The purpose of this lab was to show that photosynthesis can occur without the carbon dioxide and sodium bicarbonate in its place

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Mir Abbas
Mr. Orlinsky
AP Biology
13 November, 2017
1. INTRODUCTION
Every living thing needs food or energy to survive, some depend on others for food and
energy, while others can produce their own food. The process by which green plants use sunlight
to synthesize foods from the CO2 and water, photosynthesis in plants occur within the green
pigment chlorophyll and generates oxygen as a byproduct. Plants which are green in color make
their own food with the help of sunlight and CO2, so photosynthesis is a chemical process in
which plants produce glucose and oxygen from CO2 and H2O using sunlight as a source of
energy, the result of photosynthesis is glucose, which is stored as chemical energy in plants. Two
processes take place when the plant prepares its food with the help of H2O, CO2 in the presence
of sunlight, they are photosynthesis and cellular respiration.
Photosynthesis and cellular respiration are connected through an important relationship,
because the products of one process are the reactants of the other. So the reaction of cellular
respiration is the direct opposite of photosynthesis.
Photosynthesis- H2O+CO2+light---> Carbohydrate+O2+H2O
Cellular Respiration- Carbohydrate+O2+H2O--->H2O+CO2
Photosynthesis makes the glucose that is used in the cellular respiration to make ATP, the
glucose is then turned back to CO2 which is used in photosynthesis, so water is broken down to
form O2 during photosynthesis, and in cellular respiration O2 is combined with H2 to form H2O,

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so in all the process that take place photosynthesis requires CO2 and releases O2 and cellular
respiration requires O2 and releases CO2, It is this released O2 which is used by humans and
animals for cellular respiration, so we breathe the oxygen which is carried through our blood to
all parts of our cells in our body.
Thus the exchange of CO2 and O2 through photosynthesis or cellular respiration helps to
keep atmospheric oxygen and CO2 at stable levels.
Leaf Anatomy
The main organ of plant for the process of photosynthesis is the leaf, the outer surface of the lead
has a thin watery covering called the cuticle, which prevents the water loss within the leaf,
underneath the cuticle is a layer of cells called epidermis, the vascular tissues, xylem and phloem
are found within the veins of the leaf. The outer layer of the vein is made of cells called bundle
sheath cells, and they create a circle around the xylem and the phloem. xylem is the upper layer
of cells and is shaded a little lighter than the lower layer of cells. Within the leaf there is a layer
of cells called the mesophyll, which actually means in greek means “middle, leaf”, the mesophyll
is divided into two layers the palisade layer and spongy layer. Palisade cells are more column-
like, and lie just under the epidermis, the spongy cells are more loosely packed and lie between
the palisade layer and the lower epidermis. The air spaces between the spongy cells allow for gas
exchange. Mesophyll cells (both palisade and spongy) are packed with chloroplasts, and this is
where photosynthesis actually occurs.Epidermis also lines the lower area of the leaf (as does the
cuticle). The leaf also has tiny holes within the epidermis called stomata. Specialized cells,
called guard cells surround the stomata and are shaped like two cupped hands. Changes within
water pressure cause the stomata to open or close. If the guard cells are full of water, they swell
up and bend away from each other which opens the stoma. During dry times, the guard cells

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close.Kale or leaf cabbage refers to certain vegetable cultivars of the plant species Brassica
oleracea. A kale plant has green or purple leaves and the central leaves do not form a head. Kales
are meant to be closer to wild cabbage than most domesticated species of Brassica oleracea.
Even Though kale seeds look like cabbage seeds in all forms, the kale vegetable can hit up to
seven feet in height but most are perfect and of good posture for eating despite their coarseness
and indigestible issues. It’s annually grown from a seed and thrives in winters, it can survive in
cold temperature as low as -16 degrees which makes it even sweeter.

