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GCSEBiologyEdexcelFlashcards6. Plant Structures & their FunctionsPhotosynthesis

Photosynthesis (Edexcel GCSE Biology)

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  • FrontLimiting Factors

    Define the term limiting factor in the context of photosynthesis.

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  • Define the term limiting factor in the context of photosynthesis.

    A limiting factor is a factor that limits the rate of photosynthesis.

  • What are the three factors that limit the rate of photosynthesis?

    The three limiting factors for photosynthesis are:

    • temperature

    • light intensity

    • carbon dioxide concentration

  • Why does the rate of photosynthesis slow down at low temperatures?

    Photosynthesis occurs slowly at low temperatures because molecules (such as enzymes involved in photosynthesis) have little kinetic energy. This means that fewer successful collisions take place.

  • Why do very high temperatures cause photosynthesis to stop?

    At very high temperatures the enzymes that control photosynthesis denature, meaning that the reaction can no longer take place.

  • What is the effect of increasing light intensity on the rate of photosynthesis?

    The higher the light intensity, the faster the rate of photosynthesis.

    This continues until another factor becomes limiting. (Higher Tier Only)

  • True or False?

    In a graph of light intensity against the rate of photosynthesis, the part of the graph where the line is horizontal could indicate a point at which temperature is the limiting factor. (Higher Tier Only)

    True.

    In a graph of light intensity against rate of photosynthesis, the part of the graph where the line is horizontal is a point at which a factor other than light intensityis limiting. This factor could be temperature or carbon dioxide concentration .

  • True or False?

    The rate of photosynthesis increases consistently as temperature increases. (Higher Tier Only)

    False.

    The rate of photosynthesis only increases with temperature up to a certain point, after which higher temperatures lead to a decrease in the rate of photosynthesis. This is because high temperatures denature enzymes involved in the reactions of photosynthesis.

  • What is happening at point B on the graph? (Higher Tier Only)

    Graph showing the rate of photosynthesis in arbitrary units vs. carbon dioxide concentration (ppm) under bright light at 20°C. Photosynthesis rate increases and levels off.

    At point B the graph has levelled off, indicating that a factor other than carbon dioxide concentration is limiting, e.g. temperature or light intensity.

    Graph showing the rate of photosynthesis in arbitrary units vs. carbon dioxide concentration (ppm) under bright light at 20°C. Photosynthesis rate increases and levels off.

  • True or False?

    The rate of photosynthesis is inversely proportional to light intensity. (Higher Tier Only)

    False.

    The rate of photosynthesis is directly proportional to light intensity.

  • Why does bubble production decrease as distance between the light source and the aquatic plant increases in the graph shown? (Higher Tier Only)

    Line graph showing the number of bubbles per minute decreasing as the distance between pondweed and light in cm increases.

    The number of bubbles produced decreases as the light moves further away from the pondweed because the rate of photosynthesis is inversely proportional to the distance from a light source.

    Light intensity decreases with distance; this means that rate of photosynthesis decreases and so less oxygen is produced.

  • What is the name of the law represented by the equation below? (Higher Tier Only)

    l i g h t italic space i n t e n s i t y italic proportional to fraction numerator italic 1 over denominator d i s t a n c e to the power of italic 2 end fraction

    The equation l i g h t space i n t e n s i t y space proportional to fraction numerator italic 1 over denominator d i s t a n c e italic space to the power of italic 2 end fraction represents the inverse square law.

  • True or False?

    Doubling the distance between the lamp and a plant will result in a quarter of the light intensity. (Higher Tier Only)

    True.

    Doubling the distance will result in a light intensity that is a quarter of what it was previously. This is due to the inverse square law, e.g.

    At a distance of 10 cm = l i g h t italic space i n t e n s i t y italic proportional to italic 1 over 10 to the power of italic 2 italic equals italic 0 italic. italic 01

    At a distance of 20 cm = l i g h t italic space i n t e n s i t y italic proportional to italic 1 over 20 to the power of italic 2 italic equals italic 0 italic. italic 0025

    0.01 x 1/4 = 0.0025

  • What investigation can be carried out using the practical equipment below?

    Diagram of a photosynthesis experiment setup with a lamp illuminating a plant in a water-filled container, a plunger, a thermometer, and a ruler for measurement.

    The equipment shown in the image can be used to investigate the effect of light intensity on the rate of photosynthesis.

    Diagram of a photosynthesis experiment setup with a lamp, ruler, water container, submerged plant in a test tube, thermometer, and plunger apparatus.

  • What information is required to measure the rate of photosynthesis using the equipment below?

    Diagram of a photosynthesis experiment setup with a lamp illuminating a plant in a water-filled container, a plunger, a thermometer, and a ruler for measurement.

    To measure the rate of photosynthesis we need to know the volume of gas collected and time period during which it has been collected.

  • What would the independent variable be in the investigation shown?

    Diagram of a photosynthesis experiment setup with a lamp illuminating a plant in a water-filled container, a plunger, a thermometer, and a ruler for measurement.

    The independent variable is light intensity, which is controlled by altering the distance between the lamp and the beaker.

    Diagram of a photosynthesis experiment setup with a lamp, ruler, water container, submerged plant in a test tube, thermometer, and plunger apparatus.

  • What would the dependent variable be in the investigation shown?

    Diagram of a photosynthesis experiment setup with a lamp illuminating a plant in a water-filled container, a plunger, a thermometer, and a ruler for measurement.

    The dependent variable in this investigation is the rate of photosynthesis, which is measured by recording the volume of oxygen produced within a set time period.

    Diagram of a photosynthesis experiment setup with a lamp, ruler, water container, submerged plant in a test tube, thermometer, and plunger apparatus.

  • Give two control variables for the investigation shown.

    Diagram of a photosynthesis experiment setup with a lamp illuminating a plant in a water-filled container, a plunger, a thermometer, and a ruler for measurement.

    Control variables for this investigation would include:

    • maintaining the same environmental temperature

    • using the same species, length and age of plant in each repeat

    • dissolving sodium hydrogen carbonate (NaHCO3) in the water to maintain carbon dioxide levels

    Diagram of a photosynthesis experiment setup with a lamp, ruler, water container, submerged plant in a test tube, thermometer, and plunger apparatus.
Previous:Development of MedicinesNext:Plant Structure

    1. Topic 1

      Cell Structure

    2. Topic 2

      Enzymes

    3. Topic 3

      Movement of Substances Into & Out of Cells

    1. Topic 1

      Cell Division

    2. Topic 2

      Growth in Organisms

    3. Topic 3

      Stem Cells

    4. Topic 4

      Co-ordination & Response

    1. Topic 1

      Reproduction

    2. Topic 2

      Inheritance

    1. Topic 1

      Natural Selection & Evolution

    2. Topic 2

      Genetic Modification

    1. Topic 1

      Disease

    2. Topic 2

      Defence Against Disease

    3. Topic 3

      Development of Medicines

    1. Topic 1

      Photosynthesis

    2. Topic 2

      Plant Structure

    3. Topic 3

      Transport in Plants

    4. Topic 4

      Plant Hormones

    1. Topic 1

      Animal Hormones

    2. Topic 2

      Homeostasis

    1. Topic 1

      Transport in Animals

    2. Topic 2

      Respiration

    3. Topic 3

      Gas Exchange

    4. Topic 4

      Circulatory System

    1. Topic 1

      The Organism in the Environment

    2. Topic 2

      Feeding Relationships

    3. Topic 3

      Cycles within Ecosystems

    4. Topic 4

      Human Influences on the Environment

    5. Topic 5

      Food Production