1. (2 pts) Name four common characteristics of living organisms.

Transcription

1 7/17/2014 QUIZ Outline 1. (2 pts) Name four common characteristics of living organisms. hemistry BioSci 105 Lecture Packet 2 Reading: hapter 2 (Pages 20-30) 2. (1 pt) All the factors in an experiment that are kept the same in the experiment (water, cages, etc.) are called the. 3. (2 pt) What domain and kingdom do humans belong to? Why study hemistry? Definitions and the Basics hemistry is the basis for studying much of biology Matter is anything that takes up space and has mass. The biology of the human body follows the rules of physics and chemistry. Atoms are units of matter that cannot be broken down into simpler substances. You need to understand enough about chemistry to know what kind of things will cross a membrane, and what biological compounds make up cells, and structures within cells. Eg. What is a protein? I. Why study hemistry II. Elements Atoms Isotopes Periodic Table Electrons Bonding III. Bonds ovalent bonds Polarity Ionic bonds ydrogen bonding IV. Water V. Acids and Bases Elements in nature Text page 22 An element is a pure form of matter containing only one kind of atom. Atom Table 2.1 Review of Subatomic Particles Elements important in the human body We used to think that an atom could not be divided, now we know they are composed of parts (particles): Protons carry a positive charge Neutrons have no charge (neutral) Electrons carry a negative charge 1

2 The Atom ont. hemistry and Biology Protons and neutrons are in the center of the atom (called the nucleus) Electrons orbit around the outer edge in orbitals In each atom the # electrons = # protons Figure 2.1c Shell Model of Electrons Protons are found in the ow many electrons can be in the 1 st shell? Electrons can be visualized as residing in shells around the nucleus. The first shell can have up to two electrons The second shell can have up to eight electrons The third, fourth shells can have up to eight electrons 1. Nucleus 2. Orbital shells 1. One 2. Two 3. Four 4. Eight Nucleus Orbital shells One Two Four Eight ow many electrons can be in the 2nd shell? Periodic Table of Elements 1. One 2. Two 3. Four 4. Eight One Two Four Eight Figure 2.2 2

3 Particle Mass ow many electrons does Be have? Proton = 1 amu Neutron = 1 amu Electron = negligible The atomic number = the # of protons in an atom Atoms have equal numbers of protons and electrons Isotopes Atoms with the same number of protons but different numbers of neutrons are called isotopes Isotopes of ydrogen Radioactive Isotopes In 1896, enri Becquerel placed a rock on unexposed photographic plates inside a drawer. The rock contained uranium. The isotopes of uranium emit energy. After a few days the plate had an image of the rock. A co-worker, Marie urie, named this radioactivity. This is known as a radioisotope Radioactive Isotopes Radioisotopes are isotopes that are unstable, and become more stable by emitting energy and particles In contrast, most isotopes are stable Radioisotopes in Medicine PET scans (Positron-Emission Tomography) Patient is injected with a compound that is labeled with an unstable isotope ancer cells are growing faster and take up more of the compound than normal cells Abnormal tissue takes up less of the compounds Isotopes in medicine Figure 2.4 3

4 Isotopes are atoms of the same element that differ in their number of 1. arbon has 6 protons, 6 electrons and 6 neutrons. Its atomic number is. 1. arbon has 6 protons, 6 electrons and 6 neutrons. Its atomic weight is. 1. Protons 2. Electrons 3. Neutrons 4. None of the above 1. Six 2. Eight 3. Twelve 4. Twenty-four 1. Six 2. Eight 3. Twelve 4. Twenty-four Protons Electrons Neutrons None of the above Six Eight Twelve Twenty-four Six Eight Twelve Twenty-four Atomic number Atomic weight The atomic weight = an average of the isotopes Mass number = round the atomic weight Mass Number = (Number of Protons) + (Number of Neutrons) Number of Neutrons = Mass number - # of Protons For any element: Number of Protons = Atomic Number Number of Electrons = # Protons = Atomic Number Number of Neutrons = Mass Number - Atomic Number For Be: Number of Protons = Atomic Number = 4 Number of Electrons = # of Protons = 4 Number of Neutrons = Mass Number - Atomic Number = 9-4 = 5 hemical Bonds Electrons and Bonding hemical bonds are unions between electron structure from different atoms Molecules are when two or more atoms join together. They can be the same element ( 2 ) or different elements ( 2 O) When different elements join the molecule is referred to as a compound molecule If the outer shell is full, then it is non-reactive and stable = does not form chemical bonds. Incompletely filled outer orbital, then atom reactive and will form chemical bonds. ow many bonds it can form depends on how many empty spots in outer shell 4

