Podcast
Questions and Answers
What type of protein structure involves the arrangement of multiple polypeptide chains?
What type of protein structure involves the arrangement of multiple polypeptide chains?
Which type of bond is responsible for stabilizing the compact folded structure of myoglobin?
Which type of bond is responsible for stabilizing the compact folded structure of myoglobin?
Which feature distinguishes the 'native conformation' of a protein?
Which feature distinguishes the 'native conformation' of a protein?
What type of interactions primarily hold together the quaternary structure of proteins?
What type of interactions primarily hold together the quaternary structure of proteins?
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Which of the following is NOT a role of proteins in their native conformation?
Which of the following is NOT a role of proteins in their native conformation?
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What type of polysaccharide is primarily responsible for energy storage in animals?
What type of polysaccharide is primarily responsible for energy storage in animals?
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Which lipid is a homopolymer of glucose that provides structure in plants?
Which lipid is a homopolymer of glucose that provides structure in plants?
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What is the primary structural difference between amylopectin and amylose?
What is the primary structural difference between amylopectin and amylose?
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Which of the following is NOT a classification of lipids?
Which of the following is NOT a classification of lipids?
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What type of lipid contains a backbone of glycerol?
What type of lipid contains a backbone of glycerol?
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Which description is characteristic of chitin?
Which description is characteristic of chitin?
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How are fatty acids categorized based on their structure?
How are fatty acids categorized based on their structure?
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What do glycosidic bonds link together?
What do glycosidic bonds link together?
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What is the primary function of arachidonic acid in the body?
What is the primary function of arachidonic acid in the body?
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Which of the following describes a characteristic of omega-6 fatty acids?
Which of the following describes a characteristic of omega-6 fatty acids?
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What is the primary role of diabetic glycerol in the body?
What is the primary role of diabetic glycerol in the body?
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Which type of lipid is a major component of cell membranes?
Which type of lipid is a major component of cell membranes?
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What structure do steroids predominantly contain?
What structure do steroids predominantly contain?
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Which of the following fatty acids is classified as an omega-3 fatty acid?
Which of the following fatty acids is classified as an omega-3 fatty acid?
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What is the significance of cholesterol in the body?
What is the significance of cholesterol in the body?
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What is one of the primary functions of eicosanoids?
What is one of the primary functions of eicosanoids?
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What is the structure of triglycerides?
What is the structure of triglycerides?
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What is a primary characteristic of lipoproteins?
What is a primary characteristic of lipoproteins?
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What defines essential amino acids?
What defines essential amino acids?
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Which of the following structures is a characteristic of secondary protein structure?
Which of the following structures is a characteristic of secondary protein structure?
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How is a peptide bond formed?
How is a peptide bond formed?
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Which of these amino acids can be phosphorylated?
Which of these amino acids can be phosphorylated?
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What keeps the tertiary structure of a protein stable?
What keeps the tertiary structure of a protein stable?
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Which type of lipid includes phospholipids and sterols?
Which type of lipid includes phospholipids and sterols?
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Which amino acid is uniquely known for its role in protein bending?
Which amino acid is uniquely known for its role in protein bending?
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What is a glycosidic bond?
What is a glycosidic bond?
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What is the quaternary structure of a protein?
What is the quaternary structure of a protein?
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Which of the following fatty acids is classified as unsaturated?
Which of the following fatty acids is classified as unsaturated?
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What characterizes a monosaccharide?
What characterizes a monosaccharide?
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Which type of carbohydrate is formed by the linkage of multiple monosaccharides?
Which type of carbohydrate is formed by the linkage of multiple monosaccharides?
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What is the primary determinant of the behavior of amino acids within a polypeptide?
What is the primary determinant of the behavior of amino acids within a polypeptide?
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Which term describes the natural three-dimensional shape of a functional protein?
Which term describes the natural three-dimensional shape of a functional protein?
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What is the result of phosphorylation in proteins?
What is the result of phosphorylation in proteins?
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Which type of protein modification results in a protein functioning as a glycoprotein?
Which type of protein modification results in a protein functioning as a glycoprotein?
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What is the result of ubiquitination in protein modification?
What is the result of ubiquitination in protein modification?
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What type of monosaccharide is glucose classified as?
What type of monosaccharide is glucose classified as?
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Which of the following is a characteristic of polysaccharides?
Which of the following is a characteristic of polysaccharides?
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What type of bond is formed between two monosaccharides in a disaccharide?
What type of bond is formed between two monosaccharides in a disaccharide?
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How is a beta (b) glycosidic bond characterized?
How is a beta (b) glycosidic bond characterized?
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What occurs during the cyclisation of monosaccharides?
What occurs during the cyclisation of monosaccharides?
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Which of the following monosaccharides is a ketose?
Which of the following monosaccharides is a ketose?
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Which abnormal protein aggregation can lead to diseases like Alzheimer's?
Which abnormal protein aggregation can lead to diseases like Alzheimer's?
