2Overview: Inquiring About the World of life Evolution is the process of change that has transformed life on Earth.Biology is the scientific study of lifeBiologist ask questions such as:How does a single cell develop into an organism?How does the human brain work?How do living things interact in communities?
3Evolution, the Overarching Theme of Biology Evolution makes sense of everything we know about living organismsOrganisms living on Earth are modified descendents of common ancestors
4The Biological Hierarchy The study of life can be divides into different level of biological organization
5Life, Chemistry and Water Biology is a multidisciplinary scienceLiving organisms are subject to basic laws of physics and chemistry
6Matter, Elements & compounds Organisms are composed of matterMatter – anything that takes up space and has massMass measures the quantity of matter in an object and is defined by:Volume is how much space it takes upDensity measure concentration of matterMatter is made up of elementsAn element is a substance that cannot be broken down to other substances by chemical reactionsA compound is a substance consisting of two or more elements in a fixed ratio.A compound has characteristics different from those of its elements
7Sodium Chloride(NaCl) Table SaltSodium Chloride(NaCl)Sodium (Na)Chlorine (Cl)Is oxygen an element or a compound? What about iron? Water? Carbon di oxide?
8Essential Elements of Life About 25 of the 92 elements are essential of lifeCarbon (C), hydrogen (H), oxygen (O), and nitrogen make up 96% of living matter.Most of the remaining consist of calcium (Ca), phosphorus (P), potassium (K), sulfur (S), sodium (Na), chlorine (Cl) and magnesium (Mg).Trace elements are those required by an organism in minute quantities. Example: selenium, Zinc
9Atomic StructureEach elements consists of one type of atomEach atom consists of an atomic nucleus surrounded by fast moving, negatively charged electronsAtomic nuclei contain positively charged protons – the number of protons (atomic number) identifies an elementThe nuclei of all atoms (except hydrogen) also contain uncharged neutrons
10ISOTOPES OF CARBONIsotopesMakes atomic number not as simple as it may seemProtons and Neutrons in the nucleusNeutrons can vary independently of the number of protonsNeutrons add weight to the atomIsotopes have the same number of protons, different number of neutrons
11Isotopes are used in biological research as tracers Isotopes in ResearchRadioisotopes decay can be used to estimate the age of organic material, rocks, or fossils that contain them.Isotopes are used in biological research as tracersRadioisotopes such as 14C, 32P, and 25SStable, nonradioactive isotopes such as 15N (heavy nitrogen)
12Radioactive iodine becomes concentrated in the thyroid gland 123I can be used to visualize the thyroid glandScans of human thyroid glands after 123I was injected into the blood streamRadioactive iodine becomes concentrated in the thyroid gland
13Chemical Bonds and Chemical Reactions Atoms of reactive elements tend to combine into molecules by forming chemical bondsThe four most important chemical linkages in biological molecules are ionic bonds, covalent bonds, hydrogen bonds and van der Waals forces.Chemical reactions occur when atoms or molecules interact to form new chemical bonds or break old ones
14Chemical Bonds and Chemical Reactions Forces:Covalent bondsHydrogen bondsIonic bondsvan der Waals bondsMacromoleculesCarbohydrateProteinsNucleic acidsLipids
15Covalent Bonds Principle form to hold atoms together based on sharing electronsvery strong
16to break a C-C bond require 83 kcal/mole the bond cant be break with any physiological conditionThe bond can only be bend, stretch or rotateEnzymes: Biological catalysts that enable specific bonds to be broken or formed under physiological conditions
17Types of covalent bonds: rotateSingle bonds C-CDouble bonds C=CTriple bonds C=CsaturatedStrongerunsaturatedCan’t rotateOther molecules:Oxygen molecule O=ONitrogen molecule N=NNitrogen is strong molecule, cant be broken by any organism, but by bacteria which produce enzyme name nitrogenase
18Chirality characteristics of covalent bond Carbon can make 4 COVALENT bonds comes out as tetrahedron
19Molecules are known as Optical isomer Chirality characteristics of covalent bondMirror imageMolecules are known as Optical isomerImportant concept: At molecular level much of biology relies on interaction of complementary 3d surfaces
20Sharing of electronC-C or C-H equal sharing (non-polar bond)N-H, O-H unequal sharing (polar bond)Electronegativity
21Two Types of Covalent Bonds Nonpolar Covalent BondThe atoms participating in the bond are sharing electrons equally. There is no difference in charge between the two ends of such bonds.Polar Covalent BondAtoms participating in the bonds do not share electrons equally.One atom pulls the electrons a little more toward its "end" of the bond, so that atom bears a slightly negative charge. The atom at the other end of the bond bears a slightly positive charge.Nonpolar Covalent Bond Examples: The bonds in molecular hydrogen (H2), oxygen (02), and nitrogen (N2) mentioned earlier are examples. These molecules are some of the gases that make up air. The bonds in methane (CH3), another gas, are also nonpolar.Polar Covalent bond Examples: For example, a water molecule (H—O—H,) has two covalent bonds; both are polar. The oxygen atom in a water molecule carries a slight negative charge, and each of the hydrogen atoms carries a slight positive charge. Any separation of charge into distinct positive and negative regions is called polarity.
