Podcast
Questions and Answers
Which of these options are correct? (Select all that apply)
Which of these options are correct? (Select all that apply)
What is the main product of photosynthesis?
What is the main product of photosynthesis?
Glucose
Which of the following accurately describes the process of paper chromatography?
Which of the following accurately describes the process of paper chromatography?
The green filter in the experiment would allow red and blue light to pass through the leaf.
The green filter in the experiment would allow red and blue light to pass through the leaf.
Signup and view all the answers
The leaves covered with the black construction paper would have no starch present because they didn't receive any light.
The leaves covered with the black construction paper would have no starch present because they didn't receive any light.
Signup and view all the answers
The leaves with the blue filter would have no starch present because they didn't receive any blue light.
The leaves with the blue filter would have no starch present because they didn't receive any blue light.
Signup and view all the answers
What is the function of anthocyanins in plants?
What is the function of anthocyanins in plants?
Signup and view all the answers
Why are most plants green?
Why are most plants green?
Signup and view all the answers
The ______ test is used to detect the presence of starch in plant tissue.
The ______ test is used to detect the presence of starch in plant tissue.
Signup and view all the answers
What is the function of the 'front' in paper chromatography?
What is the function of the 'front' in paper chromatography?
Signup and view all the answers
The most polar compound will travel farther up the paper in chromatography.
The most polar compound will travel farther up the paper in chromatography.
Signup and view all the answers
Which of these is NOT a component of the electromagnetic spectrum?
Which of these is NOT a component of the electromagnetic spectrum?
Signup and view all the answers
What is the purpose of the spectrophotometer in this lab?
What is the purpose of the spectrophotometer in this lab?
Signup and view all the answers
What does the iodine solution do to the leaf in the experiment?
What does the iodine solution do to the leaf in the experiment?
Signup and view all the answers
Study Notes
Lab 11: Photosynthesis
- The lab focuses on the process of photosynthesis
- Understand photosynthetic activity via various light wavelengths
- Understand the role of pigments in photosynthesis
- Grasp how polarity separates molecules
Goals of this Lab
- Separate pigments using paper chromatography
- Evaluate photosynthetic activity using a starch test
- Create an absorption spectrum for various photosynthetic pigments
Roadmap of Today's Activities
- 6.3: Separation of Pigments: Use chromatography paper to separate pigments, one paper per student
- 6.1: Wavelengths of Light for Photosynthesis: Observe photosynthesis in a leaf with varying light filters
- 6.2: Pigments of Photosynthesis: Observe photosynthesis in leaves with various colors
- 6.4: Absorption Spectrum of Leaf Pigments: Utilize spectrophotometry to identify wavelengths best absorbed by pigments
Lab Safety
- Wear gloves, use forceps when handling flammable materials (leaves, chromatography paper)
- Never place beakers with ethanol directly on heat plates; nest them within a larger beaker with water
- Avoid inhaling solvents, close containers quickly to minimize inhalation hazards
- Report any spills immediately and do not attempt to clean up yourself
- Dispose of chemical waste in provided glass containers
Photosynthesis
- Plants absorb sunlight to produce glucose, starch, and other organic molecules
- Equation: 6H₂O + 6CO₂ → 6O₂ + C₆H₁₂O₆ + H₂O
- Occurs in three stages:
- Capturing energy from sunlight
- Producing ATP and NADPH using captured energy
- Converting CO₂ into carbohydrates using ATP and NADPH
Pigments
- Molecules that absorb light energy
- Main pigments in plants: chlorophyll a and b
- Chlorophyll absorbs light at the ends of the visible spectrum (mainly blue and red light) but reflects green light
- Photosynthesis pigments are bound to proteins within chloroplast thylakoid membranes
6.3: Paper Chromatography
- Technique to separate components within a mixture
- Stationary phase: paper (polar)
- Mobile phase: solvent (less polar)
- Mixture applied to paper, solvent moves, carrying components based on interactions
- Different components interact with paper/solvent differently, causing diverse movement speeds
Polarity
- Polar molecules adhere to paper (stationary phase)
- Less polar molecules dissolve in the solvent (mobile phase)
- More polar components move slower, staying near application site
- Non-polar components travel further up the paper with the solvent
- Estimate polarity by counting oxygen groups in a molecule's structure
Estimating Polarity
- Determine number of polar oxygen groups in pigments
- Hypothesize the behavior of pigments in paper chromatography experiments
- Predict which pigment will be most/least polar
6.1: Separation of Substances by Paper Chromatography
- Objective: Separate leaf pigments via polarity
- Mark a line 1.5 cm from the edge of the chromatography paper
- Apply leaf extract to the line using a capillary pipette, letting the paper dry between applications
- Roll the paper into a cylinder, securing with a paperclip
- Place the paper within the solvent (solvent below the line)
- Let the solvent ascend, stopping the process when the solvent front reaches 3 cm from the top
- The most non-polar substance will dissolve and move first in the solvent. The most polar substance will stay close to the paper and move last.
