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When polar covalent bonds containing hydrogen form, the hydrogen in that bond has a slightly positive charge because hydrogen’s electron is pulled more strongly toward the other element and away from the hydrogen. Because the hydrogen is slightly positive, it will be attracted to neighboring negative charges. When this happens, a weak interaction occurs between the δ + of the hydrogen from one molecule and the δ – charge on the more electronegative atoms of another molecule, usually oxygen or nitrogen, or within the same molecule. This interaction is called a hydrogen bond    . This type of bond is common and occurs regularly between water molecules. Individual hydrogen bonds are weak and easily broken; however, they occur in very large numbers in water and in organic polymers, creating a major force in combination. Hydrogen bonds are also responsible for zipping together the DNA double helix.

Like hydrogen bonds, van der Waals interactions are weak attractions or interactions between molecules. Van der Waals attractions can occur between any two or more molecules and are dependent on slight fluctuations of the electron densities, which are not always symmetrical around an atom. For these attractions to happen, the molecules need to be very close to one another. These bonds—along with ionic, covalent, and hydrogen bonds—contribute to the three-dimensional structure of the proteins in our cells that is necessary for their proper function.

Career connection

Pharmaceutical chemist

Pharmaceutical chemists are responsible for the development of new drugs and trying to determine the mode of action of both old and new drugs. They are involved in every step of the drug development process. Drugs can be found in the natural environment or can be synthesized in the laboratory. In many cases, potential drugs found in nature are changed chemically in the laboratory to make them safer and more effective, and sometimes synthetic versions of drugs substitute for the version found in nature.

After the initial discovery or synthesis of a drug, the chemist then develops the drug, perhaps chemically altering it, testing it to see if the drug is toxic, and then designing methods for efficient large-scale production. Then, the process of getting the drug approved for human use begins. In the United States, drug approval is handled by the Food and Drug Administration (FDA) and involves a series of large-scale experiments using human subjects to make sure the drug is not harmful and effectively treats the condition it aims to treat. This process often takes several years and requires the participation of physicians and scientists, in addition to chemists, to complete testing and gain approval.

An example of a drug that was originally discovered in a living organism is Paclitaxel (Taxol), an anti-cancer drug used to treat breast cancer. This drug was discovered in the bark of the pacific yew tree. Another example is aspirin, originally isolated from willow tree bark. Finding drugs often means testing hundreds of samples of plants, fungi, and other forms of life to see if any biologically active compounds are found within them. Sometimes, traditional medicine can give modern medicine clues to where an active compound can be found. For example, the use of willow bark to make medicine has been known for thousands of years, dating back to ancient Egypt. It was not until the late 1800s, however, that the aspirin molecule, known as acetylsalicylic acid, was purified and marketed for human use.

Occasionally, drugs developed for one use are found to have unforeseen effects that allow these drugs to be used in other, unrelated ways. For example, the drug minoxidil (Rogaine) was originally developed to treat high blood pressure. When tested on humans, it was noticed that individuals taking the drug would grow new hair. Eventually the drug was marketed to men and women with baldness to restore lost hair.

The career of the pharmaceutical chemist may involve detective work, experimentation, and drug development, all with the goal of making human beings healthier.

Section summary

Matter is anything that occupies space and has mass. It is made up of elements. All of the 92 elements that occur naturally have unique qualities that allow them to combine in various ways to create molecules, which in turn combine to form cells, tissues, organ systems, and organisms. Atoms, which consist of protons, neutrons, and electrons, are the smallest units of an element that retain all of the properties of that element. Electrons can be transferred, shared, or cause charge disparities between atoms to create bonds, including ionic, covalent, and hydrogen bonds, as well as van der Waals interactions.

Art connections

[link] How many neutrons do carbon-12 and carbon-13 have, respectively?

[link] Carbon-12 has six neutrons. Carbon-13 has seven neutrons.

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[link] An atom may give, take, or share electrons with another atom to achieve a full valence shell, the most stable electron configuration. Looking at this figure, how many electrons do elements in group 1 need to lose in order to achieve a stable electron configuration? How many electrons do elements in groups 14 and 17 need to gain to achieve a stable configuration?

