Pore Protein and Carrier Protein

Pore Protein or Channel

When a channel is opened with a conformational switch, it is open to both environment simultaneously (extracellular and intracellular); channels are either in open state or closed state.

Pores are continuously open to these both environment, because they do not undergo conformational changes They are always open.

Carrier Protein

Pathway in a carrier protein is not open smiltaneously to the both environment. Either its inner gate is open, or outer gate is open, or both gates are closed. 

Carrier has binding sites, but porins and channel proteins have not.

When a channel is opened, thousands to millions of ions can pass through the membrane in one time, but only one or a small amount of molecules can pass through a carrier molecule. 

Preservation of fish and vegetables

Fish

Fish is covered by salt solution which is hypertonic to the fish tissues
More water diffuses out from the tissues into the salt solution
The fish becames dehydrated
This prevent bacterial growth in the fish tissues
The bacteria cell are also plasmoysed
This prevent decay

Vegetables
Vegetables are immersed in vinegar which is acidic
Vinegar diffuses into vegetables
Vegetables becames acidic
lower pH prevent bacterial growth
this prevent decay

Similarities between facilated transport and active transport

Both methods of transportation need carrier protein in the cell membrane to bind with the molecules
Both transport specific molecules only because the carrier proteins have specific site to certain molecules
Both processes occur in living cells because carrier protiens can change shape to allow substances to move across.

Chapter 3 : Movement of Substances Across the Plasma Membrane