7. Cellular respiration
CfE Higher Human Biology
Unit 1: Human Cells
Higher Human Biology Course Specifications
Higher Human Biology Course Specifications
National 5 recap
(a) = (b) = (c ) = (d) =
(a)
(b)
(c)
(d)
The equation of respiration
Glucose + Oxygen Carbon Dioxide + Water + Energy
C6H12O6 + 6O2 6CO2 + 6H2O + 38ATP
Comes from digested carbohydrate
Inhaled with air, diffuses into cells
Waste product exhaled
Waste product excreted
Stored within the final bond in ATP
Metabolic pathways of cellular respiration
The metabolic pathway of cellular respiration
It occurs in the cytoplasm AND the mitochondria inside all human cells.
Cellular aerobic respiration is a metabolic pathway, controlled by enzymes, in which glucose is gradually broken down to ultimately produce many ATP molecules.
Adenosine Tri-Phosphate (ATP)
Adenosine
Pi
Pi
Pi
Energy stored inside this bond
Adenosine tri-phosphate or ATP is the molecule inside our cells which stores and transfers the energy we use during all our bodies processes.
Energy is stored within the final bond of the ATP molecule.
ATP is described as a high energy state molecule
Phosphorylation
Therefore, energy is stored in the final bond of ATP through the process of phosphorylation.
A molecule is phosphorylated when it has the addition of a phosphate group
Adenosine
Adenosine
Pi
Energy
stored
phosphorylation
Pi
Pi
Pi
Pi
Pi
ADP + Pi ATP
ATP is formed when inorganic phosphate (pi) bonds to ADP.
Role of ATP
Cytoplasm
Step 1: Glycolysis
Cristae of Mitochondria
Step 3: Cytochrome System
Matrix of Mitochondria
Step 2: Citric Acid Cycle
The stages in aerobic respiration
Starter activity�Cellular Respiration Simulation
You will need:-
Method:-
Optional
The three steps of aerobic respiration
Glucose
(C6H12O6)
2 x Pyruvate
(2x 3C)
Net Gain
2ATP
ENERGY INVESTMENT
2ATP 🡪 2ADP + 2Pi
ENERGY PAY OFF
4ADP + 4Pi 🡪 4ATP
If oxygen present ……..
The breakdown of glucose to pyruvate in the cytoplasm
1. Glycolysis (‘glucose splitting’)
Initially, 2 ATPs are required for the phosphorylation of glucose (energy-investment stage)
Later, 4 ATPs are produced (energy-payoff stage) so there is a net gain of 2 ATP
H
Glycolysis Summary
a) glycolysis b)citric acid cycle c) electron transport chain:
2. Label the matrix, outer and inner mitochondrial membranes on the diagram opposite
3. Describe what happens during :
b) energy pay-off
4. What is the function of the enzyme dehydrogenase?
5. Where are the hydrogen ions and electrons from NADH passed to?
6. What happens to pyruvate if oxygen is present?
2. Label the matrix, outer and inner mitochondrial membranes on the diagram below
40mm magnified 10,000 times
40/10,000
=0.004mm
0.004mm x 1000
=4 micrometre
Cytoplasm
i) State the site of glycolysis.
Phosphorylates/glucose/intermediate(s)
OR
Adds phosphate to glucose/ intermediates
OR
Gives energy to glucose/ intermediates
b) i) State the role of ATP in step 1
More (ATP) is made than is used
OR
2 ATPs are used but 4 ATPs are made
ii) Explain how glycolysis results in a net gain of ATP.
Removes hydrogen/ions and electrons (1)
Passes them to (coenzyme) NAD
OR
Turns NAD to NADH (1)
Pyruvate
Acetyl group
Acetyl CoA (Acetyl coenzyme A )
H
CO2
(+ coenzyme A)
In matrix of mitochondria
In aerobic conditions, the pyruvate is broken down to an acetyl group that combines with coenzyme A forming acetyl coenzyme A
2. Citric acid cycle
2 molecules of CO2 are released (one per pyruvate)
2. Citric Acid Cycle continued
2 x Acetyl CoA
(2 x 2C molecule)
2 x oxaloacetate
(2 x 4C molecule)
2 x Citrate
( 2 x 6C molecule)
2. Citric Acid Cycle continued
During a series of enzyme controlled steps, citrate is gradually converted back into oxaloacetate which results in the generation of some ATP and release CO2.
Acetyl CoA
Citrate
Oxaloacetate
Intermediate 1
Intermediate 2
Intermediate 3
Intermediate 4
Intermediate 5
Intermediate 6
H
CO2
H
H
CO2
THE CITRIC ACID CYCLE – lets evaluate
Acetyl coenzyme A combines with oxaloacetate to form citrate followed by the enzyme controlled steps of the cycle.
