Unit resources and assignments for January 10, 2014

1. January 10, 2014 Powerpoints and Bozeman Videos for this Unit are on the website. Turn in your Guided Readings for Chapters 2 and 3. Get ready for QQ

3. Based on this chart, which population had the least variation throughout the time period measured? Turtles Dinosaurs Snakes crocodilians

4. What is the approximate atomic mass of an atom with 16 neutrons, 15 protons, and 15 electrons?

5. Question 8 Consider the Lewis structures shown below. Which one is a valid structure?

7. The puzzle pieces have to fit! • Biological molecules recognize and interact with each other with a specificity based on molecular shape • Molecules with similar shapes can have similar biological effects • Long ago you accepted that the 4 DNA bases pair A-T and G-C, but WHY?? • Why can’t the A pair with the C?

8. The puzzle pieces have to fit! • Why does a molecule have shape in the first place? • That has to do with IMFs holding things in “place” defining its 3-D shape. The big people word for “shape” is “conformation”. • In the case of A-T vs. G-C, it’s all about lining up that IMF called “hydrogen bonding”; 2 sites for A-T and 3 for G-C

9. Ever heard of “a runner’s high”? • Our body manufactures endorphins which are made by the pituitary gland and bind to the receptors in the brain that relieve pain and produce euphoria during times of stress, such as intense exercise. • Opiates such as morphine and heroin are structured similarly, thus can bind with the receptors . These “bindings” are actually those electrostatic attractions we call IMFs.

10. The boxed regions are shaped similarly! Nitrogen Carbon Hydrogen Sulfur Natural endorphin Oxygen Morphine (a) Structures of endorphin and morphine

11. Pain killer! • The brain receptors “bind” with either with similar results. Natural endorphin Morphine Endorphin receptors Brain cell (b) Binding to endorphin receptors

12. Chemical Reactions Make and/or Break Chemical Bonds • Chemical reactions are the making and breaking of chemical bonds • The starting molecules of a chemical reaction are called reactants • The final molecules of a chemical reaction are called products

13. Photosynthesis is a mighty important chemical reaction! • Photosynthesis is an important chemical reaction • Sunlight powers the conversion of carbon dioxide and water to glucose and oxygen6 CO2 + 6 H2O →C6H12O6 + 6 O2

18. Water: The molecule that supports life on this planet! • Water is the biological medium for all life on Earth • All living organisms require water more than any other substance

19. Water: The molecule that supports life on this planet! • Most cells are surrounded by water, and cells themselves are about 70–95% water • The abundance of water is the main reason the Earth is habitable

20. FOUR Emergent Properties of water contribute to Earth’s suitability for life • Water’s cohesive & adhesive behavior • Water’s ability to moderate temperature • Water’s expansion upon freezing • Water’s versatility as a solvent.

21. What causes water molecules to both cohere and adhere? • Yep! Our good buddy the intermolecular force (IMF) named hydrogen bonding • Cohesion is when water molecules stick to each other. • Adhesion is when water molecules stick to some other type of substance like plant cell walls. Animation by scrolling over image

22. What causes water molecules to both cohere and adhere? • Surface tension is a measure of how hard it is to break the surface of a liquid. • Surface tension is a consequence of cohesion. What causes it? Go ahead, guess! Hydrogen bonding, yet again!

23. How does water moderate temperature? • Water has a high heat capacity. • Heat capacity is the amount of heat required to raise 1 gram of water by 1o Celsius (1 calorie = 4.184 J) • What does that mean? It means water can absorb large quantities of heat without much change in its own temperature, thus it’s a good thermo regulator. • But, why? Go, ahead…guess!

24. How does water moderate temperature? • Yep! Hydrogen bonding again! The fact that each water molecule can make TWOH-bonds each means they are really, really attracted to each other, thus more ENERGY must be added to the water sample to increase their molecular motion. • Remember, temperature is a measure of the average kinetic energy of a sample of molecules!

25. How does water moderate temperature? • We should also discuss this effect as it relates to “air” with regard to the amount of water vapor in the air or humidity. The more water vapor in the air, the more heat the air can absorb. • Large bodies of water absorb heat from warmer air and release stored heat to cooler air.

26. It’s a 2-way street! • Water’s high specific heat can be traced to hydrogen bonding (IMFs) • Heat is absorbed when hydrogen bonds break • Heat is released when hydrogen bonds form • The high specific heat of water minimizes temperature fluctuations to within limits that permit life

27. Care to examine some data? Formulate an explanation for the temperature data presented below. Your explanation should address the properties of water as they relate to thermoregulation.

