Carbohydrates

Biochemistry

Study of chemical substances in living organisms and their interactions.

Bioinorganic Substances

Water and inorganic salts that are essential for life.

Bioorganic Substances

Carbohydrates, lipids, proteins, and nucleic acids that are crucial for biological functions.

Life Sustaining Interactions

Isolated substances do not sustain life; their interactions within cells do.

Carbohydrates in Plants

Over half of organic carbon in plants is carbohydrate material, accounting for 75% of dry plant material.

Cellulose

A structural element of carbohydrates in plants.

Starch/Glycogen

Energy reservoirs in plants and animals, respectively.

Provide energy, serve as short-term reserves in a form of glycogen, supply carbon atoms for synthesis, form DNA/RNA components, and participate in cell recognition.

Functions of Carbohydrates

Monosaccharides

Single units of carbohydrates (e.g., glucose, fructose).

Disaccharides

Two monosaccharide units (e.g., sucrose, lactose).

Oligosaccharides

3-10 monosaccharide units.

Polysaccharides

Many monosaccharide units (e.g., starch, cellulose).

Monosaccharide Classification

Based on carbon atoms (triose, tetrose, pentose, hexose) and functional groups (aldoses and ketoses).

Chirality

Most biological molecules exhibit "handedness" due to chiral centers.

Chiral Centers

Carbon atoms attached to four different groups, leading to stereoisomerism.

right handed form

Almost all monosaccharides

left handed form

Amino acids are always

Stereoisomers

Isomers that have the same molecular and structural formulas but differ in the orientation of atoms in space

Enantiomers

Stereoisomers whose non-superimposable mirror images of chiral molecules.

Diastereomers

Stereoisomers that are not mirror images.

Fischer Projection

Two-dimensional notation for spatial arrangement around chiral centers.

Tetrahedral Geometry

Groups attached to chiral centers assume tetrahedral arrangements.

Enantiomer Properties

Similar physical properties except for interaction with polarized light; dextrorotatory and levorotatory describe light rotation.

Aldoses

Monosaccharides containing an aldehyde group.

Ketoses

Monosaccharides containing a ketone group.

Aldohexose

Monosaccharide with aldehyde group and 6 C atoms

Ketopentose

Monosaccharide with ketone group and 5 C atoms

D-Glucose

Most abundant monosaccharide important for human nutrition.

D-Galactose

Milk sugar important for brain tissue.

D-Fructose

Sweetest sugar

Chiral molecules

Molecules that have nonsuperimposable mirror images.

Mirror image

Reflection of an object in a mirror.

Superimposable mirror images

Images that coincide at all points when laid upon each other.

Achiral molecule

A molecule that has superimposable mirror images.

Nonsuperimposable mirror images

Images where not all points coincide when laid upon each other.

Chiral molecule (handedness)

A molecule that cannot be superimposed on its mirror image.

D-Ribose

A sugar that is part of complex molecules like RNA, ATP, and DNA.

Cyclic Hemiacetal

A form of monosaccharides where the carbonyl group reacts with a hydroxyl group to form a cyclic structure.

α-form of D-Glucose

The configuration where the –OH of C1 and CH2OH of C5 are on opposite sides.

β-form of D-Glucose

The configuration where the –OH of C1 and CH2OH of C5 are on the same side.

Anomers

Cyclic monosaccharides that differ only in the position of substituents on the anomeric carbon atom.

Pyranose

A cyclic monosaccharide containing a six-atom ring.

Furanose

A cyclic monosaccharide containing a five-atom ring.

Haworth Projection Formula

A two-dimensional structural notation that specifies the three-dimensional structure of a cyclic monosaccharide.

D or L Series

Determined by the position of the –OH group on C1 relative to the –CH2OH group in the Haworth projection.

Oxidation of Monosaccharides

A reaction that can convert monosaccharides into acidic sugars.

Aldonic Acid

An acidic sugar formed when weak oxidizing agents oxidize the aldehyde end of a monosaccharide.

Reducing Sugar

A carbohydrate that gives a positive test with Tollens and Benedict’s solutions.

Aldaric Acid

A dicarboxylic acid produced by strong oxidizing agents oxidizing both ends of a monosaccharide.

Alduronic Acid

An acidic sugar produced by enzymatic oxidation of the primary alcohol end of an aldose.

Sugar Alcohol

A polyhydroxy alcohol formed by the reduction of the carbonyl group in a monosaccharide.

Glycoside

An acetal formed from a cyclic monosaccharide by replacing the carbon –OH group with an –OR group.

Glucoside

A glycoside produced from glucose.

