Water and the Fitness of the Environment

Transcription

1 Chapter 3 Water and the Fitness of the Environment PowerPoint Lecture Presentations for Biology Eighth Edition Neil Campbell and Jane Reece Lectures by Chris Romero, updated by Erin Barley with contributions from Joan Sharp

2 Overview: The Molecule That Supports All of Life Water is the biological medium on Earth All living organisms require water more than any other substance 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 Mars Earth

3 Concept 3.1: The polarity of water molecules results in hydrogen bonding The water molecule is a polar molecule: The opposite ends have opposite charges Polarity allows water molecules to form hydrogen bonds with each other + + H O H + + Hydrogen bond

4 Concept 3.2: Four emergent properties of water contribute to Earth s fitness for life Four of water s properties that facilitate an environment for life are: Cohesive behavior Ability to moderate temperature Expansion upon freezing Versatility as a solvent

5 Fig. 3-3 Cohesionc Adhesion Water-conducting cells Direction of water movement 150 µm Cohesion

6 Cohesion Surface tension is a measure of how hard it is to break the surface of a liquid Surface tension is related to cohesion

7 Moderation of Temperature Water absorbs heat from warmer air and releases stored heat to cooler air Water can absorb or release a large amount of heat with only a slight change in its own temperature

8 Heat and Temperature Kinetic energy is the energy of motion Heat is a measure of the total amount of kinetic energy due to molecular motion Temperature measures the intensity of heat due to the average kinetic energy of molecules

9 Water s High Specific Heat The specific heat of a substance is the amount of heat that must be absorbed or lost for 1 g of that substance to change its temperature by 1ºC The specific heat of water is 1 cal/g/ºc Water resists changing its temperature because of its high specific heat

10 Water s high specific heat can be traced to hydrogen bonding 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

11 Fig. 3-5 Santa Barbara 73 70s ( F) 80s 90s 100s Los Angeles (Airport) 75 Pacific Ocean Burbank 90 San Diego 72 San Bernardino 100 Riverside 96 Santa Ana 84 Palm Springs miles

12 Insulation of Bodies of Water by Floating Ice Ice floats in liquid water because hydrogen bonds in ice are more ordered, making ice less dense Water reaches its greatest density at 4 C If ice sank, all bodies of water would eventually freeze solid, making life impossible on Earth

13 Fig. 3-6 Hydrogen bond Ice Hydrogen bonds are stable Liquid water Hydrogen bonds break and re-form

14 Hydrophilic and Hydrophobic Substances A hydrophilic substance is one that has an affinity for water A hydrophobic substance is one that does not have an affinity for water Oil molecules are hydrophobic because they have relatively nonpolar bonds A colloid is a stable suspension of fine particles in a liquid

15 Solute Concentration in Aqueous Solutions Most biochemical reactions occur in water Chemical reactions depend on collisions of molecules and therefore on the concentration of solutes in an aqueous solution

16 Concept 3.3: Acidic and basic conditions affect living organisms A hydrogen atom in a hydrogen bond between two water molecules can shift from one to the other: 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 (H 3 O + ), though it is often represented as H + The molecule that lost the proton is now a hydroxide ion (OH )

17 Fig. 3-UN2 Water is in a state of dynamic equilibrium in which water molecules dissociate at the same rate at which they are being reformed the dissociation of water molecules has a great effect on organisms because changes in concentrations of H + and OH can drastically affect the chemistry of a cell H H O 2H 2 O H O H H O H H Hydronium ion (H 3 O + ) O H Hydroxide ion (OH )

18 Effects of Changes in ph Concentrations of H + and OH are equal in pure water but if you add certain solutes, called acids and bases, you can modify the concentrations of H + and OH We use the ph scale to describe whether a solution is acidic or basic 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

19 Fig. 3-9 ph Scale 0 H + H + OH OH H + H + H + Acidic solution OH OH H + H + OH OH OH H + H + H+ Neutral solution OH OH OH H + OH OH OH OH H + H + H + H + Basic solution Neutral [H + ] = [OH ] Battery acid Gastric juice, lemon juice Vinegar, beer, wine, cola Tomato juice Black coffee Rainwater Urine Saliva Pure water Human blood, tears Seawater Milk of magnesia Household ammonia Household bleach 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 14 Oven cleaner

20 Buffers The internal ph of most living cells must remain close to ph 7 Buffers are substances that minimize changes in concentrations of H + and OH in a solution Most buffers consist of an acid-base pair that reversibly combines with H +