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Which carbohydrate consists of only one sugar unit?
Which carbohydrate consists of only one sugar unit?
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What type of functional group is associated with acetylation in proteins?
What type of functional group is associated with acetylation in proteins?
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What is the primary structure unit of carbohydrates?
What is the primary structure unit of carbohydrates?
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What type of amino acids contribute to the hydrophobic core of myoglobin's structure?
What type of amino acids contribute to the hydrophobic core of myoglobin's structure?
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Which type of bond stabilizes the quaternary structure of proteins?
Which type of bond stabilizes the quaternary structure of proteins?
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Which of the following determines the native conformation of a protein?
Which of the following determines the native conformation of a protein?
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In addition to cysteines forming disulphide bonds, which other type of bond is important for stabilizing myoglobin?
In addition to cysteines forming disulphide bonds, which other type of bond is important for stabilizing myoglobin?
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What describes the quaternary structure of a protein?
What describes the quaternary structure of a protein?
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What is the primary function of glycogen in animals?
What is the primary function of glycogen in animals?
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Which lipid serves as a structural component of cell membranes?
Which lipid serves as a structural component of cell membranes?
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What characterizes the structure of cellulose?
What characterizes the structure of cellulose?
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Which type of fatty acid is classified by the presence of double bonds?
Which type of fatty acid is classified by the presence of double bonds?
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What distinguishes amylopectin from amylose?
What distinguishes amylopectin from amylose?
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Which of the following lipids does not contain glycerol?
Which of the following lipids does not contain glycerol?
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What type of polysaccharide provides structural integrity in plant cells?
What type of polysaccharide provides structural integrity in plant cells?
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Which feature distinguishes lipoproteins from other lipid types?
Which feature distinguishes lipoproteins from other lipid types?
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What is the primary function of eicosanoids in the body?
What is the primary function of eicosanoids in the body?
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Which fatty acid is essential and cannot be synthesized by the body?
Which fatty acid is essential and cannot be synthesized by the body?
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What is the characteristic structure of steroids?
What is the characteristic structure of steroids?
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Which option is a major component of cell membranes?
Which option is a major component of cell membranes?
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What role does diacylglycerol (DAG) play within cells?
What role does diacylglycerol (DAG) play within cells?
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What is the significance of arachidonic acid in relation to eicosanoids?
What is the significance of arachidonic acid in relation to eicosanoids?
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Which of the following statements about essential fatty acids (EFAs) is correct?
Which of the following statements about essential fatty acids (EFAs) is correct?
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What is a primary role of lipoproteins in the body?
What is a primary role of lipoproteins in the body?
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Which of the following fatty acids is classified as an omega-3 fatty acid?
Which of the following fatty acids is classified as an omega-3 fatty acid?
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What is one of the key functions of cholesterol in the body?
What is one of the key functions of cholesterol in the body?
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Which of the following classifications of amino acids is defined by having a negative charge at neutral pH?
Which of the following classifications of amino acids is defined by having a negative charge at neutral pH?
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What structure represents the arrangement of amino acids in a polypeptide chain linked by peptide bonds?
What structure represents the arrangement of amino acids in a polypeptide chain linked by peptide bonds?
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Which structural feature is characteristic of beta (b) pleated sheets found in proteins?
Which structural feature is characteristic of beta (b) pleated sheets found in proteins?
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Which of the following amino acids can undergo phosphorylation?
Which of the following amino acids can undergo phosphorylation?
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What type of bond connects monosaccharides to form disaccharides?
What type of bond connects monosaccharides to form disaccharides?
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What is true about essential amino acids?
What is true about essential amino acids?
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Which lipids are characterized by a backbone of glycerol?
Which lipids are characterized by a backbone of glycerol?
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Which type of carbohydrate is formed by the linkage of multiple monosaccharides?
Which type of carbohydrate is formed by the linkage of multiple monosaccharides?
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What describes the concept of 'native conformation' in proteins?
What describes the concept of 'native conformation' in proteins?
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Which fatty acids are classified as saturated?
Which fatty acids are classified as saturated?
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Which amino acids are typically found at bends in protein structures?
Which amino acids are typically found at bends in protein structures?
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What is a key feature of polysaccharides?
What is a key feature of polysaccharides?
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Which structural feature is characteristic of essential fatty acids?
Which structural feature is characteristic of essential fatty acids?
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What type of post-translational modification results in the addition of a sugar group to an amino acid?
What type of post-translational modification results in the addition of a sugar group to an amino acid?
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Which protein modification is associated with adding a death signal to a protein?
Which protein modification is associated with adding a death signal to a protein?
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What structure is formed when two monosaccharides are linked together?
What structure is formed when two monosaccharides are linked together?
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Which type of sugar has the empirical formula (CH2O)n, where n can range from 3 to 7?
Which type of sugar has the empirical formula (CH2O)n, where n can range from 3 to 7?
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What type of glycosidic bond is present in lactose?
What type of glycosidic bond is present in lactose?
