Anatomy and Physiology: Cells : NursingCrib.com Updates

Posted: 14 Jan 2011 11:29 PM PST

Definition

Cells are the smallest unit or the building block of all living things.

Anatomy of a Cell

Basic parts of a cell consist of:

Nucleus
Cytoplasm
Plasma membrane

The nucleus is located at the most central part of a cell which is surrounded by a semifluid component of a cell called a cytoplasm. The cytoplasm is enclosed by the outer cell boundary called the plasma membrane.

The Headquarters: Nucleus

The control center of a cell is the nucleus. This part of a cell contains the genetic material called DNA (deoxyribonucleic acid) which is encloses all data of instruction for building a person's protein and cell production.

Parts of a nucleus

Nuclear Membrane (nuclear envelope) – a double membrane barrier that binds the nucleus. It has a selective permeability.
Nucleoplasm – a jelly-like fluid that is enclosed by the nuclear membrane. It is in this part where the nuclear components are floating.
Nucleoli – small, dark-staining round bodies. It is in this area where ribosomes are brought together. Ribosomes are the actual site of protein synthesis.
Chromatin – loose network of bumpy threads that is dispersed throughout the nucleus. When cell division occurs, the chromatin forms the chromosomes.

The Factory Area: Cytoplasm

The cytoplasm is the area where cellular activities take place. It is located outside the nucleus and inside the plasma membrane.

Major elements of a cytoplasm

Cytosol – suspends the other elements in cytoplasm.
Organelles – the metabolic machinery of a cell.
Inclusions – stored nutrients or stored cell products.

Cytoplasmic Organelles

Mitochondria – referred as the "powerhouse" of the cell as it supplies ATP. It is a sausage-shaped organelle that is composed of a double membrane situated in each side.
Ribosomes – actual site of protein synthesis.
Endoplasmic Reticulum – it carries substances (mostly protein) from one part of the cell to another.

Rough Endoplasmic Reticulum – an organelle that builds materials of cellular membranes. This structure is also referred as the cell's membrane factory and it is studded with ribosomes.
Smooth Endoplasmic Reticulum – basically functions in lipid metabolism and the clearing of drugs and pesticides. It is essential in cholesterol and fat synthesis and breakdown. Liver cells contain a large amount of smooth endoplasmic reticulum.

Golgi apparatus – situated close to the nucleus. It is involved in the modification and packaging of the proteins from the rough ER through the transport vehicles.
Lysosomes – contains digestive enzymes. These enzymes are formed by the ribosomes and packaged by the Golgi apparatus.
Peroxisomes – contains oxidase enzymes that utilize molecular oxygen to cleanse harmful and poisonous substances (e.g. alcohol and formaldehyde). More importantly, it is responsible for converting free radicals to hydrogen peroxide then to water with the presence of the enzyme catalase.
Cytoskeleton – determines the shape of the cell and provides support to other organelles.
Centrioles – direct the formation of the mitotic spindle during cell division.

image from peacethought.com, biologie.uni-hamburg.de, sciencecity.oupchina.com.hk