Name: Studying Photosynthesis by Leaf Disc Experiment-Concept
Uploaded: 2019-01-29T11:04:45.000Z
Duration: 4 min 45 s
Channel: JoVE

K12 Standards

north-carolina-k-12-science-standard-course-of-study

North Carolina K-12 Science Standard Course of Study

9-12

Biology

from-molecules-to-organisms-structures-and-processes

From Molecules to Organisms- Structures and Processes

LS.Bio.3.2

Photosynthesis

lab manual sub articles

Lab Manual Sub Articles

<p>Have you ever wondered why every autumn leaves on trees change from green to shades of yellow, orange, and red? What gives leaves their bright colors in the first place? The answer lies in the plant organelles called chloroplasts which contain pigments that absorb certain wavelengths in sunlight and reflect others. One particular pigment, chlorophyll, is the most abundant in summer. It absorbs high-energy, purple, blue, and red wavelengths from sunlight, and reflects green wavelengths giving leaves their green appearance. There are other pigments in leaves, such as carotenoids, which reflect red and yellow light. In autumn the leaves stop replenishing their pigments. Since chlorophyll degrades faster than the other pigments, the colors of these carotenoids are unmasked.</p><p>The presence of different pigments in a green leaf can be demonstrated with chromatography paper, a hydrophilic polymer that separates molecules based on their solubility in a particular solvent. First, leaf extract is loaded onto the paper. When the paper is dipped into an organic hydrophobic solvent, the solvent travels along the paper due to capillary action and along the way it separates different pigments in the leaf extract. The pigments that are the most hydrophobic are carried further up the paper. Whereas hydrophilic pigments bind to cellulose which hinders their movement. After all of the pigments are sorted by their hydrophobicity, we can calculate the retention factor or Rf values. The Rf value is the ratio of the distance traveled by a pigment to the distance traveled by the solvent. Each pigment has a unique Rf value and we can easily identify pigments by comparing calculated values to standards. Photosynthesis, the process by which plants convert carbon dioxide, water and light energy into chemical energy and oxygen, is carried out primarily in the leaves of a plant, and chlorophyll plays a critical role in this process. Chloroplasts contain dozens of chlorophyll molecules, each performing a specific task and interacting in complex ways. Ultimately, light energy causes chlorophyll molecules to give up electrons which are utilized in other metabolic processes. Therefore, chlorophyll needs a continuous supply of electrons to replace the ones it loses. These replacement electrons come from splitting water molecules into protons, electrons and oxygen molecules. At high rates of photosynthesis water is split faster to replenish electrons and oxygen is generated rapidly.</p><p>This phenomenon helps us to assess the rate of photosynthesis in the lab by simply suspending leaf discs in a bicarbonate solution where bicarbonate acts as a rich source of carbon. At the beginning of the leaf disk experiment the gases are forced out of the leaf discs by applying negative pressure with a vacuum in a syringe. The leaf discs with their gases expelled become heavier and sink to the bottom of the bicarbonate solution when transferred to a beaker. When photosynthesis takes place water in the environment is split in order to replenish chlorophyll electrons. The resulting oxygen makes the discs lighter causing them to float to the surface over time. Environments that allow for higher rates of photosynthesis have discs that float faster.</p><p>In this lab you will first separate and identify pigments in spinach leaves using chromatography paper. Then you will assess the rate of photosynthesis in water and in bicarbonate solution with a leaf disk experiment.</p>

photosynthesis

<h4>Autotrophs</h4>

<p>Almost all living organisms on Earth depend on photosynthesis, which is the process that converts sunlight energy into a simple sugar called glucose. This molecule can be used as a short-term energy source or to build more complex carbohydrates like starches for long-term energy storage. Autotrophs are organisms that capture light energy using photosynthesis. Also known as primary producers, they provide the energy necessary to the organisms that eat them, which are known as consumers.</p>

<p>Organisms that can photosynthesize are rather diverse, including cyanobacteria, some protists such as algae, as well as plants. In eukaryotic cells, photosynthesis takes place in an organelle called the chloroplast, which appear green due to its high content of the pigment chlorophyll. Pigments are molecules that absorb light at certain wavelengths. The light that is not absorbed by a pigment is reflected as visible light that can be observed as the color of the pigment. Plants produce multiple pigments with various functions that absorb light from the sun at different wavelengths. For example, chlorophyll absorbs light at red and blue wavelengths while it reflects wavelengths that correspond to green. Some other pigments such as carotenoids, anthocyanins, and betalains commonly reflect light at low-energy wavelengths between 600 and 800 nm, and thus appear yellow to red.  In temperate regions, the decrease in chlorophyll in autumn reveals these pigments when leaves change color to reds, yellows, and oranges.</p>