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What results from misfolding of proteins into amyloid fibrils?
What results from misfolding of proteins into amyloid fibrils?
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Which monosaccharide is classified as an aldose?
Which monosaccharide is classified as an aldose?
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Which of the following modifications is characterized by the addition of a fatty acid chain?
Which of the following modifications is characterized by the addition of a fatty acid chain?
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What is an example of a polysaccharide?
What is an example of a polysaccharide?
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What happens during the cyclisation of monosaccharides?
What happens during the cyclisation of monosaccharides?
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Which monosaccharide is a ketose?
Which monosaccharide is a ketose?
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Which structure is categorized by the presence of multiple sugar units?
Which structure is categorized by the presence of multiple sugar units?
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What is the main characteristic of a glycoprotein?
What is the main characteristic of a glycoprotein?
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What defines the alpha (a) configuration in glycosidic bonds?
What defines the alpha (a) configuration in glycosidic bonds?
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Which features contribute to the stability of the globular protein structure of myoglobin?
Which features contribute to the stability of the globular protein structure of myoglobin?
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Which of the following is NOT a factor that determines the native conformation of a protein?
Which of the following is NOT a factor that determines the native conformation of a protein?
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What is the primary feature of quaternary structure in proteins?
What is the primary feature of quaternary structure in proteins?
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Which of the following correctly describes the arrangement of amino acids in a globular protein like myoglobin?
Which of the following correctly describes the arrangement of amino acids in a globular protein like myoglobin?
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Which type of protein structure includes a combination of secondary structural elements like alpha-helices and beta-sheets?
Which type of protein structure includes a combination of secondary structural elements like alpha-helices and beta-sheets?
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Which polysaccharide is primarily responsible for energy storage in plants?
Which polysaccharide is primarily responsible for energy storage in plants?
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What type of glycosidic bond characterizes the structure of cellulose?
What type of glycosidic bond characterizes the structure of cellulose?
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What best describes the branching pattern of amylopectin?
What best describes the branching pattern of amylopectin?
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Which type of lipid is characterized by a structure without a glycerol backbone?
Which type of lipid is characterized by a structure without a glycerol backbone?
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How are fatty acids classified based on the number of double bonds present?
How are fatty acids classified based on the number of double bonds present?
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What is the primary role of eicosanoids in human physiology?
What is the primary role of eicosanoids in human physiology?
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Which lipid class includes lipids that are involved in cell membrane structure?
Which lipid class includes lipids that are involved in cell membrane structure?
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What characterizes the hydrocarbon chain of fatty acids?
What characterizes the hydrocarbon chain of fatty acids?
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What determines whether an amino acid is essential or non-essential?
What determines whether an amino acid is essential or non-essential?
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Which of the following statements best describes the quaternary structure of proteins?
Which of the following statements best describes the quaternary structure of proteins?
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Which of the following amino acids is classified as non-polar and aliphatic?
Which of the following amino acids is classified as non-polar and aliphatic?
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Which post-translational modification involves the addition of a phosphate group to proteins?
Which post-translational modification involves the addition of a phosphate group to proteins?
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What characterizes a glycoprotein compared to a standard protein?
What characterizes a glycoprotein compared to a standard protein?
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What role does phosphorylation play in proteins?
What role does phosphorylation play in proteins?
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Which type of carbohydrate contains several monosaccharide units linked together?
Which type of carbohydrate contains several monosaccharide units linked together?
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Which of the following is a characteristic of secondary protein structure?
Which of the following is a characteristic of secondary protein structure?
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Which type of bond is formed specifically between an anomeric carbon and another carbon in a disaccharide?
Which type of bond is formed specifically between an anomeric carbon and another carbon in a disaccharide?
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Which classification of lipids is primarily characterized by containing a glycerol backbone?
Which classification of lipids is primarily characterized by containing a glycerol backbone?
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What is the result of ubiquitination on a protein within a cell?
What is the result of ubiquitination on a protein within a cell?
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What differentiates essential amino acids from conditionally essential amino acids?
What differentiates essential amino acids from conditionally essential amino acids?
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What structural feature is a characteristic of fatty acids?
What structural feature is a characteristic of fatty acids?
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What distinguishes an aldose from a ketose monosaccharide?
What distinguishes an aldose from a ketose monosaccharide?
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Which amino acids can undergo glycosylation as a post-translational modification?
Which amino acids can undergo glycosylation as a post-translational modification?
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Which type of bond is crucial for linking monosaccharides to form disaccharides?
Which type of bond is crucial for linking monosaccharides to form disaccharides?
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Which amino acid is primarily known for its involvement in the bending of protein structure?
Which amino acid is primarily known for its involvement in the bending of protein structure?
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What is a key characteristic of nitrosylation as a post-translational modification?
What is a key characteristic of nitrosylation as a post-translational modification?
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Which of the following structures specifies the primary structure of proteins?
Which of the following structures specifies the primary structure of proteins?
