Energy and metabolism
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Energy and Metabolism. Chapter 6. Flow of Energy. Energy : the capacity to do work - kinetic energy : the energy of motion - potential energy : stored energy Energy can take many forms: chemical, mechanical , electric current, heat , light. Fig. 6.1. Flow of Energy.

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Energy and metabolism

Energy and Metabolism

Chapter 6


Flow of energy

Flow of Energy

  • Energy: the capacity to do work

    -kinetic energy: the energy of motion

    -potential energy: stored energy

  • Energy can take many forms: chemical, mechanical, electric current, heat, light


Fig 6 1

Fig. 6.1


Flow of energy1

Flow of Energy

  • Most forms of energy can be converted to heat energy.

  • Heat energy is measured in kilocalories.

  • One calorie = the amount of heat required to raise the temp of water by 1oC

    1 kilocalorie (kcal) = 1000 calories (Cal.)


Laws of thermodynamics

Laws of Thermodynamics

First Law of Thermodynamics – energy cannot be created or destroyed

-energy can only be converted from one form to another

For example:

sunlight energy chemical energy

photosynthesis


Laws of thermodynamics1

Laws of Thermodynamics

  • Second Law of Thermodynamics: disorder is more likely than order

    entropy: disorder in the universe

  • The 2nd Law of Thermodynamics states that entropy is always increasing.

  • Energy is required to keep order, to do work

    • keep cells together and organized

    • perform life processes


Laws of thermodynamics2

Laws of Thermodynamics

  • Enthalpy: All of the energy contained in a molecule’s chemical bonds

  • Free energy: the energy available to do work, to reduce disorder (enthalpy)

    • denoted by the symbol G (Gibb’s free energy)

  • free energy = enthalpy – (entropy x temp.)

    G = H - TS


Laws of thermodynamics3

Laws of Thermodynamics

  • Chemical reactions can create changes in free energy:

    ΔG = ΔH - T ΔS

  • When products of chemical reactions contain more free energy than reactants – ΔG is positive.

  • When reactants contain more free energy than products – ΔG is negative.


Laws of thermodynamics4

Laws of Thermodynamics

  • Chemical reactions can be described by the transfer of energy that occurs:

  • endergonic reaction: a reaction requiring an input of energy

    • ΔG is positive

  • exergonic reaction: a reaction that releases free energy

    • ΔG is negative


  • Laws of thermodynamics5

    Laws of Thermodynamics

    • Most reactions require some energy to get started - activation energy.

    • activation energy: extra energy needed to get a reaction started

      -destabilizes existing chemical bonds

      -required even for exergonic reactions

    • catalysts: substances that lower the activation energy of a reaction (enzymes)


    Flow of energy2

    Flow of Energy

    • Potential energy stored in chemical bonds can be transferred from one molecule to another by way of electrons.

      oxidation: loss of electrons

      reduction: gain of electrons

    • Redox reactions are coupled to each other.


    Oxidation reduction reactions

    Oxidation-Reduction Reactions

    • A chemical reaction that transfers electrons from one atom to another

      • Oxidation = loss of an electron

      • Reduction = gain of an electron


    Oxidation reduction reactions1

    Oxidation-Reduction Reactions

    • Oxidation

      • A chemical reaction in which a molecule gives up electrons

      • Oxidation releases energy

      • The molecule loosing the electron is oxidized

    79


    Oxidation reduction reactions2

    Oxidation-Reduction Reactions

    • Reduction

      • A chemical reaction in which a molecule gains electrons and energy

      • The molecule that accepts electrons is reduced

      • The molecule being reduced receives energy

    80


    Oxidation reduction reactions3

    Oxidation-Reduction Reactions

    • LEO the lion says GER

      • If it Looses Electrons during the reaction, it’s Oxidized

      • If it Gains Electrons during the reaction, it’s Reduced


    Redox reactions

    Redox Reactions

    • Oxidation and Reduction reactions always occur in pairs

      • If an atom or molecule is reduced, another atom or molecule must have been oxidized

      • If an atom or molecule is oxidized, another atom or molecule must have been reduced

    • For this reason Oxidation and Reduction Reactions are known as Redox Reactions


    Atp energy currency of cells

    ATP - Energy Currency of Cells

    • ATP is the molecule that cells use to store, transfer, and provide energy

    • The energy from ATP is used to fuel anabolic reactions

      • recall: for growth, repair, and reproduction

    • ATP = Adenosine TriphosPhate

      • Adenosine (same molecule from DNA and RNA)

        +

      • Three inorganic phosphates (functional group PO4)

    21


    Atp energy currency of cells1

    ATP - Energy Currency of Cells

    • ATP= adenosine triphosphate

      • the energy “currency” of cells

    • ATP structure:

