Also considered as the smallest independent living unit of all living organism.
Cells are the building blocks of life. Cell consists of protoplasm and nucleus. It is surrounded by a cell membrane plasma membrane that protects it from external environment and acts as a barrier.
It is almost identical to the membranes that surround nucleus and other organelles. The membrane is made up of protein-lipid bilayer consists of a polar head and a non-polar tail. The fluidity of the membrane is regulated on the basis of lipid content and responsible for proper functioning of membrane proteins.
It plays a vital role in the structure and function of the cell. The membrane is permeable to specific molecules based on the polarity of the substrate.
The structure of the membrane is unique as it exhibits specific protein-lipid content depending upon the location of the membrane. The various biological barriers exists in humans include plasma membrane, blood brain barrier, blood placental barrier etc.
Membranes are made up of phospholipids, proteins and carbohydrates. The phospholipids form a flat surface on which proteins span or float like icebergs and carbohydrates protrude out from the phospholipid layer. The phospholipids are arranged in a bilayer such a way that polar heads faces outside and non-polar tails in the middle of the surface giving a sandwich like appearance.
The fatty acids are linked together by cholesterol that strengthens the membrane. The proteins usually exits in two forms, one spanning the surface as integral proteins and other as on the surfaces of the membranes as peripheral proteins.
They are responsible for majority of the membrane properties. The carbohydrates are found on the outer surface of all eukaryotic cell membranes, and are attached to the membrane proteins or sometimes to the phospholipids.
Proteins with carbohydrates attached are called glycoproteins, while phospholipids with carbohydrates attached are called glycolipids. The carbohydrates are short polysaccharides composed of a variety of different monosaccharides, and form a cell coat or glycocalyx outside the cell membrane.
The glycocalyx is involved in protection and cell recognition, and antigens such as the ABO antigens on blood cells are usually cell-surface glycoproteins.
The membranes provide compartmentalization and are vital for the sustenance of life as they are responsible for maintenance of concentration gradient, movement, adherence, and protection.
Transport of substances across the membrane: The plasma membrane is selectively permeable that some substances can pass and some cannot.
Ions and charged molecules cannot enter because they are unable to cross lipid layer and uncharged substances can pass through it. Usually they follow the concentration gradient across the membrane and thus does not require energy hence a passive process.
The movement across the membrane can be classified in to Active process and Passive process. The molecules are transported by carrier proteins that span the membranes they utilize the energy in the form of ATP hence active process.
A carrier protein acts as a pump that initiates a substance against the concentration gradient.
A carrier protein assists molecules to move along the concentration gradient. No energy is required. Transport of molecules across the membrane Summary of Membrane Transport: Many bioactive agents are polar in nature thus unable to cross the barrier.
The therapeutic efficiency of a drug depends on the ability to reach the site of action. The major obstacle for pharmaceutical agents drugs, peptides, oligonucleotides, plasmids that show promising activities in vitro fails to act in vivo due to various pharmacokinetic and bioavailability problems.
The ability of a drug to cross such biological barrier depends on its intrinsic physical property. To enhance the activity one should enhance the efficiency of cell transfection across the membrane. Intracellular delivery of therapeutic agents is one of the challenges in drug delivery in case of gene therapy which now a days considered as a major contender in future treatment protocols for threatening diseases like cancer and AIDS.Membrane structure The plasma membrane maintains dynamic homeostasis by separating the internal metabolic events of the cell from its external environment and controlling the movement of materials into and out of the cell.
Transport Across Plasma Membrane Essay More about Essay about Cell Membrane Transport. Cell Membranes .
How do the cells in your body define their boundaries (and control what comes in or goes out)? As it turns out, cells have a sophisticated and flexible barrier, the plasma membrane, and a wide array of strategies for transporting molecules in and out. Learn more about what the membrane's made of and how different types of molecules move .
One important part of the cell structure is the cell membrane also known as the plasma membrane or cytoplasmic membrane. Historically, the plasma membrane was also referred to as the plasmalemma.
The cell membrane is a microscopic lipid-based sheath that encloses the cytoplasm of a cell and separates the interior of all cells from the . ‘The structure and importance of the plasma membrane found within and around all cells’ The plasma membrane surrounds all eukaryotic and prokaryotic cells.
Plasma Membrane Structure The plasma membrane is composed of a phospholipid bilayer, which is two layers of phospholipids back-to-back.
Phospholipids are lipids with a phosphate group attached to. The cell membrane or plasma membrane and the sub cellular membranes together constitute the biological membranes, or biomembranes. Biomembranes are dynamic, quasifluid, and selectively permeable and film like structure of about nm (75A0,) in .