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Investigating the Effect of Temperature on Respiration in Maggots

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Investigating the Effect of Temperature on Respiration in Maggots

Aim: This is an experiment to investigate how temperature effects the
respiration rate in maggots.

The formula: The simple formula of respiration is:

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[IMAGE]C6 H12O 6+ 6O26H 2O + 6CO2+ ENERGY



GLUCOSE + OXYGEN WATER + CARBON + ENERGY
========================================

DIOXIDE

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The Collins concise English dictionary explains that respiration is
'the processes by which a living organism…takes in oxygen, distributes
and utilizes it in oxidation, and gives off products, esp. carbon
dioxide'.

Background information:

Respiration is the chemical process of releasing energy from organic
compounds in living cells. The organic molecules are broken down
through a series of steps to act as fuel. The most common organic
compound for most cells is glucose however, some cells can break down
fatty acids, glycerol, and amino acids in respiration. The energy
gained from respiration is used to synthesise ATP (adenosine
triphosphate) which is required throughout the body, in order to
replenish ATP stores.

There are two types of respiration; anaerobic and aerobic. Aerobic
respiration occurs when oxygen is freely available, whilst anaerobic
respiration occurs when free oxygen is not present, and the process is
altered. We will investigate aerobic respiration.

There are four main stages of respiration (when breaking down
glucose), known as the glycolytic pathway. They are; glycolysis, the
link reaction, the Krebs cycle, and oxidative phosphorylation.

The first stage of respiration is Glycolysis, which takes place in the
cytoplasm of a cell.

Glycolysis:

Each step in the pathway is controlled by an enzyme. The product from
one enzyme controlled reaction becomes the substrate for the next.

The second and third stages occur in the matrix of the mitochondria of
a cell, and is the link reaction, and the Krebs cycle (also known as
the citric acid cycle, or TCA cycle.) (Tricarboxylic acid cycle)

Link reaction:

Krebs cycle:

The last stage occurs in the cristae of the mitochondria and is known
as oxidative phosphorylation.

Oxidative phosphorylation:

The oxygen used in the equation for aerobic respiration is used as the
terminal acceptor in the electron transport chain for oxidative
phosphorylation.

So if the rate of respiration goes up, more oxygen should be consumed.
This can be used using a respirometer.

Enzymes play a vital role in the process of respiration, as is shown
in the diagrams of the different stages above. Enzymes are globular
protein molecules, with a tertiary structure found in all living
cells. They are organic catalysts that speed up the rate of reactions.
All enzymes contain an active site, a depression in the enzyme
molecule, where a specific substrate molecule can collide and fit
into, like a key fits a lock, to bind and form an enzyme-substrate
complex. (See diagram below:)

There are four factors that can effect the rate of an enzyme reaction:

v The pH

v The concentration of enzyme solution

v The concentration of substrate solution, and

v The temperature.

We will focus on the effect of temperature.

If you increase the temperature, up to the optimum temperature, you
increase the amount of kinetic energy, increasing random movement,
allowing more collisions between the enzyme and substrate molecules to
take place. This will increase the chances of forming enzyme-substrate
complexes and speed up the rate of reaction. However if the
temperature increases past the optimum temperature, the enzymes will
denature and no products can be formed. The temperature coefficient
Q10 =2, meaning that for every ten degree rise in temperature, the
rate of the reaction is doubled.

Prediction: I predictthat the respiration rate in maggots will
increase if the temperature increases. Respiration takes place through
a series of steps, requiring enzymes in each stage. If I increase the
temperature in the experiment, the amount of kinetic energy will
increase, causing the substrates and enzymes to collide more
frequently, improving the chance of being more enzyme-substrate
complexes, which speeding up the reaction.

This prediction could be quantitative. If I increase the temperature
by ten degrees, the rate of respiration should double, so the oxygen
consumption should double.

Variables:

§ My independent variable is the temperature, as I am manipulating
this factor. The different temperatures I will use are: 10°C, 20°C,
30°C, 40°C. I will not go any higher as maggots are living creatures
and it would not be ethical to test them at high temperatures.

§ My dependant variable is oxygen consumption, as this is what I am
measuring.

I will need to control all the variables other than the independent
variable to keep the experiment fair and accurate.

§ I will keep the time I equilibrate constant, 5 minutes each time,
using a stopwatch. The amount of time I measure for, will also remain
constant (10 minutes) using the stopwatch. However, the accuracy of
this method may be limited, as times will vary slightly as reaction
times may vary, even if the same person is used.

§ The volume of soda lime will also remain constant, by using the same
mass.

§ The mass of maggots will also remain constant.

