Amino Acids Overview
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Questions and Answers

Myoglobin is a globular protein that contains disulphide bonds between amino acids.

True

The quaternary structure of a protein involves the arrangement of a single polypeptide chain.

False

The native conformation of a protein determines its biological function.

True

Hydrophobic amino acids are typically found on the outside of globular proteins.

<p>False</p> Signup and view all the answers

Ionic bonds and hydrogen bonds contribute to the stability of a protein's structure.

<p>True</p> Signup and view all the answers

Arachidonic acid has a 20 carbon chain with 4 double bonds.

<p>True</p> Signup and view all the answers

Linoleic acid is a fatty acid with a 20 carbon chain.

<p>False</p> Signup and view all the answers

Eicosanoids are derived from arachidonic acid and are part of the fatty acid family.

<p>True</p> Signup and view all the answers

Triglycerides are primarily found in the nucleus of cells.

<p>False</p> Signup and view all the answers

Cholesterol has 27 carbons and is crucial for the structure of cell membranes.

<p>True</p> Signup and view all the answers

Arachidonic acid is categorized as an omega-3 fatty acid.

<p>False</p> Signup and view all the answers

Prostaglandins are part of the eicosanoid family and have a long half-life.

<p>False</p> Signup and view all the answers

Sphingolipids are a type of phospholipid that is a major component of cell membranes.

<p>False</p> Signup and view all the answers

The breakdown product of TAG in fat digestion is monoacyl glycerol.

<p>True</p> Signup and view all the answers

Estrogens contain 21 carbons.

<p>False</p> Signup and view all the answers

Glycogen is a homopolymer of fructose, branched every 12-14 residues.

<p>False</p> Signup and view all the answers

Amylopectin is a branched polysaccharide composed of glucose, with branches occurring every 24-30 residues.

<p>True</p> Signup and view all the answers

Cellulose is a homopolymer of galactose with long straight chains.

<p>False</p> Signup and view all the answers

Lipids are organic molecules that are generally soluble in water.

<p>False</p> Signup and view all the answers

Chitin is a homopolymer of n-acetyl-galactosamine.

<p>False</p> Signup and view all the answers

Fatty acids can contain either an even or an odd number of carbon atoms.

<p>True</p> Signup and view all the answers

The structure of amylose is branched and consists of a non-helical arrangement.

<p>False</p> Signup and view all the answers

Phospholipids are a type of lipid that contains glycerol.

<p>True</p> Signup and view all the answers

Phosphorylation results in a chemical modification that is referred to as a phosphoprotein.

<p>True</p> Signup and view all the answers

Ubiquitination is a process that adds a sugar group to proteins.

<p>False</p> Signup and view all the answers

An oligosaccharide consists of many linked monosaccharides.

<p>False</p> Signup and view all the answers

A monosaccharide is a single saccharide molecule.

<p>True</p> Signup and view all the answers

In carbohydrates, a glycosidic bond is the bond between two amino acids.

<p>False</p> Signup and view all the answers

The empirical formula for monosaccharides is (CH2O)n where n can range from 3 to 7.

<p>True</p> Signup and view all the answers

Fructose is a dissacharide formed from two glucose molecules.

<p>False</p> Signup and view all the answers

Glycoproteins are carbohydrates that are associated with proteins.

<p>True</p> Signup and view all the answers

Amyloid is formed only from one type of protein.

<p>False</p> Signup and view all the answers

Nitrosylation involves the addition of a nitrous oxide group to proteins.

<p>False</p> Signup and view all the answers

An aldohexose contains six carbon atoms and has an aldehyde group.

<p>True</p> Signup and view all the answers

The position of the anomeric hydroxyl group determines whether a glycosidic bond is alpha or beta.

<p>True</p> Signup and view all the answers

Alzheimer's Disease is linked to the presence of misfolded proteins in the brain.

<p>True</p> Signup and view all the answers

Lactose is composed of alpha-galactose and glucose.

<p>False</p> Signup and view all the answers

Amino acids can be classified into essential and non-essential types.

<p>True</p> Signup and view all the answers

Proline is an amino acid known for creating a straight structure in proteins.

<p>False</p> Signup and view all the answers

Secondary protein structure is characterized by a random arrangement of amino acids.

<p>False</p> Signup and view all the answers

Amino acids contain an amino group, a carboxyl group, and a side chain called the R group.

<p>True</p> Signup and view all the answers

The glycosidic bond connects amino acids together in a protein.

<p>False</p> Signup and view all the answers

The structure of polysaccharides consists of long chains of monosaccharides.

<p>True</p> Signup and view all the answers

Hydrophobic amino acids are characterized by their affinity for water.

<p>False</p> Signup and view all the answers

The R group of an amino acid can determine if it is polar or non-polar.

<p>True</p> Signup and view all the answers

Glycine is classified as a branched-chain amino acid.

<p>False</p> Signup and view all the answers

Triacylglycerides are a classification of fatty acids.

<p>False</p> Signup and view all the answers

Serine, threonine, and tyrosine can be phosphorylated.

<p>True</p> Signup and view all the answers

Lysine and arginine are considered acidic amino acids.

<p>False</p> Signup and view all the answers

All proteins have a quaternary structure.

<p>False</p> Signup and view all the answers

Stabilization of secondary protein structures is primarily through hydrogen bonds.

<p>True</p> Signup and view all the answers

Globular proteins have hydrophobic amino acids located on the outside of their structure.

<p>False</p> Signup and view all the answers

The quaternary structure of a protein can involve the interaction of different polypeptide chains.

<p>True</p> Signup and view all the answers

Denaturation is the process where a protein loses its native conformation and biological function.

