botany final exam

Symplastic vs. Apoplastic Transport

Symplastic: to continuum of cytoplasm between cells that is joined by plasmodesmata

Apoplastic: the extracellular matrix of plant (cell walls and associated areas)

5 main types of active water transport Passive or Active

Diffusion: Passive

Facilitated: Passive

Osmosis: Passive

Active transport: Active

Endo- or exocytosis: Active

Diffusion

Passive transport where molecules like O2, H2O, and CO2 pass directly through lipid bilayer, moving from high concentration to low concentration

Facilitated Transport

Passive transport where transmembrane proteins are required to move polar or large molecules across the membrane, moving along a concentration gradient

Osmosis

Passive transport specifically for water. Water moves through a semi-permeable membrane from a region of low concentration to high concentration

Active transport

Active transport where it moves molecules against their concentration gradient (low to high)

Endo- and exocytosis

Endocytosis: cell wraps its membrane around particles to take them in

Exocytosis: vesicles fuse with the plasma membrane to release large quantities of substances outside the cell

Describe the movement of water

3 basic processes

Bulk flow: movement of water molecules all together from one place to another due to differences in potential energy

Diffusion: spontaneous movement of substances down a concentration gradient to equilibrium

Osmosis: movement of water or any solvent across a selectively permeable membrane

Functions of Aquaporins

They facilitate the rapid, passive transport of water across cell membranes while preventing the movement of ions and solutes.

Equation for water potential and its components

𝚿W=𝚿pi + 𝚿p

W=water potential

Pi=osmotic potential: measurement of waters tendency to move across a membrane as a result of solute concentrations

P= pressure potential : effect of cell wall pressure, or turgor pressure

What’s the importance of water potential to plant cells?

If the water potential inside the cell is more negative, the cell has more capacity to take up water. If the water potential inside the cell is less negative, the cell will lose water.

Functions of transpiration

Water evaporates through the stoma of leaves and stems by transpiration.

Creates a gradient of water potential that is most negative at the top. Keeps water flowing.

How the design of xylem tissues and the characteristics of water aid in transpiration.

The design of the xylem tissues and the polar nature of water facilitate transport of water upward through the plant.

The role of stomata in gas exchange

Water moves into the guard cells causing them to curve, this opens the pore and allows for gas exchange with the internal air spaces.