Chapter 6 cell energy [compatibility mode]

Chapter Chapter 66How Cells Harvest Chemical Energy

Copyright © 2009 Pearson Education, Inc.

PowerPoint Lectures for

Biology: Concepts & Connections, Sixth Edition

Campbell, Reece, Taylor, Simon, and Dickey

Lecture by Richard L. Myers

6.1 Photosynthesis and cellular respiration provide energy for life

� Energy is necessary for life processesEnergy is necessary for life processesEnergy is necessary for life processesEnergy is necessary for life processes– These include growth, transport,

manufacture, movement, reproduction, and othersand others

– Energy that supports life on Earth is captured from sun rays reaching Earth through plant, algae, protest, and bacterial photosynthesis


6.1 Photosynthesis and cellular respiration provide energy for life

� Energy in sunlight is used in photosynthesis to make glucose from CO2 and H2O with release of O2

� Other organisms use the O2 and energy in � Other organisms use the O2 and energy in sugar and release CO2 and H2O� Together, these two processes are responsible for the majority of life on Earth


Sunlight energy

ECOSYSTEM

Photosynthesisin chloroplasts

Glucose

H2O

CO2

O2

++++ ++++

The connection betweenphotosynthesis andcellular respiration

Cellular respirationin mitochondria

(for cellular work (ل

ATP

Heat energy

6.2 Breathing supplies oxygen to our cells for use in cellular respiration and removes carbon dioxide

� Breathing and cellular respiration are closely related– BreathingBreathingBreathingBreathing is necessary for exchange of CO2– BreathingBreathingBreathingBreathing is necessary for exchange of CO2produced during cellular respiration for

atmospheric O2

– Cellular respiration Cellular respiration Cellular respiration Cellular respiration uses O2 to help harvest energy from glucose and produces CO2 in the process


Breathing

Lungs

BloodstreamCO2O2

CO2O2

Cellular Respiration

Muscle cells carrying out

CO2 + H2O + ATP

Glucose + O 2

The connection between breathing and cellular respi ration

INTRODUCTION TO

CELLULAR RESPIRATION


6.3 Cellular respiration banks energy in ATP molecules

� Cellular respiration is an exergonicexergonicexergonicexergonicprocess that transfers energy from the bonds in glucose to ATP– Cellular respiration produces 38 38 38 38 ATP ATP ATP ATP molecules from each glucose moleculemolecules from each glucose molecule– Other foods (organic molecules) can be used as a source of energy as well


C6H12O6 + 6 O2 6 CO2 + 6 H2O + ATPs

Summary equation for cellular respiration

Glucose Oxygen Carbon dioxide Water Energy

6.4 CONNECTION: The human body uses energy from ATP for all its activities

� The average adult human needs about 2,200 kcal of energy per day– A kilocaloriekilocaloriekilocaloriekilocalorie (kcalkcalkcalkcal) is the quantity of heat

required to raise the temperature of 1 required to raise the temperature of 1 kilogram (kg) of water by 1oC

– This energy is used for body maintenance and for voluntary activities


Energy Consumed by Various Activities (in kcal).

6.5 Cells tap energy from electrons “falling” from organic fuels to oxygen

� The energy necessary for life is contained in the arrangement of electrons in chemical bonds in organic molecules� An important question is how do cells extract this energy?


� When the carbon-hydrogen bonds of glucose arebroken, electrons are transferred to oxygen and hydrogen – oxygen bonds of water formed.– Oxygen has a strong tendency to attract electrons


� A cellular respiration equation is helpful to A cellular respiration equation is helpful to A cellular respiration equation is helpful to A cellular respiration equation is helpful to show the changes in hydrogen atom show the changes in hydrogen atom show the changes in hydrogen atom show the changes in hydrogen atom distributiondistributiondistributiondistribution– Glucose loses its hydrogen atoms and is ultimately – Glucose loses its hydrogen atoms and is ultimately

converted to CO2

– At the same time, O2 gains hydrogen atoms and is converted to H2O

– Loss of electrons is called oxidationoxidationoxidationoxidation– Gain of electrons is called reductionreductionreductionreduction


