Questions and Answers
What is the approximate percentage of dry mass of most cells that proteins account for?
What is the type of bond formed between amino acids in a polypeptide chain?
What is the function of the dehydration reaction in amino acid polymerization?
What is the term for the end of a polypeptide chain with a free amino group?
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How many amino acids are there from which all protein molecules are made?
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What is the central atom in an amino acid molecule?
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What type of bond forms between amino acids in a peptide?
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Which end of an amino acid polymer is represented by the group NH2?
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What is the term for amino acids that cannot be synthesized by the body and must be obtained through the diet?
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What is the functional group found at the Carboxyl end of an amino acid polymer?
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What is the function of essential amino acids in the human body?
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Which of the following amino acids is an example of a semi-essential amino acid?
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What is the term for the repeating pattern of atoms in the backbone of an amino acid polymer?
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What type of reaction occurs between amino acids to form a peptide bond?
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What is the classification of amino acids based on their chemical properties?
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What is the functional group found at the Amino end of an amino acid polymer?
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Which of the following proteins is an example of a transport protein?
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What is the function of non-essential amino acids in the human body?
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What is the term for amino acids that can be synthesized by the body and do not need to be obtained through the diet?
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What is the classification of proteins based on their composition?
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Which of the following proteins is an example of a genetic protein?
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How many amino acids are classified as non-essential amino acids?
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What type of protein has a non-protein moiety in its structure?
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What is the primary structure of a protein?
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What type of bond is responsible for the secondary structure of a protein?
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What is the term for the final functional 3D structure of a polypeptide?
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Which of the following forces is responsible for the tertiary structure of a protein?
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What is an example of a derived protein?
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What are disulfide bonds primarily formed between?
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Which level of protein structure is defined as the overall shape formed by multiple polypeptide subunits?
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Which of the following is NOT a denaturing agent?
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What is a common outcome of protein denaturation?
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Which of the following statements about the reversibility of protein denaturation is true?
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Which of the following proteins is mentioned as having a quaternary structure?
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Study Notes
Proteins
- Proteins are macromolecules formed from amino acids united by peptide bonds, accounting for over 50% of the dry mass of most cells.
- There are 20 amino acids that all protein molecules are made of, and some proteins contain just a few amino acids in a chain, while others are chains of thousands of amino acids.
- Polymers of proteins are called polypeptides, and a protein consists of one or more polypeptide chain.
Structure of Amino Acids
- Amino acids are organic molecules with an asymmetric carbon atom called the alpha (α) carbon at their center.
- An amino acid has four main groups: 1) Amino group (NH2), 2) Carboxyl group (COOH), 3) Hydrogen atom (H), and 4) Side chain or radical group (R).
- The 20 amino acids are distinguished by their R-group.
Amino Acid Polymers
- Amino acids are joined together through a dehydration reaction, removing a hydroxyl group from the carboxyl end of one amino acid and a hydrogen atom from the amino group of another.
- The resulting covalent bond is called a peptide bond, and repeating this process creates a polypeptide chain.
- A polypeptide chain has an amino acid with a free amino group (N-terminus) at one end and an amino acid with a free carboxyl group (C-terminus) at the other end.
Classification of Amino Acids
- Amino acids are classified into two main groups: essential and non-essential amino acids.
- Essential amino acids are not synthesized by the body and must be obtained through diet; there are 9 essential amino acids.
- Non-essential amino acids can be synthesized by the body using essential amino acids; there are 11 non-essential amino acids.
Classification of Proteins
- Proteins are classified based on their function:
- Catalytic proteins (enzymes)
- Structural proteins (collagen, elastin, keratin)
- Contractile proteins (myosin, actin)
- Transport proteins (hemoglobin, myoglobin, albumin, transferrin)
- Regulatory proteins or hormones (ACTH, insulin, growth hormone)
- Genetic proteins (histones)
- Protective proteins (immunoglobulins, clotting factors)
- Proteins are also classified based on their composition:
- Simple proteins (albumin, globulins, histones)
- Conjugated proteins (lipoprotein, glycoprotein)
- Derived proteins (peptones, peptides, denatured proteins)
Protein Structure
- There are four orders of protein structure: primary, secondary, tertiary, and quaternary.
- Primary structure refers to the sequence of amino acids in a polypeptide chain.
- Secondary structure is the folding or coiling of the polypeptide into a repeating configuration, resulting from hydrogen bonds between the polypeptide backbone.
- Tertiary structure is the overall three-dimensional shape of a polypeptide, resulting from interactions between amino acids and R groups.
- Quaternary structure is the overall protein structure that results from the aggregation of two or more polypeptide subunits.
Forces Controlling Tertiary Protein Structure
- Hydrogen bonds between polar side chains of amino acids
- Hydrophobic forces between non-polar (R) groups of amino acids
- Electrostatic forces (ionic bonds, salt bridges) between oppositely charged (R) groups of amino acids
- Disulfide bonds between sulfur amino acids (cysteine)
Protein Denaturation
- Protein denaturation results in the unfolding and disorganization of the protein's secondary and tertiary structures, without hydrolysis of peptide bonds.
- Denaturing agents include heat, organic solvents, high pressure, mechanical mixing, strong acids or bases, detergents, and ions of heavy metals.
- Denaturation may be reversible or, more commonly, irreversible, and denatured proteins are often insoluble and precipitate from solution.
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Description
This quiz covers the basics of proteins and amino acids, including their structure, function, and composition. It is based on Lecture 10 of Dr. Wael Sobhy Darwish's biochemistry course.
