MACROMOLECULESCarbohydrates - Lipids

Proteins - Nucleic Acids

1. Most Macromolecules are Polymers

• From the greek polys for “many” and meris for “part”

• A long molecule consisting of many similar building blocks

• Building blocks are linked by covalent bonds

• Macromolecule polymers include proteins, carbohydrates and nucleic acids

• Repeating units that serve as building blocks are called “monomers”

• Monomers are connected by a reaction in which two molecules are covalently bonded to each other through a loss of a water molecule

• This is called a dehydration reaction

• Polymers are disassembled into monomers by hydrolysis

• Hydrolysis is a process where bonds between monomers are broken by a water molecule

2. Carbohydrates• Include both sugars and their

polymers

• Serve as fuel and carbon sources

Monosaccharides• Single sugar monomers

• Known as simple sugars

• Chemical formulas are multiple of CH2O

• Classified based on number of carbons and arrangement of atoms

• Sweet tasting, colorless, crystalline

Glucose – C6H12O6

Disaccharides• Consists of two

monosaccharides linked by a covalent bond formed by a dehydration reaction (water molecule is produced)

• Maltose is a disaccharide formed by linking two monosaccharides of glucose

• Also known as malt sugar

• Used as an ingredient in brewing beer

• Sucrose is the most common disaccharide

• Known as table sugar

• Its two monomers are glucose and fructose

• Plants carbohydrates from leaves to roots in the form of sucrose

• Lactose is a disaccharide present in milk

• Consists of glucose and galactose monomers

Polysaccharides

• Polymers with a few hundred to a few thousand monomers

• Some serve as storage molecules

• Some serve as building materials for structures that protect the cell

Storage Polysaccharides

• Starch is a storage polysaccharide in plants

• This stored starch represents stored energy

• To use this energy plants break the bonds between monomers by hydrolysis

• Humans can also use hydrolysis to get energy from plant starch

• Wheat, corn and rice are sources of plant starch in the human diet

• Glycogen is a storage polysaccharide in animals

• Humans and other vertebrates store glycogen mainly in liver and muscle cells

• In humans the glycogen storage is depleted in about one day unless replenished with food

Structural Polysaccahrides• Organisms build strong materials from

structural polysaccharides

• Cellulose is a major component of the tough cell walls that enclose plant cells

• Grouped cellulose molecules are called microfibrils

• Microfibrils are strong cables that are the building materials for plants

• Wood that we use for lumber is rich in cellulose

• Humans cannot digest cellulose, but it is an important part of a healthy diet

• Cellulose, or fiber, abrades the wall of the digestive tract, encouraging mucus secretion

• This aids in the smooth passage of food through the tract

• Chitin is another structural polysaccharide

• It is used by arthropods (insects, spiders, crustaceans) to build their exoskeletons

3. Lipids• Lipids are macromolecules that do not

include polymers

• Compounds called lipids are grouped together because of their hydrophobic behavior

• They consist mostly of hydrocarbons

• Lipids include fats, phospholipids and steroids

• Other families of lipids include waxes and certain pigments

butter

Skateboard wax

• The base unit for all lipids is a fatty acid

Hydrocarbon tail

Carboxyl head

Fats • A fat is constructed from two types of smaller molecules; glycerol and fatty acids

1 glycerol

3 Fatty Acids

• Fatty acids vary in length and in the number and location of double bonds

• The term saturated and unsaturated fats are commonly used in nutrition

Lard – a saturated fat

• Fats separate from water because the water molecules hydrogen bond with each other and exclude the fats.

Saturated Fatty Acid• Also known as saturated fat

• Contains no double bonds between carbons in hydrocarbon tail

• This means as many hydrogen atoms as possible are bonded to the carbon skeleton

• Most animal fats are saturated

• Solid at room temperature

• Examples are butter and lard

Unsaturated Fatty Acid• Also known as unsaturated fat

• Contains one or more double bonds due to the removal of a hydrogen atom

• A kink in the shape will occur wherever a double bond occurs

• Fats of plants and fishes are generally unsaturated

• Referred to as oils, liquid at room temperature

• Examples are corn oil and cod liver oil

Phospholipids• Similar to fats but have

only two fatty acids instead of three

• Also contain a phosphate group with the glycerol head which has an affinity for water

• Hydrocarbon tails are excluded from water

• When added to water, phospholipids self assemble into groupings that shield the tails from water

• At the surface of a cell phospholipids are arranged into a bilayer (double layer)

• This forms a boundary between the cell and its external environment

Steroids• Consist of a carbon skeleton with four fused

rings

• Cholesterol is a steroid that is a component of animal cell membranes

• Many hormones, including sex hormones, are steroids

4. Proteins• Humans have tens of thousands of

proteins

• Each protein has a specific structure and function

• They are the most structurally sophisticated molecules known

• Amino acids are the sub unit of proteins

• All proteins are polymers constructed from the same set of 20 amino acids

• Polymers of amino acids are called polypeptides

Four levels of protein structure

• Primary structure - the unique sequence of amino acids

• Secondary structure - the sequence of amino acids in a polypeptide is coiled or bent

• Tertiary structure - folding and bonding between side chains of amino acids

• Quaternary structure - two or more poly peptide chains are joined together

• Collagen is a fibrous protein

• This super-coiled protein has great strength and is found in tendons and ligaments

• Hemoglobin is a protein in blood that has a quaternary structure and is known as a globular protein

• If ph, salt concentration or temperature of a proteins environment change, the protein may unravel

• This is called denaturation

• A denatured protein can no longer perform its function

5. Nucleic Acids

• Nucleic acids are polymers of monomers called nucleotides

• There are two types of Nucleic Acids– Deoxyribonucleic acid (DNA)– Ribonucleic acid (RNA)

DNA

• Nucleic acids forms genes which enable living organism to reproduce from one generation to the next

• Nucelotides are composed of three parts

–A nitrogen base

–A pentose (5 carbon sugar)

–A phosphate group (PO4)

• Nucleotides form nucleic acids which come together to form genes

• Genes determine the structure and shape of proteins

• Genes (DNA) and their products (proteins) document the heredity background of an organism

The End

finally