5 ow many neutrons does Li have? hemistry and Biology hemical Bonds ovalent bonds Ionic ydrogen Figure 2.8 ovalent bonds ow many bonds can form? ovalent bonds The strongest bonds They form when two or more atoms share the electrons in their outer shells Each atom wants their outer shell filled. ydrogen only has one electron in its shell wants two, so it can form one bond. arbon has four electrons in outer shell, wants eight, so it can form four bonds. Double Bond ow many bonds can carbon form? ow many bonds can hydrogen form? 1. One 2. Two 3. Three 4. Four 1. One 2. Two 3. Three 4. Four One Two Three Four One Two Three Four 5

6 ow many bonds can helium form? ow many bonds can nitrogen form? ow many bonds can oxygen form? 1. None 2. One 3. Two 4. Three 1. One 2. Two 3. Three 4. Four 1. One 2. Two 3. Three 4. Four None One Two Three One Two Three Four One Two Three Four Types of ovalent Bonds 1. ovalent Bonding ovalent Bonding ovalent bonds Polar Nonpolar When two atoms with unpaired electrons in the outer most shell come together and share electrons Each atom has an attractive force for the other atoms unshared electrons, but not enough to take it completely away ovalent bonds can be polar or nonpolar Nonpolar bonds the atoms have same pull on the shared electrons ( 2 ) Polar bonds the atoms don t equally share the electrons ( 2 O) Polar ovalent Bond Polarity Some atoms have a greater pull on shared electron than other atoms The measure of this pull is electronegativity When a bond is made between atoms with different electronegativities it is a polar bond The greater the pull the more electronegative (remember that electrons are negative) Figure 2.11a 6

7 Polarity on t Polarity Water Alcohol Polar ovalent Bonding occurs with strong electrophiles (electronegative): atoms with nuclei that have a strong pull on electrons. ommon examples in biological molecules include: Oxygen Nitrogen Sulfur The oxygen side of water is slightly negative and the hydrogen sides are slightly positive 3 O Ketone 2 2 O 3 3 ydrocarbons O 2 Aldehyde 2 O N S Polar Groups arboxyl 3 3 Oxygen containing: arboxyl = - OO ydroxyl (alcohol) = - O Phosphates = -PO 4 arbonyl Ketone = - O Aldehyde = - O Nitrogen containing: Amino (-N 2 ) Sulfur containing: -S Alcohol Ketone Aldehyde Ether 322O 3-O-23 ydrocarbons 323 Nonpolar compounds Terminology hemical formulas ydrocarbons lots of carbons and hydrogens bonded together ydrophilic (water-loving) polar molecules that are attracted to water ydrophobic (water-fearing) nonpolar molecules that are pushed aside by water When we write compounds, we often write them as a formula that tells how atoms many of each element are present, but not the way the molecule is put together. You often can determine the way the molecule is put together by knowing how many bonds each element can form. 7

8 Examples Examples Examples ow would you draw this compound? ow would you draw this compound? ow would you draw this compound? 2 O O Examples Examples 2. ydrogen Bonding ow would you draw this compound? O 2 O O ow would you draw this compound? 2 4 O O Weak attraction between a hydrogen atom with a partial positive charge and another atom with a partial negative charge (electronegative atom such as oxygen, nitrogen, or sulfur). 2. ydrogen Bonding 2. ydrogen bonds 3. Ionic Bonds Individually weak, but many together can be strong. Determines shapes of many biological molecules including proteins and DNA Ion = atom that has gained or lost electrons, It no longer has a balance between protons and electrons, it is positive or negative charge Ionic bond is an association between ions of opposite charge Figure 2.11b 8

9 7/17/ Ionic bond hemical bonds Figure 2.10 Water The Life Giving Molecule Why are we so interested in finding evidence of water on Mars? What would it mean if we did not find evidence of water? Or if we find evidence? Does it matter what form the water is? Life exists here because water is abundant Water s Abundance Water is a great example of hydrogen bonding, itis the hydrogen bonds that give water much of its unique characteristics O Water is polar and forms hydrogen bonds 97.5% of the water is salt water Freshwater only accounts for 2.5% of water Only 0.53% is available to us to drink (rivers, lakes, ground water) 66% of the human body is water by weight 75-85% of a cell s weight is water Exists in Three Forms Water exists in three forms Solid - Ice Liquid Vapor O Water 71% of Earth s surface is water ydrogen bonding Table 2.2 Ice As water approaches 0, freezing temperature, the molecules slow down. Water forms more hydrogen-bonds at lower temperature and forms a lattice structure The ice is less dense due to the lattice structure and to the fact that there are less molecules present than in the same volume of liquid 9

10 Ice caps Properties of Water The floating property of ice allows the Artic Ocean s ice cap to exist This is the habitat for polar bear and young seals, as well as many other species. These ice caps are melting, as they melt the habitat for these species shrinks. So what does all this mean? The polarity and ability to form hydrogen bonds give water its properties There are four properties of water (You need to know these) 1. Water is an excellent polar solvent Because water is polar and forms hydrogen bonds, it acts as a solvent for polar molecules Like dissolves in like, so polar molecules dissolve in water Water is considered the best polar solvent due in great part to its ability to form hydrogen bonds with other molecules Why is this property important? 2. Water has ohesion Blood is approx 55% water so the fact that water is a good solvent makes blood a good way to transport things around. ells are made up of mainly water (75-85%), the water keeps salts in your cells, blood and tissues in solution (disolved). Due to the hydrogen bonding, water has cohesion (the water molecules cling together) ohesion is the capacity to resist breaking under tension 10

