Metabolism & Cellular Respiration

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Metabolism and Cellular Respiration

AP Biology Rapid Learning Series

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Rapid Learning Centerwww.RapidLearningCenter.com/© Rapid Learning Inc. All rights reserved.

AP Biology Rapid Learning SeriesWayne Huang, PhD

Andrew Graham, PhDElizabeth James, PhD

Casandra Rauser, PhD Jessica Habashi, PhD

Sara Olson, PhDJessica Barnes, PhD



Learning Objectives

Metabolism.

By completing this tutorial, you will learn about:

Anabolism pathways.

Catabolism pathways.

The energetics of biological reactions.

The management of cell resources.

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How cells use cellular respiration to produce ATP.

Aerobic and anaerobic respiration.

General Concept Map

MacromoleculesCell Biology

Metabolism Physiology

Materials for

Structures used for

A major area of study in

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BiochemistryEcology

BehaviorNutrition

The basis of studies in Determines



Metabolism Concept Map

Metabolism

Anabolism CatabolismCatabolism

AnabolismProtein

Anabolism

CarbohydrateCarbohydrateAnabolism

CatabolismProtein

CatabolismAnabolismLipid

Anabolism

CarbohydrateCatabolism

CarbohydrateCatabolism

AnabolismLipid

Anabolism

BetaProtein

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SynthesisProtein

SynthesisOxidation

BetaOxidationGlycolysisGlycolysis

Gluconeo-Gluconeo-genesis

Fatty AcidSynthesisFatty AcidSynthesis

RespirationCellular

Respiration

Breakdownote

Breakdown

AerobicAerobic AnaerobicAnaerobic

Metabolism

Building Blocks & Precursors

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Anabolism

Catabolism

The Role of ATP



What is Metabolism?

Metabolism involves the creation of complex

molecules from simple M t b li i l th molecules (anabolism).Metabolism is also the breakdown of complex molecules into simpler

ones (catabolism).

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Building Blocks From FoodAll living organisms get building

blocks for the manufacture of cellular components from food

and cellular breakdown products.

Carbohydrates

Nucleic Acids AnabolismLipids Proteins

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Catabolism breaks down molecules into smaller units and releases energy.

Catabolism Anabolism builds complex molecules from simple ones and require energy.



Review: Building Bocks

Nucleotides Amino Acids Mono-h id

Fatty

Nucleic AcidsCarbohydratesProteins Lipids

saccharides Acids

These are the precursors for the cells building blocks.

Precursors are molecules that when assembled become one of the major building blocks of the cell.

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The four organic building blocks are made from precursors.

Precursors come from the breakdown of food & cell components.

Stages of Anabolism

Anabolism is the set of metabolic processes that require energy,

released from catabolism, to build complex molecules.

1) Precursors are produced: amino acids, monosaccharides,

i id d l idcomplex molecules.

Anabolism has three stages.

2) Precursors are activated using energy from ATP to become

reactive.

isoprenoids and nucleotides.

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3) The reactive precursors are assembled into complex molecules like proteins,

polysaccharides, lipids and nucleic acids.



Anabolism ExamplesOrganisms have differing types of molecules that

they can make themselves.

Autotrophs like plants canAutotrophs, like plants can make complex molecules like polysaccharides and

proteins from simple molecules like CO2 and H2O.

Heterotrophs need a source of

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complex substances like monosaccharides and amino

acids to make complex molecules.

“Trophs” Flow SheetDon’t know how to tell if an organism is a autotroph or

heterotroph?

Follow this flow / decision chart to

determine the “troph” of an organisms.g

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Catabolism

Monosaccharide

Catabolism is the breakdown of complex molecules (polymers)

thereby releasing energy.

Polysaccharide

Fatty Acids

Nucleotides

Adenosine triphosphate is the energy storage

molecule.

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Amino AcidsProteinNucleic Acid polymer (DNA)

Catabolism and Waste

Acetic AcidAmmoniaPolymers

Lactic Acid

Acetic Acid

Urea

Carbon Dioxide

Monomers

Degraded To

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Waste Products

Cells use monomers to make new polymers or degrade monomers further making a variety of waste products and releasing ATP.

ATP



Anabolism vs. Catabolism

Anabolism Catabolism

When do cells perform anabolism or catabolism?

