Bioquímica I- Química Biológica I

1. Bioquímica I- Química Biológica I

2. Biomoléculas • La actividad de las moléculas que constituyen las células está regida por los principios básicos de química • El agua, los iones inorgánicos y las pequenas moléculas orgánicas constituyen 75-80% del peso celular • Macromoléculas (proteínas, polisacárides, DNA) constituyen el resto del peso celular

3. The Chemicals of Life Figure 2-1a

5. 2.0 The Chemicals of Life (b) Macromolecules (23%) Figure 2-1b

6. macromolécules

7. The plasma membrane separates the cell from the environment • The fundamental structure of all cell membranes is the lipid bilayer • Various membrane proteins present in the different cell membranes give each membrane a specific function Figure 1-6

8. Componentes celulares

9. Prokaryotic cells • Single cell organisms • Two main types: bacteria and archaea • Relatively simple structure Figure 1-7a

10. Eukaryotic cells • Single cell or multicellular organisms • Plants and animals • Structurally more complex: organelles, cytoskeleton

15. Eukaryotic DNA is packaged into chromosomes Each chromosome is a single linear DNA molecule associated with proteins The total DNA in the chromosomes of an organism is its genome

17. Cells associate to form tissues • Tissues are composed of cells and extracellular matrix • Tissues may form organs • Rudimentary tissues and an overall body plan form early in development due to a defined pattern of gene expression and the ability of cells to interact with other cells • Many animals share the same basic pattern of development, which reflects commonalities in molecular and cellular mechanisms controlling development

18. Evolución Molecular • La evolución es un proceso histórico que dicta la forma y la estructura de la vida • La evolución depende de las alteraciones en la estructura y organización de los genes y de sus productos • Aspectos fundamentales de la vida celular se dan en muy diversos organismos y dependen de genes relacionadoss • cambios pequenos en ciertos genes permiten a los organismos adaptarse a diferentes entornos

20. 1.3 Lineage tree of life on earth Figure 1-5

23. Covalent bonds • Formed when two different atoms share electrons in the outer atomic orbitals • Each atom can make a characteristic number of bonds (e.g., carbon is able to form 4 covalent bonds) • Covalent bonds in biological systems are typically single (one shared electron pair) or double (two shared electron pairs) bonds

24. Covalent bonds have characteristic geometries

25. Covalent double bonds cause all atoms to lie in the same plane

26. The making or breaking of covalent bonds involves large energy changes In comparison, thermal energy at 25ºC is < 1 kcal/mol

27. A water molecule has a net dipole moment caused by unequal sharing of electrons Figure 2-5

33. Ions in aqueous solutions are surrounded by water molecules Figure 2-14

34. Asymmetric carbon atoms are present in most biological molecules • Carbon atoms that are bound to four different atoms or groups are said to be asymmetric • The bonds formed by an asymmetric carbon can be arranged in two different mirror images (stereoisomers) of each other • Stereoisomers are either right-handed or left-handed and typically have completely different biological activities • Asymmetric carbons are key features of amino acids and carbohydrates

35. Stereoisomers of the amino acid alanine Figure 2-6

36. Different monosaccharides have different arrangements around asymmetric carbons Figure 2-8

37. Noncovalent bonds • Several types: hydrogen bonds, ionic bonds, van der Waals interactions, hydrophobic bonds • Noncovalent bonds require less energy to break than covalent bonds • The energy required to break noncovalent bonds is only slightly greater than the average kinetic energy of molecules at room temperature • Noncovalent bonds are required for maintaining the three-dimensional structure of many macromolecules and for stabilizing specific associations between macromolecules

39. The hydrogen bond underlies water’s chemical and biological properties Molecules with polar bonds that form hydrogen bonds with water can dissolve in water and are termed hydrophilic Figure 2-12

40. Hydrogen bonds within proteins Figure 2-13

41. Ionic bonds • Ionic bonds result from the attraction of a positively charged ion (cation) for a negatively charged ion (anion) • The atoms that form the bond have very different electronegativity values and the electron is completely transferred to the more electronegative atom • Ions in aqueous solutions are surrounded by water molecules, which interact via the end of the water dipole carrying the opposite charge of the ion

42. Hydrophobic bonds cause nonpolar molecules to adhere to one another Nonpolar molecules (e.g., hydrocarbons) are insoluble in water and are termed hydrophobic Since these molecules cannot form hydrogen bonds with water, it is energetically favorable for such molecules to interact with other hydrophobic molecules This force that causes hydrophobic molecules to interact is termed a hydrophobic bond Figure 2-16

46. 2.2 Phospholipids are amphipathic molecules Figure 2-19

47. Phospholipids spontaneously assemble via multiple noncovalent interactions to form different structures in aqueous solutions Figure 2-20

48. van der Waals interactions are caused by transient dipoles When any two atoms approach each other closely, a weak nonspecific attractive force (the van der Waals force) is created due to momentary random fluctuations that produce a transient electric dipole Figure 2-15

49. Multiple weak bonds stabilize large molecule interactions Figure 2-11

50. Multiple noncovalent bonds can confer binding specificity Figure 2-17