Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Organic Molecules (Figure 2-14; Table 2-4) • “Organic” describes compounds that contain C–C or C–H bonds • Carbohydrates – Organic compounds containing carbon, hydrogen, and oxygen – Commonly called sugars and starches • Monosaccharides – Simple sugars with short carbon chains; those with six carbons are hexoses (e.g., glucose), whereas those with five are pentoses (e.g., ribose, deoxyribose) (Figure 2-15) • Disaccharides and polysaccharides – Two (di-) or more (poly-) simple sugars that are bonded together through a synthesis reaction (Figure 2-16) Organic Molecules • Proteins (Table 2-5) – Most abundant organic compounds – Chainlike polymers – Amino acids—building blocks of proteins (Figures 2-17 to 2-19) • Essential amino acids – Eight amino acids that cannot be produced by the human body • Nonessential amino acids – 12 amino acids can be produced from molecules available in the human body Organic Molecules • Amino acids consist of: – Carbon atom – Amino group – Carboxyl group – Hydrogen atom – Side chain Organic Molecules • Levels of protein structure (Figure 2-20) – Protein molecules are highly organized and show a definite relationship between structure and function – There are four levels of protein organization: • Primary structure—refers to the number, kind, and sequence of amino acids that make up the polypeptide chain • Secondary structure—polypeptide is coiled or bent into pleated sheets stabilized by hydrogen bonds • Tertiary structure—a secondary structure can be further twisted, resulting in a globular shape; the coils touch in many places and are “welded” by covalent and hydrogen bonds • Quaternary structure—highest level of organization occurring when protein contains more than one polypeptide chain Organic Molecules • Structural proteins form the structures of the body • Functional proteins cause chemical changes in the molecules – Shape of a protein’s molecules determines its function • Denatured proteins have lost their shape and therefore their function Proteins can be denatured by changes in pH, temperature, radiation, and other chemicals • If the chemical environment is restored, proteins may be renatured and function normally Organic Molecules • Lipids (Table 2-6) – Water-insoluble organic molecules that are critically important biological compounds – Major roles: • Energy source • Structural role • Integral parts of cell membranes Organic Molecules • Lipids (cont.) – Triglycerides, or fats (Figures 2-22 and 2-23) • Most abundant lipids and most concentrated source of energy • The building blocks of triglycerides are glycerol (the same for each fat molecule) and fatty acids (different for each fat, they determine its chemical nature) – Types of fatty acids—saturated fatty acid (all available bonds are filled) and unsaturated fatty acid (has one or more double bonds) – Triglycerides are formed by a dehydration synthesis Organic Molecules • Lipids (cont.) – Phospholipids (Figure 2-25) • Fat compounds similar to triglyceride • One end of the phospholipid is water-soluble (hydrophilic); the other end is fat-soluble (hydrophobic) • Phospholipids can join two different chemical environments • Phospholipids may form double layers called bilayers that make up cell membranes Organic Molecules • Lipids (cont.) – Steroids (Figure 2-26) • Main component is steroid nucleus • Involved in many structural and functional roles Organic Molecules • Lipids (cont.) – Prostaglandins • Commonly called “tissue hormones”; produced by cell membranes throughout the body • Effects are many and varied; however, they are released in response to a specific stimulus and are then inactivated Organic Molecules • Nucleic Acids – DNA (deoxyribonucleic acid) • Composed of deoxyribonucleotides; that is, structural units composed of the pentose sugar (deoxyribose), phosphate group, and nitrogenous base (cytosine, thymine, guanine, or adenine) • DNA molecule consists of two long chains of deoxyribonucleotides coiled into double-helix shape (Figure 2-27) • Alternating deoxyribose and phosphate units form backbone of the chains Organic Molecules • DNA (cont.) – Base pairs hold the two chains of DNA molecule together – Specific sequence of more than 100 million base pairs constitute one human DNA molecule; all DNA molecules in one individual are identical and different from those in all other individuals – DNA functions as the molecule of heredity Organic Molecules • Nucleic acids – RNA (ribonucleic acid) • Composed of the pentose sugar (ribose), phosphate group, and a nitrogenous base • Nitrogenous bases for RNA are adenine, uracil, guanine, or cytosine (uracil replaces thymine) • Some RNA molecules are temporary copies of segments (genes) of the DNA code and are involved in synthesizing proteins • Some RNA molecules are regulatory, acting as enzymes (ribozymes) or silencing gene expression (RNA interference) Organic Molecules • Nucleic acids and related molecules (cont.) – NAD and FAD (Figure 2-31) • Used as coenzymes to transfer energy-carrying molecules from one chemical pathway to another – cAMP (cyclic AMP) • Made from ATP by removing two phosphate groups to form a monophosphate • Used as an intracellular signal Organic Molecules • Combined forms (cont.) – Examples: • Adenosine triphosphate (ATP)—two extra phosphate groups to a nucleotide • Lipoproteins—lipid and protein groups combined into a single molecule • Glycoproteins—carbohydrate (glyco, “sweet”) and protein Metabolism • Catabolism – Larger molecules smaller chemical units – Usually hydrolysis – Release energy + H2O Hydrolysis Large Molecule Small Molecules Metabolism • Anabolism – Smaller subunits Larger molecules – Dehydration synthesis – Requires energy (ATP) + H2O Dehydration Synthesis Small Molecules Large Molecule Metabolism • Adenosine Triphosphate (Figure 2-29) – Pentose sugar (ribose) – Nitrogen-containing molecule (adenine) – Three phosphate groups – High-energy bonds Organic Molecules • Nucleotides (cont.) – ATP (cont.) • High-energy bonds present between phosphate groups • Cleavage of high-energy bonds releases energy during catabolic reactions • Energy stored in ATP is used to do the body’s work • ATP often called the energy currency of cells • ATP is split into adenosine diphosphate (ADP) and an inorganic phosphate group by a special enzyme • If ATP is depleted during prolonged exercise, creatine phosphate (CP) or ADP can be used for energy