Cell or Plasma Membranes

There are many theories that have been proposed to explain the structure of cell or plasma membrane.
The unit theory proposed by Robertson says that it consists of two layers of phospho-lipid molecules and proteins on either side of the membrane.


The fluid mosaic model proposed by Singer and Nicholson is the most widely accepted one.It says that it consists of phospho-lipid bilayer and proteins(like unit membrane theory) but gives additional information that the molecules are amphipathic(having hydrophobic tail and hydrophilic head).The proteins are attached to the molecules either superficially(extrinsic) or inserted wholly or partially(intrinsic)


The carrier proteins along with the phospho-lipid molecules play an important role in the movement of molecules inside or outside the cell by active or passive transportation

There is typically one cell membrane in each cell. The cell membrane, also known as the plasma membrane, is a thin semi-permeable barrier that surrounds the cell and controls the movement of substances in and out of the cell.

it is mostly water with many dissolved solute such as: nutrient, gases, hormones and wastes. Most plasma protein are produced by the liver. Albumin which is 60% of plasma protein serves as blood buffer to plasma osmotic pressure( the pressure that helps to keep water in the bloodstream). Another function of is plasma distribute heat.

Carbohydrates often attach to the external surface of integral proteins. These carbohydrates may hold adjoining cells together or act as sites where viruses or chemical messengers such as hormones can attach.

Gap junctions

Roughly 1 billion but who's counting? There are 10 to 100 million viruses in one cubic cm of water or one gram of soil, unless I miss my guesstamate.

yes they do. however they do not have membrane-bound organelles

Phospholipids are lipids that are essential to cells because they make up cell membranes. When phospholipids are added to water, they self-assemble into double-layered aggregates, or bilayers, that shield their hydrophobic portions from water. The phospholipid bilayer forms a boundary between the cell and its external environment.

Nonpolar Fatty acid chains

They do not differ much. The proteins in each are slightly different.

The cell membrane is primarily composed of a phospholipid bilayer, where hydrophobic fatty acid tails face inward, away from water, while hydrophilic phosphate heads face outward toward the aqueous environment. This arrangement creates a semi-permeable barrier that regulates the movement of substances in and out of the cell. Thus, while fatty acids are a critical component of the membrane, they are part of a larger structural framework that includes phospholipids and proteins.

The YEAST cell is by far the biggest cell out of a BACTERIUM and a VIRUS....

I know this 'cos it was on my science homework and 'cos i found it on another website which gave me the urge to put it here since the question hadn't been answered....x

I think it is the sacrolemma.

4 major parts of a plasma membrane

* proteins

* lipid bilayer * carbohydrates * cholesterol

No, carbohydrates are NOT a major components of cell membranes, which are mainly comprised of lipid (fat molecules). Proteins sit in and on the membrane and SOME of the proteins are glycosylated, which means that they have sugar or carbohydrate attached to them. So there are carbohydrates in cell membranes, but they are not a major component.

depend upon your choice , hydrogen permeable but water not

Cholesterol is found in the membrane. It prevents lower temperatures from inhibiting the fluidity of the membrane and prevents higher temperatures from increasing fluidity. It stabilizes the membrane. Only animal cells have cholesterol in their membranes.

The process is know as Meiosis II, the second stage in the process of cell division for sexual reproduction.

1)enzyme is a chemical substance that digest starch and reducing sugar

2)Also, the carbohydrase enzymes break down the big starch particles...the starch particles are to big to digest - it is like having peas through a sieve!

because the thinner it is the clearer it is too see inside

as the name suggests plasma means colorless and in the same waymembrane is also colorless becoz of this cell membrane is also known as plasma membrane

The plasma membrane regulates what enters/leaves cell through the phospholipid bilayer using selective permeability, by which a membrane allows some substances into the cells while keeping others out. Picture a butterfly net, the holes in the allow knats and other bugs to pass through, while capturing other

by diffusion and osmosis

Red blood cells, white blood cells, and platelets are found in human blood.