Plant Cell Structure and Function Quiz

Plant Cell Structure and Function

• Cell Hierarchy: Molecules → organelles → cells → tissues → organs → organ systems → organisms

• Unicellular vs. Multicellular Organisms:

  • Unicellular organisms are composed of a single cell, but are not simple.
  • Multicellular organisms have specialized cells for different functions, allowing for advantages like division of labor, larger size with better transport, and interdependence of cells. However, problems with one cell can negatively affect the whole organism.

Plant Organ Systems

• Shoot System:

  • Includes leaves, stem, buds, flowers, fruit, and tubers (e.g., potatoes).
  • Specialized for photosynthesis, reproduction, food/water storage and transport.

• Root System:

  • Includes aerial roots.
  • Specialized for anchorage, water/mineral absorption, and food/water transport.
  • Both shoot and root systems are composed of dermal, ground, and vascular tissues.

Plant Tissues

• Dermal Tissue (Epidermis):

  • Outer layer, usually one cell thick, covering herbaceous plants.
  • Includes a waxy cuticle for moisture retention, disease protection, and gas exchange.
  • Root epidermis is adapted for water and nutrient uptake.
  • Shoot epidermis is adapted for gas exchange.

• Ground Tissue:

  • Makes up most of the plant.
  • Located beneath the epidermis.
  • Loosely packed allows for gas diffusion.
  • Shoot Ground tissue provides support and performs photosynthesis in leaves.
  • Root ground tissue involved in food and water storage.

• Vascular Tissue:

  • A transport system with two components: xylem and phloem. Essential for transporting materials throughout the plant.

  • Xylem:

    • Transports water and dissolved minerals from roots to leaves.
    • Primarily non-living cells.
    • As cells mature and die, they form hollow tubes to facilitate efficient water transport.

  • Phloem:

    • Transports sucrose and other sugars from leaves to other plant parts.
    • Composed of long, living sieve tube cells connected by cytoplasm.
    • Sieve tube cells rely on companion cells for direction.

Cell Development and Specialization

• Differentiation: Cells become specialized for specific tasks during development.

• Root Hairs: Tiny projections on root cells increasing surface area for water and nutrient absorption.

• Guard Cells: Specialized epidermal cells forming stomata on leaves. Essential for gas exchange and preventing water loss.

• Stomata: Tiny pores (one stoma) on leaves regulated by guard cells.

Photosynthesis

• Definition: A process in which light energy is converted into chemical energy stored in glucose molecules.
• Word Equation: Carbon dioxide + water → glucose + oxygen + energy
• Balanced Chemical Equation: 6CO₂ + 6H₂O + light → C₆H₁₂O₆ + 6O₂

Cellular Respiration

• Definition: The process by which cells break down glucose to release energy.
• Word Equation: Glucose + oxygen → carbon dioxide + water + energy
• Balanced Chemical Equation: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O

Photosynthesis and Respiration Differences

• Photosynthesis occurs in plants (during the day), converting light energy to chemical energy. Cellular respiration occurs in all cells (always), breaking down the chemical energy to provide energy for the plant's cell processes.

Leaf Structure and Function

• Mesophyll Tissue: The photosynthetic tissue in leaves, includes spongy and palisade mesophyll.
• Spongy Mesophyll: Allows for gas exchange.
• Palisade Mesophyll: Maximizes sunlight absorption.

Water Transport in Plants

• Transpiration: Water loss from plant leaves (by evaporation).

• Mechanisms for Water Transport: Cohesion, adhesion, and tension (or transpiration pull) work together to pull water against gravity.

  • Cohesion: Water molecules stick together.
  • Adhesion: Water molecules stick to other substances (e.g., xylem walls).
  • Tension (Transpiration pull): Pulling force from water evaporation from leaves.

• Root Pressure: Upward force in transport tubes due to water entering roots.

• Conditions Affecting Transpiration: Transpiration rate is temperature-dependent.

Cell Tonicity and Osmosis

• Hypotonic Solution: Water moves into the cell, causing swelling (turgidity).
• Hypertonic Solution: Water moves out of the cell, causing shrinking (plasmolysis).

Phloem Transport (Pressure Flow Theory)

• Source: Site of sugar production (leaves).
• Sink: Site of sugar storage or use.
• Mechanism: Pressure differences push sugars through phloem tissue

1. Active transport loads sugars into phloem.
2. Water moves in by osmosis.
3. Pressure builds up, forcing sugar to move toward sinks.

Plant Responses to Stimuli

• Tropism: A plant's response to a stimulus.

  • Positive tropism: Movement toward a stimulus.
  • Negative tropism: Movement away from a stimulus.

• Phototropism: Growth response to light, stems exhibit positive phototropism, roots negative phototropism.

• Gravitropism: Growth response to gravity, roots exhibit positive gravitropism, stems negative gravitropism.

• Auxin: A plant hormone that influences growth, especially involved in phototropism and other responses.

• Mechanisms that indicate direction: Starch granules in roots and shoots are thought to give plants clues regarding gravity and other environmental factors.

Test your knowledge on the structure and function of plant cells, including cell hierarchy, and the differences between unicellular and multicellular organisms. Explore various plant organ systems and their specialized functions, focusing on the shoot and root systems along with their tissue types.