Introduction to Biochemistry and Carbohydrates .pdf

BIOCHEMISTRY FIRST TERM | LECTURE A.Y 2024 - 2025 1-2 OCCURRENCE AND FUNCTIONS 1-1 INTRODUCTION TO OF CARBOHYDRATES BIOCHEMISTRY Carbohydrates are the most...

BIOCHEMISTRY FIRST TERM | LECTURE A.Y 2024 - 2025 1-2 OCCURRENCE AND FUNCTIONS 1-1 INTRODUCTION TO OF CARBOHYDRATES BIOCHEMISTRY Carbohydrates are the most BIOCHEMISTRY abundant class of bioorganic - Study of the chemical molecules on planet EARTH. substances found in the Carbohydrates constitute about living organisms and the 75% by mass of dry plant. chemical interactions of Green (chlorophyll-containing) these substances with plants produce carbohydrates each other via photosynthesis. In this process, carbon dioxide from BIOCHEMICAL SUBSTANCE the air and water from the soil - A chemical substance are the reactants, while sunlight found within a living absorbed by chlorophyll is the organism; divided into 2 energy source. groups (BIOINORGANIC AND BIOORGANIC SUBSTANCES) FUNCTIONS OF CARBOHYDRATES BIOINORGANIC AND BIOORGANIC 1. Carbohydrate oxidation provides SUBSTANCES energy. 2. Carbohydrate storage, in the form of glycogen, provides a short-term energy reserve. 3. Carbohydrates supply carbon atoms for the synthesis of other biochemical substances (proteins, lipids, and nucleic acids). 4. Carbohydrates form part of the structural framework of DNA and RNA molecules.  5. Carbohydrates linked to lipids to ten monosaccharide units are structural components of covalently bonded to each cell membranes. other. 6. Carbohydrates linked to A disaccharide is a proteins function in a variety of carbohydrate that contains two cell-cell and cell-molecule monosaccharide units covalently recognition processes. bonded to each other. A polysaccharide is a 1-3 CLASSIFICATION OF polymeric carbohydrate that CARBOHYDRATES contains many monosaccharide units covalently bonded to each Most simple carbohydrates have other. empirical formulas that fit the general formula CnH2On. 1-4 CHIRALITY: A carbohydrate is a HANDEDNESS IN MOLECULES polyhydroxy aldehyde, a polyhydroxy ketone, or a compound that yields polyhydroxy aldehyde or polyhydroxy ketones upon hydrolysis. The carbohydrate glucose is a polyhydroxy aldehyde, and the carbohydrate fructose is a polyhydroxy ketone. Most monosaccharides exist in two forms: a “left-handed” form and a “right-handed” form. These two forms are related to each other in the same way your left and right hands are related to each other. That relationship is that of a mirror image. A monosaccharide is a carbohydrate that contains a single polyhydroxy aldehyde or polyhydroxy ketone unit An oligosaccharide is a carbohydrate that contains two Science Faculty, 2024 | H. Stephen Stoker, Biochemistry, 3e. © 2017 C&E Publishing, Inc  MIRROR IMAGE RECALL: STEREOISOMERISM Stereoisomers – isomers that have the same molecular and structural formulas but differ in the orientation of atoms in space. A. Enantiomers: molecules are nonsuperimposable mirror images B. Diastereomers: molecules are not mirror images of each other (cis-trans isomers) SUPERIMPOSABLE MIRROR IMAGES - Images that coincide at 1-6 DESIGNATING HANDEDNESS USING FISCHER PROJECTION FORMULA all points NONSUPERIMPOSABLE MIRROR IMAGES A Fischer projection formula - Images where not all is a two-dimensional structural points coincide when the notation for showing the spatial images are laid upon arrangement of groups about each other. chiral centers in molecules. CHIRALITY - 4 different groups attached to the carbon atom at the chiral center In a Fischer projection formula, a