BIO 311 Chapter Notes - Chapter 4: Stereoisomerism, Amine, Side Chain

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Amino acids and peptides

• Aio aids ae the ooes, o uildig loks, of polpeptides ad poteis

• Aog all the possile aio aids, ol 0 ae usuall foud i poteis

• The geeal stutue of aio aids iludes a aio goup ad a carboxyl

goup, oth of hih ae oded to a α-carbon

• The HN+ ad COO- ionic forms of the amino group and carboxyl group,

respectively, predominate at a pH of 7

• The α-carbon is also bonded to a hydrogen and to a side chain group,

represented by the letter R

• The side hai, o ‘ goup, deteies the idetit ad popeties of the aio

acid, as well as the overall structure and function of proteins

• It is ipotat to eogize that aio aids ae thee-dimensional - in biology

Fig. 3-1, p. 66

Amino acids

Amino acids and Stereochemistry

• Ma ipotat iooleules ae said to e hial

• This eas that to oleules ae o-superimposable mirror images of each

other, e.g. left and right hands

• No-superimposable mirror image molecules are referred to as enantiomers or

stereoisomers

• A feuetl eouteed hial ete i iooleules is a ao ato ith

four different groups attached to it

• Suh a hial ete ous i all aio aids eept fo glie - glycine has

two hydrogen atoms oded to its α-carbon, as its R group is hydrogen, and thus

has symmetry

• I all the othe aio aids the α-carbon has four different groups bonded to it,

giving rise to two non-superimposable mirror images or stereoisomers

Fig. 3-2, p. 66

Amino acids and Stereochemistry

• The to steeoisoes of the hial iooleules glealdehde ad alaie ae

shown

• The to steeoisoes of eah aio aid ae desigated as L- and D-amino

acids

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• The L- form of glyceraldehyde has a hydroxyl group on the left side of the

molecule while the D- form has it on the right side

• The positio of the aio goup o the left o ight side of the α-carbon

determines the L or D designation - the amino acids that occur in proteins are all

in the L form

Summary 3-1, p. 66

Amino acids: Structure and properties

• The ‘ goups, ad thus the idiidual aio aids, ae lassified aodig to

several criteria, two of which are particularly important

• The fist of these is the pola o opola atue of the side hais

• The second depends on the presence of an acidic or basic group in the side

chain

• Othe useful iteia ilude the pesee of futioal goups othe tha aidi

or basic ones in the side chains and the nature of those groups, e.g. thiol group

(-SH) in cysteine

• Side hai ao atos ae desigated ith lettes of the Geek alphaet,

outig fo the α-carbon

• These ao atos ae i tu the β-, -, -, ad -carbons - a terminal carbon

ato is efeed to as the ω-carbon

• Aio aids ae efeed to by three-letter or one-letter abbreviations of their

names (**we will use the one-letter code)

Table 3-1, p. 69

Amino acids: Abbreviations

Non-polar (hydrophobic) amino acids (Group I)

• I seeal ees of this goup A, V, L, I eah side hai is a aliphatic hydrocarbon

group (aliphatic refers to the absence of a benzene ring)

• Polie has a aliphati li stutue, ad the itoge is oded to to a

Fig. 3-3a (2), p. 68

Non-polar (hydrophobic) amino acids

• I phelalaie F, the hydrocarbon group is aromatic rather than aliphatic - it contains a

cyclic group similar to the benzene ring

• I tptopha W, the side hai otais a idole ig, hih is also aoati

• I ethioie M, the side hai otais a sulfu ato i addition to aliphatic hydrocarbon

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Related Questions

For each of the following sentences, fill in the blanks with the best word or phrase selected from the list below. Not all words or phrases will be used; each word or phrase should be used only once. Proteins are ______________ built from amino acids, which each have an amino group and a _____________ group attached to the central _______________. There are twenty possible _______________ that differ in structure and are generally referred to as âR.â In solutions of neutral pH, amino acids are _______________, carrying both a positive and negative charge. When a protein is made, amino acids are linked together through _______________, which are formed by condensation reactions between the carboxyl end of the last amino acid and the ___________________ end of the next amino acid to be added to the growing chain.

a: amino	b: ionized	c: polypeptides
d: alpha-carbon	e: length	f: protein
g: carbon	h: noncovalent	i: R group
j: carboxyl	k: peptide bonds	l: side chains

m: hydroxide

indigofrog836

1. Polypeptide strands is the active form of a digestive enzyme in the stomach that breaks polypeptide chains into smaller polypeptides.

