OD515 Thermodynamics and Metabolism Pt1 (REDOX, Coupled Reactions, Thermodynamics)

What does ΔG represent in a reaction?

Amount of energy available to do work

What does an endergonic reaction mean in terms of ΔG?

Requires Energy, +ΔG

What does an Excergonic mean in terms of ΔG

Give off energy, -ΔG

The transfer of energy is….

Necessary for biological systems (life) to function.

Transfer of energy in living organisms…

Follow the laws of thermodynamics

Thermodynamics assess what?

Relation between energy, work, and heat

What’s is the 1st law of thermodynamics?

Total energy is constant. Can’t be destroyed or created, only transferred or transformed.

What is the second Law of Thermodynamics?

Energy spontaneously tends to disperse or become more disorderly. (Entropy)

How do living cells follow thermodynamics?

Increase in order within their system, but create disorder in surroundings

What is the system?

All reactants, products, solvent that contains them, and the immediate atmosphere.

What is an Isolated system?

Exchanges neither matter or energy with its surroundings

What is a closed system?

Exchanges energy but not matter with it’s surroundings

What is an open system?

Exchanges both energy and matter with its surroundings

(Like cells and organism)

What are Autotrophs

Use CO2 from atmosphere, sole source of Carbon

Make own food

What are Heterotrophs

Cannot use atmospheric CO2

Must obtain CO2 from enviro

Energy is often transferred via what reaction?

Oxidation-reduction redox reactions

What happens when one reactant is oxidized?

Loses electrons

What happens when an agent is reduced?

Gains electrons (oxidizing agents)

ΔS represents what?

Entropy (chaos)

What happens when ΔS is negative?

The reactants are more chaotic than the products

What happens when ΔS is Positive?

The products are more chaotic than reactants

What is ΔH?

Enthalpy, or heat content

Reflects the # and kinds of chemical bonds in reactants and products

What happens when ΔH is negative?

Release heat and is exothermic

What happens ΔH is positive

Heat is absorbed

Endothermic

What is ΔG

Amount of energy capable of doing work during reaction at constant temp and pressure

What happens when ΔG is +

Free energy is gained and reaction is endergonic

What happens when ΔG is -

Energy is released and is exergonic

In the free energy question, when ΔG -

The system proceeds spontaneously

In the free energy question, when ΔG Is +

The equation requires energy to complete, non-spontaneous

What is K’eq?

Standard equilibrium constant

ΔG’* states

when a reaction is thermodynamically favorable

A ΔG’* that is -

Is spontaneous or unfavorable at standard conditions

A ΔG’* that is +

Non-spontaneous at standard conditions

What is the relationship between K’eq and ΔG’*?

The relationship is exponential

If K’eq is > 1

its ΔG’* is - (Less reactants, more products)

If K’eq is < 1

its ΔG’* is + (More reactants, less products)

What happens when K’eq’ is 1?

ΔG = 0, is at equilibrium

How are ΔG’* s combined when individual reactions are coupled into overall reaction?

They are additive

How are the Keq’s related when reactions are coupled?

They are multiplicative

The amount of energy available to do work is always less than the theoretical. Amount of energy released because?

Entropy, some energy is wasted as heat

In a closed system, chemical reactions proceed ——- until ———

Spontaneously

Equilibrium is reach

Endergonic reactions are coupled to….

Exergonic reactions to achieve specific function

Metabolism is ——and it involves the ———- and describes the overall ——— of enzyme-catalyzed ——- and ——— pathways

Sum of the processes

Transfer of energy

Network

Catabolic and anabolic

What is intermediary metabolism?

Intricate web of chemical reactions within cells to convert absorbed nutrients into cellular building block and to generate energy

Catabolism and Anabolism

What are the intermediates of intermediary metabolism?

Metabolites

What are nearly identical in all living organisms?

Metabolic pathways

What keeps production and utilization of each metabolic intermediate in balance?

Feedback inhibition

What is the maximum energy available for work when a chemical reaction occurs?

Free-Energy Change (is sum of the two reactions)

What coupling favorable and unfavorable reaction, what drives it forward?

ATP Hydrolysis

What are enzymes?

Catalysts (usually proteins) that accelerate biochemical reactions. NOT consumed on use

How do catalysts work?

Lower activation energy, increasing reaction rates

What have higher free energy than reacts or products?

Transition states (unstable middle state)

What is activation energy?

Difference in energy between reactant in ground state and its transition state

What is enzyme regulation?

Response to external circumstances by either

• Increasing # of enzyme molecules

• changing catalytic activity of existing enzymes

What is universal energy currency in living organisms?

ATP

• highly exergonic

• Breakage of Phosphoanhydride

What does ATP help with in the body?

1. Muscle contraction

2. Pumping of solutes again [ ] gradients

3. Synth of complex molecules

What is a pathway?

Sequences w/ consecutive reactions where product of 1 is reactant in next

What is a Degradative pathway that yields free-energy captured in ATP or NAD(P)H ?

Catabolism

What is a synthetic pathway that requires input of energy to build?

Anabolism

Which pathway converges and which diverges?