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Which structure represents a cyclic hexose monosaccharide?
Which structure represents a cyclic hexose monosaccharide?
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During cyclisation of monosaccharides, what is the newly formed carbon referred to?
During cyclisation of monosaccharides, what is the newly formed carbon referred to?
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Which of the following amino acids can be classified as acidic?
Which of the following amino acids can be classified as acidic?
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How can misfolded proteins lead to diseases like Alzheimer's?
How can misfolded proteins lead to diseases like Alzheimer's?
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Which protein modification allows a protein to function as a glycoprotein?
Which protein modification allows a protein to function as a glycoprotein?
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What is the primary characteristic of monosaccharides?
What is the primary characteristic of monosaccharides?
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What type of monosaccharide is specifically identified as a pentose?
What type of monosaccharide is specifically identified as a pentose?
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Which of the following statements about phosphorylation is incorrect?
Which of the following statements about phosphorylation is incorrect?
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What is the primary role of arachidonic acid in signaling pathways?
What is the primary role of arachidonic acid in signaling pathways?
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Which fatty acid is characterized as an essential fatty acid due to its inability to be synthesized by the body?
Which fatty acid is characterized as an essential fatty acid due to its inability to be synthesized by the body?
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Which statement correctly describes the structure of triglycerides?
Which statement correctly describes the structure of triglycerides?
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Cholesterol serves multiple functions in the body. Which of the following is NOT one of those functions?
Cholesterol serves multiple functions in the body. Which of the following is NOT one of those functions?
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What is the half-life of prostaglandins in biological systems?
What is the half-life of prostaglandins in biological systems?
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Which type of lipoprotein is primarily responsible for transporting cholesterol and triglycerides in the bloodstream?
Which type of lipoprotein is primarily responsible for transporting cholesterol and triglycerides in the bloodstream?
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What is the main characteristic of eicosanoids derived from arachidonic acid?
What is the main characteristic of eicosanoids derived from arachidonic acid?
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Which structural feature is characteristic of steroids?
Which structural feature is characteristic of steroids?
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What type of fatty acid is α-linolenic acid classified as?
What type of fatty acid is α-linolenic acid classified as?
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Which component of cell membranes is primarily represented by phospholipids?
Which component of cell membranes is primarily represented by phospholipids?
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Study Notes
Amino Acids
- Basic building blocks of proteins.
- Composed of an amino group (NH2), a carboxyl group (COOH), and a side chain (R group).
- The chemical properties of amino acids depend on the nature of their R groups.
- R groups can be polar, non-polar, acidic, or basic, influencing how amino acids behave in a polypeptide chain.
Protein Structure
- Primary structure: linear chain of amino acids linked by peptide bonds.
- Secondary structure: Regular folding patterns formed by hydrogen bonds. Two main types: alpha helix and beta pleated sheet.
- Tertiary structure: 3D structure formed by further folding of the polypeptide chain.
- Quaternary structure: Arrangement of multiple polypeptide chains (subunits) in a protein.
Essential and Non-essential Amino Acids
- Essential amino acids: Cannot be synthesized by the body and must be obtained from the diet.
- Non-essential amino acids: Can be synthesized by the body.
Native Conformation
- The functional, fully folded 3D structure of a protein.
- Determined by the primary, secondary, tertiary, and sometimes quaternary structure.
- Has a unique 3D structure that is crucial for protein function.
Post-translational Modifications (PTM)
- Chemical modifications that occur to a protein after it has been translated.
- Add functional groups to amino acids, altering protein function.
- Examples include phosphorylation, glycosylation, acylation, ubiquitination, and nitrosylation.
Carbohydrates
- Organic molecules composed of carbon, hydrogen, and oxygen atoms.
- Classified as monosaccharides, disaccharides, oligosaccharides, and polysaccharides.
- Monosaccharides: Simple sugar units, classified by the number of carbon atoms (triose, pentose, hexose).
- Disaccharides: Two linked monosaccharides.
- Oligosaccharides: Short chains of 3-12 monosaccharides.
- Polysaccharides: Long chains composed of hundreds of monosaccharides.
Polysaccharides
- Homopolymers of glucose with diverse functions.
- Storage in animals: Glycogen, branched homopolymer of glucose.
- Storage in plants: Starch, composed of amylose (unbranched) and amylopectin (branched).
- Structure in plants: Cellulose, linear homopolymer of glucose.
- Structure in invertebrates: Chitin, homopolymer of N-acetyl-glucosamine.
Lipids
- A diverse group of water-insoluble molecules with various functions.
- Major sources of energy.
- Important for structural components of cells.
- Involved in various cellular signaling processes.
Classification of Lipids
- Fatty acids and their derivatives: Fatty acids, prostaglandins, leukotrienes.
- Lipids containing glycerol: Neutral lipids (mono-, di-, tri-acylglycerol) and charged lipids (phospholipids).
- Lipids not containing glycerol: Steroids, sphingolipids, terpenoids.
