Solved by a verified expert:BIOL1408 Introductory Biology Name
Lab Unit 9:
Respiration date
Dr. Flo Oxley
In this lab unit, you will follow your eSciences
ACC Lab Manual (posted in Blackboard: “Lab Manual”) to learn about the processes of energy transformation that work
inside mitochondria of your cells to support life.
This document will serve as your guide, sending
you to the relevant lab activities and introductory information found in the
ACC custom eSciences lab manual (pages for this unit are 97-106) uploaded to
Blackboard.
NOTE: I recommend that you read from this lab guide
& report document first, going to the eSciences manual materials only as
directed. The additional background
information provided in this document and the step-by-step guidance through the
eSciences lab materials is for your benefit.
In this lab, you will
study different aspects of cellular respiration: anaerobic fermentation by
yeast and aerobic respiration by germinating seeds.
BACKGROUND
INFORMATION: CELLULAR RESPIRATION
Plants obtain the energy to meet their metabolic
needs through the harvest of solar energy to transform carbon dioxide into
sugar molecules. These sugar molecules
are then used by the plant cell to fuel the necessary metabolic reactions for
their growth and for the maintenance of their cells. They are sometimes referred to as“autotrophs”, meaning literally“self-feeders”
since they do not consume other organisms in order to
survive.
In contrast, animals and other organisms that
feed off of others are referred to as“heterotrophs”, meaning literally“other-feeders”. They can be animal-eaters (carnivores), or
plant eaters (herbivores), or rely on both plants and animals for their
nutritional needs (omnivores).
Herbivores also indirectly benefit from the energy harvested by plants
from the sun, using the sugars and other biomolecules synthesized by the plants
for their own needs. And carnivores
indirectly benefit, as the carbon molecules go up the food chain.
We have a caloric requirement in our daily diet
to meet our own energy needs, derived from the foods that we eat. The primary sources of calories used in our
cellular metabolism are sugars and fats.
In this lab unit, we will focus our attention on how we derive energy
from sugars in the cell.
Cellular
RespirationBackground Questions
Go to: http://www.sumanasinc.com/webcontent/animations/content/cellularrespiration.html
to watch the“The Big Picture”animation on cellular
respiration, and answer the questions below.
1. Photosynthesis and cellular respiration are
in many ways opposites. Answer the
following questions as you watch the animation.
a. What are the reactants of the overall photosynthesis
reactions, and what are the products of the overall cellular respiration
reactions? (Include the energy sources
and products in your answer.)
b. What are the products of the overall
photosynthesis reactions, and what are the reactants of the overall cellular
respiration reactions?
c. What are the 3 major steps of cellular
respiration?
BACKGROUND
INFORMATION: FERMENTATION
The first step of cellular respiration is
glycolysis, where glucose is broken down to smaller-sized molecules (called“pyruvate, or pyruvic acid”) with the formation of some energy-harvesting
molecules (ATP and NADH). If oxygen is
available, a considerably larger amount of energy can still be extracted from
the products of glycolysis by shuttling these pyruvate molecules into the
mitochondria to undergo further digestion.
If oxygen is not available, the harvest energy
from sugars ends with glycolysis. If
this happens in your muscles during a heavy workout, your muscles will
accumulate lactic acid (formed from the pyruvic acid products of
glycolysis). The lactic acid buildup in
your muscles can cause soreness over time if you don’t do some cool-down exercises to
clear out the lactic acid.
When yeast cells are grown anaerobically (without oxygen), the
glycolytic products (pyruvate) are turned into alcohol instead of lactic
acid. (How fortunuate for us!) The process of growing yeast anaerobically is
called“fermentation”.
If any of you make your own homebrews of beer, this activity should
be very familiar to you because in the absence of oxygen, yeast cells will
ferment glucose into ethanol and carbon dioxide, both of which make the product
delightful to the taste!
C6H12O6 CO2 + 2 C2H5OH + 2 ATP
Glucose
ferments to carbon dioxide and
alcohol, releasing 2 ATP
Carbon dioxide is a by-product of anaerobic respiration, and is the
gas that will inflate the balloons in your fermentation experiment. The release of carbon dioxide in water leads
to the formation of carbonic acid, which can be detected by a pH indicator such
as Phenol Red or Bromothymol Blue.
Carbon dioxide also can be measured by its absorbance of infrared
radiation (a‘greenhouse effect’).
There is evidence for the production of beer by fermentation of
barley in prehistoric civilizations from thousands of years ago. Today, beer production is a fine art, and
breweries ferment lagers slowly at lowered temperatures, while the ales ferment
much faster at higher temperatures. The
lower temperatures slow the yeast’s metabolism, resulting in
longer periods of brewing before the sugars are converted to ethanol and carbon
dioxide.
Anaerobic fermentations have been used to leaven bread for nearly as
many years. The CO2produced
when yeast metabolize carbohydrates in bread provides thousands of small
bubbles in the dough. This is what causes the bread to“rise”.
