Chapter 6Chapter 6

Metabolism: Energy and Metabolism: Energy and EnzymesEnzymes

6.1: Cells and the flow 6.1: Cells and the flow of energyof energy Energy: the ability to do work or Energy: the ability to do work or

bring about changebring about change– Organisms need a constant supply Organisms need a constant supply

of energy to maintain organization of energy to maintain organization and carry out metabolic activitiesand carry out metabolic activities

– Flow of energy: fig. 6.1Flow of energy: fig. 6.1

Forms of EnergyForms of Energy

Kinetic: energy of motion (a ball rolling Kinetic: energy of motion (a ball rolling down a hill)down a hill)

Potential: stored energy (the food we Potential: stored energy (the food we eat has potential energy)eat has potential energy)

Chemical: chemical composition of Chemical: chemical composition of substances makes them possess substances makes them possess energy, such as lipids, carbs, etc.energy, such as lipids, carbs, etc.

Mechanical: a type of kinetic in which Mechanical: a type of kinetic in which an organism is using it’s chemical an organism is using it’s chemical energy and converting it (ie. An energy and converting it (ie. An organism walking)organism walking)

Laws of Laws of ThermodynamicsThermodynamics These two laws explain why energy These two laws explain why energy

flows in ecosystems and cellsflows in ecosystems and cells Energy starts from the sun, and flows, Energy starts from the sun, and flows,

it does not cycle. Some of the sun’s it does not cycle. Some of the sun’s energy is dissipated as heat but most energy is dissipated as heat but most of it is used by plants for of it is used by plants for photosynthesis and animals when they photosynthesis and animals when they eat. Eventually all solar energy is eat. Eventually all solar energy is dissipated as heat.dissipated as heat.

First Law of First Law of ThermodynamicsThermodynamics Law of conservation of energy: Law of conservation of energy:

energy cannot be created or energy cannot be created or destroyed, only changed from one destroyed, only changed from one form or anotherform or another

See picture on p. 102, solar energy See picture on p. 102, solar energy being used by a plant to convert being used by a plant to convert carbon dioxide and water into carbon dioxide and water into carbohydrates, and energy being lost carbohydrates, and energy being lost as heatas heat

Second Law of Second Law of ThermodynamicsThermodynamics Energy cannot be changed from Energy cannot be changed from

one form to another without a one form to another without a loss of usable energyloss of usable energy

See picture on p. 103, See picture on p. 103, carbohydrates being used for carbohydrates being used for muscle contraction and some of muscle contraction and some of the energy being lost as heatthe energy being lost as heat

Cells and entropyCells and entropy

Entropy: a relative amount of Entropy: a relative amount of disorganizationdisorganization

Processes that occur in cells naturally Processes that occur in cells naturally tend to move toward entropy. tend to move toward entropy.

See fig. 6.2 and consider the ‘messy See fig. 6.2 and consider the ‘messy room’ analogy: a neat room is more room’ analogy: a neat room is more organized but less stable than a messy organized but less stable than a messy room (it’s easier to mess up), while a room (it’s easier to mess up), while a messy room is more stable but less messy room is more stable but less organized (harder to clean up) organized (harder to clean up)

ENTROPYENTROPY

6.2 Metabolic Reactions 6.2 Metabolic Reactions and Energy and Energy TransformationsTransformations Metabolism: the sum of Metabolism: the sum of

all chemical reactions all chemical reactions that occur in the bodythat occur in the body

Reactants: substances Reactants: substances in a chemical reaction in a chemical reaction that begin the reactionthat begin the reaction

Products: the result of Products: the result of the reactionthe reaction

In the reaction on the right, In the reaction on the right, circle the reactants and circle the reactants and draw a square around draw a square around the productsthe products

Direct combinationDirect combination or or synthesissynthesis, in which 2 or , in which 2 or more chemical elements more chemical elements or compounds unite to or compounds unite to form a more complex form a more complex product: product:

NN2 + 3 2 + 3 HH2 → 2 2 → 2 NHNH

Free energyFree energy

The amount of energy available, still The amount of energy available, still ‘free’ to do work, after a chemical ‘free’ to do work, after a chemical reaction has occurredreaction has occurred

From Wikipedia, “the Gibbs free energy From Wikipedia, “the Gibbs free energy ΔGΔG equals the work exchanged by the equals the work exchanged by the system with its surroundings, less the system with its surroundings, less the work of the pressure forces, during a work of the pressure forces, during a reversible transformation of the system reversible transformation of the system from the same initial state to the same from the same initial state to the same final state.“final state.“

Exergonic ReactionsExergonic Reactions

When there is a When there is a negative negative ΔG, ΔG, therefore energy therefore energy is released.is released.

Cellular Cellular respiration is an respiration is an exergonic exergonic reactionreaction

Endergonic reactionEndergonic reaction

The ones in which The ones in which ΔG ΔG is positive is positive and energy is absorbedand energy is absorbed

Examples: protein synthesis, Examples: protein synthesis, nerve conduction, muscle nerve conduction, muscle contractioncontraction

Adenosine Adenosine Triphosphate (ATP)Triphosphate (ATP) The common energy currency of cells, The common energy currency of cells,

when cells require energy, they when cells require energy, they ‘spend’ ATP‘spend’ ATP

The more active an organism, the The more active an organism, the greater its demand for ATPgreater its demand for ATP

It is constantly being generated from It is constantly being generated from ADP (adenosine ADP (adenosine didiphosphate) and a phosphate) and a molecule of inorganic phosphatemolecule of inorganic phosphate

Glucose breakdown during cellular Glucose breakdown during cellular respiration provides the energy for the respiration provides the energy for the buildup of ATP in mitochondriabuildup of ATP in mitochondria

Structure of ATPStructure of ATP

Coupled ReactionsCoupled Reactions

When reactions are both exergonic When reactions are both exergonic and endergonic; energy is first and endergonic; energy is first released by an exergonic reaction released by an exergonic reaction and in turn used to drive an and in turn used to drive an endergonic reactionendergonic reaction

See fig. 6.4: first ATP is broken down See fig. 6.4: first ATP is broken down to get energy and then that energy to get energy and then that energy is used in muscle contractionis used in muscle contraction

Functions of ATPFunctions of ATP

Uses of ATP in living systems:Uses of ATP in living systems:– Chemical: ATP provides the cell Chemical: ATP provides the cell

energy to synthesize macromoleculesenergy to synthesize macromolecules– Transport: ATP provides energy for Transport: ATP provides energy for

cells to transport molecules across cells to transport molecules across membranesmembranes

– Mechanical: enables muscle Mechanical: enables muscle contraction, cells to move, cell contraction, cells to move, cell division, etc….division, etc….

For next For next time(MONDAY)time(MONDAY) We will finish ch. 6 notesWe will finish ch. 6 notes READ chapter 6!!!READ chapter 6!!! On page 112 do ‘reviewing ch. #1-7On page 112 do ‘reviewing ch. #1-7 Study session MON after school for Study session MON after school for

one hour!one hour! TEST (chapters 2-6) TUESTEST (chapters 2-6) TUES Come tomorrow to randomly choose Come tomorrow to randomly choose

your take home essay, due TUESyour take home essay, due TUES