Respiration
The Chemistry of
Respiration
energy and mitochondria clip
Adenosine triphosphate
► The
energy released during respiration is
not used directly by cells.
► Instead it is used to make a molecule called
ATP which stores the energy until it is
needed.
ATP =
Adenosine triphosphate
What does ATP do?
► ATP
supplies energy for all the processes
that need it.
► For example:
movement
► chemical reactions
► growth.
►
slow twitch/fast twitch investigation
Structure of ATP
adenosine
Pi
Pi
Pi
Formation of ATP
ATP is made when another molecule called
adenosine diphosphate (ADP) is bonded to
a third inorganic phosphate (Pi) using the
energy released from glucose.
Energy from respiration
adenosine
Pi
Pi
+
Pi
Enzymes
adenosine
Pi
Pi
Pi
Energy Rich bond formed
Summarised as:
ADP + Pi
ATP
The whole process is under the control of enzymes
The role of ATP
► ATP
stores the energy in the third bond
of the molecule
► The
energy is released when that bond is
broken to release the third inorganic
phosphate (Pi) .
adenosine
Pi
Pi
Pi
ATP
Enzymes
adenosine
Pi
ADP
Pi
+
Energy
released
to do work
Pi
Summary
ATP
ATP
cellular
respiration
cellular
respiration
energy
(out)
energy
(in)
energy
(out)
cell
cell
activities
activities
ADP + Pi
The whole process is an enzyme controlled reaction.
Aerobic Respiration
Aerobic respiration = respiration with
oxygen.
glucose + OXYGEN
C6H12O6 + 6O2
energy + carbon dioxide + water
(to make ATP)
38ATP + 6CO2
+ 6H2O
Cellular Respiration
►3
step process
 Glycolysis
 Krebs Cycle/Citric
Acid Cycle
 Oxidative
phosphorylation
Aerobic respiration happens in 2
stages:
Stage 1 – Glycolysis
glyco
glucose
lysis
splitting
In glycolysis, a glucose molecule is broken down into
pyruvic acid.
glucose
energy released to
make small
quantity of ATP
(2 molecules)
series of enzyme
controlled reactions
pyruvic acid
Glycolysis does not require oxygen
IT TAKES PLACE IN THE CYTOPLASM
Stage 2 – Breakdown of pyruvic acid
The pyruvic acid made in glycolysis
(stage1) still contains a lot of energy
It can only be broken down to release
the rest of the energy in the presence
of oxygen.
pyruvic acid
series of enzyme
controlled
reactions
energy released
to make large
quantity of ATP
(36 molecules)
carbon dioxide + water
ATP production – summary
glucose
2 ADP + 2 Pi =
2 ATP
pyruvic acid
Two phases:
1. Kreb’s cycle
2. Oxidative
phosphrylation
36 ADP + 36 Pi =
36 ATP
carbon dioxide + water
Summary of ATP production
► Stage
1 and 2 release all the chemical
energy in one molecule of glucose to make
a total of 38 ATP molecules.
2 molecules ATP from glucose  pyruvic acid
36 molecules ATP from pyruvic acid  carbondioxide + water
Total 38 molecules ATP
Anaerobic Respiration
(in animals)
anaerobic = in the absence of oxygen
In low oxygen conditions or
during heavy exercise, when not
enough oxygen can be supplied,
muscle cells swap to anaerobic
respiration
glucose
glycolysis still
happens as it does
not require oxygen
pyruvic acid
in absence of
oxygen pyruvic
acid is turned
into lactic acid.
lactic acid
2 ADP + 2 Pi
2 ATP
A build up of lactic acid produces muscle fatigue.
Muscle fatigue makes muscles ache and contract
less powerfully.
A recovery period is needed. During this time more
oxygen is taken in to convert the lactic acid back
into pyruvic acid again.
The volume of oxygen needed is called the oxygen
debt.
