All living things, with the exception of viruses are composed of cells.

The basic unit of life.

Estimated number of human cells is estimated to be 10 to 13th power.

have diverse components that contribute to the biochemical processes that sustain life.

All eukaryotic cells are envelope by a bilayer of lipid membrane, the plasma membrane.

The plasma membrane has two sheets of phospholipids, each sheet is one molecule thick.

The plasma membrane phospholipids have areas that are hydrophilic or hydrophobic.

The hydrophilic portions of the outer layer containing phosphate groups face the extracellular environs and those of the inner layer face the cytoplasm.

The hydrophobic parts of each layer containing fatty acid chains react within the center of the membrane.

The bilayer plasma membrane contains steroid molecules, glycoplipids, sphingolipids, proteins and glycoprotein.

The plasma membrane is altered in its physical properties by the amount of cholesterol and glycoplipids in its content.

Plasma membrane lipids fall into three classes: phospholipids, cholesterol and glycolipids.

Phospholipids in the plasma membrane are the most abundant lipids and have hydrophilic and hydrophobic aspects making it amphipathic.

Amphipathic nature of the plasma membrane phospholipids allows it to spontaneously form a lipid bilayer when placed in an aqueous environment.

There are four major phospholipids within the lipid bilayer: in the outer membrane is phosphhatidylcholine and sphingomyelin and the inner membrane has phospatidylethanolamine and phosphatidylserine.

When the asymmetry of the plasma lipid membrane is altered it can trigger inflammatory reactions.

Proteins in the plasma membrane aid in the transport of nutrients across the membrane, alters signal transduction and effects interactions between the cell and its surroundings.

Plasma cell membrane enhances cellular structural stability, protects internal organelles from the external environment, regulates the internal environment and enables interactions with the external environment.

The plasma membrane serves as an impermeable barrier to water soluble molecules.

The plasma membrane lipid bilayer is a continuous double sided dynamic membrane allowing movement of molecules laterally within a single membrane.

Plasma membrane fluidity can be altered by temperature, unsaturation of fatty acids, and its cholesterol content.

Increasing temperature increases plasma membrane fluidity while decreased temperature decreases membrane fluidity.

Unsaturation of fatty acids of the plasma membrane increases membrane fluidity and decreased of unsaturation of fatty acids decreases membrane fluidity.

Decreasing plasma membrane cholesterol content increases membrane fluidity, while increasing plasma membrane cholesterol increases fluidity.

The nucleus is the control center of the cell and contains genetically encoded DNA that directs its processes.

The nucleus is surrounded by two lipid bilayer, with the inner membrane defining its boundaries and the outer membrane continuous with the rough endoplasmic reticulum.

Nucleus contains DNA, and proteins that enable the maintenance, expression and transportation of genetic material.

most ribosomal RNA is in the nucleolus of the nucleus.

Ribosomal RNA passes through the nuclear pores to the cytoplasm, where it associates with the rough endoplasmic reticulum.

Maintenance of cellular integrity requires constancy of volume despite extracellular and intracellular osmotic changes.

Cells can shrink or swell by activating metabolic or membrane transport processes returning cell volume to its normal resting state.

Cell volume can be regulated by gain or loss of osmotically active solutes, such as Na, K, Cl, and organic osmolytes.

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