Summarize the following text to main points and sub-points and make detailed explain for them:

eral function of integral cell membrane proteins 
 
✓ Acts as channels.   
 
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Which has 2 types:  Simple 
Channels (non gated)& Gated 
Channels. 
I. Simple Channels: 
Allow passage of small molecules which 
are water soluble as ions Na &+ K+ &Ca++ 
through  
1- 
Selective permeability (leak channels allow K+ 
100 times than Na+ because hydrated Na+ 5'A 
> hydrated K+ 4'A. 
2- 
Electrochemical gradient: The more the 
difference in ions concentration , and charges, 
the more the passage of ions. 
II. Gated channels: (They 
have gates). 
They control passage of substances in 
and out of cell. There are two types: 
1- Voltage gated channels open when 
membrane 
potential is changed. 
2- Ligand 
gated channels: open 
when the chemical substances (ligands) attach 
to gates either from outside Like: hormones, 
chemical transmitters (external ligands) or 
from inside as 
C-AMP(internal ligand). 
 
They allow passage of large H2O soluble substances 
NB 
Some channels can be opened by stretch of 
membrane. 
 
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1- Passively (no energy is required) with electrochemical gradient 
from high 
concentration to low concentration 
2- Actively (energy is required) against electrochemical gradient.From low 
concentration to high concentration. 
 
 
 
III. 
Carbohydrates Plasma membranes , 
predominantly glycoproteins& glycolipids .  
Function : Carbohydrates are located on the 
surface of the cell as it responsible for cell  
recognition on  host cells .  
 
 
 
 
 
 
 
 
 
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✓ All the cell in the body must be supplied with essential substances like water 
and electrolytes. cells also must get rid of waste products and CO2. The cells 
achieve it by the means of transport mechanism across cell membrane. 
 
✓ The structure of the cell membrane is suited well for transport in and out the 
cell. it i s composed of proteins and lipids. This heterogeneity allows 
passage 
of some substances between ICF and ECF. The cell membrane serves 
as a selective barrier, controlling the movement of substances into and out of 
the cell.  
 
✓ Cellular transport is essential to maintain cellular homeostasis, uptake 
essential nutrients, excrete waste products, and communicate with their 
surroundings 
 
I. 
Passive Transport mechanism  
✓ Diffusion ( simple &  facilitated ) 
✓ Osmosis 
II. 
Active transport mechanism  
✓ Primary active transport  
✓ Secondary active transport  
III. 
Vesicular transport  
✓ Endocytosis  
✓ Exocytosis  
 
  
 
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I. Passive Transport mechanism
 
Definition: It is the transport of substances along the concentration gradient or 
electrical gradient or both (electrochemical gradient).it doesn’t energy. the substances 
move from area of higher concentration to area of lower concentration.  
 
Types  
* Simple Diffusion-   It is the movement of ions or molecules from a 
region of their high concentration to a region of their low concentration, 
without the expenditure of energy • Movement is towards the 
concentration gradient until an equilibrium is achieved. 
Simple diffusion may be: 
  Influx: moving inside from outside.   Efflux: moving outside from inside. 
 
Examples of substances moved : 
• Water soluble, small substances as   Ions diffuse through the ion channels (leak 
channel/open or  gated channel as   Voltage gated – Ligand gated – Mechano 
sensitive gate) 
• Inhaled and exhaled air O2 &CO2 across pulmonary membrane  
Factors affecting the rate of diffusion (FICK’S LAW OF DIFFUSION) 
• Diffusion gradient/ concentration difference The steeper, the higher the rate  
• Size of molecules or ions/ Molecular weight .The smaller the size, the higher the 
rate Indirectly proportional Temperature The higher the temperature, the higher 
the rate  
definition 
types  
examples 
 
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• Diffusion medium Rate in gas > rate in liquid > rate in solid Surface area The 
larger the surface area, the higher the rate 
• Solubility Directly proportional. 
•  Thickness of membrane Indirectly proportional  
 
* Facilitated diffusion (carrier mediated diffusion) 
It is the movement of specific molecules (or ions) across the plasma 
membrane, assisted by a carrier protein.  
• The direction of movement is down the concentration gradient of the 
molecules concerned.  
• No energy required. 
Examples 
            Glucose and amino acids transport 
 because the diameter of this molecule is larger than the channel so Carrier proteins 
binding transfer them across the lipid bilayer by undergoing conformational changes 
that sequentially transported from  one side of the membrane to the other. 
Factors affecting facilitated diffusion: 
1. The concentration gradient of substances (the more-the more). 
2. The number of carriers (the more-the more). 
3. Affinity (combination) between the carrier and substance. 
4. The rapidity of change of shape of carrier - the more the more.  
 
