Biology – Premed Windsor University School of Medicine

Biology Chapter 8 Cellular Respiration

Pre Med – Biology Chapter 8Cellular Respiration

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Cellular Respiration1

It is worth studying this presentation thoroughly because it is essential for an understanding of all the activities of living cells and organisms

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THE CONCEPT OF ‘Cellular Respiration’ ISCENTRAL TO ALL LIVING PROCESSES

All living cells are made up of chemical substances

The processes of living involve reactions between the substances

A reaction is an event which produces a change in a substance

For example, a reaction between carbon and oxygen (such as burning coal in air) changes the carbon in the coal, and oxygen in the air into carbon dioxide

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This reaction can be represented by the equationC + O2 CO2

carbon oxygen carbon dioxide

The reaction between carbon and oxygen also releases energy in the form of heat and light (flames)

Living organisms get their energy from reactions like this (but not reactions which are violent enough to produce flames)

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One of the energy-producing reactions is called respiration

(Respiration is not the same thing as breathing)

The chemical reactions of respiration take place in all living cells

The reaction takes place between oxygen and a substance which contains carbon. The reaction produces carbon dioxide and water, and releases energy

The carbon-containing substances come from FOOD

The oxygen comes from the AIR (or water)

The energy is used to drive other chemical reactions taking place in cells

One example of this is the release of energy in muscle cells to make them contract and produce movement

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One example of an energy-producing reaction in cells is the breakdown of sugar when it combines with oxygen

This can be represented by the equation

C6H12O6 + 6O2 6CO2 + 6H2O + energysugar

(glucose)oxygen carbon

dioxidewater

This means that one molecule of sugar reacts with six molecules of oxygen to produce six molecules of carbon dioxide and six molecules of water. Energy is released during this process

Respiration suppliesthe energy for

muscle contraction

germination

cell divisionchemical changes in cells

Some examples of the useof energy in organisms

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The blood stream brings food and oxygen to the muscle cells. Respiration occurs in the cells and releases energy which……

shoulder blade

upper armbone

lower arm bones

Energy use in muscle contraction 11

Glucose and oxygen react to produce energy for muscle contraction

4 RESPIRATION 5 Carbon dioxideis carried to the lungs by the blood

15One example of respiration in ourselves

1. Air taken in

1.Food taken in

2. The lungs absorb oxygenfrom the air

2.The stomach andintestine digest food.One of the productsis glucose

3.The blood streamcarries glucose and oxygen to the muscles

Question 1

What is the most important point about respiration?

(a) it uses oxygen

(b) It produces energy

(c) It produces carbon dioxide

(d) It needs food and air

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Question 2

In which part of the human body is respiration most likely to be occurring?

(a) The lungs

(b) The heart

(c) The muscles

(d) All of these

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Question 3

Which of these are waste products of respiration?

(a) Carbon dioxide

(b) Water

(c) Oxygen

(d) Nitrogen

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Question 4

Which of the following would be reliable indicators

of respiration in a living organism?

(a) Output of water vapour (H2O)

(b) Output of carbon dioxide (CO2)

(c) Uptake of oxygen (O2)

(d) Production of energy

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Question 5

Which of the following statements is correct?

(a) We breathe in air

(b) We breathe in oxygen

(c) We breathe out air

(d) We breathe out carbon dioxide

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What Is ATP?

Energy used by all CellsEnergy used by all Cells

Adenosine TriphosphateAdenosine Triphosphate

Organic molecule containing high-Organic molecule containing high-energy Phosphate bondsenergy Phosphate bonds

Chemical Structure of ATP

3 Phosphates Ribose Sugar

Adenine Base

How Do We Get Energy From ATP?

By breaking the By breaking the high- energy high- energy bonds between bonds between the the last two last two phosphates in phosphates in ATPATP

What is the Process Called?HYDROLYSIS (Adding HHYDROLYSIS (Adding H22O)O)

H2O

How Does That Happen?

An Enzyme!An Enzyme!

How is ATP Re-Made?

The reverse of the previous process The reverse of the previous process occurs.occurs.

Another Enzyme is Another Enzyme is used!used!

ATP SynthetaseATP Synthetase

The ADP-ATP Cycle

ATP-aseATP-aseATP ATP SynthetaseSynthetase

Copyright Cmassengale

When is ATP Made in the Body?

During a Process During a Process called Cellular called Cellular Respiration that Respiration that takes place in takes place in both Plants & both Plants & AnimalsAnimals

Cellular Respiration

• Includes pathways that require Includes pathways that require oxygenoxygen

• Glucose is Glucose is oxidizedoxidized and O and O22 is is reducedreduced• Glucose breakdown is therefore an Glucose breakdown is therefore an

oxidation-reductionoxidation-reduction reaction reaction• Breakdown of one glucose results in Breakdown of one glucose results in

36 to 38 ATP36 to 38 ATP molecules molecules

Overall Equation for Cellular Respiration

6CO6CO22 + 6H + 6H

220 + e0 + e-- + 36-38 + 36-38ATP’sATP’s

CC66HH1212OO6 6 + 6O+ 6O22

YIELDSYIELDS

What Type of Process is Cellular Respiration?

