15 Disember 2010

What Are the Elements in the Human Body?

Most of the human body is made up of water, H2O, with cells consisting of 65-90% water by weight. Therefore, it isn't surprising that most of a human body's mass is oxygen. Carbon, the basic unit for organic molecules, comes in second. 99% of the mass of the human body is made up of just six elements: oxygen, carbon, hydrogen, nitrogen, calcium, and phosphorus.

  1. Oxygen (65%)
  2. Carbon (18%)
  3. Hydrogen (10%)
  4. Nitrogen (3%)
  5. Calcium (1.5%)
  6. Phosphorus (1.0%)
  7. Potassium (0.35%)
  8. Sulfur (0.25%)
  9. Sodium (0.15%)
  10. Magnesium (0.05%)
  11. Copper, Zinc, Selenium, Molybdenum, Fluorine, Chlorine, Iodine, Manganese, Cobalt, Iron (0.70%)
  12. Lithium, Strontium, Aluminum, Silicon, Lead, Vanadium, Arsenic, Bromine (trace amounts)
Reference: H. A. Harper, V. W. Rodwell, P. A. Mayes, Review of Physiological Chemistry, 16th ed., Lange Medical Publications, Los Altos, California 1977.

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04 Disember 2010

The chemistry of love

Do you think that there is real chemistry behind love? Yes! Chemistry is at the bottom of every step in a relationship, and this field is under continuous research. When you fall in love, your brain suffers some changes and also certain chemical compounds are released. Researchs usually consider three stages in love: lust, attraction and attachment.
love
1) Lust
Lust is driven by initial physical attraction and flirting. This stage can depend on characteristics such as a symmetrical face and proportionate body dimensions. Flirting can include gazing into the eyes, touching, and mirroring in body language. The two chemicals that surface during this stage are the sex hormones (testosterone and estrogen) and pheromones.
In the animal world, PHEROMONES are individual scent "prints" found in urine or sweat that dictate sexual behavior and attract the opposite sex. The existence of human pheromones was discovered in 1986 by scientists at the Chemical Senses Center in Philadelphia and its counterpart in France. They found these chemicals in human sweat.
2) Falling in love - Attraction
The romantic or passionate love is characterized by euphoria when things are going well, and terrible mood swings when they're not. When you fall in love you may have many physical symptoms: lose of appetite, can't sleep, can't concentrate, palms sweat, butterflies in stomach... This is due to surging brain chemicals called monoamines:
- DOPAMINE: it's commonly associated with the pleasure system of the brain, providing feelings of enjoyment and reinforcement to motivate us to do certain activities. It's released by naturally-rewarding experiences, such as sex or food. Some research studies show that when female rodents were injected dopamine in the presence of a male rodent, the female will pick him out of a crowd later.
- PHENYLETHYLAMINE: It's a natural amphetamine like the known drug and can cause the same stimulation effects. It contributes to that on-top-of-the-world feeling that attraction can bring, and gives you the energy to stay up day and night with a new love.
- SEROTONIN: it controls impulses, unruly passions, obsessive behavior, aiding the sense of "being in control".
- NOREPINEPHRINE is another neurotransmitter which induces euphoria in your brain, exciting the body by giving it a booster dose of natural adrenaline. This causes the heart to beat faster and blood pressure to rise. That's why you can experience a pounding heart or sweaty palms when you see someone you're attracted to.
3) Attachment - Staying together
There is a sense of calm and stability that we feel with a long-term partner, a sort of bond that keeps couples together. This kind of love is driven these hormones:
- OXYTOCIN: it's sometimes known as "the cuddle chemical." It's the hormone best known for its role in inducing labor by stimulating contractions. But recently it has been observed that it may influence our ability to bond with others, as both genders release this hormone when touching and cuddling, with the oxytocin level peaking during orgasm.
- VASOPRESSIN: also called as "the monogamy chemical". Researchers have found that suppression of vasopressin can cause males to abandon their love nest and seek new mates.
- ENDORPHINS: they are biochemical compounds that enhance our immune system, block the lesion of blood vessel, have anti-aging, anti-stress and pain-relieving effect, and also help to improve your memory.
High levels of oxytocin and vasopressin may interfere with dopamine and norepinephrine pathways, which may explain why with the time attachment grows as mad passionate love fades.
Well, as you can see, there is real chemistry taking place in our body when we are in love! This doesn't mean that love is only chemistry, but at least now you can understand this feeling from a different point of view, don't you?
Silvia Martínez

03 Disember 2010

Teknik Jawab Kimia



 








 







 













 



http://spmchem.blogspot.com

*Kalau rasa tak nak buat, lebih baik buat. Mungkin akan membantu. Tak rugi pasti untung. Percayalah.