      • ribose, a 5-carbon sugar

      • adenine

      • three phosphates


    Energy and metabolism

    Photo Courtest of Dr. O’Steen


    Atp energy currency of cells2

    ATP - Energy Currency of Cells

    • ATP - 1 PO4 = ADP (Adenosine Diphosphate)

    • ADP - 1 PO4 = AMP (Adenosine Monophosphate)

    • ADP + 1 PO4 = ATP

    25


    Figure 5 12

    Figure 5_12


    Energy and metabolism

    ATP

    • ATP is a molecule that is used as an Energy Currency in cells

      • ATP’s can be broken down to provide energy for endergonic reactions

      • Cells use energy to build ATP’s

      • Enzymes of allow cells to efficiently build ATP’s - Cells can make ATP’s for less energy than ATP’s can provide


    Atp energy currency of cells3

    ATP - Energy Currency of Cells

    • ATP stores energy in the covalent bonds between phosphates:

      • Phosphates are highly negative, therefore:

        • the phosphates repel each other

        • much energy is required to keep the phosphates bound to each other

    • Energy is released when the bond between two phosphates is broken


    Energy currency of cells

    Energy Currency of Cells

    • When the bond between phosphates is broken:

      ATP ADP + Pi

      energy is released

    • ADP = adenosine diphosphate

    • Pi = inorganic phosphate

    • This reaction is reversible...


    Text art 5 06

    Text art 5_06

    ATP/ADP Cycling


    Energy currency of cells1

    Energy Currency of Cells

    • When the bond between phosphates is formed:

      ADP + Pi ATP

      energy is consumed

    • ATP - ADP Cycle


    Text art 5 07

    Text art 5_07

    ATP/ADP Cycling


    Energy currency of cells2

    Energy Currency of Cells

    • It costs energy to build ATPs

      ADP + 1PATP

    (Adenosine Diphosphate +1 phosphate)


    Atp adp cycling

    ATP/ADP Cycling

    ATP

    ADP


    Energy currency of cells3

    Energy Currency of Cells

    • The energy released when ATP is broken down to ADP can be used to fuel endergonic reactions.

    • The energy released from an exergonic reaction can be used to fuel the production of ATP from ADP + Pi.


    Other functions of atp

    Other Functions of ATP

    • ATP regulates enzyme activity

    • Phosphorylation and dephosphorylation - process of adding or removing phosphate groups - can activate or deactivate enzymes

    • ATP serves as a source of phosphate groups

    38


    Atp adp cycling1

    ATP/ADP Cycling


    Enzymes

    Enzymes

    • Enzymes: molecules that catalyze - speed up - biochemical reactions in living cells

    • Three rules to be considered an enzyme

      • Most are proteins (some RNA enzymes)

      • Lower the energy of activationrequired for a reaction to occur

      • Are not changed or consumed by the reaction

    • Cofactors, Coenzymes

    40


    Metabolism

    Metabolism

    • Enzymes catalyze cellular chemical reactions

    • Metabolism - the chemical reactions in a cell:

    • Two categories of cellular chemical reactions:

      • Anabolic Reactions

        • Build larger molecules for growth, repair, reproduction

        • Dehydration Synthesis Reactions

        • require energy and nutrients

      • Catabolic Reactions

        • Breakdown larger molecules

        • Hydrolysis Reactions

        • mobilize nutrients for energy making it available to the cell

    41


    Metabolism1

    Metabolism

    • Metabolism is the sum total of all anabolic and catabolic reactions that occur in the cell

    • The metabolism of cells is carried out and controlled by the enzymes

      • There are catabolic enzymes – those that cleave larger molecules into smaller ones

        • Ex. Hydrolysis Reactions

      • There are also anabolic enzymes – those that assemble smaller molecules into larger ones

        • Ex. Dehydration Reactions

    42


    Enzymes1

    Enzymes

    • Enzymes interact with substrates.

    • substrate: molecule that will undergo a reaction

    • active site:region of the enzyme that binds to the substrate

    • Binding of an enzyme to a substrate causes the enzyme to change shape, producing a better induced fit between the molecules.


