Biological role and significance of proteins
Proteins, polypeptides, and peptides are the fundamental basis of vital activity. They perform a number of critically important functions in the body. Firstly, information: many hormones are proteinaceous in nature and transmit signals between tissues. Secondly, receptor: proteins are an essential component of all cell receptors, ensuring cell interaction with the external environment. Thirdly, catalytic: absolutely all enzymes are protein structures that accelerate biochemical reactions. Finally, they perform a structural function, forming the framework of cells.
Any disorders of amino acid metabolism inevitably lead to significant metabolic disorders. As a result, the structure and function of individual organs, physiological systems, and the entire organism as a whole suffer.
Physiological requirements and norms
To maintain health, a strict correspondence between the quantity and composition of incoming protein and physiological needs is necessary. The optimal norm for an adult is from 1.5 to 2.5 g per kilogram of body weight per day. In children, this requirement calculated per kilogram of weight is significantly higher, which is associated with active growth processes.
Dietary protein accomplishes two main tasks. The first is to replenish total protein expenditure in the course of daily vital activity. The second, no less important task is to supply the body with essential amino acids. These substances are not synthesized in our cells and can only be obtained externally.
Classification of typical disorders
In pathological physiology, six main groups of protein metabolism disorders are distinguished, covering all stages of metabolism:
- Intake failing to meet physiological needs (alimentary factor) — deficiency or excess of proteins in the diet.
- Disorders of transmembrane transport — defects in amino acid transport into the cell.
- Dysproteinemias — deviations in the content and ratio of various blood plasma protein fractions.
- Maldigestion and malabsorption — impaired digestion and absorption processes in the gastrointestinal tract.
- Intermediary metabolism disorders — failures in amino acid metabolism at the intracellular level.
- Impaired excretion — disorders of the final stages of catabolism, where the excretion of nitrogenous waste products suffers.
Alimentary deficiency and types of starvation
The main cause of insufficient protein intake is starvation (alimentary deficiency). Depending on the conditions, four types are distinguished:
- Absolute starvation: the most severe condition, in which both food and water intake completely ceases.
- Complete starvation: the person is completely deprived of food, but water consumption remains at a normal level.
- Incomplete starvation: food is supplied, but its quantity is insufficient in total caloric value, which also causes protein deficiency.
- Partial starvation: the total caloric content of the diet remains sufficient, but a severe deficit of individual components (proteins, lipids, carbohydrates, vitamins, or micronutrients) arises.
Forms of mismatch and nitrogen balance
Pathologies associated with inadequate intake are divided into three main forms. The first is unbalanced alimentary deficiency, a striking example of which is kwashiorkor. The second is balanced alimentary deficiency, leading to the development of alimentary dystrophy. The third group is associated with shifts in nitrogen balance.
| Condition | Characteristic clinical manifestations |
|---|---|
| Negative nitrogen balance | Weight loss, slowed growth and development, decreased appetite and protein assimilation, insufficient tissue regeneration. |
| Positive nitrogen balance | Dyspepsia, dysbiosis, intestinal autoinfection and autointoxication, formation of aversion to protein food. |
Briefly: answers to topical questions
What types of dysproteinemia are distinguished in pathophysiology?
In pathophysiology, three main groups of dysproteinemias are distinguished, associated with changes in the content or quality of blood proteins.
- Hyperproteinemias — an increase in protein content, which can be hypersynthetic (true increase in production) or hemoconcentrational (relative increase due to blood thickening).
- Hypoproteinemias — a decrease in protein content, subdivided into hyposynthetic (decreased production) and hemodilutional (relative decrease during blood dilution).
- Paraproteinemias — the appearance in the blood of pathological, functionally defective proteins.
How do kwashiorkor and alimentary dystrophy (marasmus) differ clinically and pathogenetically?
Both forms belong to clinically significant forms of pathology caused by a violation of protein-energy status.
| Characteristic | Kwashiorkor | Alimentary dystrophy (alimentary marasmus) |
|---|---|---|
| Type of protein alimentary deficiency | Unbalanced protein alimentary deficiency | Balanced protein alimentary deficiency |
No other clinical or pathogenetic differences are indicated in the cited sources.
It is easy to remember the 6 stages of disorders by following the pathway of protein in the body: Ingestion (alimentary) → Gastrointestinal tract (digestion) → Blood (dysproteinemias) → Membrane (transport) → Cell (metabolism) → Excretion (end products).
Class and exam questions
What is the difference between complete and absolute starvation?
In absolute starvation, both food and water intake cease completely. In complete starvation, a person does not eat, but continues to drink water.
Why does the body need dietary protein?
It is necessary to replenish total protein expenditure and supply cells with essential amino acids that are not synthesized inside the body.
What does a negative nitrogen balance lead to?
It causes weight loss, slowed growth in children, impaired tissue regeneration, as well as a decrease in appetite and food assimilation.
What is partial fasting?
This is a condition where the total caloric content of the diet is sufficient, but a deficit of individual components — proteins, lipids, carbohydrates, vitamins, or micronutrients — arises.
What else to study on this topic
- Pathogenesis and clinical manifestations of kwashiorkor
- Mechanisms of development of alimentary dystrophy
- Intestinal autointoxication in protein excess
- Types of dysproteinemias and their effect on the body
- Disorders of membrane amino acid transport
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