Create new structures and enzymes

Break down food

Store unused nutrients for later use

Destroy old structures for recycling

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Excess Resources Deficient Resources

Feeding Period

Rest Event

Fasting Period

Stress Event

Energetics of Biological Reactions

EnergyThermodynamics

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ThermodynamicsActivation Energy & EnzymesRedox ReactionsThe Role of ATP in MetabolismCoupling



What is Biological Thermodynamics?Bioenergetics is the

study of energy transformation in

biological systems.

It is a quantitative study of energy transductions in living organisms and the chemical

processes involved.

Energy is the ability to do work or supply heat.

Work is the transfer of energy from one

t t th

Living cells and organisms must

f k

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system to another.perform work to live, grow and

reproduce.

First Law of ThermodynamicsThe total energy of a

system and its surroundings is constant.

Energy can take different forms: heat, motion etc.

Energy cannot be created or destroyed.

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Kinetic energy may manifest as heat.

And potential energy is the amount of energy possible.



Meaning of the First Law

The First Law of ThermodynamicsThe First Law of Thermodynamics requires that all energy released in chemical bond formation observe the following:

Must be used to break other bonds.

Released as heat

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Released as heat.

Stored in some other form.

Second Law of Thermodynamics

Ice - Low Entropy Water - Medium Entropy

Steam - Maximum Entropy

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Ice consists of highly ordered water molecules.

When the ice melts the water molecules become disordered relative to ice.

Maximum disorder when water is heated and turns into steam.



Metabolism - IntroductionLiving organisms are not at equilibrium. They require a continuous influx of free energy to maintain order in a universe where there is

By coupling the exergonic (energy releasing) reactions of nutrient oxidation and endergonic (energy consuming) reactions, they universe where there is

maximum disorder. maintain the living state.

Metabolism is the overall process through which free energy is acquired and utilized by living systems to carry out their

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systems to carry out their various functions.

Coupling of Reactions

A

B

A

B + C

D

C + D

∆Go’ = +5 kcal/mol

∆Go’ = -8 kcal/mol

∆Go’ = -3 kcal/mol

Overall free energy change for chemically

coupled series of reactions is equal to the sum of the free

Under standard conditions:

A can not be spontaneously converted into B and C, because ∆G is positive.

Conversion of B into D under standard conditions is thermodynamically feasible.

As free energy changes are additive, the conversion of

the sum of the free energy changes of the

individual steps.

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A into C and D has a ∆Go‘ of -3 kcal/mol. It means that it can occur spontaneously under standard conditions.

A thermodynamically unfavorable reaction can be driven by a thermodynamically favorable reaction that is coupled to it.

In this example, the reactions are coupled by the shared chemical intermediate B.



Glycolysis & ThermodynamicsADPATP ∆G°‘= -31 kJoules/mol

∆G°‘= +14 kJoules/mol

Glucose-6-phasphateGlucose

First reaction in glycolysis: making glucose-6-phosphate from glucose.

The hydrolysis of ATP to ADP provides the energy by thermodynamic coupling.

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ATP + H20 ↔ ADP + Pi ∆G°‘= -31 kJoules/molPi + glucose ↔ glucose-6-phospate + H20 ∆G°‘= +14 kJoules/mol

Coupled Reactions:ATP + glucose ↔ glucose-6-phosphate + ADP

Net Energy Change ∆G°‘= -17 kJoules/mol

Enzymes Affect Reaction RatesEnzymes are catalysts affecting only the rate of product formation.

Enzymes affect the rate of reaction by lowering the activation energy.

Reaction kinetics without enzyme

E

Substrate

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Reaction with enzyme

Energy BarrierLowering of

activation energy by enzymes

Products



Oxidation – Reduction Reactions

Oxidation – Reduction Reactions (Redox)

In redox reactions electrons are transferred from an electron donor

Living things get most of their free energy from redox reactions. In

photosynthesis, CO2 is reduced and

Fe3+ + Cu+ Fe2+ + Cu2+

(reductant or reducing agent) to an electron acceptor (oxidant or

oxidizing agent).

p y 2H2O is oxidized to yield carbohydrates and O2.

Cu+, the reductant is oxidized to Cu2+ while Fe3+, the oxidant, is reduced to Fe2+.

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Fe3+ + e- Fe2+ (Reduction)

Cu+ Cu2+ + e- (Oxidation)

Redox reactions may be divided into two half-reactions or redox couples, such as

Redox PotentialRedox potential is the

tendency of the solution to either gain or loose electrons.

Redox potential (E0) is a quantitative measure of the tendency of redox pair to loose or gain electrons.

These are some standard redox values for biologically i t t l l

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important molecules.