Q. What is produced during this cycle?
A. CO2 and hydrogen.
Q. What is regenerated during this cycle?
Dehydrogenase enzymes and NAD
Dehydrogenase* enzymes remove hydrogen ions and electrons and pass them to the coenzyme** NAD***, forming NADH.
*Dehydrogenase - an enzyme that activates oxidation-reduction reactions by transferring hydrogen from substrate to acceptor.
**Coenzyme - an organic non-protein compound that binds with an enzyme to catalyze a reaction.
***Nicotinamide adenine dinucleotide (NAD) is a coenzyme found in all living cells.
This occurs in both glycolysis and the citric acid cycle.
Looking back at the first steps of aerobic respiration this means the following happens every time hydrogen and electrons are released!
H
Dehydrogenase enzyme releases hydrogen and electrons during glycolysis AND the citric acid cycle
Carried to the inner membrane of mitochondria
2NAD
2NADH
H
Hydrogen and electrons passed to NAD to form NADH
Glucose
(C6H12O6)
2 x Pyruvate
H
Net Gain
2ATP
ENERGY INVESTMENT
2ATP 🡪 2ADP + 2Pi
ENERGY PAY OFF
4ADP + 4Pi 🡪 4ATP
If oxygen present ……..
Glycolysis (‘glucose splitting’)
2NAD
2NADH
Hydrogen ions and electrons released and bound to NAD to form NADH
Pyruvate
Acetyl group
Acetyl CoA (Acetyl coenzyme A )
H
2CO2
(+ coenzyme A)
2. Citric acid cycle
2NAD
2NADH
Hydrogen ions and electrons released and bound to NAD to form NADH
2. Citric Acid Cycle continued
Acetyl CoA
Citrate
Oxaloacetate
Intermediate 1
Intermediate 2
Intermediate 3
Intermediate 4
Intermediate 5
Intermediate 6
ATP
H
CO2
H
H
CO2
2NAD
2NADH
2NAD
2NADH
2NAD
2NADH
Hydrogen ions and electrons released and bound to NAD to form NADH
NAD(H) passes the hydrogen ions and electrons from glycolysis and the citric acid cycle to the electron transport chain on the inner mitochondrial membrane.
Function of NAD
Quick Questions!
Q1. Name the first 2 stages of cellular respiration and where they occur in the cell.
Q2. What is the net gain of ATP from glycolysis?
Q3. What is pyruvate broken down into when oxygen is present?
Q4. Name the molecule produced when acetyl CoA combines with oxaloacetate.
Q5. What is the name of the coenzyme which transport hydrogen to
the inner membrane of the mitochondria?
Quick Questions!
Q1. Name the first 2 stages of cellular respiration and where they occur in the cell.
A. glycolysis – cytoplasm citric acid cycle – matrix of mitochondria
Q2. What is the net gain of ATP from glycolysis?
A. more (4) ATP produced than used (2) = net gain (2)
Q3. What is pyruvate broken down into when oxygen is present?
A. Acetyl group
Q4. Name the molecule produced when acetyl CoA combines with oxaloacetate.
A. citrate
Q5. What is the name of the coenzyme which transport hydrogen to
the inner membrane of the mitochondria?
A. NAD (Nicotinamide Adenine Dinucletide)
Give an account of respiration under the following headings:
(i) Glycolysis (4 marks)
(ii) The Citric Acid cycle (4 mark)
3. Electron Transport Chain
Watch the short video summarising the processes in the electron transport chain then answer the following questions.
3. Electron Transport Chain – ATP synthesis
ATP
ATP
ATP
Step by step release of energy as
electrons are transferred through an
electron transport chain
H2O
Oxygen
This is where electrons are passed along the electron transport chain releasing energy (ATP)
NADH
NAD
3. Electron Transport Chain
The flow of these hydrogen ions back through the membrane protein ATP synthase results in the production of ATP
Movement of H+ back into the matrix of the mitochondria through ATP synthase
ATP synthase
ATP synthase is an enzyme through which hydrogen ions flow from a higher to a lower concentration.
They are located across the inner membrane of the mitochondria.
The flow of H ions rotates part of the ATP synthase, catalysing the synthesis of ATP.
3. Electron Transport Chain
Finally, the hydrogen ions and electrons combine with oxygen to form water.
NADH
NADH
3. Electron Transport Chain
The energy from the electrons allows hydrogen ions (H+) to be pumped across the inner mitochondrial membrane.
FAD is another hydrogen carrier, but you don’t need to know about it anymore in CfE Higher Biology
Rate of ATP production
Quick Questions!
