzer with a photodetector form a basic instrument. Repeating measurements across wavelength and angle constrains refractive index and film thickness through a model of the layered sample. The fitted thickness is not read directly from $\Psi$: roughness, layer structure and correlated model parameters can produce ambiguous fits.

Microscopy makes small structures observable by using an optical microscope, an electron microscope, or a scanned probe such as an atomic force microscope. Each instrument measures a different interaction with the specimen: transmitted light, scattered electrons, or the force on a tip. Consequently two images of the same object need not show the same features.

A useful measurement distinguishes magnification, optical resolution and image contrast. Enlarging a blurred image changes its displayed size without recovering the missing detail. For an optical microscope, imaging small separated objects and recording how their images merge tests optical resolution; changing the illumination while holding the specimen fixed tests whether a feature comes from specimen structure or the imaging method.

This section concerns specialists in optical instruments.

Color vision distinguishes distributions of visible light across wavelengths through the different spectral sensitivities of visual receptors. A perceived colour need not correspond to one wavelength: different optical spectra can produce the same receptor responses. Consequently the broad spectral filtering of thin-film interference need not produce pure monochromatic colours.