Ch.5 - Biological MoleculesWorksheetSee all chapters
All Chapters
Ch.1 - Introduction to Biology
Ch.2 - Chemistry
Ch.3 - Water
Ch.4 - Carbon
Ch.5 - Biological Molecules
Ch.6 - Cells
Ch.7 - The Membrane
Ch.8 - Energy and Metabolism
Ch.9 - Respiration
Ch.10 - Photosynthesis
Ch.11 - Cell Signaling
Ch.12 - Cell Division
Ch.13 - Meiosis
Ch.14 - Mendelian Genetics
Ch.15 - Chromosomal Theory of Inheritance
Ch.16 - DNA Synthesis
Ch.17 - Gene Expression
Ch.18 - Regulation of Expression
Ch.19 - Viruses
Ch.20 - Biotechnology
Ch.21 - Genomics
Ch.22 - Development
Ch.23 - Evolution by Natural Selection
Ch.24 - Evolution of Populations
Ch.25 - Speciation
Ch.26 - History of Life on Earth
Ch.27 - Phylogeny
Ch.28 - Prokaryotes
Ch.29 - Protists
Ch.30 - Plants
Ch.31 - Fungi
Ch.32 - Overview of Animals
Ch.33 - Invertebrates
Ch.34 - Vertebrates
Ch.35 - Plant Anatomy
Ch.36 - Vascular Plant Transport
Ch.37 - Soil
Ch.38 - Plant Reproduction
Ch.39 - Plant Sensation and Response
Ch.40 - Animal Form and Function
Ch.41 - Digestive System
Ch.42 - Circulatory System
Ch.43 - Immune System
Ch.44 - Osmoregulation and Excretion
Ch.45 - Endocrine System
Ch.46 - Animal Reproduction
Ch.47 - Nervous System
Ch.48 - Sensory Systems
Ch.49 - Muscle Systems
Ch.50 - Ecology
Ch.51 - Animal Behavior
Ch.52 - Population Ecology
Ch.53 - Community Ecology
Ch.54 - Ecosystems
Ch.55 - Conservation Biology
Nucleic Acids
Additional Practice
Cumulative Macromolecules

Amino acid analysis of an oligopeptide seven residures long gave the following amino acids:

Asp  Leu  Lys  Met  Phe  Tyr

The following facts were observed:

a. Trypsin treatment had no apparent effect.

b. The phenylthiohydantoin (PTH) derivative by Edman degradation was: (See th figure below)

c. Chymotrypsin treatment resulted in 3 fragments, including a dipeptide and tetrapeptide. The tetrapeptide contained the amino acids Asp, Leu, Met, and Lys (in that order).

d. Cyanogen bromide treatment yielded a dipeptide, tetrapeptide, and free Lys.

What is the amino acid peptide sequence for this heptapeptide? Label N and C termini.


a. Trypsin treatment cleaves the C-side of basic amino acids (AAs). Lys is a basic AA. The apparent lack of effect of Trypsin simply means that there are no AAs to be cleaved in the C-side of lys. Thus, lys is at the C-terminal.

b. The structure of the PTH derivative determines that Phe is the N terminal of the peptide.

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