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Related Concept Videos

The Physiology of Taste01:24

The Physiology of Taste

The perception of a salty flavor is facilitated by sodium ions within the oral salivary fluid. Upon consumption of a salty substance, salt crystals disassemble, leading to the liberation of its constituents—Na+ and Cl- ions. These ions subsequently dissolve into the salivary fluid present in the oral cavity. The external environment of the gustatory cells experiences an elevation in Na+ concentration, thereby establishing a potent concentration gradient. This gradient propels the diffusion of...
Gustation01:43

Gustation

Gustation is a chemical sense that, along with olfaction (smell), contributes to our perception of taste. It starts with the activation of receptors by chemical compounds (tastants) dissolved in the saliva. The saliva and filiform papillae on the tongue distribute the tastants and increase their exposure to the taste receptors.
NMR Spectroscopy and Mass Spectrometry of Aldehydes and Ketones01:15

NMR Spectroscopy and Mass Spectrometry of Aldehydes and Ketones

In aldehydes, the hydrogen atom connected to the carbonyl carbon helps distinguish aldehydes from other carbonyl compounds using ¹H NMR spectroscopy. The closeness of aldehydic hydrogen to the electrophilic carbonyl carbon highly deshields the hydrogen atom causing its signal to appear around 10 ppm in the ¹H NMR spectra. α hydrogens split the aldehydic proton signal, which helps identify the number of α hydrogens in the molecule. For instance, one α hydrogen creates a doublet for an aldehydic...
Structures of Aldehydes and Ketones01:04

Structures of Aldehydes and Ketones

Vanillin—a flavoring agent in vanilla, cinnamaldehyde—a molecule responsible for the distinct smell of cinnamon, and acetone—a strong-smelling ingredient in nail polish removers, all belong to a class of carbonyl compounds called aldehydes and ketones (Figure 1). Although both aldehydes and ketones contain the characteristic carbonyl (C=O) bond, their chemical structures vary with respect to the groups directly attached to the carbonyl carbon.
In aldehydes (Figures 1a and 1b), the carbonyl...
Dehydration of Aldols to Enals: Base-Catalyzed Aldol Condensation01:14

Dehydration of Aldols to Enals: Base-Catalyzed Aldol Condensation

This lesson delves into the aldol condensation catalyzed by bases, where aldols undergo dehydration to enals. As shown in Figure 1, the β-hydroxy aldehyde formed in a base-catalyzed aldol addition reaction dehydrates on heating to yield an unsaturated carbonyl product, which is commonly referred to as an enal.
C–C Bond Cleavage: Retro-Aldol Reaction00:57

C–C Bond Cleavage: Retro-Aldol Reaction

The reverse of the aldol addition reaction is called the retro-aldol reaction. Here, the carbon–carbon bond in the aldol product is cleaved under acidic or basic conditions to form two molecules of carbonyl compounds. The mechanism of the reaction consists of three steps.
In the first step, as depicted in Figure 1, the base deprotonates the β-hydroxy ketone at the hydroxyl group to form an alkoxide ion.

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Related Experiment Video

Updated: Jul 8, 2026

Taste Exam: A Brief and Validated Test
07:10

Taste Exam: A Brief and Validated Test

Published on: August 17, 2018

Bitterness in almonds.

Raquel Sánchez-Pérez1, Kirsten Jørgensen, Carl Erik Olsen

  • 1Plant Biochemistry Laboratory, Department of Plant Biology, Center for Molecular Plant Physiology, Faculty of Life Sciences, University of Copenhagen, Copenhagen, Denmark.

Plant Physiology
|January 15, 2008
PubMed
Summary

Bitterness in almonds is due to amygdalin. In bitter almonds, prunasin is synthesized in the tegument and converted to amygdalin in the cotyledon. Sweet almonds degrade prunasin, preventing bitterness.

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Last Updated: Jul 8, 2026

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Area of Science:

  • Plant biochemistry
  • Molecular biology
  • Agricultural science

Background:

  • Almond bitterness is primarily determined by the cyanogenic diglucoside amygdalin content.
  • Understanding the synthesis and degradation pathways of prunasin and amygdalin is crucial for almond breeding and quality control.

Purpose of the Study:

  • To investigate the developmental dynamics of prunasin and amygdalin synthesis and degradation in different almond genotypes.
  • To identify the specific tissues and enzymatic activities involved in the formation of bitter compounds in almond kernels.

Main Methods:

  • Utilized liquid chromatography-mass spectrometry (LC-MS) to quantify prunasin and amygdalin levels.
  • Employed radiolabeled phenylalanine to trace the synthesis pathway of prunasin.
  • Assessed beta-glucosidase activity in almond tissues using Fast Blue BB salt staining.

Main Results:

  • Prunasin specifically accumulates in the tegument of bitter almond genotypes during development.
  • The tegument is identified as the primary site of prunasin synthesis in all studied genotypes.
  • Bitter genotypes exhibit low beta-glucosidase activity in the inner epidermis of the tegument, while sweet genotypes show high activity, leading to prunasin degradation.

Conclusions:

  • Bitter almond genotypes convert tegument-synthesized prunasin into amygdalin in the cotyledons.
  • Sweet almond genotypes prevent amygdalin formation by degrading prunasin in the tegument's inner epidermis via beta-glucosidase.
  • Prunasin turnover may serve as a nitrogen buffer for developing almond cotyledons.