<h4>Chloroplasts</h4>

<p>Chlorophyll is the primary pigment in chloroplasts used in photosynthesis, whereas other pigments help channeling light energy to chlorophylls or protect the cell against light damage. Photosynthesis consists of two pathways, which are known as the light-dependent and light-independent reactions and occur at distinct locations within chloroplasts. These organelles contain three membranes: an outer membrane, an inner membrane, and the innermost thylakoid membrane, which forms long, disc-shaped folds within the chloroplast. The fluid-filled space between the inner and thylakoid membranes is called the stroma. The light-dependent reactions start when the energy in sunlight excites the electrons of chlorophyll pigments that are embedded within the thylakoid membrane. These high-energy electrons are then passed from one electron carrier molecule to another within the thylakoid membrane, collectively known as the electron transport chain. Each transfer within the electron transport chain takes the electron to a lower energy state, therefore releasing energy. Some of this energy is harnessed to synthesize small, energy-rich molecules such as Adenosine triphosphate (ATP) and nicotinamide adenine dinucleotide phosphate (NADPH). The lost electron of the chlorophyll is replaced through hydrolysis (which means water splitting), when hydrogen and oxygen atoms are separated. Hydrogen atoms generated by hydrolysis donate their electrons to the chlorophyll whereas the oxygen molecules are released into the atmosphere. Stream of electrons through hydrolysis enables chlorophyll pigments to continuously absorb the light energy by repeatedly exciting new electrons and pass them down the electron transport chain.</p>

<p>The light-independent reactions take place in the stroma. This process uses the light energy indirectly by utilizing the energy from ATP and NADPH molecules generated by the light-dependent reactions. During this pathway, carbon dioxide (CO<sub>2</sub>) is used to build a three-carbon sugar, which then can be turned into glucose or other biomolecules. This process is also known as carbon fixation or carbon sequestration, because the carbon is sequestered from the atmosphere and fixed into biomolecules.</p>

<h4>Photosynthesis and the Environment</h4>

<p>Carbon sequestration during photosynthesis is an important step of the carbon cycle, in which CO<sub>2</sub> flows from one reservoir to another at a relatively constant pace. Changes in the CO<sub>2</sub> flow rate can shift the balance of it among reservoirs. More importantly, since CO<sub>2 </sub>is a greenhouse gas, increases in its atmospheric concentration contributes to rising temperatures. Most of this CO<sub>2</sub> is emitted by burning fossil fuels, thus returning the carbon dioxide that was sequestered by photosynthesis hundreds of millions of years ago to the atmosphere at an unprecedented rate. Therefore, forests and ocean algae are evermore imperative in cooling the earth by reducing the increased CO<sub>2 </sub>levels<sup>1</sup>. This is one of many reasons why deforestation is a serious concern in a changing climate.</p>

<p>Much like how plants use photosynthesis to capture light energy into biomolecules, researchers are investigating artificial photosynthesis to create carbon neutral biofuels as an alternative to fossil fuels. Similar to solar panels, artificial photosynthesis methods obtain energy from the sun, and store it as chemical energy, some of which can be stored for long periods of time, instead of converting it directly to electricity<sup>2</sup>. Scientists have also been able to produce simple sugars and lactic acid using photosynthetic bacteria<sup>3</sup>. This approach has wide applications in manufacturing biomolecules, biofuels, and even biodegradable plastics with little to no harmful emissions. In addition, this approach may be used to remove excess CO<sub>2</sub> from the atmosphere. A similar concept is being applied in the medical field, where photosynthetic bacteria are being used to produce physiologically active substances and medications, some of which have been applied to cancer diagnosis and treatment<sup>4</sup>. Future research may increase the efficiency of producing sustainable and carbon neutral molecules while remediating the effects of increased atmospheric CO<sub>2</sub> levels.</p>

<h4>References</h4>

<ol class="references">
	<li><strong>Bonan, GB.</strong> Forests and Climate Change: Forcings, Feedbacks, and the Climate Benefits of Forests. <em>Science. </em>2008, Vol. 320, 5882 (1444-9).</li>
	<li><strong>Liu, C, et al.</strong> Water splitting&#8211;biosynthetic system with CO2 reduction efficiencies exceeding photosynthesis. <em>Science. </em>2016, Vol. 352, 6290 (1210-1213).</li>
	<li><strong>Niederholtmeyer, H, et al.</strong> Engineering Cyanobacteria To Synthesize and Export Hydrophilic Products. <em>Appl Env Microbio. </em>2010, Vol. 76, 11 (3462-66).</li>
	<li><strong>Sasaki, K, et al.</strong> Applications of photosynthetic bacteria for medical fields. <em>J Biosci Bioeng. </em>2005, Vol. 100, 5 (481-8).</li>
</ol>


Studying Photosynthesis by Leaf Disc Experiment-Concept

Autotrophs

Almost all living organisms on Earth depend on photosynthesis, which is the process that converts sunlight energy into a simple sugar called ...

Education

JoVE Lab Manual

Cellular Processes

Photosynthesis: Light, Sugars, and Carbon

Photosynthesis turns sunlight into chemical energy in the form of glucose. This process powers most life on Earth by helping autotrophs, or primary producers, make food. The glucose they make can provide quick energy or be stored as starch for later use. Consumers depend on these producers for energy.<br /><br />Photosynthesis happens in many kinds of organisms. Cyanobacteria, some protists such as algae, and plants can all carry out this process. In eukaryotic cells, it takes place in the chloroplast.

cellular respiration

Cellular Energy From Glucose Breakdown

Cellular respiration is the process cells use to release usable energy from biomolecules such as sugars and lipids. Living things need a steady energy supply for growth, repair, movement, defense, and reproduction. Cells use that energy mainly by converting adenosine diphosphate (ADP) to adenosine triphosphate (ATP).<br /><br />Autotrophs and heterotrophs get the molecules for respiration in different ways. Autotrophs, such as plants, algae, and photosynthetic and chemosynthetic bacteria, build...

