Transcript Biology_Chapter 8_Cellular_Respiration

Biology – Premed
Windsor University School of Medicine
and Health Sciences
Biology Chapter 8
Cellular Respiration
Dr. Uche Amaefuna
Pre Med – Biology Chapter 8
Cellular Respiration
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Cellular Respiration
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THE CONCEPT OF ‘Cellular Respiration’ IS
CENTRAL TO ALL LIVING PROCESSES
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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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
This reaction can be represented by the equation
C
carbon
+
O2
CO2
oxygen
carbon dioxide
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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
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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
sugar
(glucose)
oxygen
6CO2 + 6H2O +
carbon
dioxide
energy
water
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
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Some examples of the use
of energy in organisms
muscle
contraction
Respiration
supplies
the energy for
germination
chemical changes in cells
cell division
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Energy use in muscle contraction
shoulder blade
The blood stream brings food
and oxygen to the muscle
cells. Respiration occurs in
the cells and releases energy
which……
upper arm
bone
lower arm bones
One example of respiration in ourselves
2. The lungs absorb oxygen
from the air
2.The stomach and
intestine digest food.
One of the products
is glucose
4 RESPIRATION
Glucose and
oxygen react to
produce energy for
muscle contraction
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1. Air taken in
1.Food taken in
3.The blood stream
carries glucose and
oxygen to the muscles
5 Carbon dioxide
is carried to the lungs
by the blood
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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
What Is ATP?
Energy used by all Cells
Adenosine Triphosphate
Organic molecule containing highenergy Phosphate bonds
Chemical Structure of ATP
Adenine Base
3 Phosphates
Ribose Sugar
How Do We Get Energy From
ATP?
By breaking the
high- energy
bonds between
the last two
phosphates in
ATP
What is the Process Called?
HYDROLYSIS (Adding H2O)
H2O
How Does That Happen?
An Enzyme!
How is ATP Re-Made?
The reverse of the previous process
occurs.
Another Enzyme is
used!
ATP Synthetase
The ADP-ATP Cycle
ATP
Synthetase
ATP-ase
Copyright Cmassengale
When is ATP Made in the
Body?
During a Process
called Cellular
Respiration that
takes place in
both Plants &
Animals
Cellular Respiration
• Includes pathways that require
oxygen
• Glucose is oxidized and O2 is
reduced
• Glucose breakdown is therefore an
oxidation-reduction reaction
• Breakdown of one glucose results in
36 to 38 ATP molecules
Overall Equation for Cellular
Respiration
C6H12O6 + 6O2
YIELDS
6CO2 + 6H20 + e- + 36-38ATP’s
What Type of Process is
Cellular Respiration?
• An Oxidation-Reduction Process or
REDOX Reaction
• Oxidation of GLUCOSE --> CO2 +
H2O (e- removed from C6H12O6)
• Reduction O2 to H2O (e- passed to
O2)
What Carries the Electrons?
• NAD+
•
•
(nicotinadenine
dinucleotide) acts as
the energy carrier
NAD+ is a coenzyme
It’s Reduced to
NADH when it
picks up two
electrons and one
hydrogen ion
Are There Any Other Electron
Carriers?
• YES! Another
Coenzyme!
• FAD+ (Flavin
adenine
dinucleotide)
• Reduced to
FADH2
Other Cellular Respiration
Facts
• Metabolic Pathway that breaks down
carbohydrates
• Process is Exergonic as High-energy
Glucose is broken into CO2 and H2O
• Process is also Catabolic because larger
Glucose breaks into smaller molecules
What are the Stages of Cellular
Respiration?
• Glycolysis
• The Krebs Cycle
• The Electron Transport Chain
Where Does Cellular
Respiration Take Place?
• It actually takes
place in two
parts of the cell:
Glycolysis occurs in
the Cytoplasm
Krebs Cycle & ETC
Take place in the
Mitochondria
Diagram of the Process
Occurs
across
Cristae
Occurs in
Cytoplasm
Occurs in
Matrix
Glycolysis Summary
Takes place in the Cytoplasm
Anaerobic (Doesn’t Use Oxygen)
Requires input of 2 ATP
Glucose split into two molecules of
Pyruvate or Pyruvic Acid
• Also produces 2 NADH and 4 ATP
• Pyruvate is oxidized to Acetyl CoA and
CO is removed
Glycolysis
Diagram
Fermentation
 Occurs when O2 NOT present
(anaerobic)
Called Lactic Acid fermentation in
muscle cells (makes muscles tired)
Called Alcoholic fermentation in yeast
(produces ethanol)
Nets only 2 ATP
A Little Krebs Cycle History
• Discovered by Hans Krebs
in 1937
• He received the Nobel
Prize in physiology or
medicine in 1953 for his
discovery
• Forced to leave Germany
prior to WWII because he
was Jewish
Krebs Cycle Summary
• Requires Oxygen (Aerobic)
• Cyclical series of oxidation reactions that
give off CO2 and produce one ATP per
cycle
• Turns twice per glucose molecule
• Produces two ATP
• Takes place in matrix of mitochondria
Krebs Cycle Summary
• Each turn of the Krebs Cycle also
produces 3NADH, 1FADH2, and
2CO2
• Therefore, For each Glucose
molecule, the Krebs Cycle produces
6NADH, 2FADH2, 4CO2, and 2ATP
Krebs Cycle
ATP
NETS: 3NADH, 1ATP, 1FADH2, & 2CO2
Electron Transport Chain
Summary
• 34 ATP Produced
• H2O Produced
• Occurs Across Inner Mitochondrial
membrane
• Uses coenzymes NAD+ and FAD+ to accept
e- from glucose
• NADH = 3 ATP’s
• FADH2 = 2 ATP’s
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Anaerobic Respiration
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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
glucose
energy
2C2H5OH
+
2CO2
alcohol
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.
For example, our own muscles resort to anaerobic
respiration when oxygen is not delivered to them fast
enough.
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Micro-organisms
Anaerobic respiration is widely used by many micro-organisms
such 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
cell wall
there are many
species of bacteria
and they have different
shapes and sizes
nucleus
cytoplasm
0.002mm
a single bacterium
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Aerobic and anaerobic bacteria
Bacteria which need oxygen in order to respire are called
aerobic bacteria.
Aerobic bacteria are likely to be found in the air, water
and 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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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 example
of fermentation
Fermentation is involved in brewing and wine-making
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Yeasts
cell wall
cytoplasm
nucleus
0.005mm
vacuole
Yeast cells dividing
single yeast cell
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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
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
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 then
ferments 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
The yeast is mixed
with the dough
After 1 hour in a warm
place the dough has
risen as a result of the
carbon dioxide
produced by the yeast
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The ‘holes’ in the
bread are made by
the carbon dioxide
bubbles.
This gives the
bread a ‘light’
texture
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
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In what circumstances do our muscle use anaerobic
respiration ?
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