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Difference between carrier proteins (used in facilitated diffusion )   & channel proteins (used in simple 
diffusion ) • Carrier proteins bind to larger molecules, and change their shape so molecules can diffuse 
through.  
• Channel proteins provide water filled pores for charged ions to pass through only without change. 
*  0smosis :  the movement of water molecules (solvent) through a 
selectively permeable membrane/ semipermeable membrane like the cell 
membrane.  
• Water diffuses across a membrane from an area of high concentration to an area of low 
concentration. 
 
        N.B Semi-permeable membrane is permeable to water, but not to the solute i.e.,sugar  &No 
carrier &no energy  
• Tonicity : Osmolality of a solution relative to plasma •  
Sodium ion is the major contributor to tonicity of ECF   which nearly 298 to 300 
mosmol /l 
•  Hypertonic Solutions Contain a high concentration of solute relative to another 
solution (e.g. the cell's cytoplasm). •When a cell is placed in a hypertonic solution, the 
water diffuses out of the cell, causing the cell to shrivel.  
•  Hypotonic Solutions Contain a low concentration of solute relative to another 
solution. • When a cell is placed in a hypotonic solution, the water diffuses into the cell, 
causing the cell to swell and possibly explode.  
 
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•  Isotonic Solutions Contain the same concentration of solute as another solution 
(e.g. the cell's cytoplasm). When a cell is placed in an isotonic solution, the water 
diffuses into and out of the cell at the same rate.  
• The fluid that surrounds the body cells is isotonic. 
Clinical application:• Isotonic solution – 0.9% NaCl, 5% dextrose in water • Hypotonic solution – 
treat dehydration • Hypertonic solution – mannitol – treat cerebral edema 
 
 
 
II. Active transport mechanism 
 
it is the movement of substance against electrical or chemical or 
electrochemical gradient. 
 It require 2 : 
• Energy is used from the A.T.P. (adenosine triphosphate) (energy store in 
cell) 
 
• The substances must combine with carrier in cell membrane. 
 
Types of carriers: 
* Uniport: transport one substance in one direction as Ca + +. 
* Simport: transport two substances in one direction. Na+, glucose. 
* Antiport: transport two substances in two directions: Na + ,K+ 
Types of active transport: 
  
They use the energy directly from the hydrolysis of 
ATP &Sodium potassium Pump &Calcium pump .
Examples : 
definitin 
types 
examples 
 
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A. Ca++ pump: Ca++ is pumped from 
intracellular to extracellular against the 
concentration gradient (Ca+ extracellular 
10.000 times as 
intracellular). Energy is derived from 
A.T.P. ATP (adenosine 
triphosphate) 
→ ADP 
(adenosine diphosphate) + P + Energy 
B. Na+ - K+ pump: 
The main extracellular cation is Na+. The main 
intracellular cation is K+ 
Any Na+ enters into the cell is pumped out. 
Any K+ outflow outside the cell is pumped in. 
Na+ and K+ combine with carrier which has3Na+ 
binding sites and 2K+ binding sites. 
 Sodium potassium pump - present in all eukaryotic cells Functions: 
 1. Maintains sodium potassium concentration difference across the cell membrane. 
 2. Maintains volume of the cell.  
3. Causes negative electrical charge inside the cell – electrogenic pump 
 
Secondary active transport                                                                                                
• Energy utilized in the transport of one substance helps in the movement of the other 
substance.  
• Energy is derived secondarily, from energy that has been stored   originally by primary 
active transport. 
 
Example : Sodium-glucose cotransporter (SGLT) in renal tubules  
As Cotransport is driven by active sodium extrusion by sodium/potassium-ATPase, the ene

Summary :