Download What is Respiration? - Deans Community High School

Respiration
In the final topic of our unit about cells, we're going to be learning lots more about a
process which is crucial to all cells: respiration. Once again, you'll already know at
least something about respiration. This is the process by which we release energy
from our food.
Learning Outcomes:




Identify the source of energy in a cell and the reaction which releases this energy
Explain the structure and role of ATP and how it releases energy
State the cellular activities that use energy
Define aerobic respiration and fermentation and state the locations where they
occur
 Describe the steps involved in aerobic respiration and fermentation in animals
and plants
 Compare aerobic and anaerobic respiration in terms of energy yield and products
in both plant and animal cells
What is Respiration?
Energy is required by all cells in the body for even the simplest of things. We need
energy for:




Movement
For keeping warm
Cell division
To keep our bodies working as we sleep
Aerobic respiration is the enzyme-controlled chemical process where glucose is
broken down in the presence of oxygen to release energy (ATP) to allow the body to
do work and carbon dioxide and water are released as end products.
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Learning Activity 1: Measuring the energy content of food.
Collect the experiment sheet “Measuring the energy content of food”.
Careful – Make sure you follow all instructions on the card. Remember your Bunsen
safety!
Group work – be a good team player. Help out others in your group if you need to:
do not dominate but get involved in the task.
Organisation – make sure that everyone in your groups knows what is to be done
and that all safety precautions are followed.
1. Write up the experiment: include an aim, a method (including a diagram), your
table of results, a graph.
2. For the conclusion, state which type of food contains the most energy per gram.
The Release and Use of Energy
The energy released from the breakdown of glucose is used to generate molecules of
Adenosine triphosphate (ATP) inside cells.
ATP is a chemical store of energy: it is generated from molecules of Adenosine
diphosphate (ADP) and phosphate (Pi).
ATP is formed when the chemical energy released from glucose during respiration is
used to join together a single ADP molecule and a single phosphate molecule (Pi).
Adenosine
Pi
+
Pi
Pi
Adenosine diphosphate
Adenosine
Phosphate
Pi
Pi
Pi
Adenosine triphosphate
The chemical energy stored in ATP can be released whenever it is required by cells.
This is achieved by breaking the last bond in the molecule in order to make ADP
and Pi again.
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Learning Activity 2
1. Draw a simple diagram to show the link between ATP, the energy from
respiration and the energy used for cellular activities.
2. Draw a spider diagram in your jotter to show the uses of energy by cells.
Aerobic Respiration
In order for glucose to be completely broken down during respiration, aerobic
conditions must be present. This means that there must be a supply of oxygen
present.
The basic word equation for aerobic respiration is:
Glucose + Oxygen
Carbon dioxide + water + energy (38 ATP molecules)
This takes place during a number of enzyme-controlled steps.
Step 1: Glycolysis
This is the process of breaking glucose down into a substance called pyruvate. It
takes place in the cytoplasm of a cell. This step does not require aerobic conditions
(oxygen). Two ATP molecules are formed as a result.
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Step 2: Breakdown of Pyruvate
The pyruvate is further broken down to produce carbon dioxide and water. This stage
does require aerobic conditions (oxygen). It takes place in the mitochondria. During
this stage 36 ATP molecules are produced.
Pyruvate
36 ADP + 36 Pi
36 ATP
Carbon
dioxide
Water
The complete aerobic breakdown of one glucose molecule in the presence of oxygen
results in a yield of 38 molecules of ATP.
Learning Activity 3
Answer the questions below in full sentences in your jotter:
1. State the number of ATP molecules produced by the first stage of aerobic
respiration.
2. State the number of ATP molecules produced by the second stage of aerobic
respiration.
3. Name the final products that result from the complete breakdown of glucose.
4. Write down the summary word equation for aerobic respiration.
Extension:
Create a wall display poster of aerobic respiration. Include diagrams of each stage of
the process and make sure you add labels.
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Measuring the rate of Respiration in plants and animals
The rate of respiration can be measured using a respirometer. The diagram shows a
simple respirometer used to measure the respiration rate of a woodlouse.
Coloured water
Woodlouse
Sodium hydroxide
(to absorb CO2)
Gauze
The only air available to the woodlouse is inside the tube. Sodium hydroxide is used
to absorb carbon dioxide produced by the woodlouse. This way, only the oxygen
