Biology I for Non-Majors

1. Biology I for Non-Majors Chemistry of Life

2. Matter • Matter occupies space and has mass • Elements are unique forms of matter • Specific chemical and physical properties • Cannot be broken down into smaller substances by ordinary means • Designated by chemical symbols

3. Atoms • Atom= smallest unit of matter that retains all chemical properties of element • Proton- positively charged particle that resides in nucleus (core of atom) • Electron- negatively charged particle that travels around nucleus • Neutron- mass of 1 and no charge • Atomic number- equal to number of protons • Mass number- number of protons plus neutrons • Periodic Table of Elements- chart that contains atomic and mass number

4. Periodic Table of Elements

5. Arrangement of Electrons • How elements interact depends on how electrons are arranged • Electrons exist at energy levels that form shells around nucleus- closest shell filled up first (2 electrons) • Second and third energy levels hold up to 8 electrons • 7 rows on periodic table- number of shells that elements within row have

6. Isotopes • Different forms of the same element that have the same number of protons but different number of neutrons • Carbon-12 is most common type of carbon- 6 protons, 6 neutrons • Carbon-14 has 6 protons, 8 neutrons • Radioactive isotopes- unstable isotopes that lose protons or energy

7. Chemical Bonding • Atom is most stable when all of electron positions in outermost shell are filled- atoms will bond with other elements to fill the outermost shell • This leads to the formation of chemical bonds/interactions between elements • Element can donate, accept, or share electrons with other elements to satisfy octet rule (8 electrons) • Different elements do different things depending on how ‘unfilled’ the outermost shell is

8. Filling the Outermost Shelli

9. Ionic Bonds • Cations- positively charged ions formed by losing electrons • Anions- negatively charged ions formed by gaining electrons • Electron transfer- movement of electrons from one element to another • Electrolytes- necessary for nerve impulse conduction, muscle contractions, and water balance • Full of salts • Found in many sports drinks and dietary supplements that provide these lost during sweating

10. Covalent Bonds • Covalent bonds- another way octet rule can be satisfied • Stronger and more common than ionic bonds in molecules of living things • Commonly found in carbon-based organic molecules (DNA/proteins) • Strength is one of main reasons living organisms have difficult getting nitrogen • Formation of water molecules provides example of covalent bonding

11. Polar & Non-Polar Covalent Bonds • Nonpolar- form between two atoms of same element or between different elements that share electrons equally • Polar- electrons shared by atoms spend more time closer to one nucleus than the other= slightly positive or negative charge develops • Covalent bonds between hydrogen and oxygen atoms in water are polar covalent bonds

12. Hydrogen Bonds • Provide many of the critical, life-sustaining properties of water and help stabilize structures of proteins and DNA • When polar covalent bonds containing hydrogen form, hydrogen has slightly positive charge because hydrogen is pulled more strongly • Hydrogen will be attracted to negative charges- weak interaction occurs • Occurs between water molecules- weak and easily broken

13. van der Waals Interactions • Weak attractions or interactions between molecules • Occur between polar, covalently bound atoms in different molecules • Some weak attractions caused by temporary partial charges formed when electrons move around nucleus

14. Why Life Depends on Water • Water is polar • Water stabilizes temperature • Water is an excellent solvent • Water is cohesive

15. Water is Polar • Hydrogen and oxygen atoms within water molecules form polar bonds • No overall charge, but slight positive charge on each hydrogen atom and slight negative charge on oxygen atom • Each water molecule attracts other water molecules because of positive and negative charges in the different parts of the molecule • Hydrogen bonds are not readily formed with nonpolar substances such as oil and fats – won’t dissolve in water

16. Water Stabilizes Temperature • Hydrogen bonds allow it to absorb and release heat energy more slowly than many other substances • Temperature is measure of kinetic energy of molecules- as motion increases, energy is higher and thus temperature is higher • Water moderates temperature changes within organisms and in their environments • As molecular motion decreases and temperatures drop, less energy is present to break hydrogen bonds between water molecules • When water is frozen, ice is less dense than water

17. Water is an Excellent Solvent • Ionic compounds and polar molecules can readily dissolve in water • Referred to as solvent- substance capable of dissolving another substance • Charged particles will form hydrogen bonds with surrounding layer of water molecules • Positively charged sodium ion surrounded by partially negative charges of oxygen • Negatively charged chloride ion is surrounded by partially positive charges of hydrogen atoms

18. Water is Cohesive • Water molecules are attracted to each other, keeping molecules together at liquid-air interface • Gives rise to surface tension- capacity of a substance to withstand rupture when placed under tension • Cohesion and surface tension keep water molecules intact and item floating on top • Cohesive forces related to water’s property of adhesion or attraction between water molecules and other molecules

19. pH, Acids, and Bases • pH- measure of its acidity or alkalinity • High concentrations of hydrogen ions yield low pH • pH scale ranges from 0-14 • Acids- substances that provide hydrogen ions and lower pH • Bases- provide hydroxide ions and higher pH

20. Buffers • Most cells in human bodies operate at pH levels of 7.2-7.6 • Outside this range cells no longer function properly and proteins break down • Buffers are key to maintaining the limited pH range cells need • Readily absorb excess H+ or OH– • Carbon dioxide is part of a prominent buffer system in the human body

21. Quick Review • Can you draw a diagram of an atom, according to current scientific understanding? • Please define the term isotope. • Are you able to describe the behavior and location of electrons, and how these factors influence bond formation between atoms? • What is the octet rule and its role in chemical bonds? • What are the characteristics of ionic/covalent bonds and can you identify common ions of both? • Can you model a Hydrogen bond and identify its unique qualities? • Are you able to model a van der Waals interaction and identify its qualities? • Please describe the properties of water that are critical to maintaining life