celullar respiration2

8/3/2019 celullar respiration2

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CELLULAR RESPIRATION

ENERGY FOR CELLS


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WHAT IS CELLULAR RESPIRATION?

1.Conversion of food into hexosecarbohydrates such as glucose and itssubsequent breakdown

2.May involve breakdown of glucose


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Respiration can be conveniently divided intotwo parts

1. Cellular (internal or tissue) respiration - thebiochemical processes which take placewithin living cells that release the energy from

glucose2. Gaseous exchange (external respiration) -

the processes involved in obtaining oxygenneeded for respiration and the removal of

gaseous waste such as carbon dioxide.


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Three stages in cellular respiration

1.Glycolysis2.Kreb cycle

(tricarboxylic acidcycle)

3.Electron transfersystem


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WHAT ORGANELLE INVOLVED IN THISPROCESSES?

1. Vary in size2. Usually rod shape3. Diameter ~ 1.0 m4. Length ~ 2.5 m

5. The wall - twomembranes

6. Inner membraneforms cristae

7. Most necessaryenzymes attachedto inner membrane


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GLYCOLYSIS

1.The first stage in the breakdown of glucose2.Occurs in cytoplasm of the cell3.Produces two molecules of pyruvates for

each molecule of glucose degraded4.Total energy yield - two ATP directly and six

ATP from two reduced NAD molecules = 8ATP


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Stages of glycolysis

Glucose (6C)

Glucose-P (6C)

Fructose-P (6C)

Fructose bisphosphate (6C)

Triose-P (3C)

Triose phosphate (3C)

Triose-P (3C)

Triose bisphosphate (3C)

Pyruvate (3C)

ATP ADP

ADP ATP


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KREB CYCLE (Citric acid cycle/ TCA cycle)

TCA cycle involves a series of biochemical

reaction

What are the functions TCA cycle?

1.Produce energy by releasing chemical energy in acetyl

CoA (2C) produce reducing power

= NADH , FADH2

2.Produce intermediates


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but : Pyruvate cannot enter TCA cycle directly

it must be converted to Acetyl-CoA

Pyruvate can be produced in Glycolysis

We can get energy from pyruvate, BUT HOW?

Via the process in the TCA cycle

To start TCA cycle:

Acetyl CoA + OAA citrate


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Overview of Krebs cycle


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8 steps in TCA cycle.

1.Introduction of 2C as acetyl-CoA

2.Isomerization of citrate to isocitrate

3.Oxidation of isocitrate

4.Oxidation of-ketoglutarate

5.Cleaving of succinyl-CoA

6.Oxidation of succinate

7.Hydration of fumarate

8.Oxidation of malate


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Importance of Krebs cylce

1. It provides hydrogen atoms which ultimatelyyield the major part of the energy derived fromthe oxidation of s glucose molecule

2. It is a valuable source of intermediates which areused to manufacture other substances, e.g. fattyacids, amino acids, carotenoids


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Connection with otherspathways/reactions


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ELECTRON TRANSFER SYSTEM

1. At the end of Krebs cycle, glucose has beenoxidised completely

2. Much of the energy is in the form of hydrogenatoms which are attached to the hydrogen carriers

NAD and FAD3. Other carriers are iron-containing proteins called

cytochromes4. Allows the production of ATP from ADP = oxidative

phosphorylation


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Energy moleculesproduction

14

3 2


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Electron transport generates

energy.

Aerobic respiration uses

oxygen to generate Energy from

food

Oxygen diffuses easily across

cell membrane

Oxygen is highly reactive so it

accepts electron easily

ELECTRON TRANSPORTCHAIN (ETC)


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In eukaryotic cells

protons are transported from the

matrix of the mitochondria across theinner mitochondrial membrane to theintermembrane space located betweenthe inner and outer mitochondrial

membranes


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Intermembrane space

matrix


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H+ ions that are formed during ETC are transportedfrom the matrix to the intermembrane space

[H+] in the intermembrane space is higher

than in the matrix.

Consequence ?

Proton gradient arise

Proton motive force

Proton must diffuse from high concentration to lowconcentration.

But the inner membrane is impermeable to proton !

How proton will get back into the matrix ?

The chemioosmotic theory

Proton must pass through the inner membrane following the


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Proton must pass through the inner membrane following theconcentration gradient

They pass through a special proton channel = ATP synthase

The flow of proton drives the synthesis of ATP !

matrix

Intermembrane space

Lots of ATP formed !

P d ti f E f Gl


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Production of Energy from Glucose


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QuickTime and a

TIFF (Uncompressed) decompressorare needed to see this picture.

SUMMARY


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ANAEROBIC PATHWAYS

Acetaldehydefermentation

Alcoholicfermentation

Lactic acidfermentation

Produce

pyruvate

Produce

ethanol

Produce

lactateCertainanaerobicbacteria

Yeast andother plants

Higheranimalsespecially in

the muscle


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ASSIGNMENT

Give an example of the application ofaerobic or anaerobic respiration andelaborate the concepts behind it.

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