Biology in Action

Yesterday in class, we compiled the following list of what you know about our current unit on DNA. Some of you had questions that you still had. Your class list is below. For extra credit, leave a comment on the page answering the questions your classmates had.

I know now ….
There are three types of RNA
DNA makes a double helix.
DNA Makes RNA through transcription
The scientists that found DNA’s structure are Wilkins and Franklin (helix).
Watson and Crick said DNA  was a double helix.
DNA is composed of two strands.
Chromosomes are made of DNA.
Deoxyribose is the sugar in DNA.
A bonds with T
C bonds with G
A bonds with U in RNA.
DNA is made up of subunits called nucleotides.

I want to know more about. . .
Why the shape of DNA is a double helix.
Could Peter Parker become Spiderman by having his DNA changed from a spider?
Genes How are some diseases genetic?
What animals have the genetics of dinosaurs.
Why is it that the first letter of t,r and m RNA is lowercased?

The above images is from biologist, Niall Hamilton who cultured some festive bacteria and yeast.  The black in the snowman below is a yeast commonly found near bathroom sinks

Reposted from November 27, 2008

Tryptophan is one of eight essential amino acids in the human body.  Essential amino acids are so called not because they are more important to life than the others, but because the body does not synthesize them, making it essential to include them in one’s diet in order to obtain them.

Like other amino acids, tryptophan works as a building block for proteins.  Tryptophan is found in every protein including fish, steak, cheese and eggs.  Tryptophan is required for the synthesis of some specific organic compounds including:

• Serotonin and melatonin (neurotransmitters)
• Niacin (vitamin B3), and
• kynurenines

Serotonin (5-hydroxytryptamine) affects mood, melatonin helps regulate sleep, and kynurenines may be useful in regulating the immune system.

A drug called tranilast, available in Japan as an allergy medication, is chemically similar to kynurenines and shows promise for the treatment of certain autoimmune diseases, including multiple sclerosis.

Turkey isn’t even unusually high in tryptophan. Many foods, such as beef or soybeans, boast higher concentrations (read more and see the table comparing Turkey Tryptophan to other foods after the break).

Read More…

Reposted Nov 25, 2008

It’s the age old question, white meat or dark meat – what’s the difference?

All parts of the bird have their benefits and the constituents of their structure is related to their function flavor.

White Meat

White meat is made up of muscles with fibers that are called fast-twitch fibers.  Fast-twitch muscles are used for quick bursts of activity, such as fleeing from danger. These muscles get energy from glycogen, which is also stored in the muscles. Glycogen is a polysaccharide of glucose, an animal starch.   Animal starch is stored primarily in the liver and broken down into glucose when needed by the white muscle.

Dark Meat

Dark meat is made up of muscles with fibers that are called slow-twitch. These muscles are used for extended periods of activity, such as standing or walking, and need a consistent energy source. Dark meat has more myoglobin, an amazing protein.  (This is the red liquid that you may see coming from meat at the butcher’s section of your local supermarket.)  Like it’s cousin hemoglobin, myoglobin delivers oxygen to the mitochondria.  Muscles that are used more frequently have higher amounts of myoglobin. More myoglobin gives the darker color of the meat.

This explains why the farmed turkeys (above left) have whiter meat than wild turkeys (above right). Farmed poultry do not fly, and is whiter than the chest muscles of the flying birds; also, why the game meat is darker (wild animals move much more than the domestic ones). Different levels of myoglobin between species also explains the difference in meat colors.
When dark meat is cooked it turns the myoglobins to metmyoglobins, which is brown/gray. Metmyoglobins are very high in iron (albeit there is not that much in dark meat in the first place).  Dark meats tend to contain more zinc, riboflavin, niacin, thiamin, vitamins B6 and B12, amino acids, iron than white meat. Poultry dark meat contain vitamins A, K, B6, B12, niacin, folate, pantothenic acid, minerals as selenium, phosphorus and zinc.

Even the fats in most of the dark meats have healthy parts. They contain Omega-3, and Omega-6 fatty acids, and other ‘healthy’ fats.

It is the saturated fat content which lowers the true quality of dark meat. To reduce the saturated fat content of chicken dark meat, simply remove the skin.

Sources:
http://www.diet-blog.com/archives/2007/10/08/dark_meat_vs_white_meat_whats_the_difference.php

http://www.drdonmd.com/health_articles.cfm

http://news.softpedia.com/news/9-Things-You-Did-Not-Know-About-Muscles-74768.shtml

Reposted from Nov 25, 2008 
Why does a turkey continue to cook after it’s out of the oven? How can you be sure to thoroughly cook the dark meat without drying out the white meat? Is stuffing really a good idea? How do you make the skin golden?

This webcast at exploratorium investigates why temperature is critical, and investigates different cooking methods: roasting,deep frying, barbecuing, and smoking.

Source: http://www.exploratorium.edu/cooking/webcasts/turkey_cast.html