- Lipoproteins and lipopolysaccharides: Complexes of lipids and proteins or lipids and polysaccharides.
Arachidonic Acid
- Arachidonic acid is a 20-carbon chain fatty acid with four double bonds.
- It is an omega-6 fatty acid, meaning the terminal double bond is six carbons away from the omega carbon.
Essential Fatty Acids (EFAs)
- EFAs are fatty acids that the body cannot synthesize and must be obtained through diet.
- Linoleic acid (omega-6) and alpha-linolenic acid (omega-3) are essential fatty acids.
- EFA deficiency is rare, but can lead to scaly dermatitis, visual, and neurological abnormalities.
Signalling Fatty Acids
- Eicosanoids are a family of signaling fatty acids derived from 20-carbon polyunsaturated fatty acids (PUFAs).
- Prostaglandins (PG) and Leukotrienes are examples of eicosanoids synthesized from arachidonic acid.
- Prostaglandins are synthesized via cyclooxygenase (COX) and have a short half-life (seconds).
- Leukotrienes are synthesized via lipoxygenase (LOX) and have a longer half-life (up to 4 hours).
- Both prostaglandins and leukotrienes play a role in inflammation.
Monoacyl, Diacyl & Triacylglycerol
- Monoacylglycerol is a breakdown product of triacylglycerol (TAG) during fat digestion.
- Diacylglycerol (DAG) is a potent intracellular signaling molecule that mobilizes calcium.
- Triglycerides (triacylglycerols, TAG) are the principal storage form of energy in the body.
- They are composed of three fatty acids and glycerol.
- TAGs are stored in adipose tissue.
Phospholipids (Phosphoglycerates) & Sphingolipids
- Phospholipids are major components of cell membranes.
- Lecithin is an example of a glycerophospholipid.
- Sphingolipids are another type of lipid found in cell membranes.
Steroids
- Steroids contain a characteristic fused ring system with a hydroxyl or keto group on carbon 3.
- Cholesterol, Bile Acids, Progesterone, Adrenocortical Steroids, Androgens, and Estrogens are major steroid classes.
- Cholesterol plays a vital role in the structure of membranes and is a precursor for Vitamin D, Bile Acids, and Steroid Hormones.
Lipoproteins
- Lipoproteins are spherical particles found in plasma that transport lipids, including cholesterol.
- They have a hydrophobic core of triacylglycerols and cholesteryl esters.
- A phospholipid layer surrounds the core and is associated with proteins.
Amino Acids
- The chemical properties of amino acids depend on the nature of their side chain (R group).
- R groups can be polar, hydrophobic/philic, acidic, or basic.
- Amino acid properties determine how they behave in a polypeptide chain.
- Small amino acids: Glycine and Alanine
- Branched amino acids: Valine, Leucine, Isoleucine
- Sulphur-containing amino acids: Cysteine and Methionine
- Amino acid found at a bend in a protein: Proline
- Amino acids that can be phosphorylated: Serine, Threonine, and Tyrosine
- Amino acids that can be glycosylated: Asparagine, Serine, and Threonine
- Amino acid that can be nitrosylated: Cysteine
Essential and Non-Essential Amino Acids
- Essential amino acids cannot be synthesized in the body and must be obtained from the diet.
- Non-essential amino acids can be synthesized by the body from other amino acids or precursors.
- Some amino acids are conditionally essential, meaning their synthesis may not be sufficient to meet demand under all conditions.
Protein Structure
- Primary structure: Amino acids linked together with peptide bonds forming a polypeptide chain.
-
Secondary structure: Regular, repetitive folding patterns stabilized by hydrogen bonds.
- Alpha (α) helix: Found in collagen and keratin in hair.
- Beta (β) pleated sheet: Found in silk.
- Tertiary structure: Further folding of the polypeptide chain into a globular form, stabilized by various bonds and interactions between side chains.
- Quaternary structure: Arrangement of protein subunits in a multi-meric protein.
Native Conformation
- Functional, fully folded protein structure determined by primary, secondary, tertiary, and sometimes quaternary structure.
- It determines the biological function of the protein, including catalysis, protection, regulation, signal transduction, storage, and transport.
- Denaturation: Loss of native conformation, which disrupts protein function.
Post-Translational Modifications (PTM)
- Chemical modifications of a protein after translation.
- Increases the diversity of the proteome.
- Common examples:
- Phosphorylation: Addition of a phosphate group to serine, threonine, or tyrosine residues.
- Glycosylation: Addition of a sugar group to asparagine, serine, or threonine residues.
- Acylation: Addition of a fatty acid.
- Ubiquitination: Addition of ubiquitin, a signal for protein degradation.
- Nitrosylation: Addition of nitric oxide.
Abnormal Protein Aggregates and Disease
- Misfolded proteins can form fibrils, known as amyloid.
- Amyloid deposition in different tissues can lead to disease.
- Alzheimer's disease is caused by the presence of misfolded proteins in the brain.
