Big Idea 2: Biological systems utilize free energy and molecular building blocks to grow, to reproduce and to maintain dynamic homeostasis.

Transcription

1 Big Idea 2: Biological systems utilize free energy and molecular building blocks to grow, to reproduce and to maintain dynamic homeostasis. Enduring understanding 2.A: Growth, reproduction and maintenance of the organization of living systems require free energy and matter. Essential knowledge 2.A.1: All living systems require constant input of free energy.

2 Subobjective 2.1: I can explain how biological systems use free energy based on empirical data that all organisms require constant energy input to maintain organization, to grow and to reproduce.

3 What is the relationship between energy and matter? Define energy The ability to make a change Define kinetic energy Energy of motion Define heat Measure of the movement of energy from one place to another

4 Define potential energy Stored energy due to location or position

5 Define chemical energy Potential energy associated with the covalent bonds that hold atoms and molecules together

6 Define matter Anything with mass and volume Elementary particles such as neutrinos are matter, but all we care about are atoms

7 Go to the website below to get an idea about how small an atom is

8 Element A substance that cannot be broken down chemically into another substance carbon Compound A substance made of two or more different elements NaCl (sodium chloride)

9 Define emergent property Properties of a system that arise due to complexity and cannot be attributed to the properties of the parts of the system (one of the unifying themes in biology) How do compounds show emergent properties? The properties of the compound are beyond and not predictable from the properties of the elements they are composed of Sodium is a highly reactive metal and chlorine is a toxic gas, put them together and you get salt which has the property of making just about every food taste better

10 How does the structure of atoms determine an element s properties? Atom The smallest unit of an element Composed of a dense nucleus orbited by electrons

11 A model of a Carbon-12 atom

12 Describe the structure of an atom Neutrons no charge Protons +1 charge Nucleus Electrons -1 charge

13 Describe the charge of atoms Neutrons no charge Protons +1 charge Electrons -1 charge Charges are equal in magnitude but opposite. Atoms are neutral in charge because the number of protons equals the number of electrons

14 Neutrons no charge Protons +1 charge Electrons -1 charge What do protons do? Determine the kind of atom Change the number of protons and you change the kind of element

15 What do electrons do? Neutrons no charge Protons +1 charge Electrons -1 charge Determine the chemistry of the atom. In other words, they are involved in the formation of chemical bonds

16 Having trouble understanding? Watch the Khan Academy videos below.

17 How does chemical bonding between atoms determine the formation and function of molecules? Valence electrons Electrons in the outermost energy level (they are involved in bonding and therefore determine the chemistry of an atom) watch?v=qmge0w6e6zi&fe ature=related

18 Define covalent bond Sharing one or more pairs of electrons Why do covalent bonds form? Sometimes sharing one or more pairs of electrons satisfies the need of both atoms for a full valence shell

19 Define molecule 2 or more atoms covalently bonded together Define compound Molecular oxygen 2 or more different molecules bonded together Which of the molecules to the right are compounds?

20 How are covalent bonds represented?

21 Show the 4 ways of representing covalent bonds for molecules a-d

22 What is electronegativity? How good an atom or molecule is at attracting electrons

23 Having trouble understanding? Watch the Khan Academy video below.

24 Define nonpolar covalent bond A covalent bond where the electron pair is shared equally When do nonpolar covalent bonds form? When the electronegativities of the atoms involved is the same You should know that carbon forms nonpolar covalent bonds with hydrogen

25 Define polar covalent bond A covalent bond where the electron pair is shared unequally When do polar covalent bonds form? When the electronegativities of the atoms involved are different Unequal sharing of electrons gives hydrogen a slightly positive charge Unequal sharing of electrons gives oxygen a slightly negative charge

26 Define ionic compound A combination of 2 different kinds of ions in a fixed ratio. They may form from ionic atoms or ionic molecules. NaCl (Sodium chloride) Charged atoms Ionic compounds are called salts CaCO 3 (Calcium carbonate) Charged atom Charged molecule

27 Describe ionic bonds Electrons are gained or lost resulting in ions that form bonds from electrostatic attraction forming neutral compounds

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29 Define ion A charged atom or compound A negatively charged ion dissolved A positively charged ion dissolved Ionic compound Water molecules

