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

Anatomy of a Cell

Basic parts of a cell consist of:

  1. Nucleus
  2. Cytoplasm
  3. 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
  1. Nuclear Membrane (nuclear envelope) – a double membrane barrier that binds the nucleus. It has a selective permeability.
  2. Nucleoplasm – a jelly-like fluid that is enclosed by the nuclear membrane. It is in this part where the nuclear components are floating.
  3. Nucleoli – small, dark-staining round bodies. It is in this area where ribosomes are brought together. Ribosomes are the actual site of protein synthesis.
  4. 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
  1. Cytosol – suspends the other elements in cytoplasm.
  2. Organelles – the metabolic machinery of a cell.
  3. 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.
    1. 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.
    2. 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.
Plasma Membrane or Cell Membrane

The cell membrane separates the cells from the surrounding and contains all the cellular components or materials. Its structure consists of the following:

  • Phospolipids
  • Cholesterol
  • Polar heads of phospholipid molecules
  • Bimolecular lipid containing proteins – the proteins are responsible for the specialized function of the cell membrane. Proteins in plasma membrane could be:
    1. Enzymes
    2. Glycoprotein or sugar-proteins = determines blood type, serves as receptors of certain bacteria, viruses and toxins. It also plays a role in cell-to-cell communication or interaction.

Most proteins that are found on the area of plasma membrane have to do with transport functions. Water or small water-soluble molecules or ions can move through cells as proteins gather together to form tiny pores from protein channels. Other proteins are responsible for attaching to a substance and transport it towards the cell through the membrane.

  • Nonpolar tails of phospholipids molecules

A plasma membrane has two common specializations namely:

  • Microvilli
  • Membrane junctions

Microvilli are the minute finger-like projections of the plasma membrane that is responsible for increasing the cell’s surface area for absorption making the process occurring more quickly. The membrane junctions, on the other hand, vary structurally depending on their roles:

  • Tight junctions – these are resistant junctions that fuse cells together into impermeable structure that will prevent the substances from passing through the extracellular space between the cells.
  • Desmosomes – prevent cells from mechanical stress. For instance, skin cells are prevented from being pulled apart (mechanical stress) because of the presence of desmosomes.
  • Gap junctions – allow communication between cells. Neighboring cells are connected to each other by the presence of CONNEXONS.