Molecules of Life

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

Organic Compounds  Consist primarily of carbon and hydrogen atoms Carbon atoms bond covalently with up to four other atoms, often in long chains or rings  Functional groups attach to a carbon backbone Influence organic compound’s properties

An Organic Compound: Glucose  Four models

Functional Groups: The Importance of Position

Processes of Metabolism  Cells use energy to 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  Dehydration synthesis combines monomers to form polymers

Dehydration synthesis and Hydrolysis

Carbohydrates – The Most Abundant Ones  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

Oligosaccharides: Sucrose

Complex Carbohydrates: Starch, Cellulose, and Glycogen

c Glycogen. In animals, this polysaccharide is a storage form for excess glucose. It is especially abundant in the liver and muscles of highly active animals, including fishes and people. Structure of cellulose

Greasy, Oily – Must Be 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

Fats  Lipids with one, two, or three fatty acid tails Saturated  Triglycerides (neutral fats ) Three fatty acid tails Most abundant animal fat (body fat) Major energy reserves

Triglyceride Formation

Phospholipids  Main component of cell membranes Hydrophilic head, hydrophobic tails

Waxes  Firm, pliable, water repelling, lubricating

Steroids: Cholesterol  Membrane components; precursors of other molecules (steroid hormones)

Protein Structure  Built from 20 kinds of amino acids

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

Four Levels of Protein Structure 4. Quaternary structure Many proteins (e.g. enzymes) consist of two or more chains

Levels of Protein Structure

Why is Protein Structure So Important?  Protein structure dictates function  Sometimes a 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

Normal Hemoglobin Structure

VALINEHISTIDINELEUCINEGLUTAMATEVALINETHREONINEPROLINE sickle cell normal cell b One amino acid substitution results in the abnormal beta chain in HbS molecules. Instead of glutamate, valine was added at the sixth position of the polypeptide chain. c Glutamate has an overall negative charge; valine has no net charge. At low oxygen levels, this difference gives rise to a water-repellent, sticky patch on HbS molecules. They stick together because of that patch, forming rod shaped clumps that distort normally rounded red blood cells into sickle shapes. (A sickle is a farm tool that has a crescent-shaped blade.)

Clumping of cells in bloodstream Circulatory problems, damage to brain, lungs, heart, skeletal muscles, gut, and kidneys Heart failure, paralysis, pneumonia, rheumatism, gut pain, kidney failure Spleen concentrates sickle cells Spleen enlargement Immune system compromised Rapid destruction of sickle cells Anemia, causing weakness,fatigue, impaired development,heart chamber dilation Impaired brain function, heart failure d Melba Moore, celebrity spokes- person for sickle-cell anemia organizations. Right, range of symptoms for a person with two mutated genes for hemoglobin’s beta chain.

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

Nucleotides, DNA, and RNAs Nucleotide structure, 3 parts: Sugar Phosphate group Nitrogen-containing base

Nucleotide Functions: 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

Nucleotides of DNA

DNA, RNAs, and Protein Synthesis  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

covalent bonding in carbon backbone hydrogen bonding between bases