Chapter 10: Sugar (carbohydrates)

Carbohydrates role

energy source for cells, nucleic acids, ATP, cell walls, important part of glycoproteins (sugar)(see examples)

Monosaccharides/ simple sugars

•  single ring structure that are soluble in water

Disaccharide

double ring structure that are soluble in water

Oligosaccharides

• 3 to 9 ring structure that are insoluble in water

polysaccharides/ complex sugars

• multi ring polymer structures that are insoluble in water but are very stable compounds

carbohydrates found in food

Monosaccharides functional groups

• aldose and ketose, they are hydroxyl/ alcohol group

Aldose

• contains an aldehyde functional group, 3-6 carbons, all carbons except two end ones are chiral

• Glyceraldehyde, ribose, glucose, galactose 

Ketose

• contains a ketone functional group, 3-6 carbons,  all carbons except two end ones and the carbonyl carbon are chiral

• fructose

• Only the D-configuration are found in nature (not L)

• Only the D-configuration are found in nature (not L)

Anomeric carbon

• carbonyl carbon, carbon number is labeled 1 for aldose and number 2 carbon for ketose 

Forming hemiacetal bonds

• aldehyde or ketone reacts with a hydroxy group on carbon 5

beta (β) configuration

• hydroxyl group on carbon 1 is on the same side (cis) as carbon 6

alpha (α) configuration

• hydroxyl group on carbon 1 is on the opposite side (trans) as carbon 6

Monosaccharides

• single ring structures, very soluble in water, provide energy

• Glucose, fructose, galactose 

simple sugars/ monosaccharides

• all carbohydrate compounds that have two or more monosaccharides will be in the ring structure only.  

Simple sugars are very reactive

•  Because sugars have many hydroxide groups, they are able to react with acidic carbonate groups to form esters

Glycation

• non-enzymatic reaction where monosaccharides form a covalent bond with protein molecules such as fibrinogen, collagen, and proteins which denature them, excessive glucose in blood due to diabetes, tested with HbA1c Test

• Fructose is 10 times more reactive than glucose 

• Fructose is 10 times more reactive than glucose 

Glycosidic bond

• condensation reaction (removal of water) between the anomeric carbon on one monosaccharide and any of the hydroxide groups on the second monosaccharides 

Glycosidic linkage

• water molecule is removed, anomeric hydroxide is in the alpha position,

Alpha (1,4) bond

• 1 and 4 hydroxide groups are bonded, a 1, 4 glycosidic bond is formed.  If the anomeric carbon is in the alpha position.

Beta (1,4) bond

• OH on the anomeric carbon is in the beta position, hydroxide groups on each sugar is on opposite side of each sugar, can be broken by enzymes

Disaccharides

 3 most important are sucrose  lactose  and maltose, chemistry is similar to simple sugars, very sweet

Sucrose

•  table sugar

Lactose

•  sugar found in milk, hard for many adults to digest 

Maltose

•  found in beer made from barley 

Oligosaccharides

•  tri-saccharides, tetra-saccharides, penta-saccharides, aka soluble fiber because they dissolve in water but cannot be broken down, need special enzymes to break them down so they can be used for energy production 

Tri-saccharides (raffinose)

Found in many vegetables especially in grains and beans, breaks down into galactose glucose and fructose, sweetness of 22 compared to sucrose

Tetra-saccharides (Stachyose)

•  Found in many vegetables, especially peas, beans and soybeans, breaks down into 2 units of galactose, one unit of glucose and fructose, sweetness of 20

Penta- saccharides (Verbascose)

•  Found in many legumes, 3 units of galactose and one unit of glucose and fructose

Polysaccharides

• aka insoluble fibers, insoluble polymers of simple sugars, can only be broken down by specialized enzyme, no sweetness associated with them, (ex. Cellulose, starch, pectin, glycogen)

Cellulose

• from plant cells walls, connecting bonds are beta (1,4) bands

Starch

•  storing chemical energy in plants, amylose and amylopectin, formed primarily by plants, , polymer of glucose which means they are insoluble in water

Amylose

• linear, few to no branches, aka firm starch, alpha (1-6) bonds,

Amylopectin

branched, aka soft starch, alpha (1-6) bonds,

Pectin

 form plant plants cell wall

Glycogens

•  storing energy in the cells of animals especially in working muscles and liver cells, very branched, The long polymer chains are joined by alpha (1,4) bonds and the branch chains are formed by the alpha (1,6) bonds.  

Cellulose

• polymer of glucose formed by plants, connecting bonds are beta (1,4) bonds, needs specific enzyme to break which most animals and humans do not possess, used by plants to make ridged stems 

Pectin

• molecule found in plants made from multiple simple sugars bonded in multiple different ways

Blood type

•  chemical markers made from simple carbohydrates, 3 types: O= give anyone, only receive O, AB= receive anyone, only give AB