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

You are given a solution of "protein X". Protein X consists of 250 amino acid residues: 38% are valine, 24% are alanine, 20% are glycine, and 18% are isoleucine. What is the molecular weight of protein X? Describe how you determined this answer.


According to the problem, the 250-amino acid protein X is made of 38% valine, 24% alanine, 20% glycine, and 18% isoleucine. Since only the protein length is given, it will be assumed that the percentage values are based on the number of residues. The number of residues per type of amino acid can be computed as:

nAAresidue = Namino acids*(Percentage)

For valine,

nvaline = 250*0.38 = 95

Thus, the protein will be made up of 95 valine residues, 60 alanine, 50 glycine, and 45 isoleucine residues.

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