30 Cation, anion, neutral chlorine atom, neutral sodium atom, ionic bond, neutral compound Neutral sodium atom Neutral chlorine atom cation anion Neutral compound Ionic bond

31 Define hydrogen bond An intermolecular force that holds two molecules together. It results from unequal electron sharing between a hydrogen atom and another atom it is covalently bonded to

32 Having trouble understanding? What the Khan Academy video below.

33 Why are hydrogen bonds important in biological molecules? 1) They give water its unique properties 2) They are important causes of the 3-dimensional shape of proteins 3) They hold complementary strands of DNA together bfqfrm&nr=1

34 Covalent bond between oxygen and hydrogen Unequal sharing of electrons gives oxygen a slightly negative charge Hydrogen bonding in water Hydrogen bond between two water molecules Unequal sharing of electrons gives hydrogen a slightly positive charge

35 Define van der Waals forces Week interactions between atoms due to the constant movement of electrons causing brief moments of positive and negative charges around the atom This is a Gecko's foot up close. It s cell surface area is enormous allowing the week van der Waals forces to add up enough to give them the ability to walk on walls.

36 Having trouble understanding? Watch the Khan Academy video below.

37 Bond strength Hydrogen bonds are weakest (they are really intermolecular forces) *Ionic and covalent bond strengths overlap and no bond is purely ionic or purely covalent Covalent bonds remain intact in solution, but ionic bonds dissociate, so biology texts often say covalent bonds are stronger that ionic bonds. This is conceptually correct for our purposes.

38 What is the significance of molecular shape for biological systems? The shape of biological molecules allow for recognition and response among them Similarly shaped molecules often have similar effects

39 What kind of bond is shown? Single covalent

40 What kind of bond is shown? Hydrogen

41 What kind of bond is shown? Hydrogen

42 What kind of bond is shown? Single covalent

43 What kind of bond is shown? Single covalent

44 What kind of bond is shown? Ionic

45 What kind of bond is shown? Double covalent

46 What kind of bond is shown? Triple covalent

47 What kind of bond is shown? Single covalent

48 What kind of bond is shown? Double covalent

49 What kind of bond is shown? Single covalent

50 Hydrogen What kind of bond is shown?

51 Single covalent What kind of bond is shown?

52 Hydrogen What kind of bond is shown?

53 What are chemical reactions and what are their characteristics? Define chemical reaction Making and breaking bonds resulting in a rearrangement of atoms and molecules

54 What is the law of conservation of matter and how do chemical reactions like the formation of water and photosynthesis illustrate this law? Matter cannot be created nor destroyed UNDER NORMAL CONDITIONS. Radioactive decay is an example of matter being destroyed. In reality, the matter is being converted to energy.

55 2H 2 + O 2 2H 2 O Reactants Products 2 Hydrogen molecules react with 1 oxygen molecule to yield 2 water molecules each containing 2 hydrogen and 1 oxygen atoms. The atoms have been rearranged, but conserved just as the law of conservation of matter predicts!

56 Identify the reactants and products of photosynthesis and translate the equation to words CO 2 = carbon dioxide, C 6 H 12 O 6 = glucose 6CO H 2 O C 6 H 12 O 6 + 6H 2 O + 6O 2 Reactants Products 6 carbon dioxide molecules react with 12 water molecules to yield 1 glucose molecule, 6 water molecules, and 6 oxygen molecules. Notice the atom count is the same in the reactants and products. They have been rearranged, but conserved just as the law of conservation of matter predicts!

57 Having trouble understanding? What the Khan Academy video below.

58 How does life on Earth obey the laws of thermodynamics?

59 Define thermodynamics The study of energy transfers heat

60 First law of thermodynamics Energy cannot be created nor destroyed. It only changes forms

61 Second law of thermodynamics Disorder (entropy) increases in a closed system This means that usable energy is lost in the form of heat during EVERY energy conversion Free energy This is the amount of energy released when hydrogen gas is burned

62 The second law of thermodynamics means that usable energy is lost in the form of heat during EVERY energy conversion Free energy This is the amount of energy that goes into water in order to make the H 2 gas

63 Can we really run cars on H 2 0? YES! If you are concerned about the environment or your pocket book it is a bad idea

64 This HHO conversion kit claims you can increase gas mileage by 30% Either the makers of this kit are charlatans or they disserve a Nobel Prize for physics The 2 nd law of thermodynamics tells us that you can t get more energy out of H 2 gas then you put into making it from water. Additionally, since no chemical reaction is perfect (there is always energy lost to the system in the form of heat), HHO conversion kits will reduce gas millage!

