Share
Explore BrainMass

Explore BrainMass

Cell Membranes and Cell Walls

Membranes are cellular structures which separate the interior and exterior compartments of a cell or individual organelle, whereas the cell wall is required for structural support in only selective cell types. Cell membranes are found in both eukaryotic and prokaryotic cells and are associated with different organelles, such as the mitochondria.   

The cell membrane is a vital organelle which allows for compartmentalization. This is critical for all eukaryotic organisms which are multicellular because it keeps all cells separate from one another. Within the cytosol, membrane-enclosed organelles such as the golgi apparatus and endoplasmic reticulum (ER) have distinctive positions which isolate these organelles from other cellular units. This separation is possible because they have membranes.

The cell membrane is a structure which surrounds the outside of a cell and it is composed of two materials, a lipid bilayer and proteins. The lipid bilayer is comprised largely of phospholipids and smaller quantities of other lipids which are called steroids and fatty acids.  This membrane is considered to be semi-permeable due to the arrangement of the phospholipids: they have a polar head group and nonpolar tails. This semi-permeability controls the movement of substances, such as ions, into and out of the cell. Molecules which cannot pass through the cellular membrane freely by passive diffusion travel using different mechanisms requiring ATP.

In terms of the proteins, they can either be imbedded directly into the membrane or they can be peripheral proteins. These proteins are critical for regulating biological activities. For example, proteins are utilized for cell to cell communication.

On the other hand, cell walls are only found in plant and fungi cells, along with prokaryotes. These structures are located outside of the cell membrane and provide cellular support, along with protection. In terms of support, the rigidity of the cell wall maintains cellular integrity because without this wall, the cell would collapse under the pressure. For example, when water enters the cell, over-expansion is prevented by the cell wall.

 

Categories within Cell Membranes and Cell Walls

Membrane Transport

Postings: 37

Membrane transport is essential to the functioning of a cell because it allows for substances, such as ions and chemicals, to pass membrane barriers.

Inheritance and Genetic Engineering

Compare and contrast the Mendelian and non-Mendelian patterns of inheritance. Describe what you believe is the most significant difference and explain why.

why must particles be extremely small to demonstrate brownian movement?

1) Why must particles be extremely small to demonstrate brownian movement? 2) What is the difference between molecular motion and diffusion? 3) If you immerse your hand in distilled water for 15 minutes, will you cells lyse? why or why not? 4) How do cells such as algae and protists avoid lysis in fresh water?

Endoplasmic Reticulum

The endoplasmic reticulum: a) functions in internal transport of macromolecules. b) carries on cellular respiration. c) is the site of photosynthesis. d) is dispersed nuclear material of DNA and protein.

ABCD Rule and Membranes

1. Mary noticed a large, brown spot on her skin. She has been playing tennis in the sun for several years without sun protection. She reported the discovery to a friend, who told her to apply the ABCD rule to determine whether or not she had malignant melanoma. Her friend told her that if her answer was "no" to the questions tha

Why do you think the plasma membrane exists in all living things?

All life forms on Earth exist either as single cells or as collections of cells that have a plasma membrane at their periphery (though some cells have cell walls outside their plasma membrane). Why do you think the plasma membrane exists in all living things? Why aren't there living things that don't have a membrane at their per

Cell Biology

1. An integrin is an integral membrane protein in the plasma membrane of cells. It plays a role in the attachment of a cell to the extracellular matrix (ECM) and to other cells, and in signal transduction from the ECM to the cell. How is the structure of integrins reflective of this function? 5. In a cell with a resting

Cell Biology

I am wishing for information on the cell wall. I have read much information from books and/or websites that has provided a plethora of information. Thus, I was wishing for a breakdown from an individual as I thought that it would provide a better understanding than a textbook definition. I understand that it considered protec

RBCs are examined.

RBCs are permeable to urea, but does this have any physiological significance? Ideas are explored.

Fat Soluble Substances

What characteristic of cell membranes may explain why fat soluble substances like chloroform and ether rapidly affect cells?