taken in by the woodlouse is measured. As the organism uses up oxygen inside the
tube, the volume of gas decreases. The coloured water moves down the tube to fill
the space of the oxygen that has been used up by the woodlouse. The distance that
the coloured water moves is used to calculate the rate of respiration.
Learning Activity 4
1. Make a copy of the diagram above in your jotter.
2. Answer the following questions in full sentences:
a) Write down a suggestion for a suitable control for this experiment. Why do we
need a control?
b) Why is the respirometer kept at a constant temperature throughout the
experiment?
c) Explain why the sodium hydroxide must be kept away from the organism?
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Look at the apparatus below: it was used to measure the rate of respiration in
germinating peas:
A
B
Sodium
hydroxide
cotton
wool
Water Bath
Germinating Peas
Glass Beads
Coloured water
The liquid levels in tube A and B were noted at 10 minute intervals for 1 hour.
Time
(mins)
0
10
20
30
40
50
60
Tube A
(mm3)
0
10
20
30
35
40
40
Tube B
(mm3)
0
0
0
0
0
0
0
Learning Activity 5
1. Copy the table of results into your jotter.
2. Plot a line graph of oxygen uptake in mm3 against time on graph paper.
3. Answer these questions in sentences:
a) Why is there no change in the volume of coloured liquid in Tube B?
b) Calculate the average oxygen uptake per min for Tube A (mm3).
c) Give a reason for the oxygen uptake levelling off after 40/50 minutes.
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Fermentation in Animal Cells
In the absence of oxygen, respiration cannot take place as it normally would. Glucose
cannot be completely broken down. Instead, the fermentation pathway is followed.
Stage 1: Glycolysis
This stage happens as normal because it does not require oxygen.
Glucose
2 ADP + 2 Pi
2 ATP
Pyruvate
Stage 2: The incomplete breakdown of pyruvate
In the absence of oxygen in animals, pyruvate is broken down into lactic acid. This
happens frequently during strenuous exercise. Only 2 molecules of ATP are
produced.
Pyruvate
Lactic Acid
Lactic acid builds up inside muscle cells and eventually muscles tire. This is called
muscle fatigue. Following a period of recovery, where oxygen becomes available
again, the lactic acid can be converted back into pyruvate, and aerobic respiration
can resume.
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Learning Activity 6
Write the answers to the following questions in full sentences:
1. Describe the process of fermentation in animal cells.
2. State the number of ATP molecules produced during fermentation in animal
cells.
3. Name the final product that results from fermentation in animal cells.
4. Write down the summary word equation for fermentation in animal cells.
Fermentation in Plant and Yeast Cells
In plant and yeast cells, in the absence of oxygen a similar situation arises.
Glycolysis takes place as before, only this time, pyruvate is broken down into Carbon
dioxide and ethanol (alcohol).
As carbon dioxide is produced, the reaction cannot be reversed.
Pyruvate
Carbon
dioxide
Ethanol
Learning Activity 7
Write the answers to the following questions in full sentences:
1. Describe the process of fermentation in plant and yeast cells.
2. State the number of ATP molecules produced during fermentation in plant and
yeast cells.
3. Name the final products of fermentation in plant and yeast cells.
4. Write down the word equation for fermentation in plant and yeast cells.
Extension:
Use the internet and other available classroom resources to find out how
fermentation is useful in the production of the following things:
1. Bread
2. Alcohol (beer and wine).
Create a poster displaying the information that you have found out. Remember to
record all of your sources.
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Location of aerobic respiration and fermentation
The process of aerobic respiration starts in the cytoplasm and is completed in the
mitochondrion. The mitochondrion is a sausage-shaped organelle in the cytoplasm of
a cell.
Cells which require a vast amount of energy have many mitochondria within them.
These cells include muscle cells, sperm cells, nerve cells and companion cells, along
with many more.
The process of fermentation is completed in the cytoplasm.
Learning activity 8
1. Copy and complete the following table to compare aerobic respiration and
fermentation in plants and animals:
Fermentation in
Plants
Animals
and
Yeast
Aerobic
respiration
in all cell
types
Product (s)
Number of ATP
molecules
produced (per
molecule of
glucose)
2. Choose a cell type that has many mitochondria. Produce an information leaflet
on the uses of energy in your chosen cell. You can use AAL to complete this
task if no laptops are available.
You should include:



A drawing of the cell that you have chosen showing many mitochondria
present.
An explanation of the job of the cell.
An explanation of how the cell uses energy.
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