AP Biology Chapter 6

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Entropy

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244 Terms

1

Entropy

a measure of disorder or randomness

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2

In biology, equilibrium=

Death

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3

What are enzymes always?

Proteins

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4

What do enzymes do?

Catalyze chemical reactions by lowering activation energy

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5

Are enzymes parts of the reaction? In other words, do they change with the chemical reaction?

No, they do not change

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6

Metabolism

the totality of an organism's chemical reactions

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7

What is metabolism? (Hint: something to do with a chemical property)

An emergent property of life that arises from orderly interactions between molecules.

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8

Metabolic Pathway

how a specific molecule travels through a cell’s metabolism

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9

What happens to a molecule in a metabolic pathway?

A specific molecule is altered in a series of defined steps, resulting in a product

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10

How is each step made successful in a metabolic pathway?

Each step is catalyzed by a specific enzyme

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11

Catabolic pathways

a metabolic pathway that releases energy by breaking down complex molecules into simpler ones

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12

What is an example of a way the cell releases energy?

Breaking down ATP to ADP

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13

Anabolic Pathway

metabolic pathways that consume energy to build complicated molecules from simpler ones

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14

What are anabolic pathways sometimes called?

A biosynthetic pathway

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15

What is an example of an anabolic pathway?

Synthesis of a protein

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16

Bioenergetics

study of how energy flows through living organisms

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17

Energy

the capacity to cause change, the ability to arrange a collection of matter

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18

What does the work of life depend on?

The ability of cells to transform energy from one form to another

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19

Kinetic energy

the relative motion of objects

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20

Thermal energy

kinetic energy associated with the random movement of atoms or molecules

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Heat

transfer of thermal energy from one object to another

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22

Potential energy

an object’s not moving energy

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23

Chemical energy

used to refer to the potential energy available for release in a chemical reaction

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24

Thermodynamics

the study of the energy transformations that occur in a collection of matter

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System

matter under study

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Surroundings

everything outside the system

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Isolated System

unable to exchange either energy or matter with its surroundings

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28

What is an isolated system also known as?

A closed system

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Open System

energy and matter can be transferred between the system and its surroundings

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Are organisms open or closed systems?

Open systems

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First Law of Thermodynamics

energy can be transferred and transformed but cannot be created or destroyed

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32

What is the First Law of Thermodynamics also known as?

The Law of Conservation of Energy

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33

Second Law of Thermodynamics

every energy transfer or transformation increases the entropy of the universe

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34

When does an organism have a high entropy?

When an organism has more randomly arranged collection of matter in it

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35

Spontaneous Process

when a process occurs without energy required

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Are all spontaneous reactions instantaneous?

No, some are much slower like rust

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Nonspontanously

a process that cannot occur on its own

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38

What is another way to state the Second Law of Thermodynamics?

For a process to occur spontaneously, it must increase the entropy of the universe

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39

How are cell structures created? (Hint: don’t over think, has to do with Entropy)

cells create ordered structures from less organized starting material

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40

Can the entropy of a particular system decrease?

Yes as long as the total entropy of the universe increases

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41

Define the Universe in terms of Entropy

system and its surroundings

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42

Equilibrium

the forward and reverse reactions occur at the same rate and there is no further net change in the relative concentrations of products and reactants

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43

When is a process spontaneous and can perform work?

Only when it is moving toward equilibrium

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44

Exergonic Reaction

proceeds with a net release of free energy

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45

What does the greater decrease in free energy mean?

The greater amount of work can be done, change in G is negative

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46

Spontaneous change

free energy of the system decreases, system becomes more stable, released free energy can be harnessed to do work

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47

What does the breaking of bonds do?

Not release energy but requires energy and releases energy when it makes new bonds

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48

Endergonic Reaction

absorbs free energy from its surroundings, essentially stores free energy, change in G is positive

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49

What do reactions in an isolated system eventually do?

Reach equilibrium

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50

Is metabolism as a whole ever at equilibrium?

No

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What prevents metabolism from ever being at equilibrium?

The constant flow of materials in and out

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Are organisms open or closed systems?

