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Lesson 4 – Proteins Amino Acid Structure and the Peptide Bond. Heteropolymers. Proteins are heteropolymers . The amino acids they are made of are similar but different from each other. There are only ______ different amino acids that human proteins are made from. 20. Amino Acid Structure.
Proteins are heteropolymers. The amino acids they are made of are similar but different from each other.
There are only ______ different amino acids that human proteins are made from.
Like carbohydrates, amino acids also exist as D-form and L-form isomers. The L-form is found exclusively in proteins.
If the pH of the solution is neutral (like in a biological system) any amino acids in solution will be ionised.
The R-groups give the amino acids their unique chemical properties.
There are 4 classifications of R groups:
Acidic, Basic,Uncharged polar and Nonpolar
Copy the table below and complete with the information from the slides that follow.
Of the 20 amino acids there are 2 that are acidic. They both have carboxyl groups that ionise to make them acidic.
Both acidic amino acids are hydrophilic.
On your desks list the 2 acidic amino acids. Include their 3 letter abbreviation and single letter code.
There are 3 different amino acids with basic R groups. All have additional amino groups that ionise to NH3+. All are hydrophilic. Lysine is an example of a basic amino acid.
There are 5 amino acids which are uncharged and polar. All are hydrophilic. These all have different functional groups most containing at least one –OH group. We will learn 2 – serine and asparagine.
There are 10 amino acids which are non-polar. All are hydrophobic. Their R groups are hydrocarbons. We need to know 3 of these: glycine, alanine and cysteine.
Amino acid monomers are linked together to make a polypeptide through dehydration synthesis (condensation reaction).
The –OH from one amino acid bonds to the -H from the -NH2 group on another amino acid.
On your desk draw the structure of an amino acid (just include a generic R group).
Now change the R group to make it an acidic amino acid and name the one you have drawn.
Now change the R group make it a basic amino acid and name the one you have drawn.
Same to uncharged polar.
Finally for nonpolar.
Past Paper Questions
You will need to access these in the department. Please DO NOT TAKE past papers home – we have limited numbers.
2002 MC Q4
2004 MC Q13
2. Complete Scholar activities on amino acids.
3. Read and make notes on pages 30-35
4. Make sure your glossary is up to date.