cell division

Cell Cycle, Mitosis, and Meiosis

Cell division is essential for growth, repair, and reproduction in living organisms. It lets single-celled organisms create a new organism and helps multicellular organisms make new cells for development and for replacing damaged cells. In multicellular species, cell division also makes reproductive cells needed for reproduction.<br /><br />Before a cell divides, it must copy its genetic material and split it into two daughter cells. This process is called the cell cycle. Although the timing can vary...

transpiration

Water Movement in Plants

Water movement in plants depends on transpiration and the vascular system. Plants must move water and dissolved nutrients from the roots to the leaves. They also exchange materials with the environment as part of normal life processes.<br /><br />Vascular plants use bundles of tissues that run from the roots to the tips of the plant. Root hairs absorb water and nutrients, and osmosis moves water into the xylem, the main water-conducting tissue. Water then travels to the tallest parts of the plant and...

enzyme activity

Factors That Shape Enzyme Function

Enzymes are biological catalysts that help living things run biochemical reactions faster. They lower activation energy, which is the energy needed to start a reaction. Enzymes are not used up in the process, so they can keep working again and again. Most enzymes are proteins, although some ribonucleic acid molecules also have catalytic activity.<br /><br />Each enzyme usually binds only one or a few specific substrates. This selectivity depends on the enzyme’s active site, which fits its substrate like...

cellular processes

Learn how photosynthesis converts sunlight into glucose, how chloroplasts use pigments and ATP/NADPH, and why carbon fixation matters for climate.

Photosynthesis: Light, Sugars, and Carbon | JoVE K12

Pennsylvania State Academic Standards

Life Science

matter-and-energy-in-organisms-and-ecosystems

Matter and Energy in Organisms and Ecosystems

3.1.9-12.E

3.1.9-12.J

3.1.9-12.K

Louisiana Student Standards for Science

High School

Life Sciences

From Molecules To Organisms: Structures And Processes

HS-LS1-5

Environmental Science

ecosystems-interactions-energy-and-dynamics

Ecosystems: Interactions, Energy And Dynamics

HS-LS2-4

ohios-learning-standards-and-model-curriculum

Ohio’s Learning Standards and Model Curriculum

Cells

Cellular processes

Virginia  Standards of Learning

HIgh School

BIO.2

BIO.2.e

Minnesota Academic Standards in Science

3.1.1 9L.3.1.1.2

3.2.1 9L.3.2.1.3

new-jersey-student-learning-standards-for-science

New Jersey Student Learning Standards for Science

From Molecules to Organisms: Structures and Processes

Ecosystems: Interactions, Energy, and Dynamics

HS-LS2-5

Arizona Science Standards

HS.L2

HS.L2U1.21

HS+B.L2

HS+B.L2U1.8

Next Generation Science Standards

Florida Department of Education

SC.912.L.18

SC.912.L.18.7

SC.912.L.18.9

south-carolina-college-and-career-ready-science-standards

South Carolina College and Career Ready Science Standards

B-LS1-5

new-york-state-science-learning-standards

New York State Science Learning Standards

HS-LS1-5.

Georgia Standards of Excellence

Botany

SBO1.

Prepare spinach leaves, chromatography paper, bicarbonate solution, and leaf discs for a high school photosynthesis lab on pigments and floating discs.

Leaf Pigment Prep for Chromatography Labs | JoVE K12

Separate spinach pigments by chromatography, calculate Rf values, and use floating leaf discs to compare photosynthesis in light, dark, bicarbonate, and water.

Spinach Pigments and Leaf Disc Photosynthesis | JoVE K12

<ul><li><a href="#" data-time="8">Plant Pigment Chromatography
</a></li><li><a href="#" data-time="165">Floating Leaf Discs in a Vacuum
</a></li><li><a href="#" data-time="381">Results
</a></li></ul>