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The purpose of the lab is to prove that Photosynthesis and cellular respiration are connected
through an important relationship, because the products of one process are the reactants of the
other. So the reaction of cellular respiration is the direct opposite of photosynthesis. And also
photosynthesis in alternate source of carbon dioxide as bicarbonate ions and that oxygen is
accumulated in the spongy mesophyll with the help of a light source.
To prove this process occurs in our everyday life, we performed an experiment at our
biology lab “ how the floating leaf disks technique can measure the rate of photosynthesis by
testing a variable”. This experiment was designed to show photosynthesis in action.
How it works
In our daily life we don't notice how oxygen is given out by plants so we performed an
experiment practically in the lab and found out the photosynthesis at different colors of light.
Materials
• Sodium bicarbonate (Baking soda), Hole punch, Syringe, Stopwatch, Leaf material(ivy and
kale), Plastic cups, Light source.
Procedures

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Prepare a 0.2% solution of bicarbonate.
Add 1 drop of dilute liquid soap to this
solution. The soap wets the hydrophobic surface of the leaf allowing the solution to be drawn
into the leaf. Cut 10 disks of kale leaves for each trial and make sure not to cut the veins.
Infiltrate the leaf disks with sodium bicarbonate solution. First place the leaf disks into the
syringe space, then close it and suck in the solution. After the syringe has the floating disks
inside with the solution, make a vacuum in the syringe by closing the entrance with a finger and
pulling the syringe in do that until the disks sink in the syringe. Then, flush it in the plastic cups
so that the leaf disks sink in the plastic cups. Now for the light source part we chose the red color
light, which is said to be the most productive, and placed our cups on it.
Hypothesis- Normally the leaf disks floats on water, But when the air space are replaced with
water the overall density of the leaf disk increase and the disk sinks. If a small amount sodium
bicarbonate is added, were in the bicarbonate ion serves as the carbon source of photosynthesis,
then in the presence of ight photosynthesis proceeds and oxygen is released into the interior of
leaf which changes the buoyancy- causing the disks to rise, cellular respiration is taking place at
the same time, consuming O2, the rate at which the disks rise is an indirect measurement of the
net rate of photosynthesis.
2. DATA COLLECTION AND RESULTS/ANALYSIS
These are data from an experimental investigation using Kale leaf disks on Red Light.
Experiment sets #1 to #4

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Minutes Disks set #1 Disks set #2 Disks set #3 Disks set #4
1 0 0 0 0
2 0 0 0 0
3 0 0 0 0
4 0 0 0 0
5 0 0 0 0
6 0 1 0 1
7 0 3 1 2
8 0 7 1 2
9 0 9 1 2
10 0 9 1 2
11 0 9 1 2
12 0 9 1 2
13 0 9 1 2
14 0 9 1 2
15 0 9 1 2
16 0 10 1 2
17 0 10 1 2
Graph for Experiment sets #1 to #4

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The data and graph show that disks set #2 reached the all 10 leaf disks in about 16 to 17 minutes.
The disks set #1 did not have even 1 disk floating in all 17 minutes. The disks set #3 reached to 1
disk floating in 17 minutes. Finally, the disks set #4 had reached to a 2 disks floating in 17
minutes. The photosynthesis worked in three of the experiment sets with an alternate source of
carbon dioxide in the form of bicarbonate ions, therefore oxygen was accumulated in the spongy
mesophyll and thus the leaf disks were buoyant again. The point at which 50% of the leaf disks
are floating (the median or ET50, the Estimated Time is takes 50% of the disks to float) is a
reliable and repeatable point of reference for this procedure. And that point of reference for this
procedure is at about 7.5 minutes when the disks are 50% floating, this will provide a greater
reliability and repeatability for this lab and procedure. And Steucek, et. al. (1985) described this
term is referred to as the ET50.
Here is the class average on Kale leaf with the following colors

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Color Average Standard Deviation Standard Error
Red 1.15 2.86 1.127490111
Orange 0.13 0.35 0.1237436867
Yellow 1 2.24 1.001758454
Green 1.25 3.85 1.361180554
Blue 0.14 0.38 0.1436284997
Pink 0.71 1.5 0.5669467095
White 2 2.71 1.355

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3. CONCLUSION
This experiment has proved that Photosynthesis and cellular respiration are connected through an
important relationship, because the products of one process are the reactants of the other. So the
reaction of cellular respiration is the direct opposite of photosynthesis. And also photosynthesis
in alternate source of carbon dioxide as bicarbonate ions and that oxygen is accumulated in the
spongy mesophyll with the help of a light source. And we also found the ET50 point for this
procedure, which was at about 7.5 minutes.
4. QUESTIONS
1) Which kind of light will produce the fastest rate of photosynthesis?
2) What was the role of sodium bicarbonate in the experiment?

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3) How many processes takes place at the time of photosynthesis?
4) What are the small opening on the leaf called through which the leaf breathes?
5) In which part of the leaf does most of the photosynthesis occur?
6) How does the spongy mesophyll help in the process of photosynthesis?
7) What is the balanced equation for photosynthesis?

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