Atoms, Ions, and Molecules: Building Blocks of Life

1. 2.1 Atoms, Ions, and Molecules KEY CONCEPTAll living things are based on atoms and their interactions.

2. Notes to Copy

4. H O 2.1 Atoms, Ions, and Molecules Living things consist of atoms of different elements. • An atom is the smallest basic unit of matter. • An element is one type of atom. • Elements are represented by a one or two letter symbol Hydrogen atom (H) Oxygen atom (O)

5. Oxygen atom (O) outermost energy level: 6 electrons (-) Nucleus:8 protons (+)8 neutrons inner energy level: 2 electrons (-) 2.1 Atoms, Ions, and Molecules • An atom has a nucleus and electrons. • The nucleus has protons and neutrons. • Electrons are in energy levels outside nucleus.

6. 2.1 Atoms, Ions, and Molecules The nucleus has protons and neutrons. • Protons have a positive charge. • The atomic number of an element is the number of protons in the nucleus. • The atomic number is the definition of each element. • Changing the number of protons in an atom, changes it to a different element. • Neutrons have no charge (neutral). • Atoms of the same element that differ in the number of neutrons that they contain are known as isotopes. • Some isotopes are radioactive which means that their nuclei are unstable and break down at a constant rate over time. • Ex. C14 is a radioactive isotope of carbon used for dating fossils. C12 is the most stable form of carbon and makes up most of the carbon in living things.

7. 2.1 Atoms, Ions, and Molecules Electrons are in energy levels outside the nucleus. • Octet rule - most atoms want 8 electrons in their outer energy level to be stable • Atoms tend to gain, lose, or share electrons to fill the outer energy level (bonding). • Valence electrons – electrons in the outermost energy level • Because atoms have equal numbers of protons and electrons, atoms are neutral.

8. _ O H H + + 2.1 Atoms, Ions, and Molecules • A chemical compound is a substance formed by the chemical combination of two or more elements in definite proportions. • water (H2O)

9. 2.1 Atoms, Ions, and Molecules • A compound is made of atoms of different elements bonded together. • carbon dioxide (CO2) • water (H2O)

10. 2.1 Atoms, Ions, and Molecules • A compound is made of atoms of different elements bonded together. • many other carbon-based compounds in living things • water (H2O) • carbon dioxide (CO2)

11. 2.1 Atoms, Ions, and Molecules Ions form when atoms gain or lose electrons. • An ion is an atom that has gained or lost one or more electrons. • positive ions (H+) have lost one or more electrons. • negative ions (OH-) have gained one or more electrons.

12. gained electron Na loses anelectron to CI ionic bond Sodium atom (Na) Chlorine atom (CI) Sodium ion (Na+) Chloride ion (CI-) Ions form when atoms gain or lose electrons. • Ionic bonds form between oppositely charged ions. • One or more electrons are transferred from one atom to another. • NaCl (sodium chloride – table salt) is an example of an ionic compound

13. covalent bonds Oxygen atom (O) Carbon atom (C) Oxygen atom (O) Carbon dioxide (CO2 ) 2.1 Atoms, Ions, and Molecules Atoms share pairs of electrons in covalent bonds. • A covalent bond forms when atoms share a pair of electrons. • Water (H2O) and carbon dioxide (CO2) are examples of covalent compounds

14. 2.2 Properties of Water KEY CONCEPTWater’s unique properties allow life to exist on Earth.

15. Notes to copy • Water has many qualities that make it important to living things: • It is transparent, so it lets sunlight pass through it to reach organisms that live underwater. • It can form positively or negatively charged particles called ions. • It is a universal solvent that can dissolve many substances easily so that they can be transported by the blood or other body fluids. • It is found inside our cells and around our cells. • It exists as a liquid at room temperature, and its frozen state floats and does not sink. • Capillary action- the tendency of a liquid to draw up into a narrow tube due to the liquid's property of cohesion and adhesion. • Hydrogen bond- in the case of water molecules, the weak bond that occurs when the hydrogen in one water molecule is attracted to the oxygen in another water molecule. • Specific heat- the amount of heat needed to raise the temperature of one gram of a substance one degree Celsius • Because of hydrogen bonding, water also has a high specific heat. This is an important property of water. Since most living things are made up of a large percentage of water, the water regulates and maintains a fairly consistent temperature in living things.

