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
Sections
Polymers
Carbohydrates
Proteins
Nucleic Acids
Lipids
Additional Practice
Cumulative Macromolecules

Solution: A newly isolated protein was found to contain 0.873% phenylalanine by weight upon amino acid analysis.a. What is the minimum molecular weight for the protein (assuming only one Phe residue per protein

Problem

A newly isolated protein was found to contain 0.873% phenylalanine by weight upon amino acid analysis.

a. What is the minimum molecular weight for the protein (assuming only one Phe residue per protein molecule)?

b. Gel filtration of the protein gave an estimated molecular weight of 7.0 x 104 g/mol. How many Phe residues are in the protein? (Enter a whole number)

Solution

a. The minimum possible molecular weight for the problem means the protein has the lowest possible number of the amino acid in question. That means the smallest protein molecule that can have 1 Phe residue and would comprise 0.873% of the protein's total weight.

Remember that the molecular weight of Phe is 165.2g/mol. Another factor to be considered is the position of the amino acid. If Phe is in the middle of the peptide sequence, an OH and H will be remved from the C-side and the N-side, respectively due to the condensation reaction for the peptide's polymerization. The molecular weight contributed by Phe will thereby be significantly reduced by an amount equivalent to themolecular weight of water (18.0 g/mol), thus making the minimum weight of the protein less than what it would be if it is in the end of the sequence.

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