Carbohydrates
- Molecules containing carbon, hydrogen, and oxygen atoms.
- Monosaccharides: Simple sugar units, such as glucose, fructose, galactose, and mannose.
- Disaccharides: Two monosaccharides linked together, such as lactose (β-galactose + glucose) and maltose (glucose + glucose).
- Polysaccharides: Many monosaccharides linked together, such as cellulose, starch (amylose and amylopectin), and glycogen.
Monosaccharides
- Empirical formula: (CH₂O)n, where n represents the number of carbon atoms (3-7).
- Classified by the number of carbon atoms:
- Triose: 3 carbons.
- Pentose: 5 carbons.
- Hexose: 6 carbons.
- They are polyhydroxy aldehydes (aldose) or ketones (ketose).
- Hexoses (C₆H₁₂O₆) are common dietary sources of sugar.
Glycosidic Bond
- A covalent bond between two sugar molecules.
- The type of bond is determined by the number of connected carbons and the position of the anomeric hydroxyl group (alpha or beta configuration).
- Lactose has a β(1 → 4) glycosidic bond.
Polysaccharides
- Oligosaccharides: 3-12 monosaccharides linked together.
- Polysaccharides: > 12 monosaccharides linked together.
- Variations in structure include chain length, branching, and glycosidic bond types.
- Examples:
- Amylopectin: A branched polysaccharide of glucose found in starch.
- Amylose: A non-branched polysaccharide of glucose found in starch.
- Cellulose: A straight chain polysaccharide of glucose found in plants.
- Chitin: A polysaccharide of N-acetyl-glucosamine found in invertebrates.
Polysaccharide Functions: Storage and Structure
-
Storage:
- Glycogen: Stored in animals as a homopolymer of glucose.
- Starch: Stored in plants as a homopolymer of glucose, composed of amylopectin and amylose.
-
Structure:
- Cellulose: Provides structural support in plants.
- Chitin: Provides structural support in invertebrates.
Lipids
- Heterogeneous group of water-insoluble (hydrophobic) organic molecules.
- Play major roles in energy storage, cell structure, and signaling.
- Major classifications:
- Fatty acids and their derivatives.
- Lipids containing glycerol: acylglycerols (neutral lipids) and phospholipids.
- Lipids not containing glycerol: steroids, sphingolipids, and terpenoids.
- Lipoproteins and lipopolysaccharides.
Fatty Acids
- Hydrocarbon chains with a carboxyl group at one end.
- Chain length and saturation (presence of double bonds) vary.
- Notation: Number of carbons:number and positions of double bonds.
- E.g., 18:1(Δ⁹) represents an 18-carbon fatty acid with one double bond at the 9th carbon.
Glycerol-Containing Lipids
-
Neutral lipids:
- Mono-, di-, and tri-acylglycerol (triglycerides): formed by esterification of fatty acids to glycerol.
-
Charged lipids:
- Phospholipids: Contain a phosphate group, making them amphipathic (hydrophilic and hydrophobic). Important components of cell membranes.
Non-Glycerol-Containing Lipids
-
Steroids:
- Four fused ring structures; important in cell signaling.
- Cholesterol is a key steroid.
-
Sphingolipids:
- Contain sphingosine (an amino alcohol) and a fatty acid.
- Important components of cell membranes and involved in signaling.
-
Terpenoids:
- Derived from isoprene units.
- Include vitamins A, E, and K, carotenoids, and rubber.
Lipoproteins and Lipopolysaccharides
- Lipoproteins: Transport lipids in the blood.
- Lipopolysaccharides: Found in the outer membrane of Gram-negative bacteria.
Arachidonic Acid
- Arachidonic acid is a 20-carbon fatty acid with four double bonds.
- It is an ω-6 fatty acid, meaning the terminal double bond is six bonds away from the ω carbon.
Essential Fatty Acids (EFAs)
- Essential fatty acids are those that we cannot synthesize and must obtain from our diet.
- Linoleic acid is an ω-6 fatty acid with the formula CH3(CH2)4(CH=CHCH2)2(CH2)6COOH.
- α-linolenic acid is an ω-3 fatty acid with the formula CH3CH2(CH=CHCH2)3(CH2)6COOH.
- EFA deficiency can lead to scaly dermatitis, visual and neurological abnormalities.
Signaling Fatty Acids
- Eicosanoids are a family of signaling molecules derived from 20-carbon polyunsaturated fatty acids.
- Prostaglandins are synthesized from arachidonic acid via cyclooxygenase (COX).
- Leukotrienes are synthesized from arachidonic acid via lipoxygenase (LOX).
Monoacyl, Diacyl, & Triacylglycerol
- Monoacylglycerol is a breakdown product of triacylglycerols during fat digestion.
- Diacylglycerol (DAG) is a potent intracellular signaling molecule that mobilizes calcium.
- Triacylglycerols (TAGs) are the principal storage form of energy in the body.
- They are made up of three fatty acids and glycerol.
