Background knowledge
• This is the required background knowledge:
• State three uses of energy in living things
• Give an example of an energy conversion in a living organism
• State that fats and oils contain more energy per gram than carbohydrates
• State that oxygen is required for aerobic respiration
• State the word equation for aerobic respiration
• State that CO2 is a product of aerobic respiration
• State that heat may be produced by respiration
• Describe anaerobic respiration and compare it with aerobic respiration
• Explain the working of a simple respirometer.
Learning outcomes
energy release
• To understand the importance of ATP as a means of transferring chemical energy
• To state the structure of ATP
• To describe the production of ATP
• To describe the role of ATP in cell processes
• To explain the terms oxidation and reduction
Effect of ATP on muscle fibres
• This experiment shows that the energy
for muscle contraction comes from
ATP
Structure of ATP
• Adenosine triphosphate (ATP)
– Adenosine
– Three phosphate groups
• Diagram of ATP
ATP
• a high energy molecule
• continually being hydrolysed and
resynthesised.
Formation and breakdown of
ATP
• The combining of ADP + Pi to make ATP is an energy requiring process.
• The breakdown of ATP to ADP + Pi is an energy releasing process.
• The energy required for the formation of ATP from ADP + Pi comes from the respiration of glucose.
Transfer of chemical energy by ATP
Role of ATP
• ATP is the energy source for:
– Muscle contraction
– Cell division
– Building up (synthesis) of proteins
– Transmission of nerve impulses
– Active transport
Think!!
• Explain why ATP is known as the
universal energy currency.
Metabolism
• Metabolism – All reactions that take place within the
organism
– Anabolism • Build up of larger, more complex molecules
from smaller, simpler ones
– Catabolism • Breakdown of complex molecules into smaller,
simpler ones
• Releases energy
Redox Reactions
• Oxidation – Loss of electrons
– Loss of hydrogen atoms
• Reduction – Gain of electrons
– Gain hydrogen atoms
• If one substrate becomes oxidised another becomes reduced.
OIL RIG
Oxidation and Reduction
Substrate reduced Substrate oxidised
Oxidation
Hydrogen removed
Energy released
Reduction
Hydrogen added
Energy gained
Testing your progress
• Energy is defined as the ability to do ________________.
• The energy of motion is known as ___________ energy, whereas _________ energy is stored energy.
• Living organisms need energy for many reasons – __________ reactions in which simple
molecules are built up into complex ones
– The movement of material by __________ against a concentration gradient.
Progress questions
• Fireflies can produce light in a process
called bioluminescence. Outline the
energy transformations that occur in
fireflies as they use energy from their
food to produce luminescence.
• Comment on the statement below.
– Respiration produces energy to form ATP.
ERQ – 10 marks
• Discuss the role of ATP in living matter
Chemistry of Respiration
Chapter 4
Higher Biology
Unit 1: Cells
Respiration
• The complete oxidation of glucose
during aerobic respiration takes place
in three stages:
– Glycolysis
– Krebs Cycle
– Cytochrome system
Hydrogen acceptor and carrier
• Hydrogen release from respiratory
substrate is temporarily bound to a
coenzyme which acts as a hydrogen
acceptor
– NAD = coenzyme
– NADH2= reduced coenzyme
Glycolysis
• Oxidation of Glucose (6 carbon) to
two molecules of 3-carbon pyruvic
acid.
• Occurs in cytoplasm
• Net gain of 2 ATP molecules.
• Hydrogen is released and combines
with NAD to form NADH2
• oxygen is not required.
Glycolysis
Glucose (6C)
2 x Pyruvic acid (3C)
Investigating dehydrogenase
enzymes in yeast
• As glucose is oxidised, hydrogen is
released
• The release of hydrogen is called
dehydrogenation, this controlled by
dehydrogenase enzymes.
• Resazurin dye changes from blue to
colourless as it is reduced.
Investigating the activity of enzymes in
aerobic respiration
• Set up the three test tubes as shown
below. – 10ml glucose
– 10ml yeast
– 5 ml dye
Investigating the activity of
enzymes in aerobic respiration
• Shake tubes vigorously for 20 seconds, and place in a water bath set at 37oC.
