Conservapedia - User contributions [en]

Food Chain

2008-07-27T20:22:55Z

ThomasJSmith: expand

A '''food chain''' is a diagram of the transfer of [[food]] energy from [[plant]]s to one or more [[animal]]s. It is a series of plants and animals linked by their food relationships.<ref>http://www.nwrc.usgs.gov/fringe/glossary.html</ref> Energy becomes more concentrated as it passes up a food chain.

==References==

<references/>

[[Category:Ecology]]
[[Category:Biology]]

B cells

2008-07-27T20:21:21Z

ThomasJSmith:

'''B cells''' are white blood cells that help the body defend itself against infection. These cells are produced in [[bone marrow]]and develop into plasma cells that produce [[antibodies]]. A B cell produces a range of antibodies that are displayed on its cell surface. When the cell takes up a pathogen or foreign antigens by [[endocytosis]], these select which antibody the cell will produce and stimulate it to secrete these [[proteins]] into the blood. This process is called "B cell activation".

B cells are also known as [[B lymphocytes]].<ref>http://www.cdc.gov/vaccines/about/terms/glossary.htm#b</ref>

==References==
<references/>

[[Category:Medicine]]
[[Category:Biology]]

Cytoplasm

2008-07-27T20:12:49Z

ThomasJSmith:

A '''cytoplasm''' is a jelly-like fluid inside the [[cell]] in which the [[organelle|organelles]] are suspended.<ref>Wile, Dr. Jay L. ''Exploring Creation With Biology''. Apologia Educational Ministries, Inc. 1998</ref>

The cytoplasm is all of a [[cell]]'s contents inside its plasma membrane. In eukaryotes, the cytoplasm only includes what is outside the nucleus. In plants the cytoplasm moves continuously around the periphery of the cell, in a process called "cytoplasmic streaming" this orientates the chloroplasts so that their membranes are perpendicular to the light entering the cell, maximising photosynthetic efficiency.

==References==
<references/>

[[Category:Biology]]

Amoebas

2008-07-27T20:01:19Z

ThomasJSmith:

{{stub}}
'''Amoebas''' are varied tiny unicellular [[organism]]s. They were classified as [[protozoa]]ns of the [[genus]] '''Amoeba''' or related genera, but are now known to be part of the Unikonts. They have no solid form, instead consisting of a mass of [[protoplasm]] containing one or more [[nuclei]] surrounded by a flexible outer [[membrane]]. Most amoebae live in soil and are [[anaerobic]]. They move by means of [[pseudopod]]s formed by fibronectin. Some amoeba are parasites that cause amoebic dysentery and some forms of septicaemia.

According to the Colonial Theory<ref>
John O. Corliss: Systematic Zoology, Vol. 8, No. 4 (Dec., 1959), pp. 169-190</ref>, in [[evolution]] history, amoeba-like organisms are believed to have contributed to the origin of multicellular organisms by clumping together to form colonies during food shortage, and eventually differentiating into various types of cells to give rise to the first multicellular organisms.

==References==
<references/>

[[Category:biology]]

Yeast

2008-07-27T18:07:04Z

ThomasJSmith: /* Other notable yeasts */

A '''yeast''' is a single-celled [[fungi|fungus]]. It is related to other fungi that people are more familiar with. These include edible [[mushroom]]s which are available at the local supermarket, common baker’s yeast used to leaven [[bread]], [[mold]]s that ripen blue [[cheese]] as well as molds that produce [[antibiotic]]s for medical and veterinary use. Many consider [[edible]] yeast and fungi to be as natural as fruits and vegetables.

==Yeast Cells==

Over 600 different species of yeast are known. They are found in association with other microorganisms as part of the normal inhabitants of [[soil]], vegetation, marine and other aqueous environments. Some yeast species are also natural inhabitants of [[man]] and animals. While some species are highly specialized and found only in certain habitats at certain times of the year, other species are generalists and can be isolated from many different sources.

Baker’s (or brewer's) yeast (''Saccharomyces cerevisiae'') is used to leaven bread throughout the world and it is the type of yeast that people are most familiar with. It is also used in making beer and wine, although sometimes other closely related species such as ''Saccharomyces carlsbergensis'' or ''Saccharomyces bayanus'' are used instead.

A typical yeast cell is approximately equal in size to a human [[red blood cell]] and is spherical to ellipsoidal in shape. Because it is so very tiny, it takes about 30 billion yeast cells to make up to one gram of compressed baker’s yeast. Yeasts reproduce by budding, a process during which a new bud grows from the side of the existing cell wall. This bud eventually breaks away from the mother cell to form a separate daughter cell. Each budding yeast cell, on average, undergoes this budding process 12 to 15 times before it is no longer capable of budding.