System Eo volts

NAD+ /NADH -0.32Oxygen / Water +0.82



This ATP then can be used for anabolic processes

ATP Production & DestructionAnabolism uses ATP. Catabolism produces ATP.

for anabolic processes.

ADP + PiATP

Anabolism

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Catabolism releases energy which can be used to produce ATP.

Catabolism

Respiration

GlycolysisKrebs Cycle

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Krebs CycleOxidative PhosphorylationFermentation



Cellular Respiration

Cellular respiration is a term used to describe

the collective metabolic reactions and processes

Aerobic respiration includes: glycolysis, p

that a cell used to get energy from molecules.

g y yoxidative

decarboxylation of pyruvate, TCA and

oxidative phosphorylation.

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And for those processes that don’t use oxygen there

is anaerobic respiration.

Energy Coupling & ATP Formation

Pyruvate Kinase

Breakdown of PEP to pyruvate releases energy and phosphate.This reaction is coupled with the production of ATP from ADP.

Energy is needed to make ATP. ATP is produced by coupling energy from an

Phosphoenolpyruvate Pyruvate

ADP ATP

Pyruvate Kinase

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produced by coupling energy from an energy releasing reaction to run an

energy requiring reaction.



Aerobic VS Anaerobic Respiration

GlucoseCellular respiration can either be aerobic or anaerobic.

Cellular respiration can take two paths.

Glucose

Anaerobic Respiration

Oxygen?

anaerobic.

No

Yes

ATP

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Aerobic Respiration

Yes

Aerobic means “with oxygen” and anaerobic means “without oxygen.”

ATP

Respiration: Aerobic vs. Anaerobic

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Aerobic Respiration:1) Glycolysis2) Krebs Cycle3) Oxidative Phosphorylation

Anaerobic Respiration:1) Glycolysis2) Fermentation



Aerobic: Oxygen Final e- AcceptorWhen oxygen is available, aerobic respiration transports electrons down a chain to create a concentration gradient.

This gradient powers a motor to produce a large number of ATP.

Step 1: Glycolysis is the entry point and produces 2 ATP.Glycolysis

Krebs Step 2: The Krebs Cycle prepares electron carriers for delivery and

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Oxidative Phosphorylation

Cycle electron carriers for delivery and produces 2 ATP.

Step 3: Oxidative Phosphorylation creates a concentration gradient to produce 32 ATP.

Glycolysis Definition

GlucosePyruvate

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Glycolysis is the set of reactions that converts glucose into pyruvate while producing a small amount of ATP (energy).

Adenosine 5'-triphosphate (ATP)



Glycolysis: 2NADH, 2ATP, PyruvateGlucose

Glucose 6-phosphate

ATP 1

2

Fructose 6-phosphate

Fructose 1,6-phosphate

Glyceraldehyde 3-phospate

1,3-diphosphoglycerateP2 NADH2

2X

2X

3

4

5

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, p p g y

3-phosphoglycerate

2-phosphoglycerate

phosphoenolpyruvate

pyruvate

ATP2

ATP2

2X

2X

2X

6

7

8

9

Electron Transport Chain

Electron transport chain is also known as the electron transport system (ETS).It is a series of membrane associated electron carriers involved in transporting electrons produced during biochemical reactions that make ATP.

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The two sources of energy available to living organisms: oxidation-reduction redox reactions and photosynthesis.



Citric Acid CycleCitric acid cycle is also called the tricarboxylic acid cycle (TCA).

So there are four metabolic pathways involved in carbohydrate catabolism and ATP production.

TCA is involved in the conversion of carbohydrates, fats and proteins into carbon dioxide, water and energy.

The four pathways are: TCA cycle, glycolysis, pyruvate oxidation, and respiratory chain.

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TCA cycle is a series of enzyme catalyzed reactions that use oxygen as part of cellular respiration.

The Krebs Cycle

The products of the first turn of the TCA cycle are 1 GTP, 3

NADH, 1 FADH2 and 2CO2.

2 Acetyl-CoA molecules are made from every glucose

molecule so two turns of the TCA cycle are required for every glucose moleculeevery glucose molecule.

That’s right so at the end of all the cycles the total

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yproducts per glucose

molecule is: 2 GTP, 6 NADH, 2 FADH2 and 4 CO2.



Oxidative Phosphorylation = 32 ATPThis is a schematic of a

mitochondria. Look closely at its various membranes. And the Oxidative phosphorylation

creates a proton gradient that location of the TCA. creates a proton gradient that is used to generate the 32 ATP.

