Found in bones, muscles, skin, and tendons, collagen is the most abundant protein in the body.

The extracellular space in tissues contains an intricate network composed of two major classes of macromolecules: the glycosaminoglycan-protein assemblages known as proteoglycans and fibrous proteins including collagen as well as elastin, fibronectin and laminin.

Collagen is the most abundant protein in the human body, making up approximately one third of the body's protein content. The structure and synthesis of collagen are important in first semester biochemistry, and, as such, this material needs to get a share of attention for the new MCAT. The transformation of tropocollagen into collagen and the mechanism of hydroxylation of lysine and proline residues are subjects which are especially easy to envision as MCAT passages.

WikiPremed Resources

Nucleic Acids Images
Image gallery for study with links to larger teaching JPEGs for classroom presentation

Question Drill for Connective Tissue Proteins
Conceptual Vocabulary Self-Test

Basic Terms Crossword Puzzle

Basic Puzzle Solution

Learning Goals


Understand the structure of a nucleotide. Be able to distinguish deoxyribonucleotides and ribonucleotides.

Be able to characterize purines and pyrimidines and name the five bases, knowing which occur in DNA and RNA.

Be familiar with the general organic mechanism of phosphodiester bond formation in the polymerization of nucleoside triphosphates in DNA and RNA lengthening.

Understand the structure of the DNA as a helix of two complementary antiparallel strands joined by base pairing.

Be familiar at a basic level with how the A-form, B-form, and Z-forms of DNA are distinguished.

Be able to describe the processes of DNA denaturation and renaturation (annealing).

Understand why RNA is less stable under basic conditions than DNA.

In clear, basic terms, demonstrate the ability to describe the building up of the DNA superstructure in eukaryotic chromatin beginning with the formation of nucleosomes.

Understand the varieties of RNA (mRNA, tRNA, rRNA, snRNA and scRNA) in terms of their structural and functional differences.

Recall the important adenosine derivative, 3'-5'-cyclic adenosine monophosphate, cAMP and its importance as a second messenger involved in passing signal transduction events from the cell surface to internal proteins.

Suggested Assignments

Practice terminology for nucleic acids using the question server. Complete the fundamental terms crossword puzzle. Here is the solution to the puzzle.

Read pp. 114-115 in ExamKrackers Chemistry. Perform practice items 65-72 on pp. 116-117 (practice items for carbohydrates, proteins, lipids & nucleic acids).

Read pp. 3-10 in ExamKrackers Biology I. Perform practice items 1-8 on pg. 11 (subject matter for lipids, carbohydrates, and nucleic acids).

Review the web resources for nucleic acids.

Conceptual Vocabulary for Connective Tissue Proteins

Connective Tissue Proteins

Each list begins with basic conceptual vocabulary you need to know for MCAT questions and proceeds to advanced terms that might appear in context in MCAT passages. The terms are links to Wikipedia articles.
Collagen is the main structural protein in the extracellular matrix found in the various connective tissues of the body.
Fibrils, not to be confused with fibers or filaments, are structural biological materials tending to have diameters ranging from 10-100 nanometers.
Elastin is a key protein of the extracellular matrix. It is highly elastic and present in connective tissue allowing many tissues in the body to resume their shape after stretching or contracting.
Extracellular matrix
The extracellular matrix is a three-dimensional network consisting of extracellular macromolecules and minerals, such as collagen, enzymes, glycoproteins and hydroxyapatite that provide structural and biochemical support to surrounding cells.
Elastic fibers
Elastic fibers are an essential component of the extracellular matrix composed of bundles of proteins (elastin) which are produced by a number of different cell types including fibroblasts, endothelial, smooth muscle, and airway epithelial cells.
A fibroblast is a type of biological cell that synthesizes the extracellular matrix and collagen, produces the structural framework (stroma) for animal tissues, and plays a critical role in wound healing.
Vitamin C (also known as ascorbate) is a vitamin found in various foods and sold as a dietary supplement. It is used to prevent and treat scurvy.
Basement membrane
The basement membrane is a thin, pliable sheet-like type of extracellular matrix, that provides cell and tissue support and acts as a platform for complex signalling.
Prolyl hydroxylase
Hydroxyproline is produced by hydroxylation of the amino acid proline by the enzyme prolyl hydroxylase.
Ground substance
Ground substance is an amorphous gel-like substance in the extracellular space that contains all components of the extracellular matrix except for fibrous materials such as collagen and elastin.
Procollagen peptidase
Procollagen peptidase is an endopeptidase involved in the processing of collagen. The proteases removes the terminal peptides of the procollagen.
Lysyl oxidase
Lysyl oxidase catalyzes the conversion of lysine molecules into highly reactive aldehydes that form cross-links in extracellular matrix proteins.
Fibronectin is a high-molecular weight (~500 kDa) glycoprotein of the extracellular matrix that binds to membrane-spanning receptor proteins called integrins.
One of the three main classification of protein structure (alongside globular and membrane proteins), scleroproteins (also called fibrous proteins) are made up by elongated or fibrous polypeptide chains which form filamentous and sheet like structure.
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