Open systems

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53

Chemical work

the pushing of endergonic reactions that would not occur spontaneously

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Transport work

the pumping of substances across membranes against the direction of the concentration gradient

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Mechanical work

the beating of cilia, contraction of muscle cells and the movement of chromosomes during cellular respiration

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Energy Coupling

use of an exergonic process to drive an endergonic one

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What is responsible for mediating most energy coupling in cells and most cases acts as the immediate source of energy that powers cellular work?

ATP

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ATP (adenosine triphosphate)

contains the sugar ribose with the nitrogenous base adenine and a chain of three phosphate groups

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What splits ATP to ADP?

Hydrolysis

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Phosphorylated Intermediate

the recipient with the phosphate group covalently bonded to ti

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What is the key to coupling exergonic and endergonic reactions?

The formation of phosphorylated intermediate which is more reactive than the original unphosphorylated molecule

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What functions of cells are nearly always powered by the hydrolysis of ATP?

Transport and mechanical work

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63

Enzyme

a macromolecule that acts as a catalyst

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Catalyst

a chemical agent that speeds up a reaction without being consumed by the reaction

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What does charming one molecule into another general involve?

Controlling the starting molecule into a highly unstable state before the reaction can proceed

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What happens when the new bonds of the product molecules form?

Energy is released as heat and the molecules return to stable shapes with lower energy that the contracted state

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Activation Energy

the energy required to contrast the reactant molecules so the bonds can break

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How is activation energy often supplied?

By heat in the form of thermal energy that the reactant molecules absorb from the surroundings

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What does the absorption of thermal energy do?

Accelerates the reactant molecules so they collide more often and more forcefully

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Transition State

when the molecules have absorbed enough energy for the bonds to break

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What state are the reactants in?

The transition state

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What does activation energy provide?

A barrier that determines the rate of the reaction

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In most cases, what is true about the activation energy?

It is so high and the transition state is reached so rarely that the reaction will hardly proceed at all

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How does heat speed a reaction?

By allowing the reactants to attain the transition state more often

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Why does heating not work for life?

High temperatures denatures proteins and kills cells and would speed up all reactions, not just those that are needed

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What does an enzyme catalyze?

A specific reaction by lower the EA barrier, enabling the reactant molecules to absorb enough energy to reach the transition state even at moderate temperatures

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Can an enzyme make a reaction endergonic to exergonic?

No

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Can an enzyme change the change in G for a reaction?

No

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Substrate

the reactant an enzyme acts on

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Enzyme-Substrate Complex

created when an enzyme binds to a substrate

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What do most enzyme names end in?

-ase

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82

What does the specificity of an enzyme result from?

Its shape, consequence of its amino acid sequence

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83

Active site

the restricted region of the enzyme molecule that actually binds to a substrate

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84

What usually forms the active site of an enzyme?

A few of the enzymes amino acids

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85

Is the active site a rigid receptacle?

No, it changes shape slightly due to interactions between the substrate’s chemical groups on the side chains of the amino acids that form the active site

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86

Induced Fit

brings chemical groups of the active site into positions that enhance their ability to catalyze the chemical creation

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87

Are most metabolic reactions reversible?

Yes

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88

What is the activation energy proportional to?

The difficulty of breaking the bonds

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89

Optimal Conditions

conditions that the enzyme works better under, favor the most active shape for the enzyme molecule

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Denaturation

a process where a protein loses its native shape overtime due to the disruption of weak chemical bonds and interactions thereby becoming inactive

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Cofactors

non protein helpers for catalytic activity that many enzymes require

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Where are cofactors found on an enzyme-substrate complex?

Tightly bound to the enzyme as permanent residents or bound loosely and reversibly along the substrate

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Coenzyme

when a cofactor is an organic molecule

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94

What can most vitamins act as?

Coenzymes or the raw materials to make a coenzyme

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How do cofactors and coenzymes function?

In various ways bit in all cases they perform a crucial chemical function in catalysis

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96

How does an inhibitor usually attach itself to the enzyme?

By covalent bonds

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Are inhibitors reversible?

Usually irreversible

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98

Competitive Inhibitors

some reversible inhibitor who resembles the normal substrate molecules and competes for admission into the active site

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How can competitive inhibitors be overcome?

By increasing the concentration of substrate so that the active sites become available

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100

Noncompetitive inhibitors

do not directly compete with substrate to bind to the enzyme at the active site but instead impede enzymatic reactions by binding to another part of the enzyme

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