chiral center is represented as the intersection of vertical and horizontal lines. The atom at the chiral center, which is Science Faculty, 2024 | H. Stephen Stoker, Biochemistry, 3e. © 2017 C&E Publishing, Inc  almost always carbon, is not A. Aldose – A explicitly shown. monosaccharide that contains an aldehyde functional group (a polyhydroxy aldehydes) B. Ketose – A monosaccharide that contains a ketone functional group (a In Fischer projection formulas for polyhydroxy ketones) monosaccharides (the simplest type of carbohydrate), the monosaccharide MONOSACCHARIDES carbon chain is positioned vertically with the carbonyl group (aldehyde or Note: They are classified by both their ketone) at or near the top. The number of CARBON atoms and their smallest monosaccharide that has a functional group chiral center is the compound glyceraldehyde A. 6 carbon monosaccharide + (2.3-dihydroxypropanal). aldehyde FG = aldohexose B. 5 carbon monosaccharide = ketone FG = ketopentose 1-8 BIOCHEMICALLY IMPORTANT MONOSACCHARIDES The Fischer projection formulas for the Of the many monosaccharides, two enantiomers of glyceraldehyde are six that are particularly important in the functioning of the human body are the trioses D-glyceraldehyde and dihydroxyacetone and the D forms of glucose, galactose, fructose, and ribose. 1-7 CLASSIFICATION OF MONOSACCHARIDES Classified as ALDOSES or KETOSES Science Faculty, 2024 | H. Stephen Stoker, Biochemistry, 3e. © 2017 C&E Publishing, Inc  D-Galactose epimer with D-glucose D-Glyceraldehyde and synthesized from glucose in the Dihydroxyacetone mammary glands for use in – simplest of the monosaccharides, D- lactose (milk sugar) Glyceraldehyde is a chiral molecule. BRAIN SUGAR (component of glycoproteins – found in brain D-Glucose and nerve tissue – most abundant in nature and the most important from a human D-Fructose nutritional standpoint Science Faculty, 2024 | H. Stephen Stoker, Biochemistry, 3e. © 2017 C&E Publishing, Inc  1-9 CYCLIC FORMS OF MONOSACCHARIDES Biochemically most important ketohexose Also known as levulose and fruit sugar D-Ribose The cyclic hemiacetal forms of D-glucose result from the intramolecular reaction between the carbonyl group and the hydroxyl group on carbon 5. 1-10.1 HAWORTH PROJECTION FORMULAS The last three monosaccharides discussed in this section have all been hexoses. D-Ribose is a a two-dimensional structural pentose. If carbon 3 and its notation that specifies the 3D accompanying —H and —OH structure of a cyclic form of a groups were eliminated from monosaccharide the structure of D-glucose, the In a Haworth projection, the remaining structure would be hemiacetal ring system is that of D-ribose. viewed “edge on” with the oxygen ring atom at the upper Science Faculty, 2024 | H. Stephen Stoker, Biochemistry, 3e. © 2017 C&E Publishing, Inc  right (six-membered ring) or at in an a configuration, the two the top (five-membered ring) groups point in opposite directions 1-10.2 HAWORTH PROJECTION FORMULAS 1.11 REACTIONS OF MONOSACCHARIDES A. OXIDATION TO PRODUCE ACIDIC SUGARS The D or L form of a monosaccharide is determined by the position of the terminal CH2OH group on the highest Weak oxidizing agents (Tollens numbered ring carbon atom. and Benedict’s solution) oxidize In the D form, CH2OH is the ALDEHYDE end of an positioned above the ring. ALDOSE to produce ALDONIC In the L form, CH2OH is ACID. positioned below the ring. Oxidation of the ALDEHYDE end of a GLUCOSE produces GLUCONIC ACID. 1-10.3 HAWORTH PROJECTION FORMULAS Oxidation of the ALDEHYDE end of a GALACTOSE produces GALACTONIC ACID 