Molecules of Life Molecules of life are synthesized by living cells – Carbohydrates – Lipids – Proteins – Nucleic acids

Structure to Function Molecules of life differ in three-dimensional structure and function – Carbon backbone carbon and hydrogen atoms bond covalently with up to four other atoms, often in long chains or rings – Attached functional groups Influence organic compound’s properties Structures – give clues to how they function – Four models

Processes of Metabolism Cells use energy – grow and maintain themselves Enzyme-driven reactions build, – rearrange, and split organic molecules

Building Organic Compounds Cells form complex organic molecules – Simple sugars → carbohydrates – Fatty acids → lipids – Amino acids → proteins – Nucleotides → nucleic acids Condensation combines monomers to form polymers Condensation and Hydrolysis

What are carbohydrates? Three main types of carbohydrates – Monosaccharides (simple sugars) – Oligosaccharides (short chains) – Polysaccharides (complex carbohydrates) Carbohydrate functions – Instant energy sources – Transportable or storable forms of energy – Structural materials

What are complex carbohydrates? Starch – Stored form of polysaccharide in plants. Cellulose – Structural polysaccharide found in plants. Glycogen. – Stored polysaccharide in animals – abundant in liver and muscles of highly active animals, including fishes and people.

What are lipids? Lipids – Fats, phospholipids, waxes, and sterols – Don’t dissolve in water – Dissolve in nonpolar substances (other lipids) Lipid functions – Major sources of energy – Structural materials – Used in cell membranes

What are fats? Lipids with one, two, or three fatty acid tails – Saturated – Unsaturated (cis and trans) Triglycerides (neutral fats ) – Three fatty acid tails – Most abundant animal fat (body fat) – Major energy reserves

What are phospholipids? Main component of cell membranes – Hydrophilic head, hydrophobic tails

What are steroids? Cholesterol Membrane components; precursors of other molecules (steroid hormones)

What are proteins ? Proteins have many functions – Structures – Nutrition – Enzymes – Transportation – Communication – Defense Built from 20 kinds of amino acids

Protein Synthesis Carbonyl group and amino group react to form new linkages.

Four Levels of Protein Structure 1. Primary structure – Amino acids joined by peptide bonds form a linear polypeptide chain 2. Secondary structure – Polypeptide chains form sheets and coils 3. Tertiary structure – Sheets and coils pack into functional domains 4. Quaternary structure – Many proteins (e.g. enzymes) consist of two or more chains

Why is protein structure so important? Protein structure – dictates function mutation in DNA results – in an amino acid substitution that alters a protein’s structure and compromises its function – Example: Hemoglobin and sickle-cell anemia

Denatured proteins If a protein unfolds and loses its three-dimensional shape (denatures), it also loses its function Caused by shifts in pH or temperature, or exposure to detergent or salts – Disrupts hydrogen bonds and other molecular interactions responsible for protein’s shape

What are nucleotides? DNA and RNAs Nucleotide structure, 3 parts: – Sugar – Phosphate group – Nitrogen-containing base

What are functions of nucleotide ? Reproduction, Metabolism, and Survival DNA and RNAs are nucleic acids, each composed of four kinds of nucleotide subunits ATP energizes many kinds of molecules by phosphate-group transfers Other nucleotides function as coenzymes or as chemical messengers

DNA vs RNA DNA (double-stranded) – Encodes information about the primary structure of all cell proteins in its nucleotide sequence RNA molecules (usually single stranded) – Different kinds interact with DNA and one another during protein synthesis