Question

1.The cell membrane is selectively permeable. Explain.

2. how is phagocytosis different from pinocytosis?

3.explain the difference between passive transport and active trasnport.

Answer 1

1-  The cell membrane is selectively permeable, meaning it only lets certain things in and out of the cell. If you think about our building analogy, this can be a very important thing. You wouldn't want just anyone running in and out of the White House, for example. It's important to have guards who determine who's allowed in and who's not. A cell is a living thing and needs just the right balance of nutrients and water, called homeostasis. The selective permeability of the membrane allows the cell to stay in homeostasis.

2- Phagocytosis is the process by which a cell uses its plasma membrane to engulf a large particle, giving rise to an internal compartment called the phagosome. It is one type of endocytosis. In a multicellular organism's immune system, phagocytosis is a major mechanism used to remove pathogens and cell debris.

In cellular biology, pinocytosis, otherwise known as fluid endocytosis and bulk-phase pinocytosis, is a mode of endocytosis in which small particles suspended in extracellular fluid are brought into the cell through an invagination of the cell membrane, resulting in a suspension of the particles within a small vesicle.

3- active transport

* The movement of molecules across the cell membrane, pumping the molecules against the concentration gradient using ATP (energy) is called Active transport.

* The movement of molecules is from low concentration to high concentration which means they move against the concentration gradient.

* Active transport requires carrier proteins.

* This process reduces or stops as the level of oxygen content is reduced.

* Active transport allows molecules to pass the cell membrane, disrupting the equilibrium established by the diffusion.

Passive transport

* The movement of molecules within and across the cell membrane and thus transporting it through the concentration gradient, without using ATP (energy) is called Passive transport

* No energy is required.

* The movement of molecules is from high concentration to low concentration, which means they move along the concentration gradient.

* In passive transport carrier proteins are not involved. However, in facilitated diffusion certain channels are present which utilize no energy.

* A dynamic equilibrium of water, nutrients, gasses, and wastes is maintained by passive transport

Between cytosol and extracellular environment