bio 2010 cellular respiration2

8/11/2019 Bio 2010 Cellular Respiration2

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Topical Enduring

Understanding1. Change in the form of any matter involves energy.

2. Survival of the biological system depends on theconversion of energy from one form to another.

3. Changes in the organism are dependent on itsenvironment.

4. Living organisms require matter and energy tomaintain its complexity and organisation.

5. Energy flow in biological processes obeys the laws of

thermodynamics.

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Matters, System &

Organisation

Macromo lecu les

Photosyn thes is

Respirat ion

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Unit Essential Questions! Why do we need to respire?

! Do the structure and organisation of the livingsystem change when energy is released from

them?! How are respiratory systems of animals

organised efficiently to carry out its functions?

! Can there be any metabolism without enzymes?

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Answer this on your own in your journal. (5 mins)

Discuss as a class (10 mins)


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Unit Enduring

Understanding1. Living organisms release energy within the biological

molecule into forms they can use to carry out lifeprocesses.

2. Process of the release of energy is affected byexternal environment.

3. The structure and organisation of the respiratorysystem is dictated by the function that it serves.

4. Metabolic pathway is a sequence of enzyme-

controlled reactions.

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ENERGY How is the energy generated in your

body?

Do plants respire? Is the process similarto that of Man?

Compare the energy conversion in plantand in Man.


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Key Understanding1.Energy cannot be created or destroyed. It can

only be converted from one form into another.

2.Respiration is the process by which livingorganisms convert energy into forms they canuse to carry out life processes.

3.Some organisms can respire aerobically aswell as anaerobically.


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Boardworks Ltd 2003of 74

The bodies energy-making reaction needs similar

things to the energy-making process of fire.

Like fire, the body needs oxygen and a fuel.

+and the (in the form ofdigested food) comes courtesyof the digestive system.

Energy-making process

the issupplied by the

breathingsystem


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If we now think back over the journey of oxygen and

digested food through the human body, we willrealise that they both end up in the same place.

these substanceseventually arriveat the body cells

food oxygen

breathingsystem

digestivesystem



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Therefore, the raw materials for the energy-making

process eventually arrive at the bodycells.

This energy-making process is known as...

Each living cell is supplied with food and oxygen inorder to generate energy.

oxygen

blood

food

capillary

muscle cell



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No chemical reaction is 100% efficient.

Therefore, as well as producing the useful energy, respirationalso produces wasteproducts.

These waste productsmust be removed

from the body.

This is exactly what happens!

Waste products

If the process of breathing in is used to obtain theO2for respiration, it would make sense for the body

to use the process of breathing out to remove thesewaste products of this reaction.


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Cellular Respiration

The process by which organisms break downenergy rich molecules (eg. glucose) to releasethe energy in the ATP form.

Overall equation for aerobic respiration of glucose:

C6H12O6+ 6O2 6CO2+ 6H2O + energy

glucose + oxygen carbon + water + large amount dioxide of energy


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Uses of Energy

muscle contraction

protein synthesis

cell division

active transport

building up of protoplasm for growth

transmission of nerve impulses

maintenance of a constant body temperature


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Involves three metabolic stages:-

1Glycolysis(cytoplasm)

2The Krebs Cycle(mitochondrial matrix)

3Electron Transport &

oxidative phosphorylation

(inner membranes ofmitochondrion)



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Mitochondria


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Mitochondria - the power house

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Diagram from Biozone Senior Biology 1


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1. Glycolysis

- occurs in the cytoplasm

- involves breakdown of glucoseinto 2 molecules of pyruvate

Outline of cellular respiration

2. Krebs Cycle

- occurs in the mitochondrion matrix

- decomposes a derivative ofpyruvate to carbon dioxide

1

3. Electron transport and oxidative

phosphorylation

- occurs in the inner membrane ofthe mitochondrion

- Accounts for almost 90% of theATP generated by respiration

2

3

Diagram from Advanced Human and Social Biology : Students Art Notebook


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Glucose (6C) is brokeninto two molecules ofpyruvate (3C)

Glycolysis

2 ATP and 2NADH + 2H+

are generated from thisstage.

No oxygen is required(the process is

anaerobic) in cytosol/ cytoplasm of

cellDiagram from Biological Science 1 by N.P.O. Green, G.W. Stout, D. J. Taylor, Cambridge University Press


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Glycolysis

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A 2-stages process.How many ATP & NADH are generated from 1 glucose?


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The acetyl grouppasses into a cyclicreaction and combineswith a 4carbonmolecule to from a 6carbon molecule.

The CoA is released forreuse.