16. _ O H H + + 2.2 Properties of Water Life depends on hydrogen bonds in water. • Living things are made up mostly of water. • Water is a polar molecule. • Polar molecules have slightly charged regions. • Nonpolar molecules do not have charged regions.

17. 2.2 Properties of Water Hydrogen Bonding • Polar molecules form hydrogen bonds with other polar molecules • The slightly positive hydrogen atom of a molecule is attracted to a slightly negative atom of another molecule. • Hydrogen bonding occurs in three main ways in living things: • Between water molecules • Holds the two strands of a DNA molecule together • Holds a protein in its folded shape.

18. 2.2 Properties of Water Water forms hydrogen bonds with other water molecules. • Hydrogen bonds are responsible for three important properties of water: • Adhesion & cohesion • High specific heat • Universal solvent

19. 2.2 Properties of Water Hydrogen bonds are responsible for three important properties of water. • Cohesion is the attraction between molecules of the same substance • Water “sticks” to itself • ex. Surface tension (water bug walks across water), a drop of water on a leaf, and water forming a curve on top of a container when it is overfilled

20. 2.2 Properties of Water Hydrogen bonds are responsible for three important properties of water. • Adhesion is the attraction between molecules of different substances • Water “sticks” to other substances • Capillary action (water pulled up through plant tissues like a straw) • A meniscus (curve water forms when put into a container, water creeps up side of container slightly) • Water absorbed by a paper towel

21. 2.2 Properties of Water Hydrogen bonds are responsible for three important properties of water. • Water has a high specific heat • Specific heat – takes a large energy change to change the temperature of a substance. A substance must lose a large amount of energy to cool down and must absorb a large amount of energy to heat • Why water takes “forever” to boil & why you don’t freeze after standing outside for a few minutes in winter • Water’s high specific heat allows living things to resist changes in temperature & maintain homeostasis

22. solution 2.2 Properties of Water Hydrogen bonds are responsible for three important properties of water. • Water is called the universal solvent because it dissolves more substances than any other solvent. • A solution is formed when one substance dissolves in another. • A solution is a homogeneous mixture. • Solvents dissolve other substances. • Solutes dissolve in a solvent.

23. 2.2 Properties of Water Hydrogen bonds are responsible for three important properties of water. • “Like dissolves like” • Polar solvents dissolve polar solutes. • Nonpolar solvents dissolve nonpolar solutes. • Polar substances and nonpolar substances generally remain separate (oil & water don’t mix). • Water’s ability to be the universal solvent makes it essential for carrying nutrients and gases throughout the body.

24. stomach acid pH between 1 and 3 more acidic 2.2 Properties of Water Some compounds form acids or bases. • The pH scale indicates the concentration of H+ ions in solutions. • An acid releases a hydrogen ion when it dissolves in water. • high H+ concentration, low OH- concentration • pH less than 7

25. bile pH between 8 and 9 more basic 2.2 Properties of Water • A base removes hydrogen ions from a solution and produces hydroxide ions. • low H+ concentration, high OH- (hydroxide ion) concentration. • pH greater than 7

26. pure water pH 7 2.2 Properties of Water • A neutral solution has a pH of 7. • A buffer is a weak acid or base that can react with strong acids or bases to prevent sharp, sudden changes in pH

27. 2.3 Carbon-Based Molecules KEY CONCEPTCarbon-based molecules are the foundation of life.

28. 2.3 Carbon-Based Molecules Carbon atoms have unique bonding properties. • Carbon forms covalent bonds with up to four other atoms, including other carbon atoms. • Carbon-based molecules have three general types of structures. • straight chain • branched chain • ring

29. 2.3 Carbon-Based Molecules • Many carbon-based molecules are made of many small subunits bonded together. • Monomers are the individual subunits. • Polymers are made of many monomers.

30. 2.3 Carbon-Based Molecules • Macromolecules/macronutrients – large molecules that make up living organisms such as carbohydrates, proteins, lipids, & nucleic acids • Organic compounds – chemical compounds that contain carbon and that make up living organisms

31. 2.3 Carbon-Based Molecules Four main types of carbon-based molecules are found in living things. • Carbohydrates (sugars) are made of carbon, hydrogen, and oxygen in a 1:2:1 ratio. • Monomers are simple sugars called monosaccharides (most common monosaccharide is glucose).

