Biochemistry: Carbohydrates and Sugars

Carbohydrates

• Glucose is classified as an aldose sugar due to its aldehyde group.
• Naturally produced in green plants through photosynthesis.
• Glucose is present in human blood, providing essential energy.
• Fructose, a ketohexose, is recognized as the sweetest sugar among carbohydrates.
• Tetroses are rare sugars that occur in some fruits.
• Glycosidic bonds are covalent connections formed between monosaccharides in disaccharides and polysaccharides.
• Cellulose is the most abundant polysaccharide in plants and does not yield glucose upon complete hydrolysis.
• Chitin is another polysaccharide that does not break down into glucose.

Nucleic Acids and Proteins

• Nucleohistones are protein complexes in chromosomes, consisting of histone proteins that play structural roles.
• Watson and Crick developed the X-ray diffraction model of DNA, fundamental for understanding genetic architecture.
• Renin is an enzyme that digests milk protein.
• E. coli has a notable protein composition with about 4548 types.

Genetic Code and Protein Synthesis

• Nonsense codons signal termination during protein synthesis and are recognized by release factors.
• Amino acids are arranged according to the sequence coded by mRNA, which is transcribed from DNA.
• Transcription of DNA produces messenger RNA (mRNA).

Nucleobases and Amino Acids

• Purines include adenine (A) and guanine (G), while pyrimidines consist of cytosine (C), thymine (T), and uracil (U).
• Frederick Sanger is credited with determining the sequence of amino acids in proteins.
• Each turn of the alpha-helix structure in proteins corresponds to 3.6 amino acids.

RNA Types and Functions

• mRNA constitutes 3-4% of total RNA.
• tRNA makes up 10-20% and is approximately 75-90 nucleotides long, aiding in translation.
• rRNA accounts for 40-50%, forming the core of ribosomal structures.

Plant Storage Compounds

• Starch is the most important storage form of carbohydrates in plants, comprising amylose (soluble, unbranched) and amylopectin (insoluble, branched).

Lipids

• Waxes are formed from esters of fatty acids and long-chain alcohols.
• Acylglycerols consist of glycerol combined with fatty acids.
• Long-chain alkanes have carbon chains ranging from C25 to C35.

Fatty Acids

• Butyric acid is a carboxylic acid with a carbon chain length of 4.
• Palmitic acid is a fatty acid with a carbon chain length of 16, known for its significance in fats and oils.