1.11.1 REACTIONS OF MONOSACCHARIDES a or b configuration is determined by the position of the —OH group on carbon 1 relative to the CH2OH group that determines D or L series. In a b configuration, both of these groups point in the same direction; 1.11.2 REACTIONS OF MONOSACCHARIDES Science Faculty, 2024 | H. Stephen Stoker, Biochemistry, 3e. © 2017 C&E Publishing, Inc  B. REDUCTION TO PRODUCE inorganic oxyacids to form SUGAR ALCOHOLS inorganic esters. Phosphate esters, formed from phosphoric acid and various monosaccharides, are commonly encountered in biochemical systems. The carbonyl group present in a monosaccharide (either an aldose or a ketose) can be reduced to a hydroxyl group, using hydrogen as the reducing agent. 1.11.5 REACTIONS OF MONOSACCHARIDES 1.11.3 REACTION OF MONOSACCHARIDES E. AMINO SUGAR FORMATION If one of the hydroxyl groups of a monosaccharide is replaced C. GLYCOSIDE FORMATION with an amino group, an amino A glycoside is an acetal formed sugar is produced. from a cyclic monosaccharide by replacement of the hemiacetal carbon 1.12 DISACCHARIDES 1.11.4 REACTIONS OF MONOSACCHARIDES D. PHOSPHATE ESTER FORMATION The hydroxyl groups of a monosaccharide can react with Science Faculty, 2024 | H. Stephen Stoker, Biochemistry, 3e. © 2017 C&E Publishing, Inc  1.12.1 DISACCHARIDES 1.13 GENERAL CHARACTERISTICS OF POLYSACCHARIDES MALTOSE - malt sugar; a disaccharide consisting two Polysaccharide – a polymer that glucose units contains many monosaccharide units CELLOBIOSE – also contains 2 bonded to each other by glycosidic D-glucose units linkages. LACTOSE – beta D-galactose + Alternate name for polysaccharide: D-glucose; major sugar found in GLYCAN milk 1.13.1 GENERAL CHARACTERISTICS OF POLYSACCHARIDES 1.12.2 DISACCHARIDES SUCROSE – table sugar; most abundant of all disaccharides and occurs throughout the plant IMPORTANT PARAMETERS: kingdom (NON-REDUCING 1. Identity of the monosaccharide SUGAR) repeating units in the polymer chain. NOTE: If consumed excessively, 2. Length of the polymer chain. it may also contribute to the 3. Type of glycosidic linkage development of some metabolic between monomer units. syndrome such as higher risk 4. The degree of branching of the for type 2 diabetes mellitus, polymer chain. insulin resistance, gaining of weight, and obesity within children and adults Science Faculty, 2024 | H. Stephen Stoker, Biochemistry, 3e. © 2017 C&E Publishing, Inc STORAGE POLYSACCHARIDE: STARCH exercise, fasting, or normal activities), some stored glycogen is hydrolyzed back to glucose. These two opposing processes are called glycogenesis and glycogenolysis, the formation and decomposition of glycogen, respectively. STRUCTURAL POLYSACCHARIDE: STORAGE POLYSACCHARIDE: CELLULOSE GLYCOGEN Glucose storage polysaccharide in humans and animals. Liver cells and Muscle cells : storage sites for glycogen in humans Alpha type (1 to 4) and (1 to 6) linkages STRUCTURAL POLYSACCHARIDE: CHITIN IMPORTANCE: When excess glucose is present in the blood (normally from eating too much starch), the liver and muscle tissue convert the excess glucose to glycogen, which is then stored in these tissues. Whenever the glucose blood level drops (from Science Faculty, 2024 | H. Stephen Stoker, Biochemistry, 3e. © 2017 C&E Publishing, Inc  ACIDIC POLYSACCHARIDE: HEPARIN ACIDIC POLYSACCHARIDE: HYALURONIC ACID Anticoagulant regulation of the inflammatory response A glycosaminoglycan Science Faculty, 2024 | H. Stephen Stoker, Biochemistry, 3e. © 2017 C&E Publishing, Inc Science Faculty, 2024 | H. Stephen Stoker, Biochemistry, 3e. © 2017 C&E Publishing, Inc