---

Kids in Foot Ball

---

Once Upon Time in A Village. The kids are playing football. Suddenly a friend feel.....

"Come on Steve slept his ball here", exclaimed Michael.  Steve immediately ran towards Michael and was ready to pass his ball.  But suddenly.  Shit.  "Oh sick", Steve moaned. Apparently he stumbled over a stone he had not seen.  "How is this?" Ferry asked. "Are you still afford?"  "Oh, I do not think I can go on. I hope I just wrote ".  "Yes, you treat your wounds. Do not forget to clean with Alcohol 70%, "said Alex  "Alright friends. I go home first yes ".  "Okay, be careful". Steve's friends say.

That is a story about a child who fell and suffered injuries while playing the ball. One of his friends advised not to forget to give 70% alcohol to the wound. This fluid is often used as a disinfectant that serves to prevent further infection. There are actually a lot of disinfectant fluids, but the most commonly used alcohol is 70%. Maybe there is a question, why alcohol can be used as a disinfectant and why should 70%? (Maybe this can Answer Some of @suesa post about disinfectant)

---

Ethyl Alcohol

---

70%  Alcohol is a liquid containing 70% ethyl alcohol (CH3CH2OH) and 30% water. Ethyl alcohol (ethanol) kills bacteria in 2 ways, namely protein denaturation and fat membrane dissolution. Protein is one of the constituents of bacterial cells. Proteins play an important role in the cell. If likened, protein is the machine of the cell. Protein in this bacterial cell will work well if soluble in water. Well when there is ethanol in the bacterial cell environment, the protein solubility will decrease, why? ( I thinks @justtryme90 more understand about protein, he is experts of biochemistry field).

Ethanol is water soluble in all comparisons. Both ethanol and water are also called two miscible liquids. Between ethanol and water molecules will experience a strong interaction. This interaction tends to be stronger than inter-molecular force of ethanol alone. The strong interaction between ethanol and water is due to the -OH group present inside. This -OH group that causes ethanol is hydrophilic (like water). Although in the ethanol molecule itself there is a hydrocarbon chain (CH3CH2-) which also causes interactions between the ethanol molecules themselves, but the interaction is not as strong as water and ethanol. Finally, ethanol and water can dissolve completely. This is the principle of like dissolve like. 

Water that has a new friend that is ethanol began to leave his old friend, the protein. Those who usually get along together end up being seldom sociable. With the presence of ethanol before, the solubility of protein in water decreases. Little by little the protein undergoes denaturation. Due to denaturation, proteins in bacterial cells are cranky, do not want to work. As a result, important processes in bacterial cells become obstructed.

---

Bacterial Cells

---

In addition through the denaturation of proteins, the destruction of bacterial cells also through lipid membrane dissolution (fat). Bacterial cells are coated by lipid membranes. This membrane is like a bodyguard that protects from the outside environment. When there is ethanol, the lipid membrane begins to be affected by the presence of hydrophobic groups (disliking water) on ethanol. The hydrophobic group in ethanol is present in the hydrocarbon chain (CH3CH2-). Just as before, they started together. However, as a result the strength of lipid membrane began to weaken and the work of bacterial cells began to be inhibited. Like the bodyguard had diverted his attention with beautiful women so criminals are easy to entry.

The question why should 70%? Why not 96% ?, it should be more powerful. isn't it?

We know that one of the works of ethanol in damaging bacterial cells is denaturing proteins. This work will be more effective if there is water in it. Ethanol 70% is a mixture of ethanol as much as 70% by volume and 30% by volume of water (v / v). The analogy is when we bathe with soap. Can we use only soap? Of course must use water right? Well this is what causes why there should be water in the alcohol used. In addition to very high alcohol concentration will only be able to denature the protein outside the bacterial cell. Not able to penetrate the bacterial cell membrane and denature the protein inside the bacterial cell that is actually the main target.

The reason why alcohols with a concentration of 70% are widely selected as disinfectants. However, the use of 70% alcohol can only be used for closed wounds. The use of this fluid is only as prophylactic (precautionary measures). If used for open wounds it will cause pain and aggravate the wound. There will be coagulants (clots) that allow bacteria to live in them. I apologize if there is any shortage.

Reference : 

Miscible 1, 2

Like Dissolve Like

Denaturation 1, 2

---

Support Scientist By Use #science tag or join @steemSTEM

---