02 Disember 2010

Chemistry Tips - SPM 2010 Focus

Chemistry SPM Tips : Do focus on these topics. Hope it will help all of you in getting A+ in Chemistry

http://spmchem.blogspot.com/

What is cholesterol?

Everybody has heard about "bad cholesterol" and "good cholesterol"... but, what's that?
Cholesterol is a fatty substance found in the blood of humans and also in the outer lining of cells (membrane) in the body of animals. The cholesterol that we have in our blood comes from two different sources:
- liver production
- diet: meat, fish, dairy products...
cholesterol
After each meal, cholesterol is absorbed by the intestines, goes into the blood and then it's packaged inside a protein coat. These proteins are removed then by the liver.
When you go to the doctor, you are suggested to keep the "bad cholesterol" in blood low and the "good cholesterol" high. Ok. What does this mean?
# Bad cholesterol or LDL-low-density lipoprotein: These proteins deposit cholesterol on the artery walls, causing the formation of a hard substance named cholesterol plaque. With the time, this plaque leds to the narrowing of the arteries in a process called atherosclerosis. Because of it, the arteries can get blocked, so LDL is associated with a higher riks of coronary heart diseases.
artery
When the liver has many LDL receptors, this helps to remove more rapidly the LDL cholesterol from the blood, helping to keep the bad cholesterol levels low. The number of LDL receptors depends on both heredity and diet. For instance, people with familiar hypercholesterolemia have a very low number of LDL receptors, so they usually have high levels of bad cholesterol. Besides, the bad cholesterol level can raise with diets high in saturated fats (certain vegetable oils and products derived mainly from meat and dairy products).
# Good cholesterol or HDL-high-density lipoprotein: These particles extract cholesterol from the artery walls and dispose them through the liver. So they prevent atherosclerosis.
Life style factors and other conditions influence HDL cholesterol levels. HDL cholesterol levels are for instance lower in smokers, people who eat a lot of sweets, and also in those who are overweight and inactive. On the other hand, estrogen increases the HDL cholesterol level, so usually women have higher good cholesterol levels than men.
These are some websites with interesting suggestions to keep your cholesterol at healthy levels, though anyway I advise you to visit your doctor if your levels are wrong:
- Low cholesterol diet
- Cholesterol Lowdown

01 Disember 2010

Why the sky is blue?





We all can look up to the sky and see its beautiful blue colour. Why is it blue, and not red, or white for instance?


An object is coloured because of the light that it reflects. The white light from the sun contains all the wavelengths, but when it impacts on an object some of its wavelengths are absorbed and some reflected. For example blue objects reflect 'blue' light, which is light with a pretty short wavelength.
White light is formed by all the colours together:
spectrum
The colour of the sky can be explained considering a phenomena named Rayleigh scattering, that consists on the scattering of light by particles much smaller than its wavelength. This effect is especially strong when light passes through gases.
Each of the wavelengths of light suffers a different scattering when it encounters the gas particles that form the atmosphere (nitrogen, oxygen...). This effect is more prominent in the case of short light wavelengths, that are the blue end of the visible spectrum, so the blue light becomes much more dispersed and it can be seen from every direction, as you can see in the drawing below (blue arrows). This gives us the impression that the sky is blue. On the other hand, the red light is scattered much less, so it can be only seen from certain directions (red arrow). In the drawing below, both Observer 1 and Observer 2 can see the blue light, but only Observer 2 is in the right direction to see the red one, and that's why we see those beautiful red skies at sunset sometimes.
sky
Then, why the clouds are white? Well, the water droplets that form the clouds have a much larger size than the gas particles of the air, and they scatter all the wavelenghts of light in the same extent, so all of them are reflected equally and we receive then the full colour of light, that is white.

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Memerihalkan inovasi teknologi

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