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Questions and Answers
Proteins are macromolecules made up of monomers called ______.
Proteins are macromolecules made up of monomers called ______.
amino acids
A protein is a macronutrient present in all living beings and involved in various ______ pathways.
A protein is a macronutrient present in all living beings and involved in various ______ pathways.
metabolic
Proteins are made up of ______ different amino acids.
Proteins are made up of ______ different amino acids.
20
A peptide is a short chain made up of ______.
A peptide is a short chain made up of ______.
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For every peptide bond formed, there is a loss of one molecule of ______.
For every peptide bond formed, there is a loss of one molecule of ______.
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Peptides with two amino acids are termed ______.
Peptides with two amino acids are termed ______.
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The proteins of the brain are different from those in the ______.
The proteins of the brain are different from those in the ______.
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Animals cannot synthesize all amino acids necessary to make ______.
Animals cannot synthesize all amino acids necessary to make ______.
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Peptides with more than ten amino acids are termed ______.
Peptides with more than ten amino acids are termed ______.
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The bond that exists between two molecules of amino acids is called a ______ bond.
The bond that exists between two molecules of amino acids is called a ______ bond.
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One end of a polypeptide has a free amino group known as the ______-terminal.
One end of a polypeptide has a free amino group known as the ______-terminal.
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Proteins can be denatured by agents such as heat and ______.
Proteins can be denatured by agents such as heat and ______.
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When a denatured protein returns to its native state, the process is called ______.
When a denatured protein returns to its native state, the process is called ______.
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Proteins resist slight changes in pH due to their ______ capacity.
Proteins resist slight changes in pH due to their ______ capacity.
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The pH at which the total number of positive charges equals the number of negative charges is called the ______ point.
The pH at which the total number of positive charges equals the number of negative charges is called the ______ point.
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Only a few proteins, like albumins and globulins, are heat ______.
Only a few proteins, like albumins and globulins, are heat ______.
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Proteins absorb ultraviolet (UV) light at a maximum wavelength of ______ nanometers.
Proteins absorb ultraviolet (UV) light at a maximum wavelength of ______ nanometers.
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The average molecular weight of an amino acid is taken to be ______ g/mol.
The average molecular weight of an amino acid is taken to be ______ g/mol.
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Proteins can undergo ______ modifications after they have been synthesized on the ribosome.
Proteins can undergo ______ modifications after they have been synthesized on the ribosome.
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A hydrogen bond in proteins is important as it stabilizes the secondary ______ of proteins.
A hydrogen bond in proteins is important as it stabilizes the secondary ______ of proteins.
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Ionic bonds in proteins are observed between the acidic and ______ groups of the constituent amino acids.
Ionic bonds in proteins are observed between the acidic and ______ groups of the constituent amino acids.
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Disulfide bonds are a type of ______ bond found between amino acid residues in proteins.
Disulfide bonds are a type of ______ bond found between amino acid residues in proteins.
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When proteins are subjected to an electric field at their isolectric point, they become ______.
When proteins are subjected to an electric field at their isolectric point, they become ______.
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Electrostatic interactions exist between differently ______ groups present on the side chains of amino acids.
Electrostatic interactions exist between differently ______ groups present on the side chains of amino acids.
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Study Notes
Introduction to Biochemistry (BCH 201)
- This course covers introductory chemistry and protein classification.
- It includes protein structures: primary, secondary, tertiary, and quaternary.
- The course will also explore biological functions of proteins.
- Methods of protein isolation, purification, and identification will be examined.
- Basic principles of tests for proteins and amino acids will be discussed.
What are Proteins?
- Proteins are complex macromolecules composed of amino acids.
- Amino acids are the building blocks of proteins.
- An amino acid is a simple organic compound with a basic amino group (-NH2) and an acidic carboxyl group (-COOH), unique to each amino acid.
- Proteins come from various sources, including meat, fish, eggs, and dairy products, as shown in the images.
What are Amino Acids?
- Amino acids are the monomers that make up proteins.
- A specific number of amino acids link together through peptide bonds.
- There are 20 different amino acids.
Synthesis of Peptides or Peptide Bonds
- A peptide is a short chain made up of one or more amino acids.
- Peptide chains form when two or more amino acids are bonded together by peptide bonds.
- For each peptide bond formed, one water molecule is lost.
Peptides and Polypeptides
- Peptides can be categorized based on the number of amino acids: dipeptides (2), tripeptides (3).
- Polypeptides are peptides with more than ten amino acids.
- The peptide bond formed in proteins is a special amide bond.
What are Polypeptides?
- Polypeptides are long chains of amino acids joined by peptide bonds.
- One or more polypeptides form a protein.
- A polypeptide has an amino-terminal (N-terminal) end and a carboxyl-terminal (C-terminal) end.
- The sequence of amino acids is determined by the mRNA codons.
- The sequence of nucleotides in mRNA ultimately determines the sequence of amino acids in the polypeptide.
Properties of Proteins
- Solubility in Water: Proteins are generally soluble in water or dilute salt solutions.
- Denaturation and Renaturation: Proteins can be denatured by agents like heat, urea, radiation, pH, or chemical agents, causing the unfolding of polypeptide chains without hydrolysis. The denaturation of a protein affects its secondary and tertiary structures, but not its primary structure. Renaturation is the process where a denatured protein returns to its native state.
- Buffering Capacity: Proteins have buffering capacity, resisting slight changes in pH. The buffering capacity arises from the presence of amino and carboxylic groups in proteins.
- Coagulation: When proteins are denatured by heat, they form insoluble aggregates called coagulum. (e.g., albumins and globulins).
- Isoelectric Point (pI): The pH at which the overall charge of a protein is zero. At the pI, a protein will not migrate under an electric field.
- Molecular Weights: The molecular weight of a protein is determined by the total number of amino acids, with an average weight of 110 g/mol per amino acid, and range from 5000 to 10⁹ Daltons.
- Maximum absorption wavelength: Proteins absorb UV light at a maximum wavelength of 280 nm. Nucleic Acids absorb at 260 nm.
Post-translational Modifications
- Modifications (phosphorylation, glycosylation, ADP ribosylation, methylation, hydroxylation, and acetylation) occur after protein synthesis on the ribosome.
- These modifications alter the charge and interactions between amino acid residues, changing the protein's three-dimensional structure and function.
Protein Bonding
- Besides primary peptide bonds, secondary bonds contribute to protein structure stability.
- Hydrogen bonds form between electronegative atoms and hydrogen atoms in peptide linkages, stabilizing secondary structure.
- Ionic bonds arise between acidic and basic groups, aiding in protein-protein interactions, although weaker than hydrogen bonds.
- Disulfide bonds are covalent bonds formed between cysteine residues via oxidation. These bonds contribute significantly to tertiary structure stability.
- Hydrophobic and Hydrophilic Interactions: Hydrophobic R groups cluster together to minimize water interactions, while hydrophilic interactions lead to hydrogen bonding.
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Description
This quiz covers fundamental concepts in biochemistry, focusing on protein classification and structure. Explore the intricacies of amino acids, their roles, sources, and the methods used for protein isolation and purification. Test your understanding of the biological functions of proteins and amino acids.