[link] Elements in group 1 need to lose one electron to achieve a stable electron configuration. Elements in groups 14 and 17 need to gain four and one electrons, respectively, to achieve a stable configuration.

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Questions & Answers

what are the example of photosynthesis
Gamshe Reply
Is how plant covert sugar and energy, air and sunlight into energy to grow
Timileyin
An example of photosynthesis is how plants convert sugar and energy from water, air and sunlight into energy to grow.
Bernard
My cordial salam to everybody. I have a question to all. What do you mean by plasma membrane?
Mahmud Reply
Plasma membrane or Cell membrane is the outer layer of tissue surrounding the whole or part of an organ. in addition, it is the outer flexible or semi-flexible covering or waterproofing whose primary function is to exclude water.(usually in plants and animals).
Job
I have a question .... Why cell wall is not present in animals cells and why it is present in plants cells?
ShAmy
what is glucose
Sisay
how alkali metal form
Puskal Reply
what is a cytosol
Siddeeqah Reply
cytosol is the internal fluid of the cell and a large part of cell were metabolism occur
Bernard
u are right dear.
Job
what is cell
Prince Reply
I think that cell is structural unit of our body. Because I have come to know that cell is the structure and biological function of an organism in the eye of scientists.
Mahmud
Cell is the fundamental, structural and functional unit of life
Winifred
Absolutely you are right. But what do you mean by life?
Mahmud
cell is the basic unit of life
Siddeeqah
life is the study of living organisms
Bernard
Cell is the basic, structural and functional unit of life. therefor no living organisms exist without a cell or a healthy cell.
Job
synthesis of 1 molecules of glucose requires
Purvesh Reply
what is the chemical composition of water
Abigail Reply
h20
Rita
h20
Asad
H20
Mathews
H2o
Bernard
H2O
Michelle
H2O
Emzzy
What is skeleton
Emzzy
skeleton is an internal or external framework of bones
Michelle
Skeleton is the structural frame work of the body
Niimat
Skeleton is the internal bony framework of the body of living organisms.
Job
Oh, how's is it going..
Brian Reply
not too good
Monique
hy
Adeola
hi
Imamkasim
hi
Veronica
Any one else taking Bio 1406 with Stephanie Martin?
Veronica
where is it ?
ShAmy
am here Veronica
iyota
Not bad
Winifred
Part of compound microscope
Bakish Reply
a. body b. stage clip c. adjacent knob d. arm e. eye piece
Kpodo
E
Rita
give five difference between worker and queen bee.
Imamkasim
How do u know when you want to urinate
Akpo Reply
how do you know when you want to urinate
Akpo
I don't know please explain
Coded
As the bladder fills up .. the signals are sent to the brain specifying that its filling up and should be emptied and the fuller it gets, the more signals/ alerts are sent to brain ...leading to the urge to urinate .... to go pee
Khalida
OK thank you
Coded
hello
Issiya
hi
Abigail
wat
Gamshe
I want the this ecologycal terms
Catherine Reply
what are enzymes
Alvin Reply
enzymes are organic catalysts which speed the rate of chemical reaction but it's self is not used up in the process
Azeezah
what are photosynthesis
Gamshe
what are characteristics of photosynthesis
Gamshe
photosynthesis is the process where by Green manufacture their own food with the help of energy from the sun
Bernard
What is hormones
Emzzy
Hormones are chemical messenger that are secreted directly into the blood which carries them to organs and tissues of the body to exert their function
Bernard
What is the full meaning of DNA
Emzzy
what is fertilization
Ofosu Reply
fusion of male and famele gametes
Biology
fusion of female and male gametes.
Biology
form zygote to eggs
Ahmad
also known as syngamy
RESHMA
why is water called a polar molecule
Jabari Reply
enzyme that not found in mitochondria
Mukesh Reply

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Source:  OpenStax, Biology. OpenStax CNX. Feb 29, 2016 Download for free at http://cnx.org/content/col11448/1.10
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