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Photosynthesis

边玩边学

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课程笔记

What is Photosynthesis?

  • Photosynthesis is a chemical reaction that produces glucose (a type of sugar).
  • Glucose is used for respiration, where cells release energy.
  • Plants use sunlight to turn carbon dioxide and water into glucose and oxygen.
  • Word equation: carbon dioxide + water → glucose + oxygen.

Where Does Photosynthesis Happen?

  • Photosynthesis occurs in chloroplasts, which contain the green pigment chlorophyll.
  • Chloroplasts are an organelle found mainly in leaf palisade cells.
  • Palisade cells are near the top of a leaf to get the most light.
  • Leaves are adapted with a large surface area for photosynthesis.

How Does Carbon Dioxide Enter the Leaf?

  • Carbon dioxide enters the underside of a leaf through stomata.
  • The spongy mesophyll layer has loosely arranged cells with air spaces.
  • Air spaces allow carbon dioxide to diffuse through the leaf to palisade cells.

Factors Affecting the Rate of Photosynthesis

  • The rate is affected by light intensity, carbon dioxide concentration, temperature, and water availability.
  • An experiment can measure the rate using pondweed in water.
  • Cover pondweed with an inverted funnel and place a water-filled test tube over it to capture oxygen.
  • Count oxygen bubbles released in one minute to estimate the rate.
  • Adjust variables like light intensity or temperature to observe effects.

Internal structure of a leaf showing palisade and spongy mesophyll, stomata, and air spaces.

Leaf structure (cross-section)Upper epidermisNucleusPalisade mesophyllVacuoleSpongy mesophyllLower epidermisWaxy cuticleChloroplastsAir spaceGuard cellStoma

Chloroplast structure: envelope, stroma, grana, thylakoids, lamellae, and starch grain.

Chloroplast structureGranumLamellaOuter membraneInner membraneStarch grainStromaThylakoid

幻灯片

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练习题

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  1. 1.Photosynthesis is a chemical reaction that produces which type of sugar?

    Easy
    • AGlucose
    • BSucrose
    • CFructose
    • DStarch
  2. 2.Which of the following statements about photosynthesis is true?

    Easy
    • APhotosynthesis occurs in mitochondria.
    • BPhotosynthesis produces carbon dioxide and water.
    • CPhotosynthesis is a chemical reaction that produces glucose.
    • DPlants do not carry out respiration.
  3. 3.Where does photosynthesis occur in plant cells?

    Easy
    Chloroplast structureGranumLamellaOuter membraneInner membraneStarch grainStromaThylakoid
    • ANucleus
    • BChloroplast
    • CMitochondrion
    • DVacuole
  4. 4.What are the products of photosynthesis?

    Easy
    • AGlucose and oxygen
    • BCarbon dioxide and water
    • CGlucose and carbon dioxide
    • DOxygen and water
  5. 5.Which leaf cells contain the most chloroplasts and are located near the top of the leaf?

    Easy
    Leaf structure (cross-section)Upper epidermisNucleusPalisade mesophyllVacuoleSpongy mesophyllLower epidermisWaxy cuticleChloroplastsAir spaceGuard cellStoma
    • ASpongy mesophyll cells
    • BPalisade cells
    • CGuard cells
    • DEpidermal cells
  6. 6.What is the function of the air spaces in the spongy mesophyll layer?

    Medium
    • AThey allow carbon dioxide to diffuse through the leaf to the palisade cells.
    • BThey store water for the leaf.
    • CThey provide structural support to the leaf.
    • DThey absorb light for photosynthesis.
  7. 7.In an experiment using pondweed to measure the rate of photosynthesis, what is collected to estimate the rate?

    Easy
    • ACarbon dioxide bubbles
    • BOxygen bubbles
    • CGlucose produced
    • DChlorophyll released
  8. 8.Which of the following is NOT a factor that affects the rate of photosynthesis according to the source?

    Medium
    • ALight intensity
    • BCarbon dioxide concentration
    • CSoil pH
    • DTemperature

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