Anabolic: Diverge (uses product to be reactant moving down path)

Catabolic: Converge (break into a product)

What are oxidation- reduction reactions and why are they central to cellular metabolism?

Oxidation: Loss e-

Reduction: Gain e-

Transfer of electrons is required for controlled transfer (extraction of energy)

Why must oxidation and reduction always occur together in biological systems?

e-‘s can’t exist freely in solution under biological conditions. Can’t have one without the other

What is PRIMARY biological purpose of oxidation reactions in living cells?

Is to release energy stored in bonds of food molecules. By oxidizing, cells take e- and use to generate ATP synthesis

How do you identify. If a substance is oxidized or reduced in a chemical reaction?

OIL RIG

Loss of e- or increase in oxidation → oxidized

Gain e- or decrease in oxidation → reduced

Loss of H or gain of O → usually oxidized

Gain of H or loss of O → Usually reduced

In a metal ion displacement (redox) reaction, how can changes in charge indicate oxidation or reduction?

If a metal ion becomes more + charged it lost e- → oxidized

If metal ion becomes less + charged it gained e- → reduced

General categorizes of biochemical reactions in living cells?

1. Reactions make or break C-C bonds

2. Internal rearrangements, isomerizations, eliminations

3. Free-radical reactions

4. Group transfers

5. Oxidation-reductions

What are functional groups which have and can donate e-

Nucleophiles

What are electron-deficient functional groups that seek electrons?

Electrophiles

What can act as either a nucleophile or electrophile?

Carbon

_____combines with and give up electrons to___

Nucleophiles

Elecrophiles

What is the cleavage of a covalent bond where each atom leaves the bond as a radical, carrying one unpaired e-?

Homolytic cleavage (radicals)

What is the cleaver of a covalent bond where one atom retains both bonding e-

Heterolytic cleavage (more common)

What are generated by elimination of an excellent leaving group?

carbocation intermediates

What are the products of a C-C heterolytic cleavage?

Carbanion( C: ) and a Carbocation (C+)

• not common, unstable

• Forms a C-C bond

DO rearrangements change oxidation states?

No

What is an isomer?

Same chemical formula, different arrangement

What are 3 isomer reaction examples?

1. Intermolecular oxidation and reduction

2. Change in cis-trans arrangement at double bond

3. Transposition of double bonds

What is an elimination reaction?

Loss of water from alcohol, creates C=C

Also happens in amines (peptide bonds)

What are the Homolytic cleavage of covalent bonds called?

Free-radical reactions

What do free-radical reactions lead to?

Oxidative damage, aging, and chronic disease

• Antioxidants neutralize free radicals by donating e- for stabilization

What are group transfer reactions?

Moving a group from one Nucleophiles to another (common)

• Forms intermediates

• Ex: acyl, glycolysis, and phosphorylation groups transfer

• *Acyl group transfer example in lipid synthesis

What involves nucleophillic substitution at c-1 of a sugar ring?

Glycosyl group transfer

kinase enzymes catalyze an example of?

Phosphoryl group transfers with ATP as a donor

What do kinases do?

Add phosphate from ATP onto an acceptor molecule

What removes a phosphoryl group from a phosphate ester?

Phosphatases

(Dephosphorylation)

What covalently removes phosphates to other molecules?

Phosphorylases

(Phosphorolysis)

What catalyze condensation reactions in which no nucleotide triphosphate is required?

Synthases

(Condensation reaction: 2 molecules combine into 1, losing small molecule such as water in process)

What break or cleave substrate molecules into smaller products?

Lyases

What catalyze biological oxidation reaction where oxygen is the electron acceptor, but oxygen is not an oxidized product?

Oxidases

(e- passed to a different e- acceptor

What catalyzes biological oxidation reactions where oxygen IS the electron acceptor and is an oxidized product?

Oxygenases

(Cyclooxygenase (COX) enzymes)

Monooxygenases: 1 O atom is incorporated in the product

Dioxygenases: 2 O atoms are incorporated in the product

What indirectly provides much of the energy required for ATP synthesis ?

Redox Reactions

Reduced substrates such as glucose are oxidized in several steps, with the energy of oxidation steps conserved in the form of a reduced cofactor NADH

e- energy stored in NADH is used to drive synth of ATP (NAD-H)

What is loss of a C-O bond or its equivalent?

Reduction reaction, gain of e- and formation of C-H bond

What is the formation of a C-O bond or its equivalent ( C-N, C-CL)

Oxidation

Loss of C-H bond

Loss of e-

In many biological oxidation’s, a compound loses ____ and ____

2 e-‘s and 2 H ions

Catalyzed by dehydrogenases

Carbon atoms exist in ______ depending on the ____ with which they share ____

Different oxidation states

Element

e-‘s

What catalyzes redox reactions in which H is removed from the substrate?

Dehydrogenases

*NAD+ is a common e- acceptor

O2 isn’t involved

What deals with descriptions, qualities, and meanings often using non-numerical information?

Qualitative data

• things you can describe (qualify)

What involves measurements, numbers, and statistical analysis?

Quantitative data

(Things you can count)

What is the quantitative study of energy transductions?

Bioenergetics

What describes the change of one form of energy to another?

Energy transduction