<ol class="note-items"><li data-note-item="1" data-parent-collapse="">Plant Pigment Chromatography
<button class="expand">Expand</button><ul class="lab-items"><li data-sub-note-item="1-1"><div class="lab-step">NOTE: In this experiment you will separate pigments from spinach leaves using chromatography paper. Individual pigments travel along the paper at different rates and may have different colors. By calculating the relative distance the pigments travel, their resolution factor, and comparing them with literature values, you can identify different pigments.  HYPOTHESES: In this exercise the experimental hypothesis is that there will be multiple pigments within the spinach leaves that absorb different wavelengths of sunlight. The null hypothesis is that there is only one type of pigment within the spinach leaf.
</div></li><li data-sub-note-item="1-2"><div class="lab-step">Use a pencil to make a line two centimeters from one end of the chromatography paper.
</div></li><li data-sub-note-item="1-3"><div class="lab-step">Then, lay a pipe cleaner horizontally across the top of a clean 400 mL beaker.
</div></li><li data-sub-note-item="1-4"><div class="lab-step">Place the pencil-marked side of the chromatography strip at the bottom of the beaker.
</div></li><li data-sub-note-item="1-5"><div class="lab-step">Next, wrap the paper around the pipe cleaner so that the bottom edge is barely touching the bottom of the beaker and then secure it with a paperclip.
</div></li><li data-sub-note-item="1-6"><div class="lab-step">When the paper is secured around the pipe cleaner, remove it from the beaker, and then place a patted-dry spinach leaf over the marked line on the chromatography paper.
</div></li><li data-sub-note-item="1-7"><div class="lab-step">Roll a coin over the spinach leaf along the pencil line going back and forth multiple times and applying steady pressure. When the leaf is removed, a green line should be clearly present.
</div></li><li data-sub-note-item="1-8"><div class="lab-step">Next, place 8 mL of chromatography solvent in the beaker.
</div></li><li data-sub-note-item="1-9"><div class="lab-step">Lower the chromatography strip into the beaker so that the edge of the paper touches the solvent but the green line does not. Adjust the pipe cleaner if needed.
</div></li><li data-sub-note-item="1-10"><div class="lab-step">Without disturbing the beaker, observe the solvent as it moves up the paper and the individual pigments separate.
</div></li><li data-sub-note-item="1-11"><div class="lab-step">When the solvent has traveled half way up the chromatography paper, which will take approximately 10 minutes, and the pigments have separated into well-defined bands, remove the paper from the beaker.
</div></li><li data-sub-note-item="1-12"><div class="lab-step">Mark how far the solvent traveled with a pencil and then allow the paper to dry. NOTE: The solvent evaporates quickly.
</div></li><li data-sub-note-item="1-13"><div class="lab-step">Next, record the number of visible bands and describe their color and relative size.
</div></li><li data-sub-note-item="1-14"><div class="lab-step">Measure how far the solvent and pigments traveled, and record this information for each pigment in Table 1.  <a href="https://www.jove.com/CDNSource/lm/labs/7/Table_1_Photosynthesis.xlsx" style="display:block;margin:20px;" target="__blank">Click Here to download Table 1</a>
</div></li><li data-sub-note-item="1-15"><div class="lab-step">Dispose of the chromatography solvent in a waste container under a fume hood. Throw the chromatography strips into the regular trash, and then clean the beakers with soap and water.
</div></li></ul></li><li data-note-item="2" data-parent-collapse="">Floating Leaf Discs in a Vacuum
<button class="expand">Expand</button><ul class="lab-items"><li data-sub-note-item="2-1"><div class="lab-step">NOTE: In this experiment you will indirectly observe photosynthesis and cellular respiration using a floating leaf disc in a solution. During photosynthesis, air bubbles will cause the leaves to float, and during respiration, the discs will sink. HYPOTHESES: In this exercise, the experimental hypothesis is that the leaf discs will have a greater rate of photosynthesis in the bicarbonate solution, because bicarbonate provides added CO<sub>2</sub> to fuel photosynthesis, causing more leaf discs to float. Additionally, all of the discs will sink in dark conditions as they perform cellular respiration. The null hypothesis is that there will be no difference in the rate of photosynthesis, and therefore the number of floating discs, between the bicarbonate and water, or light and dark treatments.
</div></li><li data-sub-note-item="2-2"><div class="lab-step">To place leaf discs under vacuum, first remove the plungers from two 20 mL syringes, and then place 10 leaf discs inside each syringe tube. Label one syringe &#8220;bicarbonate&#8221;, and label the other syringe &#8220;water&#8221;.
</div></li><li data-sub-note-item="2-3"><div class="lab-step">Replace the plungers and push the plunger until only a small amount of air remains in the syringe. Take care not to damage the leaf discs.
