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Questions and Answers
What is the primary structure of a protein?
What is the primary structure of a protein?
Which of the following statements is true regarding protein structure?
Which of the following statements is true regarding protein structure?
What defines the tertiary structure of a protein?
What defines the tertiary structure of a protein?
Which level of protein structure involves coils and folds like α-helices and β-pleated sheets?
Which level of protein structure involves coils and folds like α-helices and β-pleated sheets?
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What characterizes the quaternary structure of a protein?
What characterizes the quaternary structure of a protein?
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What is the primary function of chaperones in protein folding?
What is the primary function of chaperones in protein folding?
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In which cellular locations can chaperones be found?
In which cellular locations can chaperones be found?
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What happens to the cap of a chaperonin during the protein folding process?
What happens to the cap of a chaperonin during the protein folding process?
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What is the correct order of actions performed by chaperonins during protein folding?
What is the correct order of actions performed by chaperonins during protein folding?
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Which of the following best describes the secondary structure of proteins?
Which of the following best describes the secondary structure of proteins?
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What technique is primarily used to determine a protein's three-dimensional structure?
What technique is primarily used to determine a protein's three-dimensional structure?
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What type of mutation causes sickle-cell disease?
What type of mutation causes sickle-cell disease?
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How many polypeptides are present in a hemoglobin molecule?
How many polypeptides are present in a hemoglobin molecule?
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What amino acid substitution occurs in the hemoglobin of individuals with sickle-cell disease?
What amino acid substitution occurs in the hemoglobin of individuals with sickle-cell disease?
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What is the primary role of hemoglobin in the body?
What is the primary role of hemoglobin in the body?
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In the context of protein structure, what does X-ray diffraction reveal?
In the context of protein structure, what does X-ray diffraction reveal?
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Which component of hemoglobin directly binds oxygen?
Which component of hemoglobin directly binds oxygen?
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What impact does a single amino acid substitution have on proteins like hemoglobin?
What impact does a single amino acid substitution have on proteins like hemoglobin?
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What is the general structure of a fatty acid?
What is the general structure of a fatty acid?
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Which of the following statements is true regarding saturated fatty acids?
Which of the following statements is true regarding saturated fatty acids?
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What distinguishes unsaturated fatty acids from saturated fatty acids?
What distinguishes unsaturated fatty acids from saturated fatty acids?
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What is the typical carbon chain length for fatty acids mentioned?
What is the typical carbon chain length for fatty acids mentioned?
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Which of the following fatty acids is classified as saturated?
Which of the following fatty acids is classified as saturated?
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What type of fats are made from unsaturated fatty acids?
What type of fats are made from unsaturated fatty acids?
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Which of the following statements is true about the physical state of saturated and unsaturated fats?
Which of the following statements is true about the physical state of saturated and unsaturated fats?
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From which sources are unsaturated fatty acids primarily derived?
From which sources are unsaturated fatty acids primarily derived?
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What is the role of enzymes in biological processes?
What is the role of enzymes in biological processes?
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Which of the following correctly describes a polypeptide?
Which of the following correctly describes a polypeptide?
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Which function is NOT attributed to proteins?
Which function is NOT attributed to proteins?
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How do proteins contribute to cellular communications?
How do proteins contribute to cellular communications?
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What is a characteristic of the sequence of amino acids in a polypeptide?
What is a characteristic of the sequence of amino acids in a polypeptide?
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Which statement about proteins is true?
Which statement about proteins is true?
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What percentage of the dry mass of most cells is made up of proteins?
What percentage of the dry mass of most cells is made up of proteins?
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Which function of proteins is related to the immune system?
Which function of proteins is related to the immune system?
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What are the two primary forms of secondary structure in polypeptides?
What are the two primary forms of secondary structure in polypeptides?
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Which structural feature is characteristic of the beta-pleated sheet?
Which structural feature is characteristic of the beta-pleated sheet?
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What kind of bonding primarily stabilizes the secondary structures of proteins?
What kind of bonding primarily stabilizes the secondary structures of proteins?
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In the context of secondary structure, what is the significance of the amino acid sequence?
In the context of secondary structure, what is the significance of the amino acid sequence?
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How would you describe the alpha-helix structure in proteins?
How would you describe the alpha-helix structure in proteins?
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Which of the following amino acid properties can influence secondary structure formation?
Which of the following amino acid properties can influence secondary structure formation?
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Which configuration of the beta-pleated sheet does NOT occur?
Which configuration of the beta-pleated sheet does NOT occur?
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What type of structure forms when a segment of a polypeptide chain coils into a repeated pattern?
What type of structure forms when a segment of a polypeptide chain coils into a repeated pattern?
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Study Notes
Macromolecules
- Macromolecules are large molecules with complex structures
- They are composed of thousands of covalently connected atoms
- Small organic molecules are joined together to form larger molecules within cells
- All living organisms are made up of 4 classes of biological macromolecules: carbohydrates, lipids, proteins, and nucleic acids
- Molecular structure and function of macromolecules are closely related
4 Major Categories of Biological Macromolecules
- Carbohydrates
- Lipids
- Proteins
- Nucleic acids
Carbohydrates
- Carbohydrates serve as fuel and building material
- Carbohydrates are composed of carbon, hydrogen, and oxygen
- The molecular formula is multiples of the unit (CH₂O)ₙ
- Examples include pentoses (C₅H₁₀O₅) like ribose and deoxyribose, and hexoses (C₆H₁₂O₆) like glucose and fructose.