Summary
glucose
pyruvic acid
oxygen debt
e.g. during hard
exercise
lactic acid
oxygen debt
repaid during
recovery time
Anaerobic Respiration
in plants
(Alcoholic fermentation)
The same process occurs in plants
and yeast in low oxygen conditions,
e.g. muddy, flooded soils.
glucose
2 ADP + 2 Pi
glycolysis still
happens, producing
2 ATP molecules
2 ATP
pyruvic acid
This time in absence of
oxygen, pyruvic acid is
turned into carbon
dioxide and ethanol
This is irreversible
ethanol + carbon dioxide
ETHANOL
BEER = alcohol + CO2 from anaerobic
respiration in plants = ALCOHOLIC
FERMENTATION
►This guy had a
serious beer
drinking problem
Comparison of aerobic and
anaerobic respiration
Aerobic respiration
Anaerobic Respiration
in animals
in plants and yeast
Oxygen required?
Yes`
no
no
Glycolysis occurs
yes
yes
yes
ATP yield
38ATP
2ATP
2ATP
Glucose completely broke
down?
yes
no
no
End products
Carbon
Lactic acid
dioxide
and water
Ethanol and
carbon
dioxide
Explain why the mouth of the thistle funnel is sealed.
Forces gases given off by seeds into test tube.
2 What is the advantage of using germinating seeds
instead of living non-germinating seeds?
Germinating seeds need a lot of energy and therefore
the rate of respiration will be high
1.
Explain why the seeds in the CONTROL are
placed in formalin?
To prevent bacterial growth which also respire
and which will affect the results.
4 Why is the apparatus left in a dark cupboard?
To prevent photosynthesis which uses any
carbon dioxide which may be given off.
5 What do you observe of the lime water after a
few days?
► EXPERIMENT: Turns milky
► CONTROL: Stays clear
6
What may we conclude from this experiment?
Germinating seeds give off carbon dioxide
3.
KOH
Lime water
Lime water
Turns milky because the snails give off CO2
No animals in C
D not milky
Place in dark cupboard to stop photosynthesis which
absorbs CO2
Ja. Because they need a lot of energy and
produce a lot of CO2 in respiration.
Why are the flasks inverted?
►
To allow CO2 which is heavier than air to pass out
of flask and not poison the seeds.
►
To be able to read the thermometer.
►
To keep the thermometer bulb immersed in the
seeds.
►
You don’t have to fill the thermos flask with seeds
so that there is air available to the respiring
seeds.
Soaking the seeds in formalin and
sterilising the flasks serve the same
function. What is it and explain why this
procedure must be carried out.
To kill bacteria which also respire and which
will affect the results.
► What is the advantage of using a:
(a) thermos flask instead on ordinary glass
flask?
Traps the heat and allows the thermometer to
record this rise in temperature.
(b) cotton wool stopper instead of a rubber
stopper?
Allows the CO2 to escape from the thermos
flask
►
► Oil/paraffin
keeps out oxygen and maintains
anaerobic conditions for the yeast to respire and
produce alcohol and carbon dioxide.
► We can test for alcohol by smelling it or igniting it
(with care)
Calculating energy in food
►A
given amount of any substance always
requires the same amount of energy to
produce a particular increase in
temperature.
► 1000g
of water needs………………..4.2 kJ
to make its temperature rise by 1 oC
Custard powder experiment
Did the food contain
energy?
•
• What kind of energy
did it have to start with?
• What kinds of energy
was this released as?
Comparing energy in carbohydrates,
proteins and fats
Use different
types of food to
calculate which will
give the most
energy
Results
Food
Material
Carbohydrate
Protein
Fat
Mass of
food
(g)
Starting
temperature
of water
(0C)
Finishing
temperature of
water
(0C)
Temperature
rise (0C)
Calculating the energy content of foods
► The
formula to calculate the energy
release is
M = mass of
► 4.2 x M x T
T=rise in
1000
► Now
water (g)
temperature
( °C)
calculate the energy content of your
foods
Calorimeter
Gases and respiration
► A:
Living Peas
B: Dead Peas
► Burn a lighted splint in each gas jar.
Do other organisms respire?
breathing and respiration
1 Which type of energy does food contain?
2 What is this energy converted to by other
organisms? Give at least 3 examples.
(i)
(ii)
(iii)
3 What name is given to the process by
which organisms release energy?
4 What kind of energy is always released in
respiration?
Or else!