22Polar Covalent BondPolarity occurs when atoms electrons unequally due to differences in electronegativities. This is seen in water (H2O).More electronegative atoms tend to pull electrons toward them creating a polar molecule.
23The polarity of water molecules results in hydrogen bonding
24Ionic BondingSodium chloride (table salt) is an example of ionic bonding, that is, electron transfer among atoms or redox reaction.
25IonizationMolecules formed by ionic bonding breakup (ionization) when dissolved in water (solvent), producing separate positive (cation) and negative (anion) ions.These ions conduct electricity and thus called electrolytes.
26Hydrogen BondsA hydrogen bond is a weak attraction between a hydrogen atom and another atom taking part in a separate polar covalent bondLike ionic bonds, hydrogen bonds form by the mutual attraction of opposite charges.Unlike ionic bonds, hydrogen bonds do not make molecules out of atoms, so they are not chemical bondsHydrogen bonds form and break much more easilyExample: Hydrogen bonds form between water molecules. The hydrogen atom has a slight positive charge and the other atom has a slight negative charge.Hydrogen bonds form and break much more easily than covalent or ionic bonds do. Even so, many of them form. Their collective strength imparts unique properties to many substances such as water. Hydrogen bonds that form among the atoms of biological molecules such as DNA hold these molecules in their characteristic shapes.
27Hydrogen BondHydrogen bonding is formed between the partially positive (hydrogen) end of a polar molecule and the negative end of another (e.g. O2 or N2).Example : Water molecules
29Water: The Molecule That Supports All of Life Water is the biological solvent on EarthAll living organisms require water more than any other substanceMost cells are surrounded by water, and cells themselves are about 70-95% waterThe abundance of water is the main reason the Earth is habitable.
30WaterWater: Polar covalent bonds gives water its unique properties that make life possibleWater is an excellent solventHydrophilic substancesHydrophobic substancesWater is stable in high temperatureWhy ice floats on waterWater has cohesive propertiesWater evaporatesWater's special properties as a liquid begin with the two polar covalent bonds in each water molecule. Overall, the molecule has no charge, but the oxygen pulls the shared electrons a bit more than the hydrogen atoms do. Thus, each of the atoms in a water molecule carries a slight charge: The oxygen atom is slightly negative, and the hydrogen atoms are slightly positive. The separation of charge means that the water molecule itself is polar. The polarity is very attractive to other water molecules, and hydrogen bonds form between them in tremendous numbers. Extensive hydrogen bonding between water molecules imparts unique properties to liquid water, and those properties make life possible.First, water is an excellent solvent. A solvent is a liquid that can dissolve other substances. When a substance dissolves, its individual molecules or ions become solutes as they disperse. Salts, sugars, and many other compounds that dissolve easily in water are polar, so many hydrogen bonds form between them and water molecules. A salt is a compound that dissolves easily in water and releases ions other than H+ and OH" when it does. Hydrogen bonding with water dissolves such hydrophilic (water-loving) substances by pulling their individual molecules away from one another and keeping them apart.You can see how water interacts with hydrophobic (water-dreading) substances if you shake a bottle filled with water and salad oil, then set it on a table and watch what happens. Salad oil consists of nonpolar molecules, and water molecules do not form many hydrogen bonds with nonpolar molecules. Shaking breaks some of the hydrogen bonds that keep water molecules together. However, the water quickly begins to cluster into drops as new hydrogen bonds form among its molecules. The bonding excludes molecules of oil and pushes them together into droplets that rise to the surface of the water. The same