2026-05-12 18:35

Status: #new

Tags: #biology #plants

Nutrient Transport

Types of Nutrient Transport

Diffusion

• Molecules move from an area of high concentration to an area of low concentration
• Requires no energy
• In small molecules, diffusion may occur across membranes

Osmosis

• Movement of water across a semi-permeable membrane
  • This is due to the polar nature of Phospholipids
• Does not require energy
• Membranes are considered semi-permeable since they allow some particles to pass through while inhibiting others.
• Cellular membranes are all semi-permeable

Biological Structures

Cell Membrane

• The protein structure allows specific non-lipid-soluble to enter through amino acid chains.

Beakers

• Water moves to make the concentrations of both sides the same. Comes into equilibrium to balance the ratio of solute to solvent.

Selectively Permeable Membrane

• The outside of a semi-permeable membrane is polar
• The inside of a semi-permeable membrane is non-polar
• Large molecules cannot squeeze through a phospholipid bilayer, while gases or small molecules can
  • Sucrose for example is too large and polar to do so
• Protein molecules can help transport specific molecules across the membrane
  • ie. Some can act as tunnels or pores
  • Some proteins change their shape to move molecules across the membrane

Xylem and Phloem Transport

Phloem Transport

• Transportation in the phloem requires living cells and enzymes, hence demanding energy
• Sucrose is continually moved along the vascular structures, as long as sucrose is convected to starch storage cells.

Translocation Processes

• This is the process off sucrose transport.
• Glucose is made in leaves through photosynthesis
• It is then convert to sucrose to be transported in the phloem
• Sucrose is then converted into long term energy storage in the roots.
• Glucose creates a higher concentration
  • When glucose turns into sucrose it lowers the concentration (sucrose molecules)

Xylem Transport (not a form of active transportation)

• Water needs to move up the plant
• Two methods: Root Pressure and Transpirational Pull
  • **Root Pressure:
    • Root cells actively move water into the plant to push water up the xylem.
    • Water also sticks to the sides of vessels to help it climb the plant (this shape is known as a meniscus)
  • **Transpirational Pull:
    • While water moves up the xylem, it pulls up additional water molecules (due to strong H-bonds)

Diagram Analysis

• Molecules are always moving $\to$ When there is a difference in concentration, there is more movement in one direction than another
• Solution types with respect to a cell:
  • Hypertonic: Solution has higher concentration than in the cell
  • Hypotonic: Solution has a lower concentration than in the cell
  • Isotonic: Solution has same concentration as the cell

Animal and Plant Solutions states

• Animal
  • Hypotonic $\to$ Lysed
  • Isotonic $\to$ Normal
  • Hypertonic $\to$ Shrivelled
• Plant
  • Hypotonic $\to$ Turgid (normal)
  • Isotonic $\to$ Flaccid
  • Hypertonic $\to$ Shrivelled (Plasmolyzed)

References

4.3 Plant Organs