carbohydrates

• Carbohydrates are composed of the

  following basic monomer:

  (CH2O)
• Monosaccharides generally have

  molecular formulas that are some

  multiple of CH2O [glucose =

  C6H12O6 which is isomers
• What are the three types of carbohydrates?

  1. monosaccharides
  2. disaccharides
  3. polysaccharides
• Monosaccharides - simple sugars with multiple

  OH groups. Based on number of carbons (3-7), a

  monosaccharide is a triose, tetrose, pentose,

  hexose, or heptose
• Disaccharides - 2 monosaccharides covalently

  linked
• Polysaccharides - polymers consisting of chains

  of monosaccharide or disaccharide units (few

  100 to 1000’s)
• Monosaccharides - Glucose

  • The first to be used by cells as energy

  * There is a hydroxyl group

  attached to each carbon, except

  one, which is double bonded to

  an oxygen to form a

  carbonyl (aldeyde) group
• examples of monosaccharides

  Glucose is the primary source of energy

  Fructose is found in fruits

  Galactose is found in lactose, which is in milk

  Glucose, fructose, and galactose have the same

  chemical formula (C6H12O6 ) so they are called

  isomers?

  
• Monosaccharides can cyclize as

  the carbonyl group reacts with an

  OH (the double bond in the

  carbonyl group breaks to form 2

  single bonds).

  
• • Cyclization of glucose produces asymmetry at C1 (C1 =

  Carbon #1)

  • To distinguish between the two isomers, we use the α & β

  symbols to indicate how the OH group on C1 is oriented:

  • α (OH below the ring)
  • β (OH above the ring)

  
• The hydroxyl of one monosaccharide and a hydroxyl of

  another monosaccharide can join together

  The resulting bond is called a glycosidic linkage

  
• example of disaccharides

  what is this linkage? glycosidic linkage

  what is this disaccharide called? (results from the joining of glucose and fructose, and is known as a table sugar)sucrose

  
• Examples of Disaccharides

  what is this disaccharide called

  Maltose is a product of starch when broken down

  Has α(1🡪4) glycosidic link between the C1 -OH & C4

  -OH of 2 glucose

  
• Examples of Disaccharides

  3. Lactose

  the sugar that is in milk

  composed of galactose & glucose

  contains β(1→4) glycosidic linkage

  
• Polysaccharides


  Some are used for storage

  material and hydrolyzed

  as needed to provide free

  sugars for energy

  
  

  Others serve as building

  material for structures or

  as protection

  
  

  Most common polysaccharides are:

  starch, glycogen, and

  cellulose
• Examples of Polysaccharides

  what example of polysaccharides is the diagram below? Amylose

  • Plants store glucose as starch
  • two types - amylose or amylopectin made entirely of glucose
  • the free end of the polysaccharide is called the reducing end
  • amylose is a polymer of glucose with α(1→4) linkages
  • It is unbranched

  
• what is the example of a polysaccharide in the diagram below?

  Amylopectin

  is a glucose polymer with mainly α(1→4)

  linkages, but it also has branches formed by α(1→6)

  linkages (Branches are generally longer than shown above)

  The branches produce a compact structure and can be

  broken down for energy much more rapidly

  
• what is the example of a

  polysaccharide in the diagram below? Glycogen

  Animals store glucose as glycogen

  is extensively branched like amylopectin but glycogen

  has more α(1→6) branches

  stored in the liver

  Most efficient for the release of glucose as energy

  consumption in muscle during exercise

  The ability to rapidly mobilize glucose is more essential

  to animals than to plants

  
• what is the example of a polysaccharide in the diagram below? celluloseS

  Cellulose is found in plants only

  Function is STRUCTURAL

  constituent of the tough plant cell walls

  consists of long linear chains of glucose with β(1→4)

  linkages

  Every other glucose is flipped over, due to the β

  linkages which allow for intra-chain and inter-chain

  H-bonds

  
• No mammal makes the necessary

  enzymes to break down cellulose

  even though it is unbranched –

  why?

  Those mammals that eat a lot of

  cellulose, like cows, need to keep

  symbiotic bacteria in their digestive

  tracks to help them digest the

  cellulose
• • Lectins are glycoproteins that

  recognize and bind to specific

  oligosaccharides

  • play a role in interactions and

  communication between cells typically

  for recognition
• Mannan-binding lectin (MBL) is

  a glycoprotein found in blood

  plasma that associates with cell

  surface carbohydrates of

  disease-causing microorganisms,

  promoting phagocytosis of these

  organisms as part of the immune

  response
• What makes up lactose? Sucrose? Maltose?

  lactose= galactose and glucose

  sucrose= glucose and fructose

  maltose= glycosidic link between the c1 -oh and c4 -oh of 2 glucose
• What makes alpha glucose different from beta?

  a is below the ring, and b is above the ring
• How are disaccharides made from

  monosaccharides?

  All disaccharides

  form from a reaction

  between two

  monosaccharides.
• How is amylose different from amylopectin?

  • amylose is a polymer of glucose with α(1→4) linkages

  It is unbranched

  • Amylopectin is a glucose polymer with mainly α(1→4)

  linkages, but it also has branches formed by α(1→6)

  linkages
• Why can’t we digest cellulose?

  we lack the enzymes needed to digest cellulose.