metabolism energy and enzyme final

8/9/2019 Metabolism Energy and Enzyme Final

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Metabolism: Energy and

EnzymesChapter 6


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Outline Forms of Energy Laws of Thermodynamics

Cells & Entropy

Metabolic Reactions

ATP

Enzymes Energy of Activation

Enzyme-Substrate Complex

Effects on Enzyme Function

Coenzymes & Cofactors

Feedback Inhibition

Oxidation-Reduction

Photosynthesis

Cellular Respiration


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Forms of Energy

Kinetic Energy- Energy of motion. Mechanical

Is used and work is performed

Potential Energy Stored energy, ready to use, like a coiled spring.

Chemical energy potential energy stored in bonds(very important to organism)


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Forms of Energy Calorie is a measure of energy. Its the energy required to

raise the temperature of 1 gram of water 1 degree Celsiusat 25 C.

1 Kilocalorie = 1 Cal = 1,000 calories

1g of protein or carbohydrate 4 kcal 1g of Fat 9 kcal

1g of alcohol 7 kcal

Living things use energy found in chemical bonds.

Cells convert the chemical bond energy in food moleculesto chemical bond energy stored in ATP molecules.

ATP energy is used to run metabolism and all other bodily

processes.


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Laws of Thermodynamics Thermodynamics is the study of energy and its

transformation

First law (law of conservation of energy) states:

Energy cannot be created or destroyed, but it can be changed fromone form to another.

Organisms can not create the energy they require in order to live They must capture energy from the environment and transform it to aform that can be used for biological work

Second law states: Energy cannot be changed from one form to another without a loss

ofusable energy (dissipated as heat).

The heat dissipated can not perform work the amount ofusableenergy available to do work in the universe decreases over time.

The total amount of energy in the universe is not decreasing over time


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Cells and Entropy

Second law can also be explained as everyenergy transformation makes the universeless organized and more disordered.

Second law means that every cellularprocess increases the total entropy of theuniverse.

Entropy is the measure ofdisorderin asystem.


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Cells and Entropy


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Cells and Entropy Consequently, entropy is always increasing.

As an analogy, you know from experience that a neat roomis more organized but less stable than a messy room,which is disorganized but more stable.

A neat room is less stable than a messy room because aneat room tends always to become more messy.

Living things are able to locally reverse the overall direction

of entropy by using a lot of energy.

The energy of living cells comes from the Sun, and it endsup as waste heat.


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Metabolic Reactions Metabolism - Sum of all the chemical

reactions that occur in a cell.

Metabolism includes: Anabolism & Catabolism

Anabolic reactions consume energy whilecatabolic reaction release energy.


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Metabolic Reactions

Free energy is the amount of energy available to perform work.

Exergonic Reactions - Reactants have more free energy thanproducts.

A + B C + D + Energy

Endergonic Reactions - Products have more free energy thanreactants.

A + B + Energy C + D

Exergonic Reactions Catabolism, cellular respiration.

Endergonic Reactions Anabolism.


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Metabolic Reactions

The basic rule: Reactions run Downhill More energetic reactants are converted to less energetic products.

If a reaction needs to run Uphill Creating products that contain more energy than the reactants,

energy in the form of ATP must be added.

Adenosine Triphosphate (ATP): Composed of adenine and

ribose (adenosine) & three phosphate groups.

ATP is the Storage & Usable form of energy in the body.


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Coupled Reactions

In coupled reactions, the energy released

by an exergonic reaction drives an

endergonic reaction.


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Function of ATP

Chemical Work - Energy needed to

synthesize macromolecules.

Transport Work - Energy needed to pump

substances across plasma membrane.

Mechanical Work - Energy needed to

contract muscles, beat flagella, etc.


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Enzymes Characteristics:

Enzymes are protein molecules.

Function as organic catalysts to speed a chemical

reaction.

Lower the activation energy.

Enzymes are very specific. Each one works on a very

limited number of similar molecules.

Enzymes are Not consumed by the reaction.


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Energy of Activation The energy that must be added:

To cause molecules to react with one another.

For the reaction to proceed.

Enzymes lowerenergy of activation by bringing

the substrates into contact with one another.

The reaction occurs thousands or millions oftimes fasterthan without the enzyme.


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Enzyme Binding Enzymes are very specific for a very limited number of

reactants (substrates).

Each enzyme has an active site

Site on enzyme surface where reactants fit. The active site holds the substrates together and causes them to

react.


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Active site undergoes a change in shape to

accommodate the substrates.

Induced fit model


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Effects on Enzyme Function

Substrate concentration

Temperature

pH


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Substrate Concentration

Generally, enzyme activity increases as substrate

concentration increases.

More collisions between substrate molecules and the

enzyme.


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Temperature As temperature rises, enzyme activity increases.

Warmer temperatures cause more effective collisions between enzymeand substrate.

Most of the enzymes in humans have an optimum temperature near body

temperature.

If temperature rises beyond a certain point, the enzyme becomes

denatured and the enzyme activity levels out.


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pH Enzymes function best within a certain range of pH.


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Coenzymes & Cofactors

Cofactors

Minerals: Non-protein Inorganic molecules which

act as enzyme activators.

Coenzymes

Vitamins: Non-protein Organic molecules which

act as enzyme activators.


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Feedback Inhibition

Many enzymes are inhibited by their

products: feedback inhibition.

If the level of a product builds up too

much, it binds competitively with its

enzymes active site.

In this way, the concentration of the

product is always kept within a certain

ran e.


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Feedback Inhibition

Most metabolic pathways are regulated by

another type of feedback inhibition.

End product of the pathway binds to an

allosteric site.

Binding shuts down the pathway, and no moreproduct is produced.


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Feedback Inhibition


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Feedback Inhibition

Allosteric enzymes undergo this type of

feedback inhibition.

Some inhibitors permanently disable the

enzyme: poisons.


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Feedback Inhibition


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Enzymes

Enzymes are named for their substrates

Substrate Enzyme

Lipid Lipase

Protein Protease

Lactose Lactase


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Oxidation-Reduction

In redox reactions, electrons pass from

one molecule to another.

Oxidation is the loss of electrons.

Reduction is the gain of electrons.

Oxidation and reduction always take place

at the same time as one molecule accepts

the electrons given up by anothermolecule.


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Photosynthesis Carbon dioxide + water + solar energy yields

glucose and oxygen.

6 CO2 + 6 H2O + energy C6H12O6 + 6 O2

Chloroplasts capture solar energy and convert

it via electron transport chain to ATP.

Coenzyme active during photosynthesis.

NADP+ + 2e- + H+ NADPH


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Cellular Respiration

Glucose + oxygen yields carbon dioxide +

water + energy.

C6H12O6 + 6 O2 6 CO2 + 6 H2O + energy

Most oxidations involve a coenzyme:NAD+ + 2e- + H+ NADH


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Electron Transport System

A series of membrane-bound carriers thatpass electrons from one carrier to another.

High-energy electrons delivered, and low-

energy electrons leave.

During this process an

H+ gradient across

membrane is created


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ATP Production Chemiosmosis: Production of ATP due to a

hydrogen ion gradient across a membrane.


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metabolism energy and enzyme final

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