C6H12O6 + 6 O2

Loss of hydrogen atoms

6 CO2 + 6 H2O + Energy(ATP)

Rearrangement of hydrogen atoms (with their electro ns)in the redox reactions of cellular respiration

(Oxidation)

GlucoseGain of hydrogen atoms

(ATP)

A cellular respiration equation A cellular respiration equation A cellular respiration equation A cellular respiration equation

(Reduction)


� Enzymes are necessary to oxidize glucose and other foods– The enzyme that removes hydrogen from an organic molecule is called dehydrogenasedehydrogenasedehydrogenasedehydrogenase– Dehydrogenase requires a coenzyme called – Dehydrogenase requires a coenzyme called NADNADNADNAD++++ (nicotinamide adenine dinucleotide) to shuttle electrons– NAD+ can become reduced when it accepts electrons and oxidized when it gives them up


Oxidation

Dehydrogenase

pair of redox reactions, occurring simultaneously

adenine dinucleotideadenine dinucleotideadenine dinucleotideadenine dinucleotide

2 H+ + 2 e–

Reduction اختزال NAD+ + 2 H NADH + H+

(carries2 electrons)

adenine dinucleotideadenine dinucleotideadenine dinucleotideadenine dinucleotide


� The transfer of electrons to NAD+

results in the formation of NADH, the reduced form of NAD+

– In this situation, NAD+ is called an electron acceptor, but it eventually becomes oxidized (loses an electron) and is then called an electron donor



� There are other electron “carrier” molecules that function like NAD+ .called FAD– They form a staircase where the electrons

pass from one to the next down the pass from one to the next down the staircase

– These electron carriers collectively are called the electron transport chainelectron transport chainelectron transport chainelectron transport chain, and as electrons are transported down the chain, ATP is generated


ATPNAD+

NADH

H+2e–

Controlledrelease ofenergy forsynthesis

of ATP

+

H+2e–

of ATP

O2

H2O

1−−−−2In cellular respiration, electrons fall

down an energy staircase and finally reduce O2

STAGES OF CELLULAR

RESPIRATION

AND FERMENTATION


6.6 Overview: Cellular respiration occurs in three main stages

Stage Stage Stage Stage 1111: : : : GlycolysisGlycolysisGlycolysisGlycolysis

Stage Stage Stage Stage 2222: : : : The citric acid cycleThe citric acid cycleThe citric acid cycleThe citric acid cycle


Stage Stage Stage Stage 3333: : : : Oxidative phosphorylationOxidative phosphorylationOxidative phosphorylationOxidative phosphorylation


� Stage Stage Stage Stage 1111: Glycolysis: Glycolysis: Glycolysis: Glycolysis– Glycolysis begins respiration by breaking glucose, a six-carbon molecule, into two

C-C-C-C-C-C

GlycolysisIn Cytoplasm

Glucose

molecule, into two molecules of a three-carbon compound called pyruvate


C-C-C C-C-C

In Cytoplasm

Pyruvate Pyruvate

Glucose

NAD+

+2

2 ADP

NADH2

P2

� In glycolysis, a single molecule of glucose is enzymatically cut in half through a series of steps to produce two molecules of pyruvate

6.7 Glycolysis harvests chemical energy by oxidizing glucose to pyruvate

2

ATP2 +

H+

2 Pyruvate

An overview of glycolysis

– In the process, two molecules of NAD+ are reduced to two molecules of NADH– At the same time, two molecules of ATP are produced by substrate-level phosphorylation


� Stage Stage Stage Stage 2222: The citric acid cycle: The citric acid cycle: The citric acid cycle: The citric acid cycle- The citric acid cycle completes the oxidation of organic

molecules supplies the third stage with electrons generating many NADH and FADH2

-It breaks down pyruvate into carbon dioxide-This stage occurs in the mitochondria.--This stage occurs in the mitochondria.-