</div></li><li data-sub-note-item="2-4"><div class="lab-step">Pull 5 mL of the bicarbonate solution into one of the syringes. Invert and swirl the syringe to suspend the leaf discs in solution.
</div></li><li data-sub-note-item="2-5"><div class="lab-step">Push as much air out as possible without expelling the solution or damaging the leaf discs.
</div></li><li data-sub-note-item="2-6"><div class="lab-step">Then pull 5 mL of the water solution into the other syringe and swirl it as previously described (step 3).
</div></li><li data-sub-note-item="2-7"><div class="lab-step">To create a vacuum, hold one finger over the tip of the syringe while pulling back on the plunger. Hold this for 10 seconds while swirling the syringe to keep the leaf discs in suspension.
</div></li><li data-sub-note-item="2-8"><div class="lab-step">Then, release the vacuum.  NOTE: The discs should have absorbed the solution into the air spaces in their tissues and you should see them sink. If the discs don&#39;t sink, you can repeat the vacuum creation up to three times.
</div></li><li data-sub-note-item="2-9"><div class="lab-step">Next, add 50 mL of bicarbonate solution to a plastic cup or a glass beaker, and then gently add the discs from the bicarbonate vacuum syringe.
</div></li><li data-sub-note-item="2-10"><div class="lab-step">For the control, add the same amount of water to an identical cup, and then add the leaf discs from the water vacuum syringe. Label the containers appropriately.
</div></li><li data-sub-note-item="2-11"><div class="lab-step">Place both cups under a light source.
</div></li><li data-sub-note-item="2-12"><div class="lab-step">Every five minutes record the number of discs floating on the surface of the cup in Table 3 until 20 minutes have passed.  <a href="https://www.jove.com/CDNSource/lm/labs/7/Table_3_Photosynthesis.xlsx" style="display:block;margin:20px;" target="__blank">Click Here to download Table 3</a>
</div></li><li data-sub-note-item="2-13"><div class="lab-step">Next, remove the cups from the light source and then swirl them so that the discs at the surface intermix with any gases also at the surface.
</div></li><li data-sub-note-item="2-14"><div class="lab-step">Move the cups to a dark place. Every five minutes record the number of leaf discs floating at the surface until 20 minutes have passed. Swirl the cup each time before placing it back in the dark.
</div></li><li data-sub-note-item="2-15"><div class="lab-step">To clean up, dispose of the leaf discs in the trash, and pour the bicarbonate solution down the drain. Wash the syringes and cups thoroughly.
</div></li></ul></li><li data-note-item="3" data-parent-collapse="">Results
<button class="expand">Expand</button><ul class="lab-items"><li data-sub-note-item="3-1"><div class="lab-step">NOTE: In the first experiment, you observed how far pigments from spinach leaves traveled on chromatography paper. Different pigments absorb light at different wavelengths.
</div></li><li data-sub-note-item="3-2"><div class="lab-step">Using colored pens or pencils, draw the positions of the pigment bands and the solvent on Figure 3.
</div></li><li data-sub-note-item="3-3"><div class="lab-step">Calculate the retention factor, or Rf values for the pigments, which is done by dividing the distance the pigment in question moved up the paper from the line by the distance the solvent moved up the paper from the line.
</div></li><li data-sub-note-item="3-4"><div class="lab-step">Compare your calculated Rf values to those in Table 2 to determine the identity of the pigment. <a href="https://www.jove.com/CDNSource/lm/labs/7/Table_2_Photosynthesis.xlsx" style="display:block;margin:20px;" target="__blank">Click Here to download Table 2</a>
</div></li><li data-sub-note-item="3-5"><div class="lab-step">Record these data in Table 1. NOTE: In the second experiment, you observed floating and sinking leaf discs as an indirect measurement of photosynthesis and respiration.
</div></li><li data-sub-note-item="3-6"><div class="lab-step">Graph the results with time and minutes on the x-axis and number of floating discs on the y-axis. Use two different lines to represent the water control and the bicarbonate treatment.
</div></li><li data-sub-note-item="3-7"><div class="lab-step">Add a line to the graph to indicate the point where the discs were removed from the light condition and placed into the dark.
</div></li><li data-sub-note-item="3-8"><div class="lab-step">Next, starting with the bicarbonate condition, use the graph to determine the point at which 50% of the leaf discs were floating. This is referred to as the effective time, or ET50.  NOTE: You will notice that the discs likely hit the 50% floating mark once in the light condition and then again in the dark condition.
</div></li><li data-sub-note-item="3-9"><div class="lab-step">Your water samples may or may not have reached the ET50 mark. If they did, add the line for this sample also.
</div></li><li data-sub-note-item="3-10"><div class="lab-step">Finally, compare your ET50 values and graphs with the rest of the class.
</div></li></ul></li></ol>