Anaerobic
RespirationBackground Questions
Go to: http://www.sumanasinc.com/webcontent/animations/content/cellularrespiration.html
to watch the“Glycolysis”animation on cellular
respiration, and answer the questions below.
1. Where in the cell does glycolysis occur?
2. Energy is harvested from glycolysis. What is the source of the energy that is
extracted?
3. How many ATP are required for the preparatory
phase, and how many ATP are harvested in the payoff phase of glycolysis?
4. What is the net yield of ATP and NADH
molecules from the glycolysis on one molecule of glucose?
5. What is the glucose molecule split into at
the end of glycolysis?
Experiment 1.
Fermentation by Yeast
CAUTION: Do not overheat your yeast as you dissolve
it. To be safe, keep the temperature
just lukewarm, or below 37C. Higher
temperatures will kill the yeast cells.
NOTE: If you do
not observe significant differences in gas heights in your respirometer tubes
after two hours, let the fermentations continue for another hour.
Results:
Table 1: Gas Production from Yeast Fermentation
Tube
Initial
Gas Height (mm)
Final
Gas Height (mm)
Net
Change (mm)
1
(1%
glucose)
7 mm
8.5
mm
1.5
mm
2
(1%
sucrose)
7 mm
9 mm
2 mm
3
(1%
Equal)
5 mm
5 mm
0 mm
4
(1%
Splenda)
4 mm
4 mm
0 mm
5
(1%
sugar)
5 mm
6 mm
1 mm
Experiment 1 Questions
1. If you
have evidence of anaerobic respiration, identify the gas that was produced.
Suggest two methods for positively identifying this gas.
2. Which
of your respirometers showed the largest amount of fermentation? Provide a plausible explanation for these
results.
3. Which
of your respirometers showed the least amount of fermentation? Provide a plausible explanation for these
results.
4.
Hypothesize why some of the sweetener solutions were not metabolized by
the yeast, while others were. Research
the formulation of Equal and Spenda to explain how it would affect yeast
respiration. Theobromine is an enzyme which the body cannot process. But
people ingest it all the time because it is found in chocolate. But the body
cannot process it, so it comes out in your urine. The chemical formula effects
of Equal™for respiration was not metabolized because it’s missing sugar. Splenda™is derived from sugar so
the respiration results were different.
5. How do
the results of this experiment relate to the role yeast plays in baking? The
experiment shows a relation between yeast and size in materials. This is what
makes bread so light and fluffy after it has been baked. The yeast makes it
rise separating the dough and when it’s baked it comes out fluffy.
6. What
would you expect to see if the yeasts’metabolism was slowed
down? How could you slow down the yeasts’metabolism to check this
out? If you slow down the yeast’s metabolism you would have slow or non-rising bread. This can and
is accomplished by using the one thing that is sure to slow down all organic
reactions, cold temperatures. Such as storage in a refrigerator.
7. Indicate plausible sources of error in your
experimental results and suggest some strategies for improvement. There was
limited activity in the time frame and heat sources I used. I used a portable
heater but there wasn’t much activity after just one hour. Also, the tubes that I worked
with weren’t
made to fit exactly into each other so this may have affected the levels
measured. 1. In some cases the human body cannot digest the substance in
question. If a child swallows a button, for example, it will just pass through
the body and come out with the feces.
BACKGROUND
INFORMATION: AEROBIC RESPIRATION
Here are some ways
in which aerobic respiration is similar to the processes found in
photosynthesis, and some ways in which it differs.
SIMILARITIES
1. Both take place in an organelle (mitochondria for
respiration vs chloroplast for photosynthesis).
2. ATP is produced as a consequence of an electron
transport system in an internal membrane system.
3. Electron transport in an internal membrane system
powers pumps in the membranes which set up a concentration gradient of
hydrogen ions (H+) that in turn powers ATP productions by ATP
Synthase enzymes.
DIFFERENCES
1. Oxygen is the terminal electron transport acceptor in
mitochondria, generating water, while water is split into oxygen and hydrogen
ions in chloroplasts to supply the electron transport system with electrons.
2. NADP is the terminal electron transport acceptor in
chloroplasts, generating NADPH, while NADH is the source of high-energy
electrons for the electrons transport system in mitochondria.
3. Chemical energy (from glucose) is harvested in
mitochondria for ATP production, while solar energy powers ATP production in
chloroplasts.
Aerobic
Respiration Background Questions
1. Go to: http://www.sumanasinc.com/webcontent/animations/content/cellularrespiration.html
to watch the“Krebs Cycle”animation on cellular
respiration, and answer the questions below.
a. What are the
carbon compounds that begin the Krebs cycle?
b. How many carbon
atoms does Acetyl-CoA contribute to the Krebs cycle? What becomes of the carbon atoms during the
oxidation reactions of the Krebs cycle?
c. As the carbon atoms
become oxidized, what becomes of the freed hydrogen atoms?
d. How do NADH and
FADH2 molecules transfer their energy to ATP molecules?
e. Sports training
results in the increase of mitochondria in muscle tissue. Why is the increase in mitochondria of
benefit?
