Cell metabolism

The human body consists of tissues and these in turn consist of tissue cells, the basic unit of biological systems. All tissue cells have a cell metabolism and are supposed to fulfil their own specific task. In addition to generating energy for energy-consuming activities, cell metabolism also serves the purpose of maintaining body functions and vital body substances. Metabolism takes place via biochemical or biophysical processes which ensure the uptake, transport and transformation of substances as well as the release of metabolic end products into the environment.

Cells that are damaged or that cannot provide enough energy for their tasks can be atrigger of many diseases, dysfunctions or pains. Disturbances of the cell metabolism become noticeable as metabolic disorder and can lead to reversible or irreversible disturbances of the cell structure or individual cell components.

Cells are named according to the type of tissue and the metabolic type.

A cartilage cell that uses its basic substance is called a chondrocyte. Bone tissue and a bone cell that degrades bone is called osteoclast, a bone cell that forms newbone tissue is called osteoblast.

Energy metabolism

An energy metabolism with the aim of producing a high energy content is necessary to supply our cells with the energy they need for their tasks. This requires the compound ATP (adenosine triphosphate). All our tissue cells are capable of producing ATP. In our cells an energy metabolism or a product metabolism can take place depending upon need.

If the primary task is energy metabolism, the cell is defined as a cyt, such as chondrocyte. If the main task is product metabolism, this is referred to as a blast, e.g. osteoblast. Blast-cells build up their basic substance, cyt-cells use their basic substance and clast-cells degrade the basic substance.

There are four possible metabolic types and two of them can take place in the tissue cell itself (cytosol or cytoplasm) and two in the mitochondria that are located within the tissue cell. We know the following types of energy metabolism:

  • Anaerobic alactacid · conversion of creatine phosphate and ADP (adenosine diphosphate) to creatine and ATP without the use of oxygen and without the formation of lactate (Lohmann reaction)
  • Anaerobic lactazide · conversion of glucose (glycogen) to lactic acid (lactate) and ATP
  • Aerobic glycolysis · conversion of glucose or glycogen with oxygen to carbon dioxide and water
  • Aerobic lipolysis · conversion of fatty acids with oxygen into carbon dioxide and water
Remarkable is the extraordinary variety of chemical reactions in the metabolism. Many hundreds of individual and specific processes take place simultaneously in one cell. Most of these processes are chemical transformations that do not take the form of a single reaction within the cell. These are processes which, through a whole series of defined reactions, are based on a gradual change in the chemical structure of a molecule. The metabolites produced (metabolic products) often enable cross-links to other metabolic pathways. Lastly, this results in a whole network of chemical interactions.


Mitochondria are also referred to as the power plant of the cell. The main task of mitochondria is the production of energy in the form of ATP. They are the decisive cell organelles in aerobic energy metabolism. Mitochondria have their own genetic material in the form of mitochondrial DNA. Depending on the energy requirements of the cell types, a few to several thousand mitochondria may be present in a cell.


One of the main functions and tasks of mitochondria is the synthesis of adenosine triphosphate (ATP) and the release of ATP into the cellular matrix, the interior of the cell outside the mitochondria.

Krebs cycle

The Krebs cycle or citrate cycle or citric acid cycle is named after its discoverer Hans Adolf Krebs. The citric acid cycle serves to provide energy by degrading substances. It is also the starting point for further biological processes. Indirectly, energy is made available in biochemically usable form (as adenosine triphosphate ATP).

Human cells have a regulated energy supply. ATP (adenosine triphosphate) is a nucleotide found in all cells. During cell respiration, 38 molecules of ATP are synthesized when glucose is completely oxidized. Accordingly, the proportion of energy conserved in ATP in the entire reaction chain is 40%.