Studying Photosynthesis by Leaf Disc Experiment-Procedure

Plant Pigment Chromatography
ExpandNOTE: In this experiment you will separate pigments from spinach leaves using chromatography paper. Individual pigments ...

<p>In this experiment you will separate pigments from spinach leaves using chromatography paper. Individual pigments travel along the chromatography paper at different rates and may have different colors. By calculating the relative distance the pigments travel, their resolution factor, and comparing them with literature values you can identify different pigments.</p><p>In this exercise the experimental hypothesis is that there will be multiple pigments within the spinach leaves that absorb different wavelengths of sunlight. The null hypothesis is that there is only one type of pigment within the spinach leaf. Use a pencil to make a line two centimeters from one end of the chromatography paper.</p><p>Then lay a pipe cleaner horizontally across the top of a clean 400-milliliter beaker. Place the pencil marked side of the chromatography strip at the bottom of the beaker. Next, wrap the paper around the pipe cleaner so that the bottom edge is barely touching the bottom of the beaker and then secure it with a paperclip.</p><p>When the paper is secured around the pipe cleaner remove it from the beaker and then place a patted dry spinach leaf over the marked line on the chromatography paper. Roll a coin over the spinach leaf along the pencil line going back and forth multiple times and applying steady pressure. When the leaf is removed a green line should be clearly present.</p><p>Next, place eight milliliters of chromatography solvent in the beaker. Lower the chromatography strip into the beaker so that the edge of the paper touches the solvent, but the green line does not. Adjust the pipe cleaner if needed.</p><p>Observe as the solvent moves up the paper and the individual pigments separate, but don't disturb the beaker. When the solvent has traveled halfway up the chromatography paper, which will take approximately 10 minutes, and the pigments have separated into well-defined bands, remove the paper from the beaker. Mark how far the solvent traveled with a pencil and then allow the paper to dry.</p><p>Next, record the number of visible bands and describe their color and relative size. Measure how far the solvent and pigments traveled and record this information for each pigment in table one. Dispose of the chromatography solvent in a waste container under a fume hood.</p><p>Throw the chromatography strips into the regular trash and then clean the beakers with soap and water. In this experiment you will indirectly observe photosynthesis and cellular respiration using a floating leaf disk in a solution. During photosynthesis air bubbles will cause the leaves to float.</p><p>And during respiration the discs will sink. In this exercise the experimental hypothesis is that the leaf discs will have a greater rate of photosynthesis in the bicarbonate solution because bicarbonate provides added CO2 to fuel photosynthesis causing more leaf discs to float. Additionally, all of the discs will sink in dark conditions as they perform cellular respiration.</p><p>The null hypothesis is that there will be no difference in the rate of photosynthesis and therefore the number of floating discs between the bicarbonate and water, or light and dark treatments. To begin, you will place the leaf discs under vacuum using a syringe. This ensures that the liquid from the bicarbonate and water test solutions fully permeates the air spaces in the leaf tissue.</p><p>To do this, first remove the plungers from two 20-milliliter syringes and then place 10 leaf discs inside each syringe tube. Label one syringe bicarbonate and label the other syringe water. Replace the plungers and push the plunger until only a small amount of air remains in the syringe, taking care not to damage the leaf discs.</p><p>Pull five milliliters of the bicarbonate solution into one of the syringes. Invert and swirl the syringe to suspend the leaf discs in solution. Push as much air out as possible without expelling the solution or damaging the leaf discs.</p><p>Then pull five milliliters of the water solution into the other syringe and swirl it in the same manner. To create a vacuum hold one finger over the tip of the syringe while pulling back on the plunger. Hold this for 10 seconds while also swirling the syringe to keep the leaf discs in suspension.</p><p>Now release the vacuum. The discs should've absorbed the solution into the air spaces in their tissues and you should see them sink. If the discs don't sink, you can repeat the vacuum creation up to three times.</p><p>Next add 50 milliliters of bicarbonate solution to a plastic cup or glass beaker. And then gently add the discs from the bicarbonate vacuum syringe. For the control, add the same amount of water to an identical cup and then add the leaf discs from the water vacuum syringe.</p><p>Label the containers appropriately. Place both cups under a light source. Every five minutes record the number of discs floating on the surface of the cup in table three until 20 minutes have passed.</p><p>Next, remove the cups from the light source and then swirl them so that the discs at the surface intermix with any gases also at the surface. Move the cups to a dark place. Every five minutes record the number of leaf discs floating at the surface until 20 minutes have passed.</p><p>Swirl the cup each time before placing it back in the dark. To clean up, dispose of the leaf discs in the trash and pour the bicarbonate solution down the drain. Wash the syringes and cups thoroughly.</p><p>In the first experiment you observed how far pigments from spinach leaves traveled on chromatography paper. Different pigments absorb light at different wavelengths. We will now try to identify what these pigments are.</p><p>Using colored pens or pencils draw the positions of the pigment bands and the solvent on figure three. Calculate the retention factor or RF values for the pigments which is done by dividing the distance the pigment in question moved up the paper from the line by the distance the solvent moved up the paper from the line. Compare your calculated RF values to those in table two to determine the identity of the pigment and then record this in table one.</p><p>In experiment B you observed floating and sinking leaf discs as an indirect measurement of photosynthesis and respiration. Graph the results with time and minutes on the x-axis and number of floating discs on the y-axis. Use two different lines to represent the water control and the bicarbonate treatment.</p><p>Add a line to the graph to indicate the point where the discs were removed from the light condition and placed into the dark. Next, starting with the bicarbonate condition, use the graph to determine the point at which 50%of the leaf discs were floating. This is referred to as the effective time or ET 50.</p><p>You will notice that the discs likely hit the 50%floating mark once in the light condition and then again in the dark condition. Your water samples may or may not have reached the ET 50 mark. If they did, add the line for this sample also.</p><p>Finally, compare your ET 50 values and graphs with the rest of the class. Do you see similar patterns?</p>

<ul><li><a href="#" data-time="4">Plant Pigment Chromatography and Floating Leaf Discs in a Vacuum
</a></li></ul>

<ol class="note-items"><li data-note-item="1" data-parent-collapse="">Plant Pigment Chromatography and Floating Leaf Discs in a Vacuum
<button class="expand">Expand</button><ul class="lab-items"><li data-sub-note-item="1-1"><div class="lab-step">On the day before the experiment, fill a container with water.
</div></li><li data-sub-note-item="1-2"><div class="lab-step">Place the spinach leaves into the water and make sure they are submerged.
</div></li><li data-sub-note-item="1-3"><div class="lab-step">Leave the spinach leaves to soak overnight at room temperature.
</div></li><li data-sub-note-item="1-4"><div class="lab-step">Wearing gloves, prepare and measure out 18 cm x 304 cm sections of chromatography paper.
</div></li><li data-sub-note-item="1-5"><div class="lab-step">Prepare a bicarbonate solution for the second experiment by combining 0.25 g NaHCO3 with 300 mL water. Add one squirt of dish soap to the solution and mix gently.
</div></li><li data-sub-note-item="1-6"><div class="lab-step">If the solution is still sudsy, add more bicarbonate.
</div></li><li data-sub-note-item="1-7"><div class="lab-step">For the control solution, combine 300 mL water with one squirt of dish soap. Mix gently and try to avoid suds.
</div></li><li data-sub-note-item="1-8"><div class="lab-step">Just before the experiment is due to begin, select a few spinach leaves of similar smoothness and thickness without too many large veins.
</div></li><li data-sub-note-item="1-9"><div class="lab-step">Use a hole punch to create 20 uniform discs from the leaves for each student or group.
</div></li></ul></li></ol>