Successive steps in thecycle remove carbon ascarbon dioxide.

in matrixofmitochondria

Krebs cycle

Diagram from Biological Science 1 by N.P.O. Green, G.W. Stout, D. J. Taylor, Cambridge University Press


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Kreb Cycle

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How many ATP, NADH & FADH are generated from 1 glucose?


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Electron Transport System

Diagram from Advanced Human and Social Biology : Students Art Notebook

1 NADH yields 3 ATP1 FADH2yields 2 ATP

in cristae of mitochondria


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Electron transport chain

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Summary of ATP production

Diagram from Biological Science 1 by N.P.O. Green, G.W. Stout, D. J. Taylor, Cambridge University Press


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Summary of ATP production

Glycolysis

2 net ATP from substrate-level phosphorylation2 NADH yields 6 ATP by oxidative phosphorylation

Transition Reaction

2 NADH yields 6 ATP by oxidative phosphorylationKrebs (Citric Acid )Cycle

2 ATP from substrate-level phosphorylation6 NADH yields 18 ATP by oxidative phosphorylation2 FADH2yields 4 ATP by oxidative phosphorylation

Total Theoretical Maximum Number of ATP Generated

per Glucose 38 ATP: 4 from substrate-level phosphorylation; 34 from

oxidative phosphorylation.


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Cellular Respiration Animation

http://www.qcc.cuny.edu/BiologicalSciences/Faculty/DMeyer/respiration.swf


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Adenosine Triphosphate

Diagram from Biozone Senior Biology 1


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Advanced Human and Social Biology : Students Art Notebook

Adenosine

TriphosphateATP is a convenient store of

energy for a cell because

it stores energy inrelatively small amount.

it is quickly hydrolysed ina one-step reaction to

release energy.

it is easily moved aroundinside cells, but cannot

pass through cellmembranes.


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Formation of ATP


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Oxygen consumption of mitochondriainteractive experiment.

http://www.cells.de/cellseng/1medienarchiv/Zellfunktionen/Memb_Vorg/Zellatmung/Atmungsaktivitaet/index.jsp


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Online Respiration Matching Game

http://www.quia.com/mc/1008211.html


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However, to call this reaction just respiration is notquite correct.

Let us try to understand why.. Think about what youdo in an average day.

sometimes

you arelow energyrequirements

What is respiration?


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sometimesyou are

high energyrequirements



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Your body requires different amounts of energy atdifferent times.

Therefore

the process of respirationmust be able to speedup and slow down

this will mean thatwe need differentamounts of food tofeed the reaction

it will also mean that we

need different amounts ofoxygen to feed the reaction

the blood will have to flow

at different speedsaccording to demand

our rate of breathing will change

this is exactlywhat happens



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Lets take two extreme examples human activity andsee how the process of respiration change...

It seems that the process of respiration changesduring the course of the day.

This may not represent the daily activities of an averagehuman, but this scenario will help us understand thisprocess of respiration in more depth.

1. sleeping

2. running amarathon



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SLEEPING

When we sleep, our body is at rest.

There is a low demand for energy.

low

energydemand

blood flowdoes not

have to berapid

lowdemand for

food andoxygen

the breathing

rate remainsnormal

In other words, the body has plenty of time to inhale theoxygen that it needs. It also has time to completely digestthe food to release the important chemicals (e.g glucose).

The blood can efficiently transport these substances to thecells without increasing its rate of flow.



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When the body is performing respiration in such a way, itis given a special name.

When the body

We say it is performingAEROBICrespiration.

has plenty of oxygenis able to completely digest foodcan supply the cells with the oxygen andfood that they need

Aerobic respiration


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So our original equation for the process of respirationis actually the equation for aerobicrespiration.

This is an efficient process... enough energy is made tosupply the whole body.

Our bodies perform aerobic respiration for much of the day.In fact, as long as the supply of oxygen remains highenough, we will continue to perform aerobic respiration.

Of course, the amount of energy we produce will drop ifthe level of oxygen drops.

Aerobic respiration

Glucose + Oxygen Carbon Dioxide + Water + Energy


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So, now we know that there is a form of respiration which isperformed when there is a supply of oxygen to the body.

But, what happens in situation 2?

Are they performing aerobic respiration?

Well, in order to answer that question, we have to thinkabout what their bodies are doing during the race.

remember the runners?

Aerobic respiration


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Energydemands

Oxygenavailable

Form orrespiration

Whats happening?

beforelow high aerobic

during

high low / none aerobic(but slowing)

after dropping none / low



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How can the body perform aerobic

respiration in this situation?

Aerobic respiration requires oxygen but when you havebeen running a race or doing strenuous exercise, youcannot inhale enough oxygen for this reaction.

Glucose + Oxygen Carbon Dioxide + Water + Energy

This process fails!