21 Threats to Water Quality Acid precipitation refers to rain, snow, or fog with a ph lower than 5.6 Acid precipitation is caused mainly by the mixing of different pollutants with water in the air and can fall at some distance from the source of pollutants Acid precipitation can damage life in lakes and streams Effects of acid precipitation on soil chemistry are contributing to the decline of some forests

22 Fig More acidic Acid rain Normal rain More basic

23 Human activities such as burning fossil fuels threaten water quality CO 2 is released by fossil fuel combustion and contributes to: A warming of earth called the greenhouse effect Acidification of the oceans; this leads to a decrease in the ability of corals to form calcified reefs

24 Fig. 3-UN6 Surface of Mars Surface of Earth water on Mars

25 You should now be able to: 1. List and explain the four properties of water that emerge as a result of its ability to form hydrogen bonds 2. Distinguish between the following sets of terms: hydrophobic and hydrophilic substances; a solute, a solvent, and a solution 3. Define acid, base, and ph 4. Explain how buffers work

26 Chapter 4 Carbon and the Molecular Diversity of Life PowerPoint Lecture Presentations for Biology Eighth Edition Neil Campbell and Jane Reece Lectures by Chris Romero, updated by Erin Barley with contributions from Joan Sharp

27 Fig. 4-1 Every living thing is made up of carbon. It is in our atmosphere, in the earth's crust, and in the bodies of both plants and animals. When we breathe, we exhale carbon-dioxide. When plants respire, they take in carbon-dioxide.

28 Without Carbon Life would not be possible!

29 Carbon is essential in life s processes Photosynthesis Respiration Decomposition

30 Carbon is the chemical basis for most of the molecules that are important to maintaining life. Carbohydrates Lipids Proteins Nucleic acids

31 The Formation of Bonds with Carbon With four valence electrons, carbon can form four covalent bonds with a variety of atoms This makes large, complex molecules possible In molecules with multiple carbons, each carbon bonded to four other atoms has a tetrahedral shape However, when two carbon atoms are joined by a double bond, the molecule has a flat shape

32 Concept 4.2: Carbon atoms can form diverse molecules by bonding to four other atoms Electron configuration is the key to an atom s characteristics Electron configuration determines the kinds and number of bonds an atom will form with other atoms Hydrogen (valence = 1) Oxygen (valence = 2) Nitrogen (valence = 3) Carbon (valence = 4)

33 Fig. 4-3 Name Molecular Formula Structural Formula Ball-and-Stick Model Space-Filling Model (a) Methane (b) Ethane (c) Ethene (ethylene)

34 The electron configuration of carbon gives it covalent compatibility with many different elements The valences of carbon and its most frequent partners (hydrogen, oxygen, and nitrogen) are the building code that governs the architecture of living molecules

35 You should now be able to: 1. Explain why carbon is critical to life. 2. Explain how carbon s electron configuration explains its ability to form large, complex, diverse organic molecules 3. Describe how carbon skeletons vary and explain how this variation contributes to the diversity and complexity.

36 Lab 3: Osmosis and Diffusion Exercise 12 pp OSMOSIS the diffusion of water (across a semipermeable membrane) ie: the cell membrane The water molecules are the small blue shapes, and the salt is green. Demonstration India Ink

37 Solute: the substance dissolved in the water, the dissolved substance. In lemonade solute is the sugar and lemon juice. Solvent: the dissolving substance. In lemonade the Solvent is water

38 Selectively Permeable - membranes that allow some things through, the cell membrane is selectively permeable, water and oxygen move freely across the cell's membrane, by diffusion. A simple rule to remember is:

39 Salt is a solute, when it is concentrated inside or outside the cell, it will draw the water in its direction. This is also why you get thirsty after eating something salty.

40 Transport Diffusion and Osmosis are both types of PASSIVE TRANSPORT - that is, no energy is required for the molecules to move into or out of the cell. Water potential is the tendency of water to move from 1 place in favor of another. Water moves from a HIGH water potential to a lower water potential.

41 Types of Solutions

42 If you take a red blood cell and drop it into distilled water the water will move into the cell until it POPS (see hypotonic below) If you do the same with a plant cell, the water moves in and fills the cell, but the cell wall prevents the plant cell from exploding. A plant with turgid cells is stiff and plump looking, one with flaccid cells is floppy.

43 Lab 3: Osmosis and Diffusion Exercise 12 pp Your first lab report is due on this lab. Be sure to take a lab report instruction sheet before you start! Work with your lab team, but write the report on your own! It must be typed. Only do part 3 Osmosis in living cells A - potato. Write out a hypothesis (before you start!) of what you think will happen to each potato cube. Cut skin off of potato and cut the cubes the same size and shape. Record your results on page 67. Lab report is due Sept 26.