11 2. Water has ohesion Why is this property important? 3. Water has igh heat capacity What allows bugs to walk on water? ydrogen-bonds create surface tension At the surface of water, where water meets air, the water molecules are being pulled down with a much greater force than they are being pulled up towards the air The cohesion of water allows blood move easier in the blood vessels. Also is responsible for moving water in plants It takes a great deal of energy to raise the temperature of water as compared to other compounds. When you increase the temperature of something, the molecule in it move faster, hydrogen bonds keep the water molecules in place so it takes lots of energy to break the bonds and heat the water Why is this property important? 4. Water has igh heat of Vaporization Why is this property important? Water in our bodies keep us at a constant temp. It takes a great deal of energy to make water evaporate (change water from a liquid to a gas). Sweat is mainly water, when we sweat the body uses its heat to vaporize the water cooling us off. ydrogen bonds must be broken in order to change water from liquid to vapor 2 is a(n) ydrophobic molecules are by water What type of bond between water molecules creates surface tension that gives water cohesion? 1. Atom 2. Molecule 3. ompound molecule 33% 33% 33% 1. Attracted 2. Repelled 1. Ionic 2. ovalent 3. ydrogen 33% 33% 33% Atom Molecule ompound molecule Attracted Repelled Ionic ovalent ydrogen 11

12 7/17/2014 Which property of water provides the cooling effect of sweating Water 1. Makes ionic bonds 2. Is nonpolar 3. Is polar 33% 33% 33% 1. ohesiveness 2. igh heat capacity 3. igh heat of vaporization 4. Excellent solvent Acids and Bases We are already familiar with acids and bases ommon acids: Lemon juice Sodas Vinegar ommon bases: M ak es io nic s nd bo Is ola np no r Is la po r siv he o e en ss ig h a he tc ac ap h ig it y h fv to ea ap... iz or Ex c e ell s nt olv e nt Acids and Bases Ph Scale The strength of acids and bases is measured using the p scale. p = -log10[+] [+] = conc in moles per liter It is inverse relationship: Acids Substances that donates hydrogen ions when in solution l + + l- Bases Substances that accept hydrogen ions when in solution (sometimes we say that bases release O- (hydroxyl ions) Ammonia Many household cleaners Bleach Ph Scale Scale from is the most acidic 14 is the most basic 7 is neutral (pure water) igher the p the lower the concentration of + NaO Na+ + O- Logarithmic: In solution: Each point increase in p represents a ten-fold decrease in + concentration. + + l- + Na+ + O- 2O + Nal Acids and Bases Table

13 The higher the p a solution has, the higher the + concentration Is a p of 8 acidic or basic? 1. True 2. False 1. Acidic 2. Basic True False Acidic Basic Biological Fluids Buffers Buffers Blood p 7.35 hanges in p of ± 0.1 can damage cells, p of 7.8 can be lethal Biological fluids have buffers to keep the p stable. Most biological fluids are between 6 8 Stomach fluid p of under 2 Buffers resist p changes because they are chemicals that can take up excess + or O- Our body wants to keep its fluids at an even p. Blood contains buffers that are weak acids that can dissociate into ions. For example when O 2 enters the blood it combines with 2 O to form carbonic acid ( 2 O 3 ). This weak acid dissociates to form + and bicarbonate ion (O 3- ) Important oncepts Reading for next lecture: hapter 2 (pages 25 36) What are the three particles of an atom, where are they located, what is their charge, and mass. Be able to determine how many bonds each element can form. Be able to recognize if a molecule is drawn correctly. Important oncepts Be able to read the periodic table to determine the number of protons, neutrons and electrons in the atoms of all the biologically important elements. What are the three most common elements in the human body Be able to draw the atom of any biologically important element, with the correct number of protons, neutrons, and electrons. Be able to draw the electrons in their correct shell. Be able to identify polar and nonpolar molecules 13

14 Important oncepts Be able to describe the types of chemical bonds What are three electronegative elements found in biological molecules? Be able to draw a water molecule and hydrogen bonding between water molecules Be able to describe the four properties of water and their importance in living organisms. Definitions Matter, Atom, Element, Isotopes, Radioisotopes, hemical bonds, single bond, double bond, Molecules, ompound Molecules, Ion, Ionic bond, ovalent bond, Nonpolar bonds, Polar bonds, electronegativity, ydrogen bond, ydrophilic, ydrophobic, ohesion, acid, base, buffers, logarithmic, inverse, p, solvent, solute, solution Understand the p scale 14