What is it called when molecules are released by the cell membrane?

What is exocytosis? Exocytosis definition and purposes. Exocytosis is the process by which cells move materials from within the cell into the extracellular fluid. Exocytosis occurs when a vesicle fuses with the plasma membrane, allowing its contents to be released outside the cell.

What is cell membrane permeability?

The permeability of a membrane is the rate of passive diffusion of molecules through the membrane. These molecules are known as permeant molecules. Permeability depends mainly on the electric charge and polarity of the molecule and to a lesser extent the molar mass of the molecule.

What does the smooth ER do?

smooth endoplasmic reticulum (SER), meshwork of fine disklike tubular membrane vesicles, part of a continuous membrane organelle within the cytoplasm of eukaryotic cells, that is involved in the synthesis and storage of lipids, including cholesterol and phospholipids, which are used in the production of new cellular …

What is the term used to describe how the cell membrane lets certain things in and not others?

In other words, plasma membranes are selectively permeable—they allow some substances through but not others.

What type of molecules are transported by molecular pumps?

During active transport, a protein pump uses energy, in the form of ATP, to move molecules from an area of low concentration to an area of high concentration. An example of active transport is the sodium-potassium pump, which moves sodium ions to the outside of the cell and potassium ions to the inside of the cell.

How large molecules are transported across the membrane?

It is possible for large molecules to enter a cell by a process called endocytosis, where a small piece of the cell membrane wraps around the particle and is brought into the cell. If the particle is solid, endocytosis is also called phagocytosis. If fluid droplets are taken in, the processes is called pinocytosis.

Does membrane permeability affect the rate of diffusion?

The two factors that are particular to diffusion through a membrane are surface area and permeability. A membrane with smaller surface area or lower permeability will impede molecular movement and thus lead to slower diffusion.

How does molecular size affect permeability?

For a particular partition coefficient, the permeability of a smaller molecule is generally higher than that of a larger molecule. For molecules of equal size, the one with greater solubility in lipids will pass more quickly into the cell. For molecules of equal solubility, smaller ones penetrate faster.

What molecules are manufactured by the smooth ER?

It synthesizes lipids, phospholipids as in plasma membranes, and steroids. Cells that secrete these products, such as cells of the testes, ovaries, and skin oil glands, have an excess of smooth endoplasmic reticulum. The smooth endoplasmic reticulum also carries out the metabolism of carbohydrates and steroids.

What organelle does smooth ER work with?

The vesicles often move to the Golgi apparatus for additional protein packaging and distribution. Smooth ER (SER) acts as a storage organelle. It is important in the creation and storage of lipids and steroids. Steroids are a type of ringed organic molecule used for many purposes in an organism.

What is true about the rate of diffusion through a selectively permeable membrane?

During osmosis, water moves_____its concentration gradient. Which of the following is true about the rate of diffusion through a selectively permeable membrane? Smaller molecules diffuse faster than larger molecules through a membrane.

Which variables affect the rate of diffusion select all that apply?

Several factors affect the rate of diffusion of a solute including the mass of the solute, the temperature of the environment, the solvent density, and the distance traveled.