interaction occurs at the thin, oily membrane that separates the water inside of cells from the water outside of them. The organization of membranes—and of life—starts with such interactions.A second property of water is temperature stability. Temperature is a way to measure the energy of molecular motion: All molecules jiggle nonstop, and they jiggle faster as they absorb heat. However, extensive hydrogen bonding restricts the movement of water molecules—it keeps them from jiggling as much as they would otherwise. Thus, compared with other liquids, water absorbs much more heat before its temperature rises. Temperature stability is an important component of homeostasis, because most of the molecules of life function properly only within a certain range of temperature.Below 0°C (32°F), water molecules do not jiggle enough to break hydrogen bonds, and they become locked in the rigid, lattice-like bonding pattern of ice. Individual water molecules pack less densely in ice than they do in water, so ice floats on water. During cold winters, ice sheets may form near the surface of ponds, lakes, and streams. Such ice "blankets" insulate liquid water under them, so they help keep fish and other aquatic organisms from freezing.A third life-sustaining property of liquid water is cohesion, which means that water molecules resist separating from one another. This property is important in many processes that sustain multicelled bodies. As one example, water molecules constantly escape from the surface of liquid water as vapor, a process called evaporation. Evaporation is resisted by the hydrogen bonding that keeps water molecules together. In other words, overcoming water's cohesion takes energy. Thus, evaporation sucks energy in the form of heat from liquid water, which decreases its surface temperature. Evaporative water loss can help you and some other mammals cool off when you sweat in hot, dry weather. Sweat, which is about 99 percent water, cools the skin as it evaporates.Take-Home Message: Why is water essential to life?Being polar, water molecules hydrogen-bond to one another and to other polar (hydrophilic) substances, and repel nonpolar (hydrophobic) substances.Extensive hydrogen bonding between water molecules gives water unique properties that make life possible: cohesion, temperature stability, and a capacity to dissolve many substances..
33OSMOSISOsmosis is the net diffusion of water down its own concentration gradientWater molecules can readily permeate the plasma membraneSlower ProcessAquaporinsOne molecule of solute can displaceone molecule of water
34OSMOSISOsmosis when pure water is separated from a solution containing a nonpenetrating solute. The net diffusion of water down its concentration gradient through a selectively permeable membrane is known as osmosis
35MOVEMENT OF WATER AND SOLUTE WHEN A MEMBRANE SEPARATES UNEQUAL SOLUTIONS OF A PENETRATING SOLUTE Solutes that can penetrate the plasma membrane do not contribute to osmotic differences between the ICF and ECF and do not affect cell volume (although before equilibrium is achieved, transient changes in volume may occur as a result of differing rates of diffusion of water and the solute across the membrane
36TonicityThe effect of a solution on the osmotic movement of H20.The tonicity of a solution has no units and is a reflection of its concentration of nonpenetrating solutes relative to the cell’s concentration of nonpenetrating solutesIsotonicEqual tension to plasma.RBCs will not gain or lose H20.Hypotonic:Osmotically active solutes in a lower osmolality and osmotic pressure than plasma.RBC will hemolyse.Hypertonic:Osmotically active solutes in a higher osmolality and osmotic pressure than plasma.RBC will crenate.
37MOVEMENT OF WATER WHEN A MEMBRANE SEPARATES EQUAL AND UNEQUAL SOLUTIONS OF A NONPENETRATING SOLUTE
38Acids and Bases What is pH Acids: Fossil fuel, N2 containing fertilizers, Acid rainBasesBuffersHydrogen ions contribute to pH. Acids release hydrogen ions in water; bases accept them. Salts release ions other than H+ and OH-.Buffers keep the pH of body fluids stable. They are part of homeostasis.