- Biologically important carbohydrates are also called sugars
- Monosaccharides are the simplest carbohydrates, single sugars (monomers)
- Polysaccharides are carbohydrate polymers composed of many sugar building blocks
- There are four categories of carbohydrates:
- Monosaccharides (e.g., glucose, fructose)
- Disaccharides (e.g., maltose, sucrose, lactose)
- Oligosaccharides (composed of 20–30 monosaccharides)
- Polysaccharides (e.g., starch, glycogen, cellulose, chitin)
- Monosaccharides serve as fuel for cells and raw materials for building molecules
- Monosaccharides are classified by:
- The location of the carbonyl group (as aldose or ketose)
- The number of carbons in the carbon skeleton
- Monosaccharides can be linear but in aqueous solutions many form rings
- A disaccharide is formed when a dehydration reaction joins two monosaccharides; this covalent bond is called a glycosidic linkage. Common examples include maltose (glucose + glucose), lactose (glucose + galactose), and sucrose (glucose + fructose).
- Polysaccharides include storage polysaccharides (starch and glycogen) and structural polysaccharides (cellulose and chitin).
- Starch, the major storage polysaccharide in plants, consists of amylose (20-30%) and amylopectin (70-80%).
- Glycogen, the storage polysaccharide in animals, is highly branched and functions to store glucose.
- Cellulose, a structural polysaccharide in plant cell walls, is a glucose polymer with different glycosidic linkages from starch. Cellulose is difficult to digest for humans.
- Chitin, a structural polysaccharide in fungal cell walls and arthropod exoskeletons, is similar in structure to cellulose but contains nitrogen.
Lipids
- Lipids are hydrophobic - they do not mix with water
- Lipids are a diverse group of hydrophobic molecules that do not consist of polymers
- Biologically important lipids: fats, phospholipids, steroids
- Fats are triglycerides: glycerol + 3 fatty acids (important energy source)
- Phospholipids have a glycerol backbone, two fatty acid "tails", and a phosphate group "head". Phospholipids are amphipathic (hydrophilic head and hydrophobic tails)
- Steroids have four fused carbon rings (e.g., cholesterol, hormones). Cholesterol is important for cell membranes in animals.
Proteins
- Proteins have many structures, thus a wide range of functions
- Proteins account for more than 50% of the dry mass of most cells
- Protein functions include structural support, storage, transport, cellular communication, movement, and defense against foreign substances)
- Proteins are polymers of amino acids
- Polypeptides range in length from a few to more than a thousand monomers
- Amino acids have carboxyl and amino groups that differ in properties due to differing R-groups
- The 20 amino acids are categorized as nonpolar, polar, or electrically charged.
- Proteins have four levels of structure:
- Primary structure: the unique sequence of amino acids forming a polypeptide chain
- Secondary structure: coils and folds in the polypeptide chain (e.g., α-helices and β-pleated sheets)
- Tertiary structure: the 3D structure of the polypeptide chain determined by interactions among various side chains (R groups)
- Quaternary structure: results when a protein consists of multiple polypeptide chains (subunits)
- Enzymes are specific types of proteins that act as catalysts, speeding up chemical reactions
- Protein conformation depends on physical and chemical conditions of the protein's environment
- Denaturation is the loss of a protein's native conformation due to the unraveling of the protein, causing it to lose its function. Denaturation can result from pH changes, salt concentration changes, temperature changes, and other environmental factors.
Nucleic Acids
- Nucleic acids store and transmit hereditary information
- The amino acid sequence of a polypeptide is encoded by a unit of inheritance called a gene. Genes are made of DNA. DNA is a nucleic acid.
- DNA stores information for protein synthesis.
- DNA directs RNA synthesis.
- DNA directs protein synthesis through mRNA (messenger RNA)
- Nucleic acids exist as polymers called polynucleotides
- Each polynucleotide consists of monomers called nucleotides
- A nucleotide = nitrogenous base + pentose sugar + phosphate group
- There are two types of nucleic acids: DNA and RNA.
- DNA is double-stranded while RNA is single-stranded.
- The sequence of bases along a nucleotide polymer is unique for each gene and specifies the amino acid sequence of a protein.
- DNA replication is the copying of all DNA molecules into a second set, required before cell division.
Protein-Folding & Chaperones
- Most proteins fold into a specific 3D structure to become fully functional.
- Chaperones are proteins that help other proteins fold correctly, assist as needed.
- Chaperones locate in cytosol, mitochondria, chloroplasts, and ER.
Protein Structure Determination
- X-ray crystallography is used to determine a protein's three-dimensional structure.
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Description
Explore the fascinating world of biological macromolecules in this quiz. Learn about the four major categories: carbohydrates, lipids, proteins, and nucleic acids, and their structures and functions. Understand how these molecules are essential to all living organisms.