Q1. Where does the electron transport chain take place in a cell?
A. In the inner mitochondrial membrane
Q2. Name the molecule that is pumped across the electron transport chain using energy from electrons
A. hydrogen
Q3. Name the membrane enzyme that produces ATP?
A. ATP synthase
Q4. What causes the this enzyme to produce ATP
A. hydrogen ions flowing back through the membrane
Q5. What is the final acceptor of hydrogen and electrons and what is
produced?
A. Oxygen is the final acceptor. Water is produced.
Booklet Questions
1. In the citric acid cycle, what does the acetyl from acetyl coenzyme combine with to form citrate?
2. During a series of steps, citrate is gradually converted back into oxaloacetate which results in the generation of which 2 substances?
3. What are these steps controlled by?
4. Where does this citric acid cycle occur?
5. In both glycolysis and the citric acid cycle, which enzyme removes hydrogen ions and electrons and pass them to the coenzyme NAD, forming NADH?
6. The hydrogen ions and electrons from NADH are passed to the electron transport chain. Where does the electron transport chain occur?
7. Electrons are passed along the electron transport chain releasing energy. This energy allows which ions to be pumped across the inner mitochondrial membrane?
8. The flow of these ions back through which membrane protein results in the production of ATP?
9. Finally, hydrogen ions and electrons combine with what to form water?
Booklet Answers
1. In the citric acid cycle, what does the acetyl from acetyl coenzyme combine with to form citrate?
Oxaloactetate
2. During a series of steps, citrate is gradually converted back into oxaloacetate which results in the generation of which 2 substances?
Carbon dioxide and ATP
3. What are these steps controlled by?
Enzymes
4. Where does this citric acid cycle occur?
Matrix of the mitochondria
5. In both glycolysis and the citric acid cycle, which enzyme removes hydrogen ions and electrons and pass them to the coenzyme NAD, forming NADH?
Dehydrogenase
6. The hydrogen ions and electrons from NADH are passed to the electron transport chain. Where does the electron transport chain occur?
Inner mitochondrial membrane
7. Electrons are passed along the electron transport chain releasing energy. This energy allows which ions to be pumped across the inner mitochondrial membrane?
Hydrogen
8. The flow of these ions back through which membrane protein results in the production of ATP?
ATP synthase
9. Finally, hydrogen ions and electrons combine with what to form water?
Oxygen
Describe the role of hydrogen ions in ATP synthesis.
2
Give an account of the structure of the inner membranes of mitochondria and the function of the electron transport chain in cellular respiration. 8
1. Carbohydrates
Starch (plants) and glycogen (animals) can be broken down to release glucose. Other sugars (maltose & sucrose) are converted to glucose or glycolysis intermediates.
Substrates for respiration
Fat is broken down into fatty acids and glycerol. Glycerol is converted to a glycolytic intermediate and fatty acids are metabolised into acetyl CoA.
2. Fats
3. Proteins
Proteins are broken down into amino acids. These amino acids can be metabolised into many intermediates which then enter glycolysis and the citric acid cycle.
Glucose
Pyruvate
Acetyl CoA
Fatty acids converted into Acetyl CoA
Amino acids converted to intermediates
Citrate
Oxaloacetate
Glycerol converted into an intermediate compound
When the carbohydrate glucose is not available alternative substrates are used to create ATP
Substrates for respiration
Give an account of respiration under the following
headings:
Essay time
Quick Questions!
Q1. Explain why phosphorylation in glycolysis is described as the energy
investment stage.
A. it uses 2 ATP but later 4 are produced (in pay-offstage)
Q2. State the role of dehydrogenase enzymes in respiration.
A. remove hydrogen and electrons from substrate (then passes to NAD)
Q3. Describe the role of NAD?
A. Transports hydrogen and electrons to the electron transport chain
Q4. Name the mitochondrial membrane enzyme that catalyses the
regeneration of ATP?
A. ATP synthase
Q5. Describe the role of electrons on the electron transport chain.
A. electrons pass along the electron transport chain releasing energy to
pump hydrogen across the membrane.
Q6. State the role of oxygen in the electron transport chain?
A. is final electron and hydrogen acceptor (producing water).
Starter question
3. What is phosphorylation?
4. How many ATPs are produced when one molecule of glucose is broken down?
Starter questions
1 =
2 =
3 =
4 =
5 =
1
2
3
4
5
5
5
Starter question
Draw the whole process of aerobic respiration from glucose to CO2 and water from memory (don’t worry about the electron transport chain)
Starter questions
5. What is the function of coenzyme NAD?
6. Where exactly is the electron transfer chain where most ATP is produced
7. What molecule is the ‘final electron acceptor’