28. Ever sweat? Ever perspire? • Evaporation is transformation of a substance from liquid to vapor • Heat of vaporization is the heat a liquid must absorb for 1 g to be converted to vapor • As a liquid evaporates, its remaining surface cools, a process called evaporative cooling • Evaporative cooling of water helps stabilize temperatures in organisms (sweating, panting, etc.)and bodies of water

29. Water is a freak! It expands upon freezing! Liquid water: transient hydrogen bonds Ice: stable hydrogen bonds

30. Water is a freak! It expands upon freezing! • Ice floats in liquid water because hydrogen bonds in ice are more “ordered” forming a hexagonal shape with a hole in the middle, making ice lessdense. • Water reaches its greatest density at 4°C, which is excellent news if you’re a fish! • If ice sank, all bodies of water would eventually freeze solid, making life impossible on Earth

31. Water is a freak! It expands upon freezing! Hydrogen bond Liquid water: Hydrogen bonds break and re-form Ice: Hydrogen bonds are stable

32. Water’s Versatility as a Solvent • A solution is a liquid that is a homogeneous mixture of substances • A solvent is the dissolving agent of a solution or “dissolver” • The solute is the substance that is dissolved or “disolvee” • An aqueous solution is one in which water is the solvent

33. Water’s Versatility as a Solvent • Water is a versatile solvent due to its polarity, which allows it to form hydrogen bonds easily. • When an ionic compound is dissolved in water, each ion is surrounded by a sphere of water molecules called a hydration shell

34. Water’s Versatility as a Solvent • Water can also dissolve compounds made of nonionic polar molecules • Even large polar molecules such as proteins can dissolve in water if they have ionic and polar regions

35. Hydrophilic vs. Hydrophobic • A hydrophilic substance is one that has an affinity for water • A hydrophobic substance is one that does not have an affinity for water; “fears water” • Oil molecules are hydrophobic because they have relatively nonpolar bonds • A colloid is a stable suspension of fine particles in a liquid (like milk—fat suspended in water—Yummy!)

36. Acids, Bases and Buffers ACIDIC AND BASIC CONDITIONS AFFECT LIVING ORGANISMS • A bonded hydrogen atom within a water molecule can shift betweentwo water molecules (from one molecule to the other).

37. Acids, Bases and Buffers • The hydrogen atom leaves its electron behind and is transferred as a proton, or hydrogen ion (H+) • The molecule with the extra proton is now a hydronium ion (H3O+), though it is often represented as H+ • The molecule that lost the proton is now a hydroxide ion (OH–)

38. Acids, Bases and Buffers • Though statistically rare, the dissociation of water molecules has a great effect on organisms • About 2 in every billion water molecules exist as H+ and OH– • Changes in concentrations of H+ and OH– can drastically affect the chemistry of a cell

39. Acids, Bases and Buffers • Concentrations of H+ and OH– are equal in pure water • Adding certain solutes, called acids and bases, modifies the concentrations of H+ and OH– • Biologists use something called the pH scale to describe whether a solution is acidic or basic (the opposite of acidic; also known as alkaline)

40. Acids, Bases and Buffers Simply put, • An acid is any substance that increases the H+ concentration of a solution • A base is any substance that reduces the H+ concentration of a solution Bleach

41. Acids, Bases and Buffers Buffers • The internal pH of most living cells must remain close to pH 7 • Buffers are substances that RESIST changes in concentrations of H+ and OH– in a solution, therefore they RESIST a change in pH • Most buffers consist of an acid-base pair that reversibly combines with H+

42. Buffers in Action Acidification: A Threat to Water Quality • Human activities such as burning fossil fuels threaten water quality • CO2 is the main product of fossil fuel combustion • About 25% of human-generated CO2 is absorbed by the oceans • CO2 dissolved in sea water forms carbonic acid; this process is called ocean acidification

43. Buffers in Action • As seawater acidifies, H+ ions combine with carbonate ions to produce bicarbonate • Carbonate is required for calcification (production of calcium carbonate) by many marine organisms, including reef-building corals

44. Acid Rain • The burning of fossil fuels is also a major source of sulfur oxides (SOx) and nitrogen oxides (NOx) • These “socks and knocks” compounds react with water in the air to form strong acids that fall within rain or snow • Acid precipitation is rain, fog, or snow with a pH lower than 5.2 • Acid precipitation damages life in lakes and streams and changes soil chemistry on land

45. Acid Rain: Before & After

46. The pH Scale • An acid is any substance that increases the H+ concentration of a solution • A base is any substance that reduces the H+ concentration of a solution • The scale was designed to compare WEAK acids and bases.

47. The pH Scale • In any aqueous solution at 25°C the product of H+ and OH– is constant and can be written as the autoionization constant of water • The pH of a solution is defined by the negative logarithm of H+ concentration, written as • For a neutral aqueous solution, [H+] is 10–7, so [H+][OH–] = 10–14 pH = –log [H+] pH = –(–7) = 7

48. The pH Scale • Acidic solutions have pH values less than 7 • Basic solutions have pH values greater than 7 • Most biological fluids have pH values in the range of 6 to 8

49. Created by: René McCormick National Math & Science Dallas, TX