Understanding the Cells in Your Body

All physiological processes of the body are based on cellular activity and cells of all species exhibit remarkable biochemical unity. It is amazing that all organisms are composed of cells. Cells are the simplest structural and functional unit of life. An organism’s structure and all of its functions are ultimately due to cells.

Cells come from only preexisting cells, and do not come from nonliving matter. This is the prime reason that all life traces its ancestry to the same original cells.

Cells are progressively organized into tissues, organs, systems, and the whole body. There are five levels in which they are organized:

Organ System
Organs
Tissue
Cellular
Chemical

Homeostasis

Homeostasis is essential for cell survival, and each cell, as part of an organized system contributes to homeostasis. A change in an internal environment initiates a reaction to minimize change within the system. The purpose of this is to maintain stable conditions in the body. A loss of homeostasis tends to cause illness or even death.

Different concepts of homeostasis:

Extrinsic Control
- Permits coordinated regulation of several organs
Dynamic Equilibrium
- A balanced change around a set point
Major Control Systems
- Nervous and Endocrine
Negative Feedback
- Body senses a change and reverses in opposite direction
Positive Feedback
- Change brings upon more change
Requires cell-to-cell communication via chemical messengers

Components:

Effector
- A molecule, cell, or organ that carries out a response to a stimulus and restores homeostasis
Integrating Center
- A mechanism that processes information relates it to other available information and makes a decision about what the appropriate response should be
Receptor
- Senses change in the body
- A cell or organ specialized to detect a stimulus

Chemical Concepts

Cell survival depends on chemical reactions to carry out cell functions and build and maintain cell structure.

Let’s break down some concepts to make sure everyone is on the same page here before we move on.

Matter is anything that has mass and occupies space
An element is the simplest form of matter to have unique chemical properties
An atom consists of protons (+), neutrons, and electrons (-)

Electrons

Electrons determine the chemical properties of an atom, thereby governing what molecules can exist and what chemical reactions can occur. Electrons swarm about the nucleus in concentric regions called electron shells. Each shell has a limited number of electrons. The electrons in the outermost shell are called valance electrons and they determine the chemical bonding properties of an atom.

Ions

Some atoms will either give up electrons or acquire additional in order to form a complete outer shell. Ions are charged particles with unequal numbers of protons and electrons. The charge on an ion is called its valence. An anion is negatively charged while a cation is positively charged. Molecules that ionize in water and form solutions capable of conducting electricity are called electrolytes (Gatorade ring a bell?).

Chemical Bonds

Atoms chemically bond with each other to form molecules or different elements form compounds. Chemical bonds are a force that attracts one atom to another.

Ionic Bond
- Due to the attraction of oppositely charged ions to each other

Covalent Bond
- Results from the sharing of electrons
- Polar bonds are those in which the electrons are not shared equally, so regions of the molecule have a different charge associated with them
- Nonpolar bonds are when electrons are shared equally, thus the molecules have no regions of different charge
- These are the strongest of the bonds
Hydrogen Bond
- Occurs when there is a weak attraction between a slightly negative oxygen or nitrogen atom in one molecule and a slightly positive hydrogen ion.
- They can form between different regions of the same molecules, such as proteins and DNA
- These are the weakest of the bonds

Chemical Reactions

A chemical reaction is a process in which a chemical bond is formed or broken. Reactants are substances that enter into a reaction and are consumed by it. Products are substances produced by the reaction that took place. Law of mass action states that reversible reactions proceed from the side with the greater quantity of reactants to the side with the lesser quantity. The basis for chemical reactions is molecular motion and collisions.

Reactions are affected by:

Catalysts
- Work by temporarily binding to reactants and holding them in a favorable position to react with each other
Concentration of reactants
Temperature

The basics of Acids and Bases:

Chemical solutions that resist changes in pH are called buffers
Electrolytes that release hydrogen ions in water are called acids
Electrolytes that release hydroxyl ions that combine with hydrogen in water are called bases
pH = 7.0 (neutral)
pH < 7.0 (acidic)
pH > 7.0 (alkaline)

Conclusion

This was a cliff-note version on cells. There is so much information out there that gets more in-depth on the topic than what we got into with this article. The information found in this article will help you understand a little more about what your body does at a cellular level and will hopefully give you a better appreciation of what your body does on a daily basis without you even knowing or feeling it.

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