- TAGs are stored in adipose tissue.
Phospholipids
- Phospholipids are major components of cell membranes.
- Lecithin is an example of a glycerophospholipid.
Sphingolipids
- Sphingolipids are another type of lipid found in cell membranes.
Steroids
- Steroids contain a characteristic fused ring system with a hydroxyl or keto group on carbon 3.
- Cholesterol is a major steroid with 27 carbons and plays a vital role in the structure of membranes.
- Bile acids are steroids with 24 carbons.
- Progesterone and adrenocortical steroids are steroids with 21 carbons.
- Androgens are steroids with 19 carbons.
- Estrogens are steroids with 18 carbons.
Functions of Cholesterol
- Cholesterol is a metabolic precursor to vitamin D, bile acids, and steroid hormones.
- We need a constant supply of cholesterol.
Lipoproteins
- Lipoproteins are spherical particles found in plasma that transport lipids, including cholesterol.
- They have a hydrophobic core of triacylglycerols and cholesteryl esters.
- They have a phospholipid layer associated with the core.
Amino Acid Properties
- The side chain (R group) of an amino acid determines its chemical properties, including polarity, hydrophobicity/hydrophilicity, acidity, and basicity.
- Amino acid properties influence how they behave within a polypeptide chain.
Amino Acid Characteristics
- Small amino acids: glycine and alanine
- Branched-chain amino acids: valine, leucine, isoleucine
- Sulphur-containing amino acids: cysteine and methionine
- Proline: found at bends in a protein
- Phosphorylated amino acids: serine, threonine, and tyrosine
- Glycosylated amino acids: asparagine, serine, and threonine
- Nitrosylated amino acid: cysteine
Essential and Non-Essential Amino Acids
- Essential amino acids: cannot be synthesized by the body and must be obtained from the diet. Examples include methionine, arginine, threonine, tryptophan, valine, isoleucine, leucine, phenylalanine, histidine, and lysine.
- Non-essential amino acids: can be synthesized by the body from other amino acids or precursors. Examples include alanine, aspartic acid, asparagine, cysteine, glutamic acid, glycine, proline, serine, and tyrosine.
- Conditionally essential amino acids: their synthesis may not be sufficient to meet demand under certain conditions and may need to come from the diet. Examples include arginine and glutamine (in children).
Protein Structure
- Primary structure: amino acids are linked together in a polypeptide chain via peptide bonds. The chain has directionality, with the amino terminus (N-terminus) as the start and the carboxyl terminus (C-terminus) as the end.
- Secondary structure: regular repetitive folding pattern stabilized by hydrogen bonds. Examples include alpha (α) helix and beta (β) pleated sheet.
- Tertiary structure: further folding of the polypeptide chain into a globular form. Stabilized by various bonds and interactions between side chains, including disulfide bonds, hydrophobic interactions, ionic bonds, and hydrogen bonds.
- Quaternary structure: arrangement of protein subunits in a multi-meric protein. It consists of two or more tertiary polypeptides, which may be the same or different, held together by non-covalent interactions and inter-chain disulfide bonds.
Native Conformation
- The functional, fully folded protein structure, which is unique and determined by the primary, secondary, tertiary, and sometimes quaternary structures.
- It determines the biological function of the protein, including catalysis, protection, regulation, signal transduction, storage, and transport.
Post-Translational Modifications
- Chemical modifications that occur after protein translation, resulting in changes in protein function. Examples include:
- Phosphorylation: addition of a phosphate group to serine, threonine, or tyrosine residues.
- Glycosylation: addition of a sugar group to asparagine, serine, or threonine residues.
- Acylation: addition of a fatty acid.
- Ubiquitination: addition of ubiquitin, which can signal protein degradation.
- Nitrosylation: addition of nitric oxide.
Abnormal Protein Aggregates
- Misfolded proteins can aggregate into fibrils, which can lead to diseases like Alzheimer's disease. Fibrils are known as amyloid and can be formed from over 20 proteins.
Carbohydrates
- Molecules containing carbon (C), hydrogen (H), and oxygen (O) atoms.
- Monosaccharides: single saccharide units, also called simple sugars. Examples include glucose, fructose, galactose, and mannose.
- Disaccharides: two monosaccharides linked together. Example: lactose, which is formed by a β (1→ 4) glycosidic bond between β-galactose and glucose.
- Oligosaccharides: a few linked monosaccharides.
- Polysaccharides: consist of many monosaccharides linked together. Examples include cellulose, glycogen, and starch.
Monosaccharide Structure
- Empirical formula: (CH2O)n, where n is the number of carbons.
- Triose (n=3), pentose (n=5), and hexose (n=6) are common types.
- They are polyhydroxy aldehydes (aldoses) or ketones (ketoses).
Hexoses
- Six-carbon sugars, including glucose, fructose, galactose, and mannose.
- Isomers: same chemical formula but different structures.
- Dietary sources:
- Glucose: fruit juices, starch, glycogen, lactose, maltose, cane sugar.
