Biology Chapter 8: Photosynthesis and Respiration

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Questions and Answers

What is the primary purpose of using KOH in the respirometer during the measurement of respiration rates?

KOH absorbs CO2 produced by the organisms, allowing measurement of oxygen consumption.

Explain how the Scholander respirometer setup allows for the measurement of respiration rates.

The respirometer measures the movement of a fluid in response to oxygen consumption by organisms in a sealed vial.

Describe how gas exchange principles are demonstrated in the functioning of the Scholander respirometer.

Gas exchange occurs as organisms consume O2 and release CO2, affecting pressure and fluid levels in the respirometer.

What kind of data can be collected from the Scholander respirometer and how is it analyzed?

<p>Data on the volume of oxygen consumed over time can be collected and analyzed to compare respiration rates between organisms.</p> Signup and view all the answers

How does the pressure difference in the respirometer correlate with the metabolism of the organisms being studied?

<p>A pressure difference indicates oxygen consumption; as oxygen is used, the volume decreases, resulting in fluid movement.</p> Signup and view all the answers

How can the respiration rates of organisms be determined using data collected from a Scholander respirometer?

<p>Respiration rates can be calculated by measuring the volume change of gas in the respirometer over time and converting it to moles of O2 using the relationship provided in Equation 2.</p> Signup and view all the answers

What is the significance of the relationship between volume of gas and moles of gas in respiration experiments?

<p>The relationship allows researchers to accurately convert the volume of gas exchanged during respiration into the corresponding number of moles, which is essential for understanding metabolic rates.</p> Signup and view all the answers

Describe the setup required for using a Scholander respirometer to measure respiration rates.

<p>The setup involves placing the organism in a sealed chamber connected to a syringe for measuring gas changes, with an appropriate KOH solution to absorb CO2, ensuring accurate O2 measurements.</p> Signup and view all the answers

What role does KOH play in respiration studies using a respirometer?

<p>KOH absorbs CO2 produced during respiration, allowing for an accurate measurement of the oxygen consumed by the organism.</p> Signup and view all the answers

Explain how the consumption or production of glucose relates to the moles of O2 exchanged during respiration.

<p>According to Equation 1, for every mole of glucose consumed or produced, 6 moles of O2 are involved, meaning respiration rates in terms of glucose are 1/6 that of O2 rates.</p> Signup and view all the answers

Flashcards

Cellular Respiration

The process where organisms use oxygen to break down glucose, releasing energy in the form of ATP.

Scholander Respirometer

A device used to measure the rate of respiration in organisms by measuring gas volume changes.

KOH (Potassium Hydroxide)

A chemical used to absorb CO2 gas, allowing for measurement of O2 consumption.

Respiration rate

The amount of oxygen consumed or carbon dioxide produced by an organism per unit of time.

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Manometer

A scientific instrument used to measure pressure, in this case, gas pressure differences.

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1 mL of gas

Equivalent to 4.0 x 10-5 moles of gas.

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Respiration Rate Calculation

Involves converting volume change of oxygen to moles of oxygen using the conversion factor 1.0 mL of gas = 4.0 x 10-5 moles of gas, then dividing by time and tissue weight to get moles O2/hr/g

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Moles of Glucose & Oxygen

1 mole of glucose is consumed or produced for every 6 moles O2 consumed or produced

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Study Notes

Objectives

  • Illustrate the relationship between photosynthesis and cellular respiration
  • Illustrate two different methods of measuring reaction rates
  • Investigate conditions necessary for photosynthesis in isolated chloroplasts
  • Measure respiration rates in germinating seeds and small animals

Additional Reference Material

  • Textbook chapter 8 on Photosynthesis is helpful

Introduction

  • Cells in plants and animals have complex structures
  • Maintaining this structure requires energy
  • Energy is needed for membrane repair, transport of molecules, and protein production
  • Cells are distinguishable from their surroundings due to orderly molecular structures
  • Organisms need energy and mechanisms to utilize energy for their structure and growth

Autotrophs, Heterotrophs, and Glucose

  • Autotrophs use sunlight to produce energy-rich cellular compounds
  • Heterotrophs obtain energy from compounds produced by autotrophs
  • Glucose (a sugar molecule with carbon, hydrogen, and oxygen) is important for heterotrophs
  • Photosynthesis is the light-driven synthesis of glucose and oxygen
  • Cellular respiration is the consumption of glucose and oxygen

Equation 1

  • Photosynthesis: 6CO2 + 6H2O → C6H12O6 + 6O2 (requires energy from the sun)
  • Respiration: C6H12O6 + 6O2 → 6CO2 + 6H2O (liberates energy as ATP)

Chloroplasts and Mitochondria

  • Photosynthesis occurs in chloroplasts
  • Respiration occurs in mitochondria
  • Chloroplasts have a double membrane, and internal thylakoids (grana, lamellae)
  • Mitochondria have a double membrane with folded inner membranes (cristae)
  • Chloroplast stroma contains the Calvin cycle for glucose production
  • Mitochondrial matrix contains intermediates in glycolysis
  • Electron transport chain and ATP production occur in the cristae

Measuring Reaction Rates

  • Measuring reaction rates is essential in biochemistry and cell biology
  • Techniques include monitoring the levels or concentrations of reactants or products
  • Variables that influence reaction rates must be controlled or constant
  • Examples include: measuring O2 concentration in a closed chamber (manometric) or monitoring the appearance or disappearance of a colored material (colorimetric).

Exercise 1: Examining Respiration Rates

  • Scholander respirometer measures respiration rates
  • Process measures changes in gas volume due to CO2 production/O2 consumption
  • Organisms are placed in a vial with KOH (or NaOH) to trap CO2
  • Change in fluid level indicates gas volume change

Exercise 2: Photosynthesis

  • Colorimetric method measures photosynthesis rates in isolated chloroplasts
  • The chemical indicator changes color as the substance produced by the reaction changes, showing photosynthetic activity
  • Spectrophotometer is used to quantify color changes.
  • Procedures for preparing cuvettes and handling components have been detailed

Exercise 3: Fluorescence

  • Chlorophyll absorbs light and re-emits it at a different wavelength (fluorescence)
  • Fluorescence can be a method used to study the processes of photosynthesis
  • Preparing a chloroplast suspension is essential for this procedure

Exercise 4: Observation of Cellular Organelles

  • Mitochondria: Present in liver cells as small, dark blue dots
  • They are involved in cellular respiration.
  • Chloroplasts in parenchyma cells (plant cell tissue) are visible as small green granules within the cytoplasm
  • Cytoplasmic streaming is a movement of cytoplasm and chloroplasts within cells

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