lipids
Post on 23-Mar-2016
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LipidsA. Classified based on solubility (like dissolves like)
1. insoluble in polar solvents2. soluble in nonpolar solvents3. lipids are hydrophobic
B. Triglycerides (fats and oils)1. contain fatty acids
a. -COOH functional group at end of a carbon chainb. always have an even number of carbonsc. can be saturated (with H)d. can be unsaturated
have C=C double bonds
polyunsaturated
B. Triglycerides (cont.)2. contain glycerol
a. is a 3-carbon alcoholb. has 3 -OH functional groups
C. Triglyceride synthesis1. -COOH groups react with -OH groups
form covalent bonds
2. fats: solid at room temperature
3. oils: liquid at room temperatureusually saturated
mostly unsaturatedfrom plants
4. the greater the unsaturation, the lower the melting point (more likely to be liquid at room temp.)
D. Phospholipids1. one fatty acid replaced with a -PO4 functional group2. has both hydrophobic and hydrophilic portions
(amphiphilic/amphipathic)
E. Steroids1. all have basic structure of 4 rings of carbon2. differences are in functional groups and their locations3. cholesterol is the precursor for animal steroids
ProteinA. Polymer of amino acids
1. 20 naturally occurring amino acids- eight of these are “essential” in humans
2. three componentsa. amino groupb. carboxyl groupc. R group
accounts for the 20 different amino acids
B. Amino acids are linked together by peptide bonds.
Polymers > 100 amino acids long may be considered proteins
C. Sizeglucose (carb) = C6H12O6
hemoglobin = C2952H4664O832N812S8Fe4
Figure 3.14A–D Protein structure (layer 1)Levels of Protein Structure
Gly ThrGly Glu
Ser Lys
Cys
ProLeu Met
ValLys
ValLeu Asp Ala Val Arg Gly Ser
Pro
Ala
Ile
Asn ValAla
ValHis Val
Amino acids
PheArg
Figure 3.14A–D Protein structure (layer 2)Levels of Protein Structure
Gly ThrGly Glu
Ser Lys
Cys
ProLeu Met
ValLys
ValLeu Asp Ala Val Arg Gly Ser
Pro
Ala
Ile
Asn ValAla
ValHis Val
CN
O C
C
N H
O C
C
H
Hydrogenbond
O C
N HC
CO
N H
O C
CN H
C
N
O CC
N HO C
CN H
CO
C
H
N H
CO
H C R
HN
Alpha helix
Amino acids
C N
H
C C
H HO
NR C C
ON
H
O
C C NH
CC
O
N
H
O
C C NH
C
O
C N
H
O
C C NH
C
O
O
CC
N
H
CC
O
N
H
C C
O
N
H
CC
O
N
H
CC
O
N
H
C C
O
NH
C C
O
N
H
CC
O
H
NC
Pleated sheet
PheArg
Figure 3.14A–D Protein structure (layer 3)Levels of Protein Structure
Gly ThrGly Glu
Ser Lys
Cys
ProLeu Met
ValLys
ValLeu Asp Ala Val Arg Gly Ser
Pro
Ala
Ile
Asn ValAla
ValHis Val
CN
O C
C
N H
O C
C
H
Hydrogenbond
O C
N HC
CO
N H
O C
CN H
C
N
O CC
N HO C
CN H
CO
C
H
N H
CO
H C R
HN
Alpha helix
Amino acids
C N
H
C C
H HO
NR C C
ON
H
O
C C NH
CC
O
N
H
O
C C NH
C
O
C N
H
O
C C NH
C
O
O
CC
N
H
CC
O
N
H
C C
O
N
H
CC
O
N
H
CC
O
N
H
CC
O
NH
C C
O
N
H
CC
O
H
NC
Pleated sheet
Polypeptide(single subunitof transthyretin)
PheArg
most tertiary structures are either globular or fibrous
Figure 3.14A–D Protein structure (layer 4)Levels of Protein Structure
Gly ThrGly Glu
Ser Lys
Cys
ProLeu Met
ValLys
ValLeu Asp Ala Val Arg Gly Ser
Pro
Ala
Ile
Asn ValAla
ValHis Val
CN
O C
C
N H
O CC
H
Hydrogenbond
O C
N HC
CO
N H
O C
CN H
C
N
O CC
N HO C
CN H
CO
C
H
N H
CO
H C R
HN
Alpha helix
Amino acids
C N
H
C C
H HO
NR C C
ON
H
O
C C NH
CC
O
N
H
O
C C NH
C
O
C N
H
O
C C NH
C
O
O
CC
N
H
CC
O
N
H
C C
O
N
H
CC
O
N
H
CC
O
N
H
CC
O
NH
C C
O
N
H
CC
O
H
NC
Pleated sheet
Polypeptide(single subunitof transthyretin)
Transthyretin, withfour identicalpolypeptide subunits
PheArg
examples having quaternary structure: hemoglobin, collagen
Biological Functions of Proteins• Enzymes• Structural
molecules• Regulatory molecules (hormones and transmitters)• Transport (hemoglobin)• Protection (keratin, antibodies)• Movement (muscle fibers)
Also:
(globular) (fibrous)
A given type of protein will have a unique amino acid sequence.
A protein typically has only a single function in nature.
- like different combinations of letters create different words
- an antibody can’t do the job of a muscle fiber (etc).
Shape of a protein determines which molecules can bind to it.The 3-D shape of a protein determines its function.
Change shape Change function
Protein Denaturation
• Unfolding of proteins due to chemicals, changes in pH, and/or increased temperature
Protein Denaturation• Irreversibly denatured proteins cannot refold and
are formed by extreme pH or temperature changes- think of an egg white
Hydrolysis“Breakdown” to individual amino acids
Breakage of peptide bonds
GlyThr
Gly GluSer Lys
Cys
Pro
Leu Met
Val
Lys
ValLeu Asp Ala Val Arg Gly Ser
Pro
Ala
Ile
Asn Val
Ala
ValHis
ValPhe
Arg
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