Citric Acid Cycle

Pyruvate Electrons

CO2


� Stage Stage Stage Stage 3333: Oxidative phosphorylation: Oxidative phosphorylation: Oxidative phosphorylation: Oxidative phosphorylation– At this stage, electrons are shuttled through the electron transport chain– As a result, ATP is generated through oxidative phosphorylation

associated with chemiosmosis– This stage occurs in the inner mitochondrion membrane


PyruvateCitric Acid

CycleElectrons

CO2

Electron Transport Chain

O2

H2O ATP

Oxidative Phosphorylation

Mitochondria

Chemiosmosis

MitochondrionNADH

High-energy electronscarried by NADH

NADH

CITRIC ACIDCYCLE

GLYCOLYSIS

PyruvateGlucose

andFADH2

OXIDATIVEPHOSPHORYLATION(Electron Transportand Chemiosmosis)

An overview of cellular respiration

CO2 CO2ATP

Substrate-level phosphorylation Substrate-level phosphorylation

and Chemiosmosis)

Oxidative phosphorylation

ATPATP

CytoplasmInner mitochondrial

Membrane

6.13 Fermentation enables cells to produce ATP without oxygen

� FermentationFermentationFermentationFermentation is an anaerobic (without oxygen) energy-generating process – It takes advantage of glycolysis, producing two producing two producing two producing two

ATPATPATPATP molecules and reducing NAD+ to NADHATPATPATPATP molecules and reducing NAD+ to NADH

– The trick is to oxidize the NADH without passing its electrons through the electron transport chain to oxygen



دون الحاجة الى ا�وكسجين ATPيجعل التخمر الخ�يا قادرة على انتاج

� Your muscle cells and certain bacteria can oxidize NADH through lactic acid lactic acid lactic acid lactic acid fermentationfermentationfermentationfermentation

� NADH is oxidized to NAD+ when pyruvate is reduced to lactate

� In a sense, pyruvate is serving as an “electron sink,” a place to dispose of the electrons generated by oxidation reactions in glycolysis


Glucose جلوكوز

NADH

NAD+

2

22 ADPP

ATP2

2 Pyruvate بايروفيت 2

GLY

CO

LYS

ISي

وزوك

جلل

حلت

Lactic acid fermentation تخمر الحامض اللبني

++++ 2

NADH2

NAD+2

2 Pyruvate بايروفيت 2

2 Lactate $كتيت 2


� The baking and winemaking industry have used alcohol alcohol alcohol alcohol fermentationfermentationfermentationfermentation for thousands of years

� Yeasts are single-celled fungi that not only can use respiration for energy but can ferment under anaerobic conditions� They convert pyruvate to CO2 and ethanol while oxidizing NADH back to NAD+


2 ADPP

ATP2 GLY

CO

LYS

IS

NADH

NAD+

2

2

2 Pyruvate

Glucose

++++ 2

NADH2

NAD+2

2 Pyruvate

2 Ethanol

Alcohol fermentation CO22Released

INTERCONNECTIONS BETWEEN

MOLECULAR BREAKDOWN

AND SYNTHESIS


6.15 Cells use many kinds of organic molecules as fuel for cellular respiration

تستخدم الخ�يا العديد من المركبات العضوية كوقود للتنفس الھوائي

�Although glucose is considered to be the primary source of sugar for respiration and fermentation, there are actually three sources of molecules for generation of ATP

–Carbohydrates Carbohydrates Carbohydrates Carbohydrates (disaccharides)–Proteins Proteins Proteins Proteins (after conversion to amino acids)–FatsFatsFatsFats


Food, such aspeanuts

ProteinsFatsCarbohydrates

Amino acids GlycerolSugarsأحماض امينية Fatty acids

Amino groups

GlucoseOXIDATIVE

PHOSPHORYLATION(Electron Transportand Chemiosmosis)

CITRIC ACIDCYCLE

Acetyl CoA

GLYCOLYSIS

Pyruvate

Amino groups

G3P

ATP

Pathways that break down various food molecules

Science

Chapter 6 cell energy [compatibility mode]