Molecules of Life Chapter 2. Protein Functions Act as enzymes Structural- cytoskeleton (actin,...
-
Upload
avis-sanders -
Category
Documents
-
view
222 -
download
0
Transcript of Molecules of Life Chapter 2. Protein Functions Act as enzymes Structural- cytoskeleton (actin,...
Molecules of Life
Chapter 2
Protein Functions Act as enzymes Structural- cytoskeleton (actin, tubulin, others) Mechanical- actin and myosin in muscle Cell signaling Immune responses Cell adhesion Cell cycle transport
The 20 amino acids
You don’tHave to memorize these
Proteins
Built from 20 common monomers called amino acids (aa)
polypeptide=polymer
Amino acid = monomerPeptide bond
aa aa aa aa aa aa aa
Polypeptide- A chain of amino acids bonded together by peptide bonds in a condensation reaction
Fig. 3-16a, p. 44
A DNA encodes the order of amino acids in a new polypeptide chain. Methionine (met) is typically the first amino acid.
B In a condensation reaction, a peptide bond forms between the methionine and the next amino acid, alanine (ala) in this example. Leucine (leu) will be next. Think about polarity, charge, and other properties of functional groups that become neighbors in the growing chain.
Peptide Bond Formation
Fig. 3-16b, p. 45
D The sequence of amino acid subunits in this newly forming peptide chain is now met–ala–leu–trp. The process may continue until there are hundreds or thousands of amino acids in the chain.
C A peptide bond forms between the alanine and leucine.
Tryptophan (trp) will be next. The chain is starting to twist and fold as atoms swivel around some bonds and attract or repel their neighbors.
Stepped Art
Globin Chains in Hemoglobin
Fig. 3-19a, p. 47
valine histidine leucine threonine prolineglutamic acid
A Normal amino acid sequence at the start of the hemoglobin beta chain.
glutamic acid
Molecular Basis of Sickle Cell Anemia
Fig. 3-19b, p. 47
valine histidine leucine threonine proline valine glutamic acid
B One amino acid substitution results in the abnormal beta chain of HbS molecules. The sixth amino acid in such chains is valine, not glutamic acid.
Molecular Basis of Sickle Cell Anemia
Nucleotides
Nucleotide (the monomer of nucleic acid)
Monomer
Two kinds of nucleic acids: RNA DNA
Four Nucleotides of DNA
Fig. 3-22, p. 49
covalent bonding in sugar–phosphate backbone
hydrogen bonding between bases
The DNA Molecule
Nucleic Acids- Informational Polymers
Nucleic acids
Proteins
Lipids
Summary: Organic Molecules in Living Things