    Enzymes2

    Enzymes

    Enzymes interact with substrates

    • Substrates: molecules that will undergo a reaction when bound to the enzyme

      • lactose, hydrogen peroxide (H2O2)

    • On the Enzymes:

      • Active site: region of the enzyme that binds to the substrate

      • Allosteric site: region of the enzyme that binds substances other that the substrate

    44


    Figure 5 02

    Figure 5_02


    Enzymes3

    Enzymes

    • Enzymes are very specific:

      • Enzymes will only interact with a specific substrates

      • The substrate fits into the active site like a key fits into a lock (Lock and Key Hypothesis)

      • Substrate binding causes the enzyme to change shape, producing a better induced fit between the molecules (Induced Fit Hypothesis)

    • Changing the shape of an enzyme affects its ability to function

    46


    Enzymes4

    Enzymes

    • Enzyme/Substrate Complex:

      E + S ES EP E + P

    • The Enzyme and the Substrate come together (E+S)

    • The Enzyme/Substrate Complex is formed (ES)

    • The Enzyme’s Substrate is changed to the Enzyme’s

      • Product in the active site of the enzyme (EP)

    • The Enzyme and Product Separate (E+P)

    • The Enzyme is free to bind to another Substrate

    48


    Figure 5 03b

    Figure 5_03b


    Enzyme naming convention

    Enzyme Naming Convention

    • Because enzymes catalyze specific reactions each enzyme has a unique name:

      • The first part of an enzyme’s name usually describes the substrate

      • The second part of an enzyme’s usually indicates the type of reaction it will catalyze

    • Most enzyme names end in the suffix -ase

    • Examples of enzymes:

      • DNA polymerase

      • Glycogen synthetase

      • Lactase

      • Catalase

    51


    How enzymes work

    How Enzymes Work

    • Enzymes lower the activation energy of biochemical reactions.

    • Enzymes make it easier for chemical reactions to occur:

      • by destabilizing the bonds in the substrate

      • by bringing substrates together so they react

      • by decreasing entropy - disorder - in the system

    • Enzymes make the chemical reactions possible in the cell’s environment

    • Enzymes make cells very efficient

    52


    How enzymes work1

    How Enzymes Work

    Enzymes make cells very efficient

    • Through enzymes, cells can carry out anabolic and catabolic reactions and end up with a net profit of energy

    • Cellular respiration is the process of breaking down glucose and storing the excess energy from the molecule into a form of energy that is available and useful to the cell

    55


    Cells use enzymes to process energy and matter

    Cells Use Enzymes to Process Energy and Matter

    • Reactions that break chemical bonds release their internal potential energy.

      • Example: burning wood

      • Oxidation reactions

    • Organisms obtain energy through enzyme-catalyzed biochemical reactions.


    Coenzymes and cofactors

    Coenzymes and Cofactors

    • Many enzymes require special molecules to help them function correctly:

      • Cofactors

        • inorganic molecules ions, such as zinc or iron

      • Coenzymes

        • organic molecules

    • Vitamins are the precursors for many coenzymes.

    • Vitamins must be acquired from the diet, cells cannot make them.


    The role of coenzymes

    The Role of Coenzymes

    • ADase oxidizes alcohol

    • Alcohol cannot be oxidized unless

    • something else is reduced

    • NAD+ is reduced to NADH


    The environment affects enzyme function

    The Environment Affects Enzyme Function

    • The rate at which an enzyme can bind to a substrate is called the turnover number.

    • The turnover number is maximized under the ideal conditions for that enzyme.

    • Conditions that can change an enzyme’s 3-dimensional shape can change its function

    • Each enzyme has ideal conditions that include:

      • Temperature

      • pH

      • Substrate concentration

      • Regulatory molecules

    59


    1 temperature

    1. Temperature

    • Temperature has two effects on enzymes:

    • Changes the rate of molecular motion

      • Increasing temperature increases molecular motion and increases turnover number

      • Decreasing temperature decreases molecular movement and decreases turnover number

    • Causes changes in the shape of an enzyme

      • Temperature changes above optimum will denature the enzyme.

      • This changes its shape, and it can no longer bind substrate and catalyze the reaction.


    Page 118

    Page 118


    Energy and metabolism

    2. pH

    • Enzymes are composed of amino acids

      • In a basic environment

        • The acidic side chains (R groups) could donate protons which affects the charge of the side chain

        • A neutral side chain that donates protons would become negatively charged

      • In an acidic environment

        • The basic side chains (R groups) could accept protons which affects the charge of the side chain

        • A neutral side chain that accepts protons would become positively charged

    • Both of these events can change the enzyme’s shape

    63


    Enzymes5

    Enzymes

    • Enzymes work together in chains of reactions known as biochemical or metabolic pathways

    • Biochemical pathways are a series of reactions in which the product of one reaction becomes the substrate for the next reaction.

    • Examples: photosynthesis, cellular respiration, protein synthesis, etc.