But, if this process fails when the oxygen levels drop, thebody would be left with absolutely no energy.



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No energy would lead to stop working!

This would mean that the body wouldstop working whenever it becameshort of oxygen.

The problem is that we often do exercise and ourbodies continue working.

What must be happening when our oxygen levelsdrop to zero?

The body must be able to keep working throughshort periods of low/no oxygen.

But how?


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Now because it is releasing energy from food, it is still

performing respiration.But it is not aerobicrespiration because there is

oxygen present. (aero- means of air)

Therefore we call it respiration.

The energy being made by breaking down the foodwithout oxygen.

This seems a better process!

To be able to make energy without needing oxygen would

be very beneficial.

However, there is a problem.

Anaerobic respiration


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Remember the last time you ran a race, carried a

heavy weight or swam under water for too long and ranshort of breath.

It probably felt uncomfortable.

Well, if anaerobic respiration was as efficient as itsounds, this lack of comfort would not happen.



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When the cell breaks down the food to release theenergy, it also makes a potentially harmful wasteproduct.

The breakdown of the food is also incomplete.

It is not an efficient process.


So, what is the problem with anaerobic respiration?


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Glucose Lactic Acid + (some) Energy

This waste product is known as LACTIC ACID.

Therefore the equation for anaerobic respiration is

from thedigestive system

wasteproduct

not as much energyas with aerobic

respiration

You will notice that this reaction is only an option for shortperiods of time.

This is because the waste product is harmful and notenough energy is made to satisfy the body.



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Why is lactic acid so harmful?

Well, this chemical can stop muscles within the body,

from contracting and relaxing.

The lactic acid soaks the muscle cells andprevents the muscle cell from doing its job.

relaxation

contraction

If the muscles in your body stop contracting and

relaxing they are said to be fatigued.They eventually seize and you experience cramp.


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If you want to consider the full impact of damage caused

by the presence of lactic acid, just remember that theheart is made of muscle cells!

This leaves us with a problem...

if we want to do exercise

We want the energythat anaerobic

respiration produces

YES NO

So the answer is for anaerobic respiration to be a gap-fillduring periods of very low / no oxygen availability.

Why is lactic acid so harmful?

But we dont want thelactic acid waste

product


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time

oxygenlevels

rest

exercise

exercise

stops

aerobic

anaerobic

Anaerobic respiration keeps our bodies going until wecan breathe in more oxygen again.

Whilst we are performing anaerobic respiration, ourbodies are building up a debt of oxygen.



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When our bodies convert

from aerobic to anaerobicrespiration, we startmaking lactic acid.

As soon as this begins, thebody starts building anoxygen debt.

This is equivalent to theamount of oxygen it would

have used if aerobicrespiration had continued.

Lactic acid


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This oxygen debt will have to be repaid when theexercise stops.

Oxygen will be used to break down the lactic acid that ispresent in the body.

The oxygen oxidises the lactic acid.

In fact, the lactic acid is oxidised into carbon dioxideand water.

In this way, the process of aerobic respiration can be converted into

The process of anaerobic respiration which can then turn back into...

Lactic acid


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The body has the ability to produce energy, despite changesin the supply of oxygen.

Here are the two forms of respiration.

glucose + oxygen carbon dioxide + water + energy

Aerobic respiration(complete breakdown of food)

Anaerobic respiration(incomplete breakdown of food)

Aerobic respiration is performed when oxygen is present.

Anaerobic respiration is performed when oxygen is absent.

Summary

glucose + oxygen carbon dioxide + water + lacticacid + little energy


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Anaerobic Respiration

All organisms can metabolize glucose

anaerobically (without O2) using glycolysis in

the cytoplasm, but the energy yield is very

low and it produces much more toxic wasteproducts.

In yeast and plants, alcoholic fermentation

occurs.

In animals, production of lactic acid.


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Muscle cells can respire anaerobically forshort periods of time when there is a shortageof oxygen. It incur an oxygen debt.

Oxygen debt is the amount of O2required tooxidise the lactic acid produced

Lactic acid is produced which causes fatigue

Lactic acid is transported to the liver andconverted back into glucose when the body is

no longer short of O2.



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Summary of pathways of anaerobic respiration

Diagrams from Biological Science 1 by N.P.O. Green, G.W. Stout, D. J. Taylor, Cambridge University Press


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Overall Equations for Anaerobic Equations

Plants & Yeast

C6H12O6 C2H5OH + CO2 + energy

glucose ethanol + carbon + small amountdioxide of energy

AnimalsC6H12O6 C3H6O3 + energy

glucose lactic acid + small amount

of energy

bio 2010 cellular respiration2

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