32. 2.3 Carbon-Based Molecules • Carbohydrate polymers are also called polysaccharides. • Polysaccharides include starches, cellulose, and glycogen. • Carbohydrates are polar and dissolve in water. • Carbohydrates can be broken down to provide energy for cells.

33. 2.3 Carbon-Based Molecules • Living things store extra sugar as complex carbohydrates (polysaccharides) • Starch is found in plants • Glycogen is found in animals Polymer (starch) Starch is a polymer of glucose monomers that often has a branched structure.

34. Polymer (cellulose) Cellulose is a polymer of glucose monomers that has a straight, rigid structure monomer 2.3 Carbon-Based Molecules • Some carbohydrates are part of cell structure. • Cell walls in plants are made up of cellulose (polysaccharide)

35. Triglyceride 2.3 Carbon-Based Molecules • Lipids have several different functions and are generally NOT soluble in water (nonpolar) • Lipids are nonpolar molecules that include fats, oils, and cholesterol. • Many contain carbon chains called fatty acids. • Fats and oils contain fatty acids bonded to glycerol. • Contain C, H, & O, not in a 1:2:1 ratio (much less O than C & H)

36. 2.3 Carbon-Based Molecules • Fats and oils have different types of fatty acids. • saturated fat • unsaturated fatty acids • Fats & oils are used as long-term energy storage & insulation (conserve body heat & cushions organs)

37. 2.3 Carbon-Based Molecules • Lipids have several different functions. • Oils & waxes are used as water-proofing • Cholesterol is used to make steroid hormones (ex. testosterone & estrogen)

38. Phospholipid 2.3 Carbon-Based Molecules • Phospholipids make up all cell membranes. • Polar phosphate “head” • Nonpolar fatty acid “tails”

39. 2.3 Carbon-Based Molecules • Proteins are polymers of amino acid monomers, and are also called polypepetides. • Twenty different amino acids are used to build proteins in organisms.

40. 2.3 Carbon-Based Molecules • Proteins are polymers of amino acid monomers. • Amino acids differ in side groups, or R groups. • Twenty different amino acids are used to build proteins in organisms.

41. 2.3 Carbon-Based Molecules • Proteins are polymers of amino acid monomers. • Amino acids are linked by peptide bonds. • Twenty different amino acids are used to build proteins in organisms. • Amino acids differ in side groups, or R groups.

42. hydrogen bond Hemoglobin 2.3 Carbon-Based Molecules • Amino acids interact by forming hydrogen bonds with one another to give a protein its shape. • Proteins differ in the number and order of amino acids. • Proteins have a wide variety of functions such as making up body & cell structures as well as acting as enzymes.

43. 2.3 Carbon-Based Molecules • Nucleic acids are polymers of monomers called nucleotides.

44. nitrogen-containing molecule,called a base A phosphate group deoxyribose (sugar) 2.3 Carbon-Based Molecules • Nucleic acids are polymers of monomers called nucleotides. • Nucleotides are made of a sugar, phosphate group, and a nitrogen base.

45. DNA RNA 2.3 Carbon-Based Molecules • Nucleic acids are polymers of monomers called nucleotides. • DNA stores genetic information. • Nucleotides are made of a sugar, phosphate group, and a nitrogen base. • RNA builds proteins.

46. Triglyceride nitrogen-containing molecule,called a base A phosphate group deoxyribose (sugar) 2.3 Carbon-Based Molecules • Proteins & nucleic acids contain nitrogen, carbohydrates & lipids do not!

47. 2.4 Chemical Reactions KEY CONCEPT Life depends on chemical reactions.

48. Notes to Copy

49. 2.4 Chemical Reactions Bonds break and form during chemical reactions. • Chemical reactions change substances into different ones by breaking and forming chemical bonds. • Reactants are changed during a chemical reaction. • Products are made by a chemical reaction.

50. 2.4 Chemical Reactions • Bond energy is the amount of energy that breaks a bond. • Energy is added to break bonds. • Energy is released when bonds form. • A reaction is at equilibrium when reactants and products form at the same rate. CO2 + H2O H2CO3