Movement into and out of cells

Movement into and out of the cell

Introduction to necessary terms

Osmosis: Osmosis is the movement of water molecules from a region of their higher water potential to a region of their lower water potential down the water potential gradient through a partially permeable membrane.

Osmosis doesn't require energy
Requires a partially permeable membrane

Diffusion: Diffusion is the movement of particles from a region of their high concentration to a region of their low concentration down the concentration gradient.

Diffusion doesn’t require energy
No partially permeable membrane required

Active Transport: Active transport is the movement of charged particles from a region of their low concentration to a region of their high concentration against the concentration gradient using energy from respiration through carrier protein in the cell membrane.

Active transport is always against the concentration gradient
Energy is needed
Partially permeable membrane is needed

For example:

Uptake of glucose through the gut
Uptake of ions by root using energy from respiration

Active transport takes place in root hair cells to take nitrate ions. In human intestine glucose can actively be transported from lumen of intestine to the cells of villi. In kidney tubules glucose is actively transported out of the tubule into the blood.

Situational effects

Effect of osmosis in plant cell placed in a hypotonic solution

Plant cells are enclosed by a rigid cell wall. When the plant cell is placed in a hypotonic solution, it takes up water by osmosis and starts to swell, but the cell wall prevents it from bursting. The plant cell is said to have become “turgid”.

Effect of osmosis in plant cell placed in a hypertonic solution

Water from inside the cell’s cytoplasm diffuses out and the plant cell is said to have become “flaccid”.
When viewed under microscope it can be seen that cytoplasm has shrunk and has been pulled away from the cell wall, this is called “plasmolysis”.
The region between cell wall and cell membrane contains the same solution the cell is placed into.