2. Cleavage of proteins by pepsin in the stomach results in formation of pepsinogen which get broken down further in the small intestine.

3. An amino acid chain made up of three amino acids joined together is called a tripeptide.

4. Dipeptide describes an amino acid chain made up of two amino acids joined together.

5. The 20 different amino acids are the building blocks used for protein synthesis.

6. Amino acid pools are stockpiles found in the blood and other cells of the body that can be used to build new proteins.

7. The continual process of degrading and synthesizing protein is called protein turnover.

8. The stomach produces pepsin, which denatures protein.

9. Denaturation occurs when a protein is exposed to heat, acid, bases, or mechanical agitation resulting in unfolding of the protein, though the peptide bonds remain intact.

10. The part of an amino acid that contains nitrogen is called the amine group.

11. The acid group is also known as the carboxyl group.

12. Single amino acids that are absorbed in the small intestine travel to the liver via the portal vein.

Please correct these sentences AS SOON AS POSSIBLE.. Some of them are not correct and I didn't figure out what are they!

violetdog828

Protein Structure

a.Different function of proteins and examples:

b. Protein building blocks:

1. atomic composition of building block:

2. "parts" or "functional groups" of the building block:

c. Importance of side chain (R group):

d. Hydrophobic amino acids characteristics:

e. Hydrophilic amino acids characteristics:

f. Charged amino acids characteristics

Copy and complete the table below regarding the characteristics and which groups in the polypeptide interact together at each structural level of the protein.

	characteristics	groups interacting
Primary structure
Secondary structure
Tertiary structure
Quartenary structure

Value: 2

Choose the correct statement(s). You may choose more than one answer.

[mark all correct answers]
a. Proteins are the building blocks of amino acids.

b. Enzymes are a type of protein.

c. Quartenary structure consists of two or more polypeptide chains interacting.

d. Amino acids are made of carbon, hydrogen, nitrogen and phosphorus.

e. The primary structure of a protein is formed due to the interaction of side groups.

Value: 3

Put the following statements regarding the structural levels of a protein formation in the correct order.

Below is a sequence of events. Place them in the order they should occur, number 1 being the first item. Select the step number from the drop down next to each item.

Items to order:

1. Individual amino acids are bonded together via peptide bonds.

2. Two or more polypeptide chains interact via bonds.

3. Hydrogen bonds form between neighboring amino acids within a polypeptide chain allowing the chain to coil or form pleated sheets.

4. Side groups (R) of the individual amino acids interact with each other allowing the protein to assume its three dimensional shape.

Value:4

Put the following statements regarding the structural levels of a protein formation in the correct order

Individual amino acids are bonded together via peptide bonds.	1 2 3 4
Two or more polypeptide chains interact via bonds.	1 2 3 4
Hydrogen bonds form between neighboring amino acids within a polypeptide chain allowing the chain to coil or form pleated sheets.	1 2 3 4
Side groups (R) of the individual amino acids interact with each other allowing the protein to assume its three dimensional shape.	1 2 3 4

Value: 5

Hydrophobic amino acids will be found _______________.

a. In the interior (inner core) of a protein, away from the watery environment.

b. in the interior of a plasma membrane.

c. Both A and B

d. Neither

Value: 6

A protein's function is defined by ____________.

a. enzymatic reactions

b. it's shape.

c. chain of nucleotides.

d. the presence of carbon and hydrogen.

Value: 7

Which of the following is NOT considered a protein function?

a. transport of substances across membrane

b. enzymatic reactions

c. provides structural support

d. carries genetic information

BIO 311 Chapter Notes - Chapter 4: Stereoisomerism, Amine, Side Chain

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