<div class="section-question"><h4 class="question-sect">What is photosynthesis?</h4><p>Photosynthesis is the conversion of sunlight into usable and storable energy. Autotrophs (such as plants) use carbon dioxide, water, and energy harnessed from sunlight to generate glucose and oxygen through photosynthesis, thus providing a major energy source in the food web.
</p></div><div class="section-question"><h4 class="question-sect">How do plants harness energy from the sun?</h4><p>Plants produce pigments, such as chlorophyll that allow them to absorb energy from sunlight. For example, light energy excites the electrons of the pigment molecule. This energy is later harnessed and converted into chemical bonds of simple sugars.
</p></div><div class="section-question"><h4 class="question-sect">What part of the plant cell is responsible for photosynthesis?</h4><p>The chloroplast&#8212; which contains pigments in its innermost membrane layer known as thylakoids&#8212;is primarily responsible for carrying out photosynthesis.
</p></div><div class="section-question"><h4 class="question-sect">What is carbon sequestration?</h4><p>During photosynthesis, carbon dioxide is used to generate simple sugars. This carbon dioxide is sequestered or removed from the atmosphere, therefore this process is known as carbon sequestration.
</p></div><div class="section-question"><h4 class="question-sect">How does photosynthesis influence the climate?</h4><p>Plants get carbon from CO2, a greenhouse gas and contributor to global warming. During photosynthesis, plants remove CO2 from the atmosphere, which has a cooling effect on the earth.
</p></div>

Studying Photosynthesis by Leaf Disc Experiment-Prep

Plant Pigment Chromatography and Floating Leaf Discs in a Vacuum
ExpandOn the day before the experiment, fill a container with water.
Place the spinach ...

<p>On the day before the experiment you should prepare the spinach leaves by first filling a container with water, then place the spinach leaves into the water and make sure they are all submerged. Leave them to soak overnight at room temperature. Next, wearing gloves, prepare and measure out 18 centimeters by three to four centimeters sections of chromatography paper.</p><p>For the second experiment prepare the bicarbonate solution by combining 0.25 grams of sodium bicarbonate with 300 milliliters of water. Add one squirt of dish soap to the solution and mix gently. If the solution is still sudsy add a little more bicarbonate solution.</p><p>For the control combine 300 milliliters of water with one squirt of dish soap. Mix it gently and try to avoid suds. Finally just before the experiment is due to begin select a few spinach leaves of similar smoothness and thickness without too many large veins.</p><p>Use a hole punch to create 20 uniform disks from the leaves for each student or group. Please take time to review the material list and the student protocol video to be fully prepped for the lab</p>

Compounds Essential to Human Function

The human body is composed of cells that are fundamentally made up of several different molecules. These molecules are essential to carry out all ...

Macromolecules

Biomolecules
Organisms contain a wide variety of organic molecules with numerous functions which depend on the chemical structures and properties of these ...

Solution Preparation
ExpandCAUTION: It is important to always use care when handling reagents. For example, iodine will stain clothes and skin so wear ...

Identifying Macromolecules with Indicator Solutions
ExpandHYPOTHESES: In this activity, the experimental hypothesis might be that the addition of an ...

pH Regulation in Cells

pH plays a critical role in maintaining normal cellular activities. It helps maintain the structure and function of various proteins, dictates the charge ...

Chemistry of the Cell

Overview of Functional Groups

Functional groups are a group of atoms with characteristic properties, which when linked to the carbon skeleton of a molecule, alter the properties of ...

Introduction to Carbohydrates

Carbohydrates, proteins, and fats are the primary macronutrients in the human diet. However, carbohydrates are the most favored source of energy in the ...

Carbohydrate Metabolism

Sugars as Energy Storage Molecules

What are Lipids?

lipid-derived-compounds-in-the-human-body

Lipid-derived Compounds in the Human Body

Fats and lipids are crucial components in the human body. Some lipid-derived compounds, such as fat-soluble vitamins, eicosanoids, lipoproteins, and ...

Fats as Energy Storage Molecules

What are Proteins?

Protein Organization

Globular Proteins

In organisms, proteins are the most abundant macromolecules. They act as the building blocks of life and play various crucial roles in the body. Proteins ...

Fibrous Proteins

Fibrous proteins are either long and narrow proteins or assemble to form long and thin structures. They contain repetitive units and usually consist of ...

Protein Denaturation

The function of proteins depends on their native three-dimensional structure, which is dictated by the amino acid sequence of the specific protein. ...

Role of Proteins in the Human Body

Proteins are the building block of life. They are also&#160; the most abundant macromolecules with as many diverse roles in the body. They are part of ...

Nucleic Acids and Nucleotides

Nucleic acids are the most important macromolecules for the continuity of life. They carry the cell&#39;s genetic blueprint and have instructions for its ...

Nucleic Acid Structure

The pentose sugar in DNA is deoxyribose, while in RNA the pentose sugar is ribose. The difference between the sugars is the presence of the hydroxyl group ...

