Biological Macromolecules: Lipids and Hydrolysis

General Information

• The course title is Biology for Health Sciences.
• The course code is BIOL 111.
• The textbook is "Biology A Global Approach 11th edition" by Campbell, Reece, et, al.
• There are 2 credit hours, consisting of a 1-hour lecture and a 1-hour lab.
• The course duration is 10 weeks.

Macromolecules of Life Overview

• All living things consist of four classes of large biological molecules including carbohydrates, lipids, proteins, and nucleic acids.
• Macromolecules are large polymers composed of thousands of covalently connected monomers.

Polymers

• Three of the four classes of life’s large organic molecules are polymers: carbohydrates/polysaccharides, proteins, and nucleic acids.

Synthesis and Breakdown of Polymers

• A condensation reaction, specifically dehydration reaction, occurs when two monomers bond through releasing a water molecule.
• Polymers disassemble into monomers through hydrolysis, the reverse of dehydration reaction.

Carbohydrates

• Include sugars and polymers of sugars.
• Monosaccharides, or single sugars, are the simplest carbohydrates
• Carbohydrate macromolecules are polysaccharides, which are polymers made of many sugar building blocks.

Monosaccharides

• Molecular formulas are usually multiples of CH2O.
• Glucose (C6H12O6) is the most common monosaccharide.
• Classified by:
  • Location of the carbonyl group in the carbon skeleton.
  • Number of carbons in the carbon skeleton.
• It's a major fuel for cells and raw material for building molecules.

Disaccharides

• A disaccharide forms when a dehydration reaction joins two monosaccharides.
• The covalent bond is a glycosidic linkage/bond.
• Lactose intolerance is the inability to breakdown lactose (glucose + galactose) in dairy products due to lactase deficiency.
• Symptoms can include abdominal pain, diarrhea, gas and bloating.
• Dairy-free alternatives or lactose-free milk can be consumed as alternatives.

Polysaccharides

• Polymers of sugars with storage and structural roles.
• Its structure and function are determined by its sugar monomers and the positions of glycosidic linkages.

Storage Polysaccharides

• Starch, a storage polysaccharide in plants, solely consists of glucose monomers.
• Plants store surplus starch as granules within chloroplasts and other plastids
• Glycogen, is a storage polysaccharide in animals found in the liver and muscle cells.
• Hydrolysis of glycogen in these cells releases glucose when sugar is needed.

Structural Polysaccharides

• Cellulose, a major component of tough plant cell walls.
• It's a polymer of glucose, but the glycosidic linkages differ.

Lipids

• Lipids are one class of large biological molecules that aren’t true polymers, or macromolecules.
• Lipids are hydrophobic and don't mix well with water.
• Mainly consist of hydrocarbons with nonpolar covalent bonds.
• The biologically important lipids include fats, phospholipids, and steroids.

Fats

• Fats are constructed from two types of smaller molecules: glycerol and fatty acids.
• A fatty acid consists of a carboxyl group attached to a long carbon skeleton (hydrocarbon).
• Three fatty acids join glycerol via an ester linkage, creating a triacylglycerol, also known as triglyceride.
• Fatty acids vary in length based on the number of carbons and the location of double bonds.
• Saturated fatty acids have the maximum possible number of hydrogen atoms and no double bonds.
• Unsaturated fatty acids have one or more double bonds.
• Fats made from saturated fatty acids are called saturated fats, and they are solid at room temperature and are mostly from animal origin.
• Fats made from unsaturated fatty acids are called unsaturated fats or oils, are liquid at room temperature, and are usually of plant or fish origin.
• Diets rich in saturated fats may cause cardiovascular disease through plaque deposits.
• Hydrogenation converts unsaturated fats into saturated fats by adding hydrogen, however, it creates unsaturated fats with trans double bonds.
• Trans fats may contribute more than saturated fats to cardiovascular diseases.
• The main function of fats is energy storage.
• Humans and other mammals store their long-term food reserves in adipose cells.
• Adipose tissue cushions vital organs and insulates the body.

Phospholipids

• A phospholipid consists of two fatty acids and a phosphate group attached to glycerol
• Fatty acid tails are hydrophobic, while the phosphate group and its attachments form a hydrophilic head.
• When added to water, phospholipids self-assemble into a bilayer where the hydrophobic tails point inward.
• It results in a bilayer arrangement found in cell membranes.
• It's also the major component of all cell membranes.

Steroids

• Lipids characterized by a carbon skeleton consisting of four fused rings.
• Cholesterol, a type of steroid, is a component found in animal cell membranes and is a precursor for other steroids.
• High cholesterol levels in the blood may contribute to cardiovascular disease.