Attracting Abundance

- 100 -

The Law

Belief - XII

Our Cellular Biology - XI

Recall that cell membranes protect and organize cells. All cells have an outer plasma membrane that regulates not only what enters the cell, but also how much of any given substance comes in. Also the organelles inside the cells have their own membranes that control the exchange of essential cell components. Both types of membranes have a structure that facilitates their gate-keeping function. Cell membranes are semi-permeable, which means that some molecules can diffuse across the lipid bi-layer but others can not. Small hydrophobic molecules and gases like oxygen and carbon dioxide cross membranes rapidly. Small polar molecules, such as water and ethanol, can also pass through membranes, but they do so more slowly. On the other hand, cell membranes restrict diffusion of highly charges molecules, such as ions, and large molecules, such as sugars and amino acids. the passage of these molecules relies on specific transport proteins embedded in the membrane.

Membrane transport proteins are specific and selective for the molecules they move, and they often use energy to catalyze passage. Also, these proteins transport some nutrients against the concentration gradient, which requires additional energy. the ability to maintain concentration gradient and sometimes move materials against them is vital to cell health and maintenance. thanks to membrane barriers and transport proteins, the cells can accumulate nutrients in higher concentration than exist in the environment, and conversely dispose off waste products.

Other membrane, called receptor proteins have communication-related jobs. They bind signals, such as hormones or immune mediators, to their extra-cellular portions. Binding causes a conformational change in the protein that transmits a signal to the intra-cellular messenger molecules. Like transporter proteins, receptor proteins are also specific and selective for the molecules they bind.

Note: A receptor is aprotein-molecule that receives chemical-signals from outside a cell. When such chemical-signals bind to a receptor, they cause some form of cellular/tissue-response, e.g. a change in the electrical-activity of a cell.

have commun The transporter and receptor proteins are integral with the membrane i.e. they are deeply embedded within the membrane bi-layer. Hence these proteins are also known as integral proteins. there is a second type of proteins known as the peripheral membrane proteins which are associated with the membrane but not embedded in the bi-layer. Rather they are bound to other proteins in the membrane. Some peripheral proteins form a filamentous network under the membrane to which the trans-membrane proteins attach themselves. Other peripheral proteins are secreted by the cells, which form an extra-cellular matrix that functions in cell recognition.

See the video:

Namaste



See you soon



Prabir