    Metabolic pathways

    Metabolic Pathways

    • Metabolic Pathwaysare series of chemical reactions carried out by separate enzymes

    • It is a sequence of chemical reactions where each reaction is controlled by a separate enzyme

    • The product of one enzyme serves as the substrate for the enzyme of subsequent reaction in the metabolic pathway


    Enzymes6

    Enzymes

    • These biochemical pathways offer certain advantages:

      1.The product of one reaction can be directly delivered to the next enzyme

      2.The possibility of unwanted side reactions is eliminated

      3. All of the reactions can be regulated


    Regulation of biochemical pathways

    Regulation of Biochemical Pathways

    • Metabolism is tightly regulated

    • There is a delicate balance between all of the reactions that take place in the cell

    • Metabolism is commonly regulated 3 ways:

      • Enzymatic competition for substrate

      • Gene regulation

      • Enzyme inhibition

    70


    Enzyme regulation

    Enzyme Regulation

    1. Enzymatic competition for substrate

    • Enzymatic competition occurs when more than one enzyme interacts with the same substrate

    • Each enzyme converts the substrate to a different product.

    • The enzyme that “wins” is the one that is the most abundant at the time.

    71


    Figure 5 07

    Figure 5_07


    Enzyme regulation1

    Enzyme Regulation

    2. Gene regulation

    • Enzymes are proteins.

    • Protein production is controlled by genes.

    • Certain chemicals in the cell turn particular enzyme-producing genes on or off depending on the situation.

      • Called gene-regulator proteins

        • Those that decrease the amount of an enzyme made are called gene-repressor proteins.

        • Those that increase the amount of an enzyme made are called gene-activator proteins.

    73


    Enzyme regulation2

    Enzyme Regulation

    3. Enzyme inhibition

    • Inhibitors are molecules that attach to enzymes and make them unable to bind to substrate.

    • Many drugs, pesticides and herbicides target enzymes.

    • Three types of inhibition:

      • Negative Feedback Inhibition

      • Competitive Inhibition

      • Noncompetitive Inhibition

    74


    A negative feedback inhibition

    A. Negative-Feedback Inhibition

    • The end-product of the metabolic pathways accumulate

      • Those molecules feedback and bind to an enzyme early in the sequence.

      • They inhibit that enzyme, and stop the sequence.

      • This decreases the amount of end-product made.

    • This functions to keep levels of the end-product within a certain range.

    75


    Energy and metabolism

    Feedback Inhibition


    Text art 5 05

    Text art 5_05


    Enzyme regulation3

    Enzyme Regulation

    • Inhibitors are molecules that bind to an enzyme to decrease enzyme activity.

      • competitive inhibitors compete with the substrate for binding to the same active site

      • noncompetitive inhibitors bind to sites other than the enzyme’s active site


    B competitive inhibition

    B. Competitive Inhibition

    • Competitive inhibitors closely resemble the substrate.

      • they bind to the active site of the enzyme and block the substrate from binding.


    Figure 5 09

    Figure 5_09


    Enzyme regulation4

    Enzyme Regulation

    • Allosteric enzymes exist in either an active or inactive state.

      • possess an allosteric site where molecules other than the substrate bind

      • allosteric inhibitors bind to the allosteric site to inactivate the enzyme

      • allosteric activators bind to the allosteric site to activate the enzyme


    C noncompetitive inhibition

    C. Noncompetitive Inhibition

    • Noncompetitive inhibitors bind to sites other than the enzyme’s active site - allosteric sites

    • “allo” = other; “steric” = shape

      • binding to an allosteric site changes the shape of the enzyme and affects its function

    • Noncompetitive because the noncompetitive inhibitor does not compete with the substrate to bind to the active site

    82


    Cellular respiration

    Cellular Respiration

    • Cellular Respiration is a metabolic pathway that breaks down glucose and extracts the energy to produce energy

      C6H12O6 + 6O2 6H2O + 6CO2 + Energy

      Glucose Oxygen Water Carbon Dioxide

    • The Energy is in the form of ATP

    84


    Metabolism2

    Metabolism

    • The metabolism of cells is carried out and controlled by ENZYMES

    • There are catabolic enzymes – those that cleave larger molecules into smaller ones

      • Ex. Hydrolysis Reactions

    • There are also anabolic enzymes – those that assemble smaller molecules into larger ones

      • Ex. Dehydration Reactions


    Cellular respiration1

    Cellular Respiration

    • Glucose contains energy that can be extracted

    • Cellular Respiration is a metabolic pathway that breaks down glucose and extracts the energy to produce ATP

    • Recall:

      C6H12O6 + 6 O2 6 H2O + 6 CO2 + Energy

      Glucose Oxygen Water Carbon Dioxide

    • The Energy is in the form of ATP


    Cellular respiration2

    Cellular Respiration

    C6H12O6 + 6 O2 6 H2O + 6 CO2 + Energy

    -Now-

    C6H12O6 + 6O2 + 38 ADP + 38 P 6 H2O + 6CO2 + 38 ATP


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