§ The apparatus volume and size will remain constant by keeping the
same apparatus throughout the experiment.

§ The water bath will remain the same temperature, using a pre-set,
pre-heated electronic water bath. The temperature of surrounding must
be kept constant whilst readings are taken because changes in
temperature and pressure, alter the volume of the air in the
apparatus.

Preliminary:

Our preliminary experiment was not very successful. We tested the
respiration rate of five and ten maggots in the respirometer, but
found that more maggots were required as to get a significant result.
We realised that twenty maggots would give a better result, but found
it difficult to find maggots the same size. Instead we have decided to
use the same mass of maggots. (5 grams)

Risk assessment: We will be working with living maggots so some
precautions should be made. Maggots usually feed on dead or rotten
flesh of meat, which carries a lot of bacteria. Therefore maggots may
be carrying germs and may be infected with diseases such as
salmonella, if the maggots had been into contact with infected chicken
meat. Equipment will be used to handle the maggots however, if one
maggot escapes, handling may be required. After the experiment all
hands, surfaces and equipment should be washed to destroy any
bacteria.

Lab safety also includes no running and removing all obstacles from
the floor, to avoid tripping up.

· There were two sets of apparatus I could use to create a
respirometer. I could have used a capillary tube instead of a
manometer, by measuring with a ruler, (see below) but decided a
manometer would be easier to read, and restart again. My chosen method
and apparatus also allows me to use a control tube to compensate for
any environmental variables I cannot control, like atmospheric
pressure changes.

Apparatus:

· Clamp

· Stand

· Boss

· Screw clip

· 5g live maggots

· Test tube x2

· Bung x2

· Soda-lime

· Stopwatch

· Control tube

· Glass beads

· 1 cm ² syringe

· Three-way tap

· Capillary U-tube containing manometer fluid and manometer

· Gauze platform

· Water bath set at 10°C, 20°C, 30°C, and 40°C.

I will use a stand, clamp and boss to hold the test tubes into place
and to keep them stable throughout the experiment. It will also keep
them at the same height, so the variables concerned are controlled,
(for example, the temperature, or amount of light at this level.) The
screw clip is left opened to allow for equilibration, and closed when
we start recording the respiration rates. 5 grams of maggots will be
used, as mass is more accurate than the number of maggots, as each
maggot varies in size/weight, so may not be the same. One test tube
will be the experimental tube, with the maggots, and the other will be
the control tube, with the beads. The same mass of soda lime will be
used. it is used to absorb the carbon dioxide, which is produced in
respiration. The stopwatch is fairly accurate, and will be used to
tell us when to take the readings, to ensure that each reading is
taken at the same time. The same person will use the stopwatch to as
people have different reaction times. (This will eliminate this
variable). The glass beads are used as a control, so that any

environmental changes will be compensated for. The syringe is used to
'push' the liquid back to zero after each reading. The three-way
attaches the syringe to the bung. The capillary U-tube which will
contain the manometer fluid is what we use to measure the respiration
rate. The scale of the manometer allows us to do this easily. The
gauze platform keeps the maggots off the soda lime, but still allows
respiratory gases through. The water baths are used to investigate the
respiration rate at different temperatures. They are accurate and can
be kept at the same temperature for long periods of time.

Diagram of apparatus:

Method:

i. Set up apparatus as shown in diagram

ii. Weigh maggots (5 grams)

iii. Place maggots in test tube

iv. Place test tube into water bath (10°C) for 5 minutes to allow time
to equilibrate. With the screw clip open. Use a stopwatch to measure
the time.

v. After the 5 minutes, set liquid to start (0), using syringe and
tighten the screw clip.

vi. Start stopwatch

vii. At 10 minutes observe how far the liquid has moved (mm), and
record data in a table.

viii. Repeat two more times at the same temperature

ix. Repeat at temperatures of 20°C, 30 °C, 40°C, using electronic
water baths.

References:


BOOKS
-----

¨ Collins, W. (1978). Collins Concise English Dictionary. William
Collins Sons & Co. Ltd, Glasgow.

¨ Jones, M et al. (2000) Biology 1. Cambridge: CUP (Cambridge
University Press)

ISBN 0 521 78719 x paperback

¨ Jones, M. and Gregory, J. (2001) Biology 2. Cambridge University
Press, Cambridge. ISBN 0-521-79714-4

¨ Simpkins J and Williams, J. (1987) Advanced Human Biology. Collins
educational.

WEBSITES

¨ www.s-cool.co.uk AS & A2 Level Biology. Respiration: some basics

: glycolysis

: krebs cycle

:electron transport chain/ oxidative phosphorylation

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