Transport Mechanisms in Cells

Diffusion in Unicellular Organisms

• Unicellular organisms, being small, rely on diffusion for the movement of substances into and out of the cell.
• Diffusion is sufficient because the distance substances need to travel is short.

Transport Systems in Multicellular Organisms

• Multicellular organisms require transport systems to efficiently move substances throughout their bodies.
• Diffusion over long distances is too slow and inefficient.

Phloem Transport

• Phloem transports sucrose and amino acids between the leaves (where they are made) and other parts of the plant (where they are needed).
• Phloem transports these materials through translocation.

Xylem Transport

• Xylem transports water and mineral ions from the roots to the rest of the plant.
• This upward movement is called the transpiration stream.

Water Absorption by Root Hair Cells

• Root hair cells increase the surface area for water absorption from the soil.
• Water moves into the root hair cells by osmosis.

Transpiration

• Transpiration is the evaporation of water from a plant's surface, primarily from leaves.
• This process drives the movement of water and minerals up the plant.

Factors Affecting Transpiration Rate

• Humidity: High humidity slows transpiration due to less of a difference between the air and leaf surface moisture.
• Wind speed: Higher wind speed increases transpiration as it removes water vapor from around the leaf.
• Temperature: Higher temperatures increase transpiration due to faster evaporation rates.
• Light intensity: Higher light intensity usually increases transpiration as plants undergo photosynthesis, opening stomata more.

Environmental Factors and Transpiration Rate Investigations

• Environmental factors (humidity, wind, temperature, light) influence the rate of transpiration from a leafy shoot.
• Investigations can measure changes in these variables to determine transpiration rates.

Explore the essential transport mechanisms in both unicellular and multicellular organisms. Understand how diffusion suffices for unicellular organisms while transport systems are necessary for multicellular life. Dive into the specifics of phloem and xylem transport in plants, and examine root hair cells and their role in water absorption.