65 One of the trends of evolution is an increase in complexity over time Disclaimer: this doesn t mean evolution guarantees complexity or that complexity is a goal of evolution (evolution has no goal) Prokaryotes are relatively simple cells that were among the first life forms on this planet and they are still the dominant life form on this planet. They have retained their simple cellular structure over 3.8 billion years of evolution!

66 Doesn t the increase in complexity over time that has occurred because of evolution violate the 2 nd law of thermodynamics? Why or why not? Species composition has changed DRAMATICALLY over time

67 Earth is NOT a closed system! The Sun allows for an itty bitty little bit of order in a microscopic insignificant bit of the Universe for a short period of time as it burns up increasing the entropy of the Universe all the while

68 The average American eats nearly one ton of food per year! That means you have to eat about 10 times your weight every year to maintain your weight. In other words, every year you create 10 times more disorder (entropy) on this planet than the amount of order your body accounts for.

69 How does life transform an increase in entropy from the Sun into a decrease in entropy on Earth?

70 Plants capture energy from the Sun and store it in chemical bonds We break these chemical bonds, which releases energy We use that energy to make new chemical bonds and do energy requiring things like breathing

71 Order is potential energy This is order This is the mechanism in place to harness the change in energy that will occur based on the 2 nd law of thermodynamics

72 The Sun! How did the water get up here?

73 Order is potential energy This is order A concentration gradient of protons was established using energy from the Sun

74 The potential energy of the proton gradient was used to make glucose, which has potential energy associated with its chemical bonds

75 How does free-energy change of a reaction tells us whether or not the reaction occurs spontaneously? Define free energy The portion of a system s energy that can perform work when temperature and pressure are uniform What is the equation that describes free energy change? ΔG = ΔH - T ΔS Change in free energy Change enthalpy Temperature Change in entropy

76 Define spontaneous process A chemical reaction or change that occurs without the input of energy (occurs if the change increases the entropy of the system) The molecules above will spread out evenly between the two sides without the input of energy

77 Order is potential energy This is order There is no mechanism in place to harness the change in energy that will occur based on the 2 nd law of thermodynamics

78 Define enthalpy Total energy of a system If G < 0 the reaction will occur spontaneously

79 Predict whether the following reactions will occur spontaneously or not and explain why G = 5.2kcal/mol G = -2.3 kcal/mol ΔG = ΔH - T ΔS No: G is positive so entropy decreased (more order) or enthalpy (total energy of the system) increased Yes: G is negative so entropy increased (less order) or enthalpy (total energy of the system) decreased

80 Define chemical equilibrium When forward and backward reactions occur at the same rate

81 A process or chemical reaction can occur spontaneously if it is moving towards equilibrium When - G the system is moving towards equilibrium When + G the system is moving away from equilibrium

82 Define exergonic reaction A reaction were the free energy is lost ( G is negative)

83 Define endergonic reaction A reaction were the free energy is gained ( G is positive)

84 How would you describe a cell at metabolic equilibrium? Dead This system is at equilibrium, so it cannot generate energy. A cell that cannot generate energy is dead.