• An Oxidation-Reduction Process or An Oxidation-Reduction Process or REDOX ReactionREDOX Reaction

• Oxidation of GLUCOSE --> COOxidation of GLUCOSE --> CO22 + + HH22O O (e(e-- removed from C removed from C66HH1212OO66))

• Reduction  OReduction  O22  to  H  to  H22O O (e(e-- passed to passed to OO22))

What Carries the Electrons?

• NADNAD++ (nicotinadenine (nicotinadenine dinucleotide) acts as dinucleotide) acts as the energy carrierthe energy carrier

• NADNAD++ is a is a coenzymecoenzyme• It’s It’s ReducedReduced to to

NADHNADH when it when it picks up two picks up two electrons and one electrons and one hydrogen ionhydrogen ion

Are There Any Other Electron Carriers?

• YES! Another YES! Another Coenzyme!Coenzyme!

• FAD+FAD+ (Flavin (Flavin adenine adenine dinucleotide)dinucleotide)

• ReducedReduced to to FADHFADH22

Other Cellular Respiration Facts

• Metabolic PathwayMetabolic Pathway that breaks down that breaks down carbohydratescarbohydrates

• Process is Process is ExergonicExergonic as High-energy as High-energy Glucose is broken into COGlucose is broken into CO22 and H and H22OO

• Process is also Process is also CatabolicCatabolic because larger because larger Glucose breaks into smaller moleculesGlucose breaks into smaller molecules

What are the Stages of Cellular Respiration?

• GlycolysisGlycolysis

• The Krebs CycleThe Krebs Cycle

• The Electron Transport ChainThe Electron Transport Chain

Where Does Cellular Respiration Take Place?

• It actually takes It actually takes place in two place in two parts of the cell:parts of the cell:

Glycolysis occurs in Glycolysis occurs in the Cytoplasmthe Cytoplasm

Krebs Cycle & ETC Krebs Cycle & ETC TakeTake place in the place in the MitochondriaMitochondria

Diagram of the Process

Occurs in Cytoplasm

Occurs in Matrix

Occurs across Cristae

Glycolysis Summary

Takes place in the Takes place in the CytoplasmCytoplasm

Anaerobic Anaerobic (Doesn’t Use Oxygen)(Doesn’t Use Oxygen)

Requires input of Requires input of 2 ATP2 ATP

Glucose split into two molecules of Glucose split into two molecules of PyruvatePyruvate or or Pyruvic AcidPyruvic Acid

• Also produces Also produces 2 NADH and 4 ATP2 NADH and 4 ATP

• Pyruvate is oxidized to Pyruvate is oxidized to Acetyl CoAAcetyl CoA and and COCO22 is removed is removed

Glycolysis

Glycolysis Diagram

Oxidation of Pyruvate to Acetyl CoA

Citric Acid Cycle

A Little Krebs Cycle History• Discovered by Discovered by Hans KrebsHans Krebs

in 1937in 1937• He received the He received the Nobel Nobel

PrizePrize in physiology or in physiology or medicine in 1953 for his medicine in 1953 for his discoverydiscovery

• Forced to leave Germany Forced to leave Germany prior to WWII because he prior to WWII because he was Jewishwas Jewish

Krebs Cycle Summary• Requires Oxygen (Aerobic)Requires Oxygen (Aerobic)• Cyclical series of oxidation reactions that Cyclical series of oxidation reactions that

give off give off COCO22 and produce and produce one ATP per one ATP per cyclecycle

• Turns Turns twicetwice per glucose molecule per glucose molecule• Produces Produces two ATPtwo ATP • Takes place in Takes place in matrix of mitochondriamatrix of mitochondria

Krebs Cycle Summary

• Each turn of the Krebs Cycle also Each turn of the Krebs Cycle also produces produces 3NADH, 1FADH3NADH, 1FADH22, and , and

2CO2CO22

• Therefore, For Therefore, For each Glucoseeach Glucose molecule, the Krebs Cycle produces molecule, the Krebs Cycle produces 6NADH, 2FADH6NADH, 2FADH22, 4CO, 4CO22, and 2ATP, and 2ATP

Krebs Cycle

ATP

NETS: 3NADH, 1ATP, 1FADHNETS: 3NADH, 1ATP, 1FADH22, & 2CO, & 2CO22

Electron Transport Chain

Electron Transport Chain Summary

• 34 ATP34 ATP Produced Produced• HH22OO Produced Produced• Occurs Across Occurs Across Inner Mitochondrial Inner Mitochondrial

membranemembrane• Uses coenzymes Uses coenzymes NAD+ and FAD+ to accept NAD+ and FAD+ to accept

e- from glucosee- from glucose• NADH = 3 ATP’sNADH = 3 ATP’s• FADHFADH22 = 2 ATP’s = 2 ATP’s

Fermentation

Occurs when OOccurs when O22 NOT present NOT present

(anaerobic)(anaerobic)

Called Called Lactic AcidLactic Acid fermentation in fermentation in muscle cells (makes muscle cells (makes muscles tiredmuscles tired))

Called Called Alcoholic fermentationAlcoholic fermentation in yeast in yeast (produces (produces ethanolethanol))

Nets only Nets only 2 ATP2 ATP

Anaerobic Respiration23

The process of respiration described so far has been defined as the release of energy when foodstuffs such as glucose react with oxygen to produce carbon dioxide and water.

