The Nature of Molecules Chapter 2

2 Atomic Structure All matter is ____________ atoms. Understanding the structure of atoms is critical to understanding the nature of biological molecules.

3 Atomic Structure Atoms are composed of -protons – ________________ particles -neutrons – _____________ particles -electrons – ________________ particles __________________ are located in the nucleus. Electrons are found in______ ______________________________-

4 Atomic Structure

5 Every different atom has a characteristic number of protons in the nucleus. atomic number =___________________ Atoms with the same atomic number have the same chemical properties and belong to the same___________.

6 Atomic Structure Each proton and neutron has a mass of approximately 1 dalton. The _____________________________ is the atom’s atomic mass. Isotopes – atoms of the same element that have____________________________ _______________________________.

7 Atomic Structure

8 Neutral atoms have the _____ number of protons and electrons. Ions are ____________atoms. -cations – have more __________________and are ________________charged -anions – have more __________than protons and are ____________charged

9 Atomic Structure Electrons are located in ______surrounding the nucleus. The first orbital can contain ____ all of the rest _______electrons. Electrons possess potential energy, with electrons ________the nucleus having the most energy.

10 Atomic Structure

11 Atomic Structure Electrons can be transferred from one atom to another, while still retaining the energy of their position in the atom. -oxidation = ____ of an electron -reduction = ____of an electron

12 Elements Valence electrons are the electrons in the ______________________of an atom. An element’s chemical properties depend on______________________________ _______________________________ ______________________________.

13 Elements The Periodic Table arranges all elements according to their______________. The table identifies elements with_______ _______________________________

14 Periodic Table of the Elements

15 Elements Octet rule: Atoms tend to establish ___________outer energy levels. Atoms with full energy levels are _____reactive than atoms with unfilled energy levels.

16 Elements

17 Elements There are ___________occurring elements. Only ___ elements are found in living organisms in substantial amounts. Four elements make up 96.3% of human body weight: -______________________________

18 Chemical Bonds Molecules are groups of atoms held together______________________. Compounds are molecules_________ ______________________________ Atoms are held together in molecules or compounds by chemical bonds.

19 Chemical Bonds Ionic bonds are formed by the attraction of oppositely charged ions.

20 Chemical Bonds Covalent bonds form when atoms______ _________________________________ Covalent bond strength depends on the number of __________shared by the atoms. single bond double bond triple bond < <

21 Chemical Bonds

22 Chemical Bonds Electronegativity is an atom’s____________ ___________________________________ Differences in electronegativity dictate how electrons are distributed in covalent bonds. -nonpolar covalent bonds = ____ ____________________________ -polar covalent bonds =______________ ________________________________

23 Chemical Bonds Chemical reactions involve the_______ ________________________________ Whether a chemical reaction occurs is influenced by -___________________________ -concentration of -availability of

24 Chemical Bonds Chemical reactions are written with the reactants first, followed by the products. 6H 2 O + 6CO 2 C 6 H 12 O 6 + 6O 2 reactantsproducts Chemical reactions are often reversible. C 6 H 12 O 6 + 6O 2 6H 2 O + 6CO 2

25 Water Chemistry All living organisms are dependent on _____. The __________ of water is the basis for its unique properties. The most important property of water is the ability to form ________bonds.

26 Water Chemistry Within a water molecule, the bonds between oxygen and hydrogen are highly polar. Partial electrical charges develop: - oxygen is partially negative - hydrogen is partially positive

27 Water Chemistry

28 Water Chemistry Hydrogen bonds are ____________ between the partially _________ oxygen of one water molecule and the partially __________hydrogen of a different water molecule. Hydrogen bonds can form between water molecules or between water and another charged molecule.

29 Water Chemistry

30 Water Chemistry The __________of water causes it to be cohesive and adhesive. cohesion: water molecules stick to other _________molecules by hydrogen bonding adhesion: water molecules stick to other _______molecules by hydrogen bonding

31 Water Chemistry

32 Water Chemistry

33 Properties of Water 1. Water has a high specific heat. - A ________________is required to change the temperature of water. 2. Water has a high heat of ___________. - The evaporation of water from a surface causes cooling of that surface.

34 Properties of Water 3. Solid water is _____________than liquid water. - Bodies of water freeze from the____ ___________________ 4. Water is a good ________. - Water dissolves polar molecules and ions.

35 Properties of Water

36 Properties of Water 5. Water organizes nonpolar molecules. - hydrophilic: “____________________” -hydrophobic: “_________________” - Water causes hydrophobic molecules to aggregate or assume specific shapes. 6. Water can form ions. H 2 O  OH -1 + H +1 hydroxide ionhydrogen ion

37 Acids and Bases Hydrogen ion (H +1 ) is the basis of the___ ________________________ __________ H +1 concentration --- lower pH (acidic) _________ H +1 concentration --- higher pH (basic)

38 Acids and Bases

39 Acids and Bases Acid: a chemical that _________ H +1 ions. Base: a chemical that _______ H +1 ions. Buffer: a chemical that accepts/releases H +1 as necessary to keep pH ____________

40 Acids and Bases Most biological buffers consist of ______ __________, one an acid and one a base.

41 Acids and Bases