6.1 Results
- The most non-polar pigment will dissolve in the non-polar solvent first
- The most polar pigment will be attracted to the polar paper and move last
6.1 Wavelengths of Light used in Photosynthesis
- Certain wavelengths of light reach the leaf via filters
- Visible light contains all wavelengths, but only certain wavelengths will be absorbed (or reflected) by the leaf
- Non-absorbed light wavelengths pass through the leaf
6.1 Predictions
- Leaves with various filters will have differing levels of starch present, implying various amounts of photosynthesis
- Leaves under green light will have no starch present because the green light is predominantly transmitted (not absorbed)
- Leaves under blue light will likely have some starch because blue light is absorbed, impacting photosynthesis
6.1 Procedure
- Remove leaves, ensuring you note the location of filters/construction paper
- Remove filters/paper/clips
- Place leaves in ethanol, immerse in boiling water
- After color loss, place leaves in water in a petri dish
- Add iodine until solution turns amber; leave for 5 minutes
Procedure and Predictions
- Predict which wavelengths of light will be transmitted or absorbed by leaves
- Observe the experimental results, noting various starch levels in leaves based on the used light filters
- Collect experimental data in a tabular format (e.g., table 1)
6.2: Coleus Leaves (Demo)
- Coleus leaves contain multiple visible pigments
- Green areas contain chlorophyll
- Pink areas contain anthocyanins
- Dark-purple regions contain both chlorophyll and anthocyanins
- White/light-yellow regions feature no pigments
6.2: What are the Pigments Used in Photosynthesis?
- Detach a multicolored Coleus leaf
- Map the colors' outlines
- Place the leaf in a beaker with 80% ethanol and boiling water
- Note the color loss; remove and rest the leaf in a petri dish of water
- Add I2KI until the water turns amber, leaving the leaf in the solution for 5 minutes
- Observe and record starch presence on the leaf, comparing regions with their predicted starch presence
Predictions and Results: What are the Pigments used in Photosynthesis?
- This table compares predicted and actual starch presence in various leaf regions of a Coleus leaf, correlating with specific pigments. (Table 2)
Iodine Test for Starch
- Results support the hypothesis, suggesting photosynthesis only occurs where chloroplasts are present
- Excess glucose is stored as starch for plant use
- Chlorophyll-containing regions in the leaf should exhibit starch production
- Regions containing only anthocyanins should exhibit no starch
6.4: Absorption Spectrum of Various Leaf Pigments
- Cut pigment bands from paper chromatography
- Place pigment bands in a beaker with ethanol
- Label two cuvettes: one for pigment ("P"), the other as blank ("B")
- Fill cuvettes with appropriate solution
- Set the spectrophotometer's wavelength to 400 nm
- Record the absorbance readings for samples from 400 nm to 720 nm, with 20-nm increments, and for each pigment
Predictions and Results: Absorption Spectrum
- Summarizes predicted and observed wavelengths of the peak absorbance for the different pigments and their respective wavelengths. (see page 25)
Results: Absorption Spectrum
- Graphical data illustrating the absorbance spectrum of chlorophylls a and b, carotene, and xanthophyll. Displays how each pigment absorbs light at distinct wavelengths.
Lab Report
- Write a lab report in two drafts (first draft due November 7th).
- Include information regarding hypotheses, predictions, tables, and diagrams (see Table 1 and 2)
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Related Documents
Description
This lab explores the process of photosynthesis, emphasizing the role of light wavelengths and pigments. Students will use paper chromatography to separate pigments and evaluate photosynthetic activity through starch testing. Activities include observing light's effects on leaves and creating an absorption spectrum for pigments.