During commercial production, yeast is grown under carefully controlled conditions on a [[sugar]] containing medium typically composed of [[beet]] and [[cane]] molasses. Under ideal growth conditions a yeast cell reproduces every two to three hours. Under anaerobic (devoid of oxygen) conditions the yeast cell will carry out the metabolic process of [[fermentation]] to produce ethanol and carbon dioxide.

==Other notable yeasts==

''Schizosacharomyces pombe'' is a yeast first isolated from East African millet beer (''pombe'' is the Swahili word for beer). However, it is most important as a laboratory experimental organism for the investigation of cell biology. Sir Paul Nurse won the 2001 Nobel Prize for Physiology and Medicine for his discoveries of how the cell division cycle is regulated in ''S. pombe''. <ref> http://nobelprize.org/nobel_prizes/medicine/laureates/2001/ </ref>

''Candida albicans'' is a common [[commensal]] yeast which lives on human skin and in the gut. About 50% of people carry it, with no noticeable effect. It is most well known as the cause of thrush, although less frequently it can cause nasty oral infections. In severely immunocompromised patients it can spread through the body as [[hyphae]] and invade vital organs, with a high mortality rate. <ref> http://www.healthscout.com/ency/68/312/main.html </ref> The switch between harmless single cells and pathogenic hyphae is regulated by the numbers of yeast cells in a particular environment, in a process known as [[quorum sensing]].

==References==

<references/>

[[Category:Food and Drink]]
[[Category:Fungi]]
[[Category:microbiology]]

Actin

2008-07-27T17:57:41Z

ThomasJSmith:

'''Actin''' is a [[helical]] [[protein]] that forms [[microfilament|microfilaments]]. It is an essential element of the [[cytoskeleton]] of a [[biological cell]]. Actin binds GTP, allowing the filaments to extend and contract rapidly, with a force of up to 200 piconewtons.

[[Category:Biology]]

Cell Wall

2008-07-27T17:52:16Z

ThomasJSmith:

A '''cell wall''' is a structure formed of [[cellulose]] that surrounds plant cells. Cell walls typically have transport [[protein]]s that pass through to allow movement between adjacent [[cell]]s. These pores are known as tight junctions, and are also important in holding cells together in tissues.

[[Category:Biology]]

Endospore

2008-07-27T17:46:48Z

ThomasJSmith:

The [[DNA]] of a [[bacteria|bacterium]] or fungus that is coated with several hard layers.<ref>Wile, Dr. Jay L. ''Exploring Creation With Biology''. Apologia Educational Ministries, Inc. 1998</ref> Endospores can resist freezing, drying and high temperatures since the DNA is held in a complex with [[protein]]s called potamines that protect it from damage.

==References==
<references/>

[[Category:Biology]]

Blood clotting cascade

2008-07-27T17:40:42Z

ThomasJSmith:

A number of proteins are involved in the series of events that lead to vertebrate blood clotting.

Michael Behe describes it thus:
<blockquote>
When an animal is cut, a protein called Hagemann factor (XII) sticks to the surface of cells near the wound. Bound Hagemann factor is then cleaved by a protein called HMK to yield activated Hagemann factor. Immediately the activated Hagemann factor converts another protein, called prekallikrein, to its active form, kallikrein. <ref>Behe, M. 1996. Darwin's Black Box. New York: The Free Press</ref>
</blockquote>

Behe, who is a supporter of [[Intelligent Design]], argues that all of these components must be in place before the system will work:
<blockquote>
...none of the cascade proteins are used for anything except controlling the formation of a clot. Yet in the absence of any of the components, blood does not clot, and the system fails. <ref>Behe, M. 1996. Darwin's Black Box, p.86. New York: The Free Press</ref>
</blockquote>

Although, as Behe points out, Factor XII initiates the "cascade of proteins" in vertebrates, dolphins lack Factor XII <ref>Robinson, A. J., M. Kropatkin, and P. M. Aggeler, 1969. Hagemann Factor (Factor XII) Deficiency in Marine Mammals. Science 166: 1420-1422</ref> and yet their blood is known to clot. Similarly, molluscs such as snails have only four components in their blood clotting cascade, with a single protease step. This appears to contradict the notion of [[irreducible complexity]] in regard to this process.

==References==
<references/>
[[category:biology]]

Conjugation

2008-07-27T17:30:05Z

ThomasJSmith:

:''For conjugation in grammar, see [[Verb]].''
'''Conjugation''' is a temporary union of two [[organism|organisms]] for the purpose of [[DNA]] transfer.<ref>Wile, Dr. Jay L. ''Exploring Creation With Biology''. Apologia Educational Ministries, Inc. 1998</ref> Conjugation is most common in bacteria, and is a major factor in horizontal gene transfer. Conjugation between two cells of the same bacterial species involves a thin tube joining the cells and transferring DNA, but when two different species are involved the bacteria form a larger structure called a protoplast, where the cell walls form the bridge between the cells.

==References==
<references/>

[[Category:Biology]]