Biology Chapter on Molecules of Life

Molecules of Life

• Cells are primarily composed of carbon-based molecules, with water being the majority component.
• Organic compounds contain carbon atoms.
• The simplest organic compounds are hydrocarbons, consisting only of carbon and hydrogen.
• Four major classes of organic molecules are carbohydrates, lipids, proteins, and nucleic acids.

Organic Molecules

• Organic molecules are often called macromolecules because of their large size.
• They are also called polymers due to their structure from identical building blocks (monomers) bonded together.
• Monomers are the subunits used to build larger molecules (polymers).
• Polymers are large molecules that are chains of monomers.

Carbohydrates

• Carbohydrates are the primary energy source for cells.
• The building blocks of carbohydrates are simple sugars.
• There are three types of carbohydrates: monosaccharides, disaccharides, and polysaccharides.

Monosaccharides

• Monosaccharides are simple sugars, which are monomers of carbohydrates.
• Examples: glucose, fructose, galactose

Disaccharides

• Disaccharides are formed when a dehydration reaction joins two monosaccharides.
• Examples: Sucrose (glucose + fructose), Maltose (glucose + glucose), Lactose (glucose + galactose)

Polysaccharides

• Polysaccharides are long chain polymers composed of simple sugars (monosaccharides).
• Examples: Starch (storage polysaccharide in plants, composed of glucose monomers), Glycogen (storage polysaccharide in animals, composed of glucose monomers), Cellulose (polymer of glucose that forms plant cell walls).

Lipids

• Lipids are hydrophobic (water-fearing) compounds.
• The most important biologically important lipids are fats, phospholipids, and steroids.

Fats

• Fats are energy-storage molecules.
• Fats are constructed from glycerol and fatty acids.
• Dietary fat mainly consists of triglycerides.
• A triglyceride is a combination of glycerol and three fatty acids.

Phospholipids

• Phospholipids are structurally similar to fats and are a crucial component of cell membranes, forming a bilayer.
• A phospholipid has two fatty acid tails (hydrophobic) and a phosphate group attached to glycerol (hydrophilic head).

Steroids

• Steroids are lipids composed of fused ring structures.
• Cholesterol is a steroid that plays a significant role in the structure of cell membranes.
• Cholesterol is the precursor for the synthesis of sex hormones.

Proteins

• Proteins are polymers built from amino acid monomers.
• All proteins are constructed from a common set of 20 amino acids.
• Amino acids are linked together by peptide bonds, creating a long protein chain.
• Amino acids have an amino group, a carboxyl group, and a side chain (R group) differing between the 20 kinds of amino acids.

Peptide Bond Formation

• A peptide bond forms between the amino group of one amino acid and the carboxyl group of another amino acid through a dehydration reaction, releasing water.

Protein Functions

• Proteins perform various functions, including structural components (actin & myosin), defensive proteins (antibodies), transport molecules (hemoglobin), cell surface receptors and channels, enzymes (catalysts speeding up chemical reactions), and hormones (insulin, growth hormone).

Nucleic Acids

• Nucleic acids are polymers called polynucleotides, comprising deoxyribonucleic acid (DNA) and ribonucleic acid (RNA).
• A polynucleotide is made of monomeric units called nucleotides.
• Each nucleotide consists of a pentose sugar, a phosphate group, and a nitrogenous base.

DNA Function

• DNA stores the genetic material.

RNA Function

• RNA transfers genetic information from the nucleus to the cytoplasm for protein synthesis.

This quiz explores the fundamental organic molecules essential for life, including carbohydrates, lipids, proteins, and nucleic acids. It covers the composition of cells, the structure of organic compounds, and the types of carbohydrates. Test your understanding of macromolecules and their building blocks with this quiz.