Phosphate Ester

A compound formed when hydroxyl groups of a monosaccharide react with inorganic oxyacid.

Amino Sugar

A sugar formed when one hydroxyl group of a monosaccharide is replaced with an amino group.

Chitin

A polysaccharide that contains amino sugars as

Carbonyl Group

A functional group in monosaccharides that can be reduced to a hydroxyl group using hydrogen as a reducing agent.

Sugar Alcohol

The product formed when the carbonyl group of a monosaccharide is reduced to a hydroxyl group; also known as alditol.

Sorbitol

A sugar alcohol used as a moisturizing agent in foods and cosmetics and as a sweetening agent in chewing gum.

Glycoside

An acetal formed from a cyclic monosaccharide by replacing the carbon –OH group with an –OR group.

Glucoside

A glycoside produced from glucose.

Galactoside

A glycoside produced from galactose.

α and β Forms

The two anomeric forms in which glycosides can exist.

Phosphate Ester

A compound formed when hydroxyl groups of a monosaccharide react with inorganic oxyacid.

Stability in Aqueous Solution

Phosphate esters of monosaccharides are stable in water and play important roles in carbohydrate metabolism.

Amino Sugar

A type of sugar formed when one hydroxyl group of a monosaccharide is replaced with an amino group.

C2 Hydroxyl Group

The specific hydroxyl group in naturally occurring amino sugars that is replaced by an amino group.

Building Blocks of Polysaccharides

Amino sugars and their N-acetyl derivatives are essential components of polysaccharides like chitin and hyaluronic acid.

Maltose

A disaccharide made of 2 D-glucose units, one being α-D-glucose, linked via an α(14) glycosidic linkage.

Digestion of Maltose

Easily digested by humans due to an enzyme that breaks α(14) linkages.

Cellobiose

A disaccharide produced as an intermediate in the hydrolysis of cellulose, containing two D-glucose units linked by a β(14) glycosidic linkage.

Digestion of Cellobiose

Cannot be digested by humans.

Lactose

A disaccharide made of a β-D-galactose unit and a D-glucose unit joined by a β(14) glycosidic linkage.

Source of Lactose

Milk is rich in lactose, with human milk containing 7%-8% and cow's milk containing 4%-5%.

Lactase

An enzyme that hydrolyzes β(14) glycosidic linkages in lactose.

Lactose Intolerance

A condition where individuals lack the enzyme lactase, preventing the digestion of lactose.

Causes of Lactase Deficiency

Can be due to genetic defects, physiological decline with age, or injuries to intestinal mucosa.

Symptoms of Lactose Intolerance

Undigested lactose attracts water, causing fullness, discomfort, cramping, nausea, and diarrhea.

Bacterial Fermentation of Lactose

Produces lactic acid and gas, contributing to discomfort in lactose-intolerant individuals.

Sucrose

The most abundant disaccharide found in plants, commonly known as table sugar.

Sources of Sucrose

Produced commercially from sugarcane and sugar beets, with sugarcane containing up to 20% sucrose and sugar beets up to 17%.

Oligosaccharides

Carbohydrates that contain 3–10 monosaccharide units bonded via glycosidic linkages.

Raffinose

An oligosaccharide made of 1 galactose, 1 glucose, and 1 fructose.

Stachyose

An oligosaccharide made of 2 galactose, 1 glucose, and 1 fructose units.

Common sources of oligosaccharides

Found in onions, cabbage, broccoli, and whole wheat.

Human blood types

Classified into four types – A, B, AB, and O.

Blood type differences

Based on the type of oligosaccharides present in the blood.

Transfusion reactions

Wrong blood type transfusions can cause blood cells to clump, leading to potentially fatal reactions.

Universal donors

People with type O blood can donate to any blood type.

Universal recipients

People with type AB blood can receive from any blood type.

Common blood types in the U.S.

Type O is the most common, followed by type A.

Biochemical basis of blood types

Involves oligosaccharides on the plasma membranes of red blood cells.

Key oligosaccharides for blood groups

D-galactose and its derivatives.

Solanine

An oligosaccharide found in potatoes, associated with an alkaloid.

Bitter taste of potatoes

Caused by relatively higher levels of solanine.

Polysaccharides

Polymers of many monosaccharide units bonded with glycosidic linkages.

Homopolysaccharide

A type of polysaccharide composed of only one type of monosaccharide.

Heteropolysaccharide

A type of polysaccharide composed of two or more different types of monosaccharides.

Sweetness

Polysaccharides are not sweet, unlike monosaccharides which are sweet.

Tollen’s and Benedict’s tests

Polysaccharides do not show positive results in these tests, while monosaccharides do.