ATP Energy Storage and Release

ATP and Macromolecule Synthesis

Biological macromolecules are organic compounds, predominantly composed of carbon atoms. The carbon atoms are covalently bonded with hydrogen, oxygen, ...

Construct an explanation to illustrate relationships between structure and function of major macromolecules essential for life.

LS.Bio.1.1

Introduction to Enzymes

The use of enzymes by humans dates to 7000 BCE. Humans first used enzymes to ferment sugars and produce alcohol without knowing that this was an ...

Enzymes and Activation Energy

The activation energy (or free energy of activation), abbreviated as Ea, is the small amount of energy input necessary for all chemical reactions to ...

Introduction to Enzyme Kinetics

Enzyme kinetics studies the rates of biochemical reactions. Scientists monitor the reaction rates for a particular enzymatic reaction at various substrate ...

Turnover Number and Catalytic Efficiency

The turnover number of an enzyme is the maximum number of substrate molecules it can transform per unit time. Turnover numbers for most enzymes range from ...

Catalytically Perfect Enzymes

The theory of catalytically perfect enzymes was first proposed by W.J. Albery and J. R. Knowles in 1976. These enzymes catalyze biochemical reactions at ...

introduction-to-mechanisms-of-enzyme-catalysis

Introduction to Mechanisms of Enzyme Catalysis

For many years, scientists thought that enzyme-substrate binding took place in a simple &#34;lock-and-key&#34; fashion. This model stated that the enzyme ...

Ligand Binding and Linkage

Cooperative Allosteric Transitions

Ribozymes

Carry out investigations to illustrate how enzymes act as catalysts for biochemical reactions and how environmental factors affect enzyme activity.

LS.Bio.1.2

What are Cells?

Cells are the smallest and basic units of life, whether it is a single cell that forms the entire organism, e.g., in a bacterium or trillions of them, ...

Cell Size

Cell sizes vary widely among and within organisms. Bacterial cells range between 1-10 micrometers (&#x3BC;m)and are considerably smaller than most ...

Eukaryotic Compartmentalization

One of the distinguishing features of eukaryotic cells is that they contain membrane-bound organelles, such as the nucleus and mitochondria, that carry ...

Prokaryotic Cells

Prokaryotes are small unicellular organisms that include the domains&#x2014;Archaea and Bacteria. Bacteria include many common organisms, such as ...

Cytoplasm

The cytoplasm consists of organelles and a framework of protein scaffolds called the cytoskeleton suspended in an aqueous solution, the cytosol. The ...

The Nucleus

The nucleus is a membrane-bound organelle that acts as a control center in a eukaryotic cell. It contains chromosomal DNA, which controls gene expression ...

Endoplasmic Reticulum

Endoplasmic ReticulumThe endoplasmic reticulum (ER) is an extensive network of membranous sacs and tubules in eukaryotic cells, continuous with the outer ...

Ribosomes

Ribosomes translate genetic information encoded by messenger RNA (mRNA) into proteins. Both prokaryotic and eukaryotic cells have ribosomes. Cells that ...

Golgi Apparatus

As they leave the Endoplasmic Reticulum (ER), properly folded and assembled proteins are selectively packaged into vesicles. These vesicles are ...

Lysosomes

Lysosomes are membrane-enclosed spherical sacs derived from the Golgi apparatus. The most important function of the lysosome is degrading macromolecules ...

Peroxisomes

Peroxisomes and mitochondria are two important oxygen-utilizing organelles in eukaryotic cells. Mitochondria carry out cellular respiration&#x2014;the ...

Introduction to the Cytoskeleton

Overview of the Cytoskeleton
The cytoskeleton is a network of protein filaments present within the cell, having three distinct filaments ...

Introduction to Actin

Actin is a highly conserved cytoskeletal protein found abundantly in eukaryotic cells. It constitutes 10% weight of the total cellular protein in muscle ...

Cell Structure

Background
Cells represent the most basic biological units of all organisms, whether it be simple, single-celled organisms like bacteria, or large, ...

overview-of-myosin-structure-and-function

Overview of Myosin Structure and Function

Myosins are a family of molecular motor proteins, first identified in the skeletal muscles, where they are responsible for muscle contraction. Along with ...

Visualizing Onion and Cheek Cells
ExpandImmediately before the experiment, wash and peel onion bulbs for the class.
Remove the entire brown outer skin and ...

Microtubules

Microtubules are the thickest cytoskeletal filaments with a diameter of 25 nm. In prokaryotic organisms, microtubules are commonly found in locomotory ...

The Structure of Intermediate Filaments

The intermediate filaments are one of three widely studied cytoskeletal filaments. They are so named as their diameter (10 nm) is in between that of ...

Types of Intermediate Filaments

The intermediate filaments are an essential component of the cytoskeleton. Presently six types of intermediate filament have been identified. Type I and ...

Gap Junctions

Multicellular organisms employ a variety of ways for cells to communicate with each other. Gap junctions are specialized proteins that form pores between ...

Use models to explain how the structure of organelles determines its function and supports overall cell processes.

LS.Bio.1.3

Analyze how the relationship between structure and function supports life processes within organisms.

Photosynthesis

Description

Autotrophs

Transcript

Tags

More videos by Standards