Cellular Homeostasis: Root Hair Cell & Villi Cell

How could regulation of substances in and out of cells results in cellular homeostasis? 

Root Hair Cell:

If the internal water potential decreases, the receptor will be stimulated. Water from the external environment which has a higher water potential will be absorbed by the root hair cell which has lower water potential through osmosis.








Villi Cell:

Concentration of nutrients from outside the villi cells is higher. Nutrients are being absorbed into the villi cells, which are structured in folds and thus increases the surface area to volume ratio and rate of absorption.

Water Regulation

Regulating blood water potential

Stimulus
Water potential of blood increases (e.g. due to large intake of water)

Receptor
Hypothalamus stimulated

Corrective mechanism

• Less ADH released by pituitary gland into the bloodstream
• Less ADH transported to the kidneys
• Cells in the walls of the collecting ducts become less permeable to water
• Less water reabsorbed into the bloodstream
• More water excreted 
• Urine is more diluted
• More urine produced

Water potential of blood decreases

Stimulus

Water potential of blood decreases (e.g. due to loss of water through profuse sweating)

Receptor

Hypothalamus stimulated

Corrective mechanism

• More ADH released by pituitary gland into the bloodstream
• More ADH transported to the kidneys
• Cells in the walls of the collecting ducts become more permeable to water
• More water reabsorbed into the bloodstream
• Less water excreted 
• Urine is more concentrated
• Less urine produced

Water potential of blood increases

Cell Structure and Function

Structure of Cell

A: Nucleus (contains genetic material, DNA) (controls all the cellular activities)

B: Cytoplasm (consists of cytosol and organelles) (cytosol is a aqueous matrix where organelles are suspended)

C: ?? Lysosomes (to digest food) (autophagy: break down damaged organelles)

D: Cell surface membrane  (control substances going in and out of the cell)

E: Mitochondria (stores energy as ATP)

F: Golgi Apparatus (cis face and trans face)

G: ?? Free ribosomes

H: Smooth Endoplasmic Reticulum

I: Rough Endoplasmic Reticulum 

J: ?? Bound ribosomes