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Questions and Answers
What primarily determines the identity of an amino acid?
What primarily determines the identity of an amino acid?
What type of bond links amino acids together in a protein?
What type of bond links amino acids together in a protein?
Which of the following amino acids is considered hydrophobic?
Which of the following amino acids is considered hydrophobic?
What characterizes the secondary structure of proteins?
What characterizes the secondary structure of proteins?
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Which of the following statements about water is NOT true?
Which of the following statements about water is NOT true?
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What differentiates the quaternary structure of proteins from the tertiary structure?
What differentiates the quaternary structure of proteins from the tertiary structure?
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Which type of amino acids are involved in forming salt bridges in protein structure?
Which type of amino acids are involved in forming salt bridges in protein structure?
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What is the primary function of fibrous proteins?
What is the primary function of fibrous proteins?
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Study Notes
Water in Biological Systems
- Water is the primary solvent in the body (cytosol/intracellular fluid)
- Water is also found in interstitial fluid and plasma (extracellular fluid)
- Oxygen is more electronegative than hydrogen, leading to uneven electron distribution in a water molecule.
- Hydrogen bonds form between water molecules.
- Water molecules can ionize (decompose) into H+ and OH- ions.
Biological Molecules
- Cytosol is primarily water.
- DNA, RNA, carbohydrates, proteins, and lipids are key biological molecules within cells.
Amino Acid Structure
- Proteins are polymers of amino acids linked by peptide bonds.
- All naturally occurring amino acids are L-amino acids.
- Amino acids consist of a central carbon atom, an amino group, a carboxyl group, a hydrogen atom, and a variable R-group (side chain).
- The R-group determines the specific properties of each amino acid (e.g., acidic, basic, hydrophilic, hydrophobic).
- There are 20 common amino acids.
Protein Structure
- Primary Structure: The linear sequence of amino acids determines the protein's primary structure.
- Secondary Structure: Two common secondary structures are alpha helices and beta pleated sheets. These are stabilised by hydrogen bonding.
- Tertiary Structure: The 3D folding of the polypeptide chain, stabilized by interactions amongst R groups of different amino acids.
- Quaternary Structure: If multiple polypeptide chains are present, then their interaction to form a larger protein complex results in quaternary structure.
Structural Proteins (Examples)
- Globular Proteins: Generally spherical and partially soluble in water, involved in various biological processes.
- Fibrous Proteins: Usually elongated, provide structural support, such as collagen.
- Collagen: Found in connective tissue, provides tensile strength. Collagen tripeptides form microfibrils, leading to larger collagen fibres. Disorganization causes tissue atrophy.
Moodle Recap Quiz
- Aspartic acid is an acidic amino acid.
- Glycine is a hydrophilic amino acid.
- Histidine is a basic amino acid.
- Methionine is a sulfur-containing amino acid.
- Alanine is a hydrophobic amino acid.
- Glu-Lys-Pro-Ser-Asp is a polypeptide.
- There is no natural limit to the number of amino acids that can be linked together.
- All naturally occurring amino acids are L-amino acids.
- There are 20 different alpha-amino acids.
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