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Chemistry of Carbohydrates (Part - 1) : Biochemistry for MBBS 1st year, BDS, BHMS and BAMS

Dr.G Bhanu Prakash Animated Medical Videos・47 minutes read

Dr. Puja Johori discusses the composition and classification of carbohydrates, focusing on different types like monosaccharides and disaccharides. Understanding carbohydrate chemistry is essential for medical students to grasp their role in the body, metabolism, and dietary requirements.

Insights

  • Carbohydrates are classified based on functional groups and carbon atom numbers, with examples like glyceryl aldehyde and glucose representing different categories.
  • Understanding the chemistry of carbohydrates, including isomerism, helps in grasping their significance in bodily functions, metabolism, and medical implications, crucial for aspiring medical professionals.

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Recent questions

  • What are carbohydrates composed of?

    Carbon, hydrogen, oxygen.

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Summary

00:00

"Chemistry and Classification of Carbohydrates"

  • Dr. Puja Johori introduces the topic of carbohydrates in a live session, highlighting their composition of carbon, hydrogen, and oxygen.
  • Carbohydrates are classified as polyhydroxy derivatives of aldehydes and ketones, yielding aldehydes and ketones upon hydrolysis.
  • Classification of carbohydrates includes ldoses with aldehyde functional groups and ketoses with ketone functional groups, linked as isomers.
  • Carbohydrates are also classified based on the number of carbon atoms, such as trioses, tetroses, pentoses, and hexoses.
  • Examples include glyceryl aldehyde for trioses, erythros and erythreose for tetroses, ribose and ribulose for pentoses, and glucose and fructose for hexoses.
  • Carbohydrates are further categorized into monosaccharides, disaccharides, oligosaccharides, and polysaccharides based on the number of units.
  • The session delves into the chemistry of monosaccharides like glucose, fructose, mannose, and galactose, focusing on their structures, isomerism, and properties.
  • Isomerism in carbohydrates includes structural isomers like glucose and fructose, and stereoisomers like D-glucose compared to glyceryl aldehyde.
  • Chiral carbon atoms in molecules lead to the formation of enantiomers, non-superimposable mirror images, crucial in understanding carbohydrate structures.
  • Understanding the chemistry of carbohydrates is essential for comprehending their role in the body, metabolism, and dietary requirements, crucial for medical students and future doctors.

22:46

Chirality and Stereoisomers in Glucose Chemistry

  • An atom with all four substituents different forms a non-superimposable mirror image, leading to chirality.
  • Glucose is named based on Kalyani Fischer synthesis, where a three-carbon sugar can generate up to six or seven carbon atoms.
  • The second carbon atom in glucose behaves as the second last carbon atom in successive sugars, with the OH group dictating the position.
  • Glycerol aldehyde is formed when the OH group is on the right side, while LD glycerin is formed when it's on the left side.
  • Glucose is named based on the position of the OH group, with D-glucose being the most stable form.
  • Glucose is predominantly found in the D form due to its stability, with L-glucose also existing but less stable.
  • D and L forms of stereoisomers are enantiomers, with stability dictating the orientation in space.
  • Optical isomers rotate polarized light in specific directions, with a polarimeter used to measure this rotation.
  • Dextrose represents capital D glucose due to its stability, while a racemic mixture nullifies optical rotation.
  • Anomers differ only at the first carbon atom, while epimers differ at any other position except the first.

44:24

"Anomers, Epimers, and Reducing Sugars Explained"

  • Anomers are isomers differing only at the C1 position, which is the functional group.
  • Anomers have a free functional group at C1, making them reducing sugars.
  • Epimers are isomers differing at any position except C1, such as C2, C3, C4, or C5.
  • Examples of epimers include Manos as a C2 epimer, Alos as a C3 epimer of glucose, and Galactose as a C4 epimer.
  • Epimers can also be reducing sugars if they have a free functional group at C1.
  • All sugars are reducing except sucrose, which is a non-reducing sugar.
  • Reducing sugars undergo mutarotation, where they can change between open chain, Alpha, and Beta forms.
  • Osa Zone formation is a test for reducing sugars, where crystals are formed with phenylhydrazine.
  • The shape of Osa Zone crystals varies for different sugars, like needle-like for glucose and ornate for galactose.
  • Sucrose does not form Osa Zone crystals as it is a non-reducing sugar.

01:08:18

Enzymes in Carbohydrate Metabolism and Cataracts

  • Enzymes discussed include alcohol dehydrogenase (ADH) and aldol reductase (AR), with a focus on their roles in the oxidation of glucose and fructose to form sorbitol, galactitol, and mannitol.
  • The significance of carbohydrates as universal energy sources is highlighted, with excess carbohydrates converting to fats and proteins essential for muscle mass.
  • Hyperglycemia is explained as an increased concentration of glucose leading to elevated levels of sorbitol, causing ocular pressure issues and potential cataract formation.
  • Inhibitors of aldol reductase can help minimize sorbitol levels in hyperglycemia, reducing ocular pressure and potential cataract formation.
  • Galactose metabolism leads to the formation of galactitol, with implications for galactosemia and different types of cataracts, while mannitol reduces intracranial pressure in injuries.
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