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CELLULAR REGULATIONS OF METABOLIC ACTIVITIES

KENYATTA UNIVERSITY

MECHANISMS AVAILABLE FOR CELLULAR REGULATIONS OF METABOLIC

ACTIVITIES

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METABOLLIC ACTIVITIES AND CELLULAR REGULATIONS

Introduction

Metabolism refers to the chemical processes occurring within a living cell or organism that are

necessary for the maintenance of life. Some substances are broken down to yield energy for vital processes

while those necessary for life undergo metabolic synthesis. These processes allow organisms to grow and

reproduce, maintain their structures, and respond to their environment. Cellular regulations refer to the body's

ability to regulate its inner environment to ensure stability in response to fluctuations in the outside environment

and the weather, the liver, kidneys, and the brain maintain this.

Discussion

Metabolic activities

All metabolic reactions fall into one of two general categories:

Catabolic reactions refer to the processes of breaking down organic matter, for example to

harvest energy in cellular respiration. These mainly involve the use of the carbohydrates, fats,

proteins, and minerals consumed in the diet to synthesize complex molecules, such as the

structural material of the skeleton, connective tissue, and cell membranes; nutrient stores for later

use; and secreted hormones and proteins, from cells into the blood or into the digestive tract. Inorder for these anabolic processes to precede efficiently, provision of the correct raw materials,

the ability to extract them from the blood and the presence of appropriate enzymes within the cell

are essential. The synthesis of these enzymes happens within the cells after the activation of the

appropriate genes in the cell nucleus. Digestion is a catabolic process because the molecules that

make up foods are too large to pass through the lining of the digestive system and go directly

into the bloodstream. The digestive process breaks down the large food molecules into smaller

particles to facilitate diffusion into the bloodstream and then transportation throughout the

bodys cells.

Anabolic reactions refer to the use of energy to construct components of cells such as

proteins and nucleic acids. Adenosine triphosphate or ATP, an energy carrier formed when

adenosine diphosphate (ADP) combines with a phosphate group, captures and stores energy
http://en.wikipedia.org/wiki/Liverhttp://en.wikipedia.org/wiki/Kidneyshttp://www.answers.com/topic/skeletonhttp://www.answers.com/topic/proteinshttp://en.wikipedia.org/wiki/Proteinhttp://en.wikipedia.org/wiki/Liverhttp://en.wikipedia.org/wiki/Kidneyshttp://www.answers.com/topic/skeletonhttp://www.answers.com/topic/proteinshttp://en.wikipedia.org/wiki/Protein

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released in catabolic reactions. Energy from an ATP molecule can be of use in combining

simpler molecules together to make complex molecules. For example, if a cell needs to repair

a rupture in its cell membrane, it will need to produce new protein molecules made from

hundreds or thousands of amino-acid molecules.

Sometimes, these processes alter, either through a person's choice or through outside factors, and

metabolic disorders follow. Such disorders range from anorexia andbulimia to obesity. These are all

examples of an unhealthy, unnatural alteration to the ordinary course of metabolism; on the other hand,

hibernation allows animals to slow down theirmetabolic rates dramatically as a means of conserving

energy during times when food is scarce.

Cellular regulations

Thermoregulation is the ability of an organism to keep its body temperature within certain boundaries,

even when the surrounding temperature is very different. Thermoregulation is an important aspect of

human homeostasis. Humans are warm-blooded, maintaining a near-constant body temperature.

Temperature may enter a circle of positive feedback, when temperature reaches extremes of 45C

(113F), at which cellular proteins denature, causing the active site in proteins to change, thus causing

metabolism stop and ultimately death.

Iron is an essential element for human beings. The control of this necessary but potentially toxic

substance is an important part of many aspects of human health and disease especially because iron is

essential to red blood cells. In fact, most of the human body's iron is contained in red blood cells'

hemoglobin, and iron deficiency is the most common cause of anemia.

Osmoregulation is the active regulation of the osmotic pressure of bodily fluids keeping the body's

fluids from becoming too dilute or too concentrated. Osmotic pressure is a measure of the tendency of

water to move into one solution from another by osmosis. The higher the osmotic pressure of a solution

the more water wants to go into the solution.

The kidneys remove excess ions from the blood and expelling them as urine, thus affecting the osmotic

pressure.
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Hemostasis is the process whereby bleeding is halted. A major part of this is coagulation. Platelet

accumulation causes blood clotting in response to a break or tear in the lining of blood vessels. Unlike

the majority of control mechanisms in human body, the Hemostasis utilizes positive feedback, for the

more the clot grows, the more clotting occurs, until the blood stops. Another example of positive

feedback is the release of oxytocin to intensify the contractions that take place during childbirth.

Homeostatic control mechanisms, which maintain a constant internal environment, ensure the

maintenance of balance between fluid gain and fluid loss. The hormones Anti-diuretic Hormone and

Aldosterone play a major role in this ensuring that:

If the body is becoming fluid-deficient, the secretion of Anti-diuretic Hormone causes fluid to be

retention by the kidneys and the reduction of urine output. In the cases of excessive fluid levels, there is

suppression of the secretion of the hormones causing less retention of fluid by the kidneys and there is

increase in the production of urine. In addition, too much Carbon Dioxide in the blood causes the blood

to be acidic, heavy respiration reduces the levels of the carbon dioxide in the blood.

Cellular Regulations involved in Metabolic Activities

Regulation of metabolic activities is normally dependent on the needs of the body and the

flow of metabolites along their respective metabolic channels. For such processes to occur, various

aspects of metabolism must be fulfilled. For instance, metabolic substrates or nutrients must be

partitioned between organs and tissues when they are still in their different nutritional states. Therefore,

certain specific enzymes and/or proteins must be expressed into the required forms in order for them to

influence specific metabolic properties of the affected tissue. This is because some tissues do not express

particular enzymes whereas others do express the specified enzymes. For instance, glucose-6-

phosphatase enzyme that is responsible for producing glucose from glucose 6-phosphate is expressed by

the liver but the skeletal muscle does not. Hence, the breakdown of liver glycogen contributes directly to

blood glucose whereas the breakdown of skeletal muscle glycogen does not.

Another form of metabolic regulation in cellular organisms is achieved through the

alteration of substrates through the bloodstream. A good example for this scenario is the use of fatty

acids as fuels in the skeletal muscle as opposed to using glucose. The reason is simple, increased

presence of glucose concentration in circulation after an intake of a carbohydrate rich meal calls for the

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reduction of fatty acids to utilize the glucose. The adipose tissue in muscles will be required to release

fatty acids into circulation. These fatty acids are switched off by insulin, and therefore muscles will be

deprived of utilizing the fatty acids. In the end, a metabolic balance will be achieved in cellular activities

just as evidenced in the cooperation of metabolic regulation between tissues in the whole body.

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