This form of respiration, which needs oxygen, is called aerobic respiration.

There is another form of respiration which does not need oxygen and is called anaerobic respiration.

In anaerobic respiration, glucose is still broken down to carbon dioxide with the release of energy, but without the involvement of oxygen

The glucose is not completely broken down to CO2 and H2O but to CO2 and alcohol (ethanol).

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Anaerobic respiration can be represented by the equation

C6H12O6 2C2H5OH + 2CO2

glucose alcohol

energy

For example, our own muscles resort to anaerobic respiration when oxygen is not delivered to them fast enough.

The energy released by anaerobic respiration is considerably less than the energy from aerobic respiration.

Anaerobic respiration takes place at some stage in the cells of most living organisms.

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Micro-organismsAnaerobic respiration is widely used by many micro-organismssuch as bacteria and yeasts.

Bacteria and yeasts are microscopic single-celled organisms.

Bacteria are to be found everywhere, in or on organisms,in water, air and soil

Yeasts are usually found in close association with vegetable matter such as fruit

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Bacteria

0.002mm

a single bacterium

there are manyspecies of bacteria and they have different shapes and sizes

cell wall

nucleus

cytoplasm

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Aerobic and anaerobic bacteria

Bacteria which need oxygen in order to respire are calledaerobic bacteria.

Aerobic bacteria are likely to be found in the air, waterand soil where oxygen is available

Bacteria which can respire without needing oxygen are called anaerobic bacteria

Anaerobic bacteria are to be found in situations where oxygen is lacking, such as in stagnant water, waterlogged soils or the intestines of animals

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Yeast

Fermentation

One form of anaerobic respiration in bacteria and yeasts is called fermentation.

During fermentation, sugar is broken down to alcohol and carbon dioxide

The reaction described in slide 25 is an exampleof fermentation

Fermentation is involved in brewing and wine-making

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Yeasts

0.005mm

single yeast cell

Yeast cells dividing

cell wall

nucleuscytoplasm

vacuole

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Wine making

Grapes are crushed and the sugar they contain is fermented by yeasts to produce alcohol and carbon dioxide.

The carbon dioxide usually escapes but if the wine is bottled before fermentation is complete, the carbon dioxide dissolves and escapes as bubble when the bottle is opened

This is the case with ‘sparkling’ wines such as Champagne

Different varieties of grape produce different types of wine

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Black grapes growing in a vineyard

© Ilan’s Wine Making

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Brewing

In brewing beer, a sugary product (malt) is dissolved out of germinating barley

Yeast is added to this solution and fermentation begins, producing alcohol and carbon dioxide

Some of the carbon dioxide escapes but the rest dissolves in the beer when it is bottled or put into casks

When the bottles or casks are opened, the dissolved CO2 escapes as bubbles

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Beer fermenting

©Stuart Boreham/CEPHAS

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Baking

In baking, yeast is added to a mixture of flour and water, made into the form of a dough

The yeast first changes the flour starch into sugar and thenferments the sugar into alcohol and CO2

The CO2 forms bubbles in the dough which cause it to expand (‘rise’)

When the dough is baked, the heat evaporates the alcohol but makes the trapped bubbles expand giving the bread a ‘light’ texture

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Dough rising 36

The yeast is mixedwith the dough

After 1 hour in a warmplace the dough has risen as a result of the carbon dioxideproduced by the yeast

The ‘holes’ in the bread are made bythe carbon dioxidebubbles.This gives the bread a ‘light’ texture

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Question 1

Which statements are correct ?

Anaerobic respiration is different from aerobic respiration because

a it produces CO2

b it does not need glucose

c it does not need oxygen

d it produces less energy

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Question 2

In what circumstances do our muscle use anaerobicrespiration ?

a When insufficient glucose reaches the muscles

b When the carbon dioxide level increases

c When insufficient oxygen reaches the muscles

d When we are asleep

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Question 3

Anaerobic bacteria are most likely to be found

a in the middle of a compost heap

b in the air

c in fast-flowing streams

d on the surface of the skin

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Question 4

In which of the following is the production of CO2 more important than the production of alcohol ?

a Brewing beer

b Fermenting grape juice

c Making bread

d Bottling wine

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