85 Why don t living cells reach equilibrium? They are constantly taking in materials, transforming them, and excreting the products This system is not at equilibrium and materials are flowing in and out, so it can continue to generate energy

86 How does ATP power cellular work? Define energy coupling Use of an exergonic pathway to drive an endergonic pathway utilizing ATP as an intermediate Define hydrolysis Water cutting A chemical reaction that consumes one water molecule and breaks up one molecule into two releasing energy

87 Describe the hydrolysis of ATP ATP + H 2 O ADP + P i G = -7.3 kcal/mol (-30.5 kj/mol) Kilocalories and kilojoules are both units of energy A mole is a unit of count like a dozen This means if I hydrolyze a mole of ATP molecules, I will release 7.3 kilocalories of heat

88 What is the structure of ATP? 1) An adenine molecule 2) A ribose molecule 3) 3 negatively charged phosphate groups It is the same molecule used to make RNA

89 How does ATP store and release energy? kcal ATP H 2O ADP Pi 7.3 mol

90 How does ATP store and release energy? The negative charges of the phosphate molecules repel each other so ATP is like a loaded spring ATP with 3 negative ions close together ADP with 2 negative ions not as close together

91 How does the hydrolysis of ATP perform work? Define phosphorylated intermediate A molecule that is phosphorylated, which couples an exergonic and endergonic reaction Will this reaction occur spontaneously? Why or why not? No, because G is positive so energy needs to be added to the system

92 How is ATP used to make this endergonic reaction occur?

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94 Describe the ATP cycle

95 Subobjective 2.2: I can defend a scientific claim that free energy is required for living systems to maintain organization, to grow, or to reproduce, but that multiple strategies for obtaining and using energy exist in different living systems.

96 What is the relationship between metabolism and homeostasis? Define metabolism All of the chemical reactions that sustain an organism No chemical reaction is perfect. The system always looses a little energy in the form of heat. This means the greater the metabolism the greater generation of heat. Animals have high metabolisms and therefore have relatively high body temperatures. Plants have low metabolisms and therefore relatively low body temperatures.

97 What are the 2 sub categories of metabolism? Catabolism Breaking down complex molecules into smaller ones releasing energy Anabolism Building up complex molecules from smaller ones consuming energy

98 Define metabolic rate The amount of energy an organism uses per unit of time How is metabolic rate measured? Consumption of O 2, production of CO 2, or production of heat

99 Define homeostasis Maintenance of conditions within a narrow range

100 Skunk cabbage likes a flower temperature at about 23⁰C. When temperatures drop, they can increase their metabolic rate to that of a small rodent, which produces enough heat to melt ice. When temperatures increase, they can decrease their metabolic rate and therefore decrease heat production and maintain temperature homeostasis.

101 Heat production decreases Response: Decrease metabolic rate Sensor/control center: unknown Stimulus: temperature increases Set point: Skunk cabbage flowers at 23⁰C Heat production increases Stimulus: temperature decreases Response: Increase metabolic rate Sensor/control center: unknown

102 How do form, function, and behavior influence thermoregulation? How do organisms thermoregulate? Changing metabolic rate and how they interact with the external environment Define endothermic An organism that maintains a relatively constant internal body temperature mostly by generating heat from metabolism Mammals, birds, some fish, reptiles, and insects are endotherms

103 Define ectothermic An organism that mainly heats its internal environment with external sources What does the graph show? Ectotherms require less energy to survive Endotherms require lots of energy to stay warm and lots of energy to stay cool Dependent variable is metabolic rate measured by O 2 consumption Independent variable is temperature

104 What conclusions can you make from the graph? Pythons increase metabolic rate (measured by O 2 consumption) by shivering to keep their eggs warm

105 How is this an adaptation for thermoregulation? Large surface areas allow for more heat exchange with the environment. Conversely, feathers are excellent insulators. How is this an adaptation for thermoregulation? It isn t! Goosebumps are a vestige of the muscles used to raise the fur we inherited from our ancestors. A raised fur coat is a good insulator. This is why you get goosebumps when you are cold. You are trying to raise a nonexistent fur coat!

106 How do emperor penguins thermoregulate? 1) Increasing metabolic rate 2) Insulating with lots of subcutaneous fat 3) Behaviorally by grouping tightly together

107 How does the nervous system maintain temperature homeostasis? This is an example of a negative feedback mechanism were the response reduces the stimulus. You need to remember that the hypothalamus is the sensor and control center

108 Explain the difference in energy used for thermoregulation between endotherms and ectotherms Endotherms generate heat through metabolism to increase body temperature while ectotherms get their heat from the environment

109 Explain the difference in energy used for thermoregulation between humans and mice Humans are a large organism and mice are small. Mice have a much larger surface to volume ratio so they exchange more heat with the environment.