- Fructose: fruit juices, honey, cane sugar.
- Galactose: milk (lactose).
- Mannose: plants and gums.
Cyclisation of Monosaccharides
- Monosaccharides tend to cyclize, forming a ring structure.
- In aldoses, cyclization occurs at carbon 1 (C1), which becomes the anomeric carbon. The anomeric carbon can have either an alpha (α) or beta (β) configuration.
- In ketoses, cyclization occurs at carbon 2 (C2).
Disaccharides and Glycosidic Bonds
- A glycosidic bond links two monosaccharides together.
- The type of bond depends on the connected carbons and the position of the anomeric hydroxyl group (α or β).
Polysaccharides
- Polymers of monosaccharides with varying chain lengths (oligosaccharides: n=3-12, polysaccharides: n>12).
- Polysaccharides can have branches, different types of glycosidic bonds, and variations in structure.
Polysaccharide Functions
-
Storage:
- Glycogen: branched homopolymer of glucose in animals, storing energy.
- Starch: homopolymer of glucose in plants, composed of amylopectin (branched) and amylose (unbranched).
-
Structure:
- Cellulose: straight chain homopolymer of glucose in plants, providing structural support.
- Chitin: homopolymer of N-acetyl-glucosamine in invertebrates, providing structural support.
Lipids
- Water-insoluble (hydrophobic) organic molecules.
- Key functions:
- Energy source: major source of energy in the body.
- Structural components: of cells and organelles.
- Cellular signaling: involved in signaling events (steroids, prostaglandins, leukotrienes).
Lipid Classification
- Fatty acids and their derivatives: including prostaglandins and leukotrienes.
-
Lipids containing glycerol:
- Neutral lipids: mono-, di-, and tri-acylglycerol (triglycerides).
- Charged lipids: phospholipids.
-
Lipids not containing glycerol:
- Steroids: examples include cholesterol, testosterone, and estrogen.
- Sphingolipids: examples include sphingomyelin and cerebrosides.
- Terpenoids: examples include vitamin A and carotenoids.
- Lipoproteins and lipopolysaccharides: involved in lipid transport and bacterial cell walls, respectively.
Fatty Acids
- Chain lengths are indicated by the number of carbons before the colon, and the location and number of double bonds are indicated after the colon.
- Example: 18:2 (Δ9,12) indicates an 18-carbon fatty acid with two double bonds, located at the 9th and 12th carbons from the carboxyl group.### Arachidonic Acid
- A 20 carbon chain with 4 double bonds
- Also known as an omega-6 (n-6) fatty acid
- The terminal double bond is 6 bonds in from the omega carbon
Essential Fatty Acids (EFAs)
- Essential for human health as we cannot synthesize them
- Linoleic acid (omega-6): 18:2(n-6)
- Alpha-linolenic acid (omega-3): 18:3(n-3)
- EFA deficiency (rare) can lead to:
- Scaly dermatitis
- Visual and neurologic abnormalities
Signalling Fatty Acids
- Prostaglandins and Leukotrienes belong to the eicosanoid family
- Synthesized from arachidonic acid - a 20:4 fatty acid
- Prostaglandins are synthesized via COX (cyclooxygenase)
- Potent
- Short half-life (seconds)
- Multiple roles including inflammation and platelet homeostasis
- Leukotrienes are synthesized via LOX (lipoxygenase)
- Longer half-life (up to 4 hours)
- Multiple roles including inflammation and neutrophil adhesion
Monoacyl, Diacyl & Triacylglycerol
- Monoacyl glycerol is a breakdown product of TAG in fat digestion
- DAG (Diacylglycerol) is a potent intracellular signal
- Involved in the mobilization of calcium
- Triglycerides (Triacylglycerols)
- Made up of 3 fatty acids and glycerol
- Principal storage form of energy in the body
- Stored in adipose tissue
Phospholipids (Phosphoglycerates) & Sphingolipids
- Major component of cell membranes
- Lecithin is an example of a glycerophospholipid
- Sphingolipids are another class of lipids that are found in cell membranes
Steroids
- Contain a characteristic fused ring system with a hydroxyl or keto group on carbon 3
- Major classes of steroids:
- Cholesterol (27 carbons)
- Bile acids (24 carbons)
- Progesterone and adrenocortical steroids (21 carbons)
- Androgens (19 carbons)
- Estrogens (18 carbons)
- Functions of Cholesterol:
- Metabolic precursor of Vitamin D, bile acids, and steroid hormones
- Plays a vital role in the structure of membranes
- We need a constant supply of cholesterol
Lipoproteins
- Spherical particles found in plasma that transport lipids, including cholesterol
- Hydrophobic core of triacylglycerols and cholesteryl esters
- Phospholipid layer associated with the core
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Description
This quiz covers the fundamentals of amino acids and protein structure, including their classifications, chemical properties, and levels of structural organization. You'll explore both essential and non-essential amino acids and understand their role in building proteins.