how to determine if amino acid is basic, acidic?

[sangria1986]

how do you know if the amino acid is basic or acidic based on its R groups?

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[sangria1986]

also how do you determine which direction amino acid would travel based on electrophoresis? how about DNA?

 

[vsl5]

Basic: histidine, arginine, lysine
acidic: glutamic acid, aspartic acid

theres only 5, so just memorize them (or acidic has -COOH somewhere in its R group and basic has amino groups in its R group).

Electrophoresis: All amino acids travel toward the anode (+ve) in SDS-PAGE based on size, b/c the SDS imparts a negative charge on ALL proteins. DNA also does the same because its naturally negatively charged due to phosphate 5' groups.

Amino acids in isoelectric focusing gels travel according to their charge at certain pHs. They stop migrating when they are at a pH which matches their isoelectric point. pH<isoelectric point means the protein is positive, pH> isoelectric point = protein is negatively charged.

 

[gunj122]

you said anode is positive...i thought it was negatively charged while the cathode is postively charged?

 

[vsl5]

In electrophoresis, the apparatus works like an electrolytic cell where the anode is positive and cathode is negative. In a galvanic cell, anode is negative and cathode is positive.

 

[sangria1986]

Dd

 

[Rabolisk]

Uh Thats not true. In galvanic electrons go from anode to cathode. In fact anode is where oxidation occurs-increase in positive

You should always verify your information before you post. First rule when trying to "help" people.

 

[seraphkz]

Correct me if I'm wrong.

I thought cathodes have a POSITIVE CORE and accumulate NEGATIVE charge on their SURFACE. Therefore cations migrate to the cathodes due to their negative charge buildup.

Anodes have a NEGATIVE CORE and accumulate POSITIVE charge on their surface. Therefore anions flow to anodes due to the positive charge buildup.

 

[sangria1986]

You should always verify your information before you post. First rule when trying to "help" people.

My apologies. Although everything I Else I said was correct the anode is negative and cathode is positive

 

[sangria1986]

Correct me if I'm wrong.

I thought cathodes have a POSITIVE CORE and accumulate NEGATIVE charge on their SURFACE. Therefore cations migrate to the cathodes due to their negative charge buildup.

Anodes have a NEGATIVE CORE and accumulate POSITIVE charge on their surface. Therefore anions flow to anodes due to the positive charge buildup.

Yes. I was wrong.

 

[AcclratngCharge]

You should always verify your information before you post. First rule when trying to "help" people.

Agreed. Unless you really need a good curve and want to sabotage...if you're evil like that.

From what I have seen (aamc's) you do not need to know which acids are basic vs acidic. It helps to be able to recognize one of the 20 aa's if you see it, such as knowing glycine IS an amino acid, not it's class.

It's also important to know why an amino acid is basic, acidic, nonpolar, polar...