110 Explain the difference in energy used for reproduction between humans and mice Humans have few offspring and give them a lot of care, while mice have many offspring and give them less care

111 Explain what this graph tells us Dependent variable is basal metabolic rate measured by O 2 consumption (metabolic rate of an organism at rest and not growing) Independent variable is the log of the body mass in kilograms

112 All of these organisms have similar shapes. This means that the bigger they are the less surface area they have per unit of volume, so they don t exchange heat with the environment as much. Shrews have a very high surface to volume ratio so they must generate a lot of heat to stay warm. Elephants have a very low surface to volume ratio so they don t lose much heat to the environment and therefore use very little metabolism for generating extra heat.

113 What are some strategies organisms use maximize reproductive success while minimizing free energy loss? Biennial reproduction in some plants like onions In the first year, the plant grows and stores free energy It goes dormant in the winter to conserve free energy The following year it flowers (reproductive structures) and produces seeds converting stored free energy into offspring and dies

114 Most bird species and humans require both the mother and father to raise offspring Watch the video and explain how penguins reproduce in terms of free energy changes in the father, mother, and chick

115 Subobjective 2.3: I can predict how changes in free energy availability affect organisms, populations, and/or ecosystems. Watch this video before continuing

116 How do free energy changes affect individuals and populations? Energy in is greater than Energy out When energy in is greater than energy out we have a + G for the cow. This free energy change is used to grow and reproduce.

117 Energy in is less than Energy out Where did the free energy for cow growth and reproduction come from? The grassland This means the we have a - G for the ecosystem which follows the 2 nd law of thermodynamics

118 Energy in is less than Energy out Is this a sustainable scenario? No!

119 Energy out Energy in is less than This results in a negative free energy change (- G). The cow gets smaller (loses mass from fat and muscle) and does not reproduce

120 Population Population Time Time In order for individuals to grow and for populations to increase, they need a continuous source of free energy

121 Consumers heat How does free energy flow in an ecosystem? It s one way!! Consumers heat Producers heat

122 Consumers heat All ecosystems are dependent on producers Consumers Producers heat heat Make their carbon compounds by photosynthesis or chemosynthesis Making carbon compounds using energy from the bonds holding inorganic molecules together (examples are hydrogen gas (H 2 ) and hydrogen sulfide (H 2 S)

123 Define autotroph An organism that makes its own organic molecules by photosynthesis or chemosynthesis (all autotrophs are producers) Define heterotroph An organism that gets its organic molecules from other organisms (all heterotrophs are consumers)

124 What does this bar graph show? The dependent variable is trophic levels Feeding level (where on a food chain you get your organic molecules) The independent variable is productivity (available free energy)

125 The chart shows that the number of trophic levels sustainable is dependent on the amount of free energy made available by producers

126 How much biomass is transferred between trophic levels? Roughly 10% (you need to memorize this) and you need to be able to make calculations and predictions based on this rule Mass and energy are related. A 90% decrease in dry mass from one trophic level to the next means a 90% decrease in free energy.

127 How much hawk mass could be made from 8,587grams of grasshopper mass if hawks eat grasshoppers? 8,587g X 0.10 = 858.7g Grasshopper mass 10% is transferred from one trophic level to the next Hawk mass

128 How much hawk mass could be made from 8,587grams of grasshopper mass if hawks eat mice? 8,587g X 0.10 X 0.10 = 85.87g Grasshopper mass 10% is transferred from grasshoppers to mice 10% is transferred from mice to hawks Hawk mass

129 Where is the vast majority mass and therefore free energy in an ecosystem? With the producers If you wanted to feed as many people as possible in the most sustainable way, what would you feed them and why? Fruits, vegetables, and grains because this would require the least amount of primary productivity and therefore the least decrease in free energy in the ecosystem

130 Explain why about 55% of life on Earth went extinct 65 million years ago in terms of free energy and primary productivity (watch the video) Soot, dust, and aerosols from the impact of the asteroid and possibly from volcanic eruptions blocked and reflected sunlight. This decreased free energy from the Sun, which decreased primary productivity, which decreased free energy available to heterotrophs globally, which caused food webs to collapse and mass extinction v=5qjptjmnwnk