2. Go to: http://www.sumanasinc.com/webcontent/animations/content/cellularrespiration.html
to watch the“Electron Transport”
animation on cellular respiration, and answer the
questions below.
a. Where in mitochondria does the electron
transport chain occur?
b. What are the
electron donors for the electron transport chain? Where does this released energy end up?
c. Where in the
process of electron transport is oxygen required? What happens if oxygen is not available?
d. What powers the
proton pump in the inner membrane of mitochondria? What is purpose of this c oncentration gradient?
e. Which of the 3
stages of aerobic respiration results in the highest yield of ATP?
Experiment 2.
In this experiment,
you will observe the metabolism of sugars aerobically (with oxygen) which
includes the action of mitochondria.
Carbon dioxide is by-product of aerobic cellular respiration, the final
breakdown product of glucose molecules.
In the process, ATP harvests the energy:
C6H12O6 + 6 O2 6 CO2 + 6 H2O + enough energy to make 38 ATP
The CO2 generated will acidify water, causing the pH to
drop, as measured by a pH indicator such as Phenol Red or Bromothomol
Blue. Notice how this overall chemical
reaction is very similar to that of photosynthesis which we studied in the last
lab–except the reaction is in opposite direction! In photosynthesis, we observed the rise of pH
as carbonic acid was consumed by photosynthesis, and in this lab, we observe
the drop in pH as carbonic acid is generated by cellular respiration.
Pay attention to the
controls in this experiment, and what variables they eliminate in any
conclusions that you might draw. Having
one beaker with no beans eliminates the variable of the air itself. Any effect
from the air will be present in all three beakers. Having one beaker with dry
beans eliminates the variable of the bean itself affecting the results. The
controls are necessary to show that it is respiration, and no other variable,
that is affecting the results. Without
ruling out these factors, you might draw the wrong conclusions from your
experimental results.
Results:
Table 2:
Bromothymol Blue Color Change Over Time for Pinto Bean Experiment
Time
Beaker with Pre-Soaked
Beans
Beaker with Un-Soaked, Dry
Beans
Beaker with No Beans
0 min
Blue
Blue
Blue
30 min
Light Green
Blue
Blue
60 min
Green
Blue
Blue
90 min
Dark Green
Blue
Blue
120 min
Green
Dark Green
Blue
150 min
Light Green
Dark Green
Blue
180 min
Light Yellow
Green
Blue
24 hours
Yellow
Green
Blue
Table 3:
Bromothymol Blue Color Change Over Time for Kidney Bean Experiment
Time
Beaker with Pre-Soaked
Beans
Beaker with Un-Soaked, Dry
Beans
Beaker with No Beans
0 min
Blue
Blue
Blue
30 min
Green
Blue
Blue
60 min
Green
Blue
Blue
90 min
Yellowish Green
Blue
Blue
120 min
Green
Light Green
Blue
150 min
Green
Light Green
Blue
180 min
Yellow
Green
Blue
24 hours
Dark Yellow
Dark Green
Blue
Experiment 2 Questions
1. What
are the controls in this experiment, and what factors did they rule out? Why is it important to have a control for
this experiment? The control in this experiment is the beaker of Bromothymol
by itself. This is because it has no variables, beans in other words, in it.
This proves that it is the beans themselves that is doing any changes to the
fluids in the beakers. It is important to have a control because you cannot
tell difference if the CO2 gas is released.
2. What
is the chemistry that causes the bromothymol blue solution color change? Bromothymol
blue solution is an indicator that changes color in the presence of a weak acid
or base. So the mechanism would be the release of carbon dioxide into water
which turns into a weak acid. Therefore the cellular respiration is the
mechanism that is ultimately driving
the color change.
3. What
evidence do you have to prove cellular respiration occurred in beans? Explain
your reasoning. Cellular respiration had to occur in the beans because the
bromothymol changed color. This
proves that the beans had to release either
CO2, which would make a weak acidic
compound or blue when it is in a basic
solution.
4. Were
there differences in the rates of respiration in pinto beans vs. kidney beans?
If so, why?
I know that during germination, the kidney beans need more space as they are
producing more oxygen vs the pinto beans which can be placed closer together.
5. If
this experiment were conducted at 0°C,
what difference would you see in the rate of respiration? Why? The rate
would be much slower at 0C because cold temperatures inhibit both the release
of gas and most metabolic and cellular functions in organic substances. This
means that the color change and release of CO2 would be much slower at room
temperature.
6. What
effect would extremely high temperature (e.g.,greater than 55°C) have on respiration in beans? Design an
experiment to test your hypothesis, complete with controls.
7. What
would you predict your results to look like if you added cyanide to the
environment of germinating beans.
8. Would
you expect to find CO2in your breath? Why? Carbon Dioxide is the results of cellular
respiration and is carried to the lungs to be exchanged with oxygen, there for
it is expelled during respiration and is found when youexhale.
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