• Leave for a few minutes and observe what happens
• Draw a diagram of your results
• Can you explain your results.
Investigating the activity of
dehydrogenase enzyme in yeast
• Tube A
– Colour change from blue via pink to
colourless.
– Hydrogen has been rapidly released and
has reduced the dye.
– For this to happen – enzymes present in
yeast cells must have acted on the
glucose, the respiratory substrate, and
oxidised it.
Investigating the activity of
dehydrogenase enzyme in yeast
• Tube B – Change from blue – pink – colourless
– Reaction is slower since no glucose was added.
– enzymes could only act on any small amount of respiratory substrate already present in the yeast cells.
• Tube C – Boiling has killed the yeast and denatured the
enzymes.
Aerobic Respiration
• Kreb’s cycle
– Occurs in the matrix of mitochondria
• Cytochrome system
– Across the inner mitochondrial membrane
Structure of Mitochondria
• Mitochondria have a double plasma
membrane surrounding a fluid filled
matrix
• The inner mitochondrial membrane is
folded into cristae which provide a
large surface area for the attachment
of stalked particles.
Fate of pyruvic acid
• Molecules of pyruvic acid enter the cells
mitochondria.
• Mitochondria are sausage shaped
organelles surrounded by a double
plasma membrane.
• The inner membrane is folded into
cristae,
– provide a large surface area for the stalked
particles on which ATP is produced.
Fate of pyruvic acid
• Pyruvic acid diffuses into the matrix of the mitochondria
• pyruvic acid is converted into 2C acetyl coenzyme A (Acetyl CoA),
• Hydrogen is released and combines with NAD
• Carbon dioxide is released – Enzymes that control the release of CO2
are called decarboxylases.
Kreb’s Cycle
• Acetyl CoA (2C) combines with a 4 carbon compound to form citric acid (6C).
• Citric acid is coverted back into the 4 carbon compound by decarboxylation (removal of CO2) and dehydrogenation.
• Enzymes involved in these steps are dehydrogenases and decarboxylases.
• Hydrogen combines with NAD to form NADH2.
Cytochrome System
• NADH2 (reduced coenzyme) transfers hydrogen to a chain of hydrogen carriers known as Cytochrome system.
• Each carrier molecule is alternately reduced and oxidised.
• The hydrogen from each NADH2 releases energy to form 3 ATP molecules from ADP and Pi.
• This process is known as oxidative phosphorylation.
• Oxygen is the final hydrogen acceptor to form water (controlled by cytochrome oxidase)
Respiratory Substrates
• Fats and proteins can also be used as
respiratory substrates
Respiratory substrates
Glycogen or starch
Glucose
Pyruvate
Acetylcoenzyme A
Krebs cycle
Protein
Amino Acids
Lipid
fatty Acids
Anaerobic Respiration
• Partial breakdown of glucose
• If oxygen absent only glycolysis can
occur
• Glucose is broken down to two
molecules of pyruvic acid, with a net
yield of 2 ATP molecules.
Anaerobic respiration in plants
(and yeast)
Glucose (6C)
pyruvic acid (3C)
ethanol (2C) + CO2
Anaerobic respiration in animals
• Glucose pyruvic acid lactic acid
• During lactic acid formation an
oxygen debt is build up
Respirometer
Respirometer
• Sodium hydroxide absorbs all CO2 from the air in the apparatus from the beginning.
• As the germinating seeds use oxygen and the pressure reduces in tube A so the manometer level nearest to the seeds rises.
• Any CO2 excreted is absorbed by the sodium hydroxide solution.
Respirometer
• The syringe is used to return the manometer
fluid levels to normal.
• The volume of oxygen used is calculated by
measuring the volume of gas needed from
the syringe to return the levels to the original
values
• If water replaces the sodium hydroxide then
amount of carbon dioxide given off can be
measured
Simple Respirometers
Na-K pump
• 3 Na+ leave the cell
• 2 K+ enter the cell
• Potential difference is created across
the neurone membrane for nerve
impulses.
Key
1
3
• Summary of
the sodium
potassium
pump!
