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
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
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
c Glycogen. In animals, thispolysaccharide 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
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
Why is Protein StructureSo 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
VALINE HISTIDINE LEUCINE GLUTAMATEVALINETHREONINE PROLINE
sickle cell
normal cell
b One amino acid substitution results in theabnormal beta chain in HbS molecules. Insteadof glutamate, valine was added at the sixthposition 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 togetherbecause 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
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