Macromolecules (Carbohydrates and Lipids)

4 Classes of Molecules of Life

Carbohydrates, Lipids, Proteins, Nucleic Acids

Monomers

small organic molecules that serve as the building blocks of larger organic molecules

Polymers

large organic molecules that are composed of many similar monomers which are linked together by covalent bonds

Polymer reaction 1: Dehydration (synthesis) reaction

links 2 monomers together by losing a water molecule.

Dehydration reaction process

• One monomer loses a H⁺ while the other monomer loses and OH^-

• H⁺ + OH^- → H₂O

• Used to form polymers

Polymer reaction 2: Hydrolysis

reaction that breaks the bond between monomers by adding a water

Hydrolysis process

• H₂O → H⁺ + OH^-

• H⁺ binds to one monomer

• OH^- binds to the other monomer

• Used to break down polymers

Macromolecules

very large organic molecules

Macromolecules characteristics

• Polymers of carbohydrates, proteins, and nucleic acids

• Lipids are not considered macromolecules - lack monomers and polymers

CARBOHYDRATES (carbon, water)

Organic molecules composed of carbon, hydrogen, and oxygen in the form of sugars

Functions of carbohydrates

• Energy storage

• Building material

Monosaccharides

one sugar molecules

Characteristics of monosaccharides

• Monomer of carbohydrates

• Are multiples of CH₂O

• Have one carbonyl group and several hydroxyl groups

Classification of monosaccharides (1)

• Number of carbons - 3 to 7

  • Triose - sugars with 3 carbons

  • Pentose - sugars with 5 carbons

  • Hexose - sugars with 6 carbons

  • The name of most sugars end in -ose

Classification of monosaccharides (2)

• Position of the carbonyl group

  • Aldose sugar - carbonyl group is at one end of the molecule

  • Ketose sugar - carbonyl group is in the middle of the molecule

  • Aldose and ketose sugars with the same number of carbons are structural isomers

In monosaccharides, what forms rings in aqueous solutions?

5 and 6-carbon sugars

Monosaccharides have how many forms of glucose?

two, α glucose and β glucose

α glucose

hydroxyl group on number 1 carbon is below the plane of the ring

β glucose

hydroxyl group on number 1 carbon is above the plane of the ring

Disaccharides

2 monosaccharides bonded together by
a glycosidic linkage

Glycosidic linkage

covalent bond between 2 monosaccharides formed by a dehydration reaction

Polysaccharides

polymer with many monosaccharides bonded together by glycosidic linkages

Storage polysaccharides

• store energy

  • starch

  • glycogen

Starch

• polysaccharide used for energy storage in plants

  • Composed of α glucose molecules

  • Angle of bonds between glucose molecules causes starch to have a helical structure

Glycogen

• polysaccharide used for energy storage in animals

  • composed of α glucose molecules

  • Has a helical structure

  • More extensively branched than starch

  • Stores about a day’s supply of energy

Structural polysaccharides

• form cell walls (rigid structures covering the exterior of the cell)

  • Cellulose

  • Chitin

Cellulose

• polysaccharide used to
  form the cell wall in
  plants

  • Composed of only
    β glucose

  • Every other glucose is upside down

  • Cellulose is not digestible by most animals - fiber

  • Cellulose is straight - not helical

  • Never branched

  • Hydroxyl group of some glucoses form hydrogen bonds with hydroxyl groups of other glucoses lying parallel in the cell wall

Chitin

• polysaccharide used to form
  the cell walls of fungi and exoskeletons of arthropods

  • Has only β glucose - similar in structure to cellulose

  • Glucose has a nitrogen containing functional group

LIPIDS

Water insoluble molecules

General information of lipids

• composed of mostly hydrophobic regions with a few polar covalent bonds

• Functions

  • Energy storage

  • Form barriers

  • Internal communication

Functions of fats (Triglycerides)

• energy storage

• insulation

• cushioning and padding

Structure of fats

Glycerol, fatty acid, monoglyceride, diglyceride, triglyceride

Glycerol

3-carbon alcohol with a hydroxyl group bonded to each carbon

Fatty acid

long chain of hydrocarbons (16-18 carbons)

Structure of fatty acids

• Head - carboxyl group which bonds fatty acid to glycerol

• Tail - long nonpolar chain of hydrocarbons

• One fatty acid binds to each hydroxyl group of glycerol

• ester linkage - bond between glycerol and fatty acid

Monoglyceride

glycerol with one fatty acid

Diglyceride

glycerol with two fatty acids

Triglyceride

glycerol with three fatty acids

Two types of fats

Saturated and unsaturated fatty acids

Saturated fatty acids

• contain the maximum number of hydrogens in the fatty acid tail

  • single bond between all carbons in tail

  • straight tails

Saturated fats have

saturated fatty acids

• can pack closely together - straight tails

• are solid at room temperature

• animal products - meat, butter, and lard

• Linked to atherosclerosis - accumulation of plaque in blood vessels

Unsaturated fatty acids

contain less than the maximum number of hydrogens in the fatty acid tail

• double bond between carbons in tail

• have bent tails

• monounsaturated fats

• polyunsaturated fats

Monounsaturated fats

have one double bond in tail

Polyunsaturated fats

have multiple double bonds in tail

Unsaturated fats have

unsaturated fatty acids

• characteristics:

  • cannot pack closely together

  • liquid at room temperature

  • plants and fish - oils

  • less likely to cause cardiovascular disease

unsaturated fat isomers

Cis and trans

Cis

natural arrangement which results in kinks in the molecules

Trans

artificially produced arrangement that results in straight tails, which allow trans fats to pack together like saturated fats

Trans fats

unsaturated fats with
the double bond in the trans
formation

• behave like saturated fats

• found in hydrogenated vegetable oil

What are two essential fatty acids that the body cannot manufacture?

omega-6 fatty acids and omega-3 fatty acids

Characteristics of omega-6 fatty acids and
omega-3 fatty acids

• both are polyunsaturated fats

• omega refers to the position of the double bond closest to the end of the tail

• Important components for phospholipid formation

• Found in fish, shellfish, and plant oils

Phospholipids

lipid with a phosphate group bonded to
the glycerol

• Head - phosphate group bonded to one carbon of the glycerol molecule

  • phosphate group often has a charged or polar attachment

• Tail - two fatty acids bonded to the glycerol

  • Digylceride

Phosphate group is hydrophilic while the rest of the lipid is

hydrophobic

In aqueous solutions,
phospholipids form a
? with the phosphate
groups facing outward
and the tails facing inward

bilayer

Phospholipids are used to form what in cells?

membranes

Waxes

• Long fatty acid chain with an ester bond to a large alcohol

• Form waterproof coverings on plant leaves, and insect cuticles

• Energy storage molecule in some plankton

Steroids

lipids with a carbon skeleton of 4 fused rings

Characteristics of steroids

• Do not have glycerol and fatty acids

• Component in cell membranes

• Forms hormones - molecules used for internal communication

Cholestorol

• Precursor to many steroid hormones

• 2 types:

  • LDL cholesterol

  • HDL cholesterol

• If LDL is too high or HDL is too low, cholesterol can accumulate in blood vessels and lead to atherosclerosis

LDL cholesterol

carries cholesterol from liver
to tissues where it can form plaque

HDL cholesterol

carries cholesterol from tissues to liver