NADH and FADH2 from TCA cycle unload their electrons and pass them to the

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and pass them to the membrane bound protein machines I, II, III, IV.

The electrons are passed down an electron transport chain to oxygen as the final electron acceptor.

TCA & ETC

Mitochondria

In eukaryotes TCA / ETC cycle takes place in the mitochondria.

In prokaryotes the TCA cycle occurs in the cytoplasm.

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The cycle requires the presence of oxygen.

Intermediates can also act as a precursors to many other biosynthetic pathways.

Lost intermediates are replenished by anaplerotic

reactions.



Summary: Aerobic Respiration

Glycolysis Krebs Cycle Oxidative Phosphorylation

1. Glucose is b k d

1. Acetyl CoA li

1. NADH and FADHbroken down

into pyruvate.

2. Energy Production Total: 2 ATP.

runs a cyclic reaction which produces NADH and FADH2

2. CO2 is produced as

FADH2 pass electrons down chain which pumps H+ to create gradient.

2. H+ gradient flows to power ATP synthase.

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waste.



Anaerobic Respiration

Anaerobic respiration occurs when there is an energy requirement but no oxygen.

Anaerobic respiration runs glycolysis repeatedly.

Step 1: Glycolysis is the entry point and produces 2 ATP.Glycolysis

Anaerobic respiration runs glycolysis repeatedly.

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Step 2: Fermentation regenerates reactants needed for the glycolysis reaction to proceed again.Fermentation



Fermentation

Fermentation is respiration under anaerobic conditions with no

external electron acceptor.

Fermentation does not have to be in an anaerobic environment.

Yeast cells even in the presence of oxygen, prefer fermentation to p yg , poxidative phosphorylation if

sugars are available.

Sugars are the common

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common substrate of

fermentation and typical products

are: ethanol, lactic acid and

hydrogen.

In muscle under intense exercise with no external

electron acceptors lactic

acid is produced.

Summary: Anaerobic Respiration

Glycolysis Fermentation

1. Glucose is 1. Pyruvate is broken down into pyruvate.

2. Production of 2 ATP.

used to regenerate intermediates of glycolysis.

2. Glycolysis begins anew.

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ATP Production TotalsAerobic Respiration vs. Anaerobic Respiration.

ATP MadeAerobic

2+ Krebs CycleGlycolysis 2

= Grand Total 36+ 32+ Oxidative Phosphorylation

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0+ Fermentation

ATP Made

Glycolysis 2

= Grand Total 2

Anaerobic

Question: ReviewAn exergonic reaction _______ energy.

___________releases

endergonic______ reactions are energy

i ___________

___________

endergonic

glycolysis

Cellular Respiration

consuming.

Glycolysis, TCA cycle, oxidative decarboxylation of pyruvate and oxidative

Glucose is broken down into pyruvate in what pathway?

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___________Cellular Respirationpyruvate, and oxidative phosphorylation.

____ a set of metabolic pathways that require energy to build complex molecules from simple one.

___________Anabolism



The steps of aerobicThe steps of aerobic

Metabolism is all of the chemical

Metabolism is all of the chemical

The steps of anaerobic respirationare: glycolysis and

lactic acid

The steps of anaerobic respirationare: glycolysis and

lactic acid

Learning Summary

Cellular respiration powers theCellular respiration powers the

The steps of aerobic respiration are:

glycolysis, the Krebs Cycle, and oxidative

phosphorylation.

The steps of aerobic respiration are:

glycolysis, the Krebs Cycle, and oxidative

phosphorylation.

reactions in a cell and thus the entire

organism.

reactions in a cell and thus the entire

organism.

lactic acid fermentation.

Anaerobic respiration does not produce

much ATP.

lactic acid fermentation.

Anaerobic respiration does not produce

much ATP.

Anabolism is the constructionAnabolism is the construction

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Cellular respiration powers the cell by producing ATP from the breakdown of sugar. Aerobic

respiration occurs when there is oxygen whereas anaerobic respiration occurs when there

is not.

Cellular respiration powers the cell by producing ATP from the breakdown of sugar. Aerobic

respiration occurs when there is oxygen whereas anaerobic respiration occurs when there

is not.

Anabolism is the construction of complex molecules

whereas catabolism is the breakdown of complex molecules. Anabolism

requires energy whereas catabolism releases energy.

Anabolism is the construction of complex molecules

whereas catabolism is the breakdown of complex molecules. Anabolism

requires energy whereas catabolism releases energy.

Congratulations

You have successfully completed the core tutorial

Metabolism and Cellular Respiration

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