<p>True</p> Signup and view all the answers

Disulphide bonds are the only interactions that stabilize the structure of proteins.

<p>False</p> Signup and view all the answers

The native conformation of a protein is determined solely by its tertiary structure.

<p>False</p> Signup and view all the answers

Phosphorylation results in the formation of a phospholipid.

<p>False</p> Signup and view all the answers

An oligosaccharide consists of two monosaccharides linked together.

<p>False</p> Signup and view all the answers

Lactose is a disaccharide composed of beta-galactose and glucose.

<p>True</p> Signup and view all the answers

Amyloid can be formed from over 20 different proteins.

<p>True</p> Signup and view all the answers

Glucose and fructose are examples of diastereomers.

<p>False</p> Signup and view all the answers

Nitrosylation refers to the addition of nitric oxide to a protein.

<p>True</p> Signup and view all the answers

The empirical formula of monosaccharides is C6H12O6.

<p>False</p> Signup and view all the answers

The structure of cellulose consists of many disaccharide units.

<p>False</p> Signup and view all the answers

Fatty acids can only be categorized by their carbon chain length.

<p>False</p> Signup and view all the answers

Proteins that have undergone ubiquitination are marked for degradation.

<p>True</p> Signup and view all the answers

Isomers have the same chemical formula but different physical structures.

<p>True</p> Signup and view all the answers

Glycogen has a branched structure, similar to amylopectin.

<p>True</p> Signup and view all the answers

In a ketose, the carbonyl group is located at carbon 1.

<p>False</p> Signup and view all the answers

Acylation adds a fatty acid to a protein.

<p>True</p> Signup and view all the answers

Polysaccharides can only be formed from aldoses.

<p>False</p> Signup and view all the answers

Amino acids can be classified based on the properties of their side chains (R groups).

<p>True</p> Signup and view all the answers

The primary structure of a protein is determined by the sequence of its polypeptide chains.

<p>False</p> Signup and view all the answers

Phospholipids are categorized as a type of carbohydrate.

<p>False</p> Signup and view all the answers

The glycosidic bond connects monosaccharides to form polysaccharides.

<p>True</p> Signup and view all the answers

Cysteine and methionine are sulfur-containing amino acids.

<p>True</p> Signup and view all the answers

The tertiary structure of proteins involves the interaction between multiple polypeptide chains.

<p>False</p> Signup and view all the answers

Essential amino acids cannot be synthesized by the body and must be obtained from the diet.

<p>True</p> Signup and view all the answers

Arachidonic acid is a type of saturated fatty acid.

<p>False</p> Signup and view all the answers

Quaternary structure is the highest level of protein structure.

<p>True</p> Signup and view all the answers

Beta-pleated sheets and alpha helices are examples of primary protein structure.

<p>False</p> Signup and view all the answers

Lipids such as triglycerides are generally soluble in water.

<p>False</p> Signup and view all the answers

Hydrophobic amino acids are usually found on the interior of proteins, contributing to their structural stability.

<p>True</p> Signup and view all the answers

Glycogen is a branched polymer of glucose with branches every 8-12 residues.

<p>True</p> Signup and view all the answers

The empirical formula for fatty acids can be represented as CnH2nO2.

<p>True</p> Signup and view all the answers

Glycogen is a homopolymer of glucose, branched every 12-14 residues.

<p>True</p> Signup and view all the answers

Cellulose is a homopolymer of glucose with branched chains.

<p>False</p> Signup and view all the answers

Amylopectin comprises about 15-20% of starch and is branched every 24-30 residues.

<p>True</p> Signup and view all the answers

Lipids are a group of water-soluble organic molecules.

<p>False</p> Signup and view all the answers

Monosaccharides are formed by linking multiple saccharide units.

<p>False</p> Signup and view all the answers

Chitin is a homopolymer of glucose and is primarily found in plants.

<p>False</p> Signup and view all the answers

Prostaglandins are classified as cholesterol.

<p>False</p> Signup and view all the answers

Lipids can serve as a major source of energy in the body.

<p>True</p> Signup and view all the answers

Arachidonic acid is classified as an -3 fatty acid.

<p>False</p> Signup and view all the answers

Cholesterol contains 27 carbon atoms and plays a vital role in the structure of cell membranes.

<p>True</p> Signup and view all the answers

Linoleic acid has a carbon chain length of 20 carbons.

<p>False</p> Signup and view all the answers

Prostaglandins have a short half-life of seconds and play multiple roles in the body.

<p>True</p> Signup and view all the answers

Sphingolipids are considered a major component of the lipid bilayer in cell membranes.

<p>True</p> Signup and view all the answers

Eicosanoids are derived from saturated fatty acids only.

<p>False</p> Signup and view all the answers

Triglycerides are made up of two fatty acids and one glycerol molecule.

<p>False</p> Signup and view all the answers

Insufficient intake of essential fatty acids can lead to scaly dermatitis and neurologic issues.

<p>True</p> Signup and view all the answers

The structure of monoacyl glycerol is derived from the formation of diacyl glycerol.

<p>False</p> Signup and view all the answers

Arachidonic acid undergoes synthesis through lipoxygenase.

<p>False</p> Signup and view all the answers

The native conformation of a protein refers to its initial polypeptide sequence.

<p>False</p> Signup and view all the answers

Quaternary structure in proteins involves a single polypeptide chain.

<p>False</p> Signup and view all the answers

Hydrophobic amino acids are generally located on the surface of globular proteins to interact with water.

<p>False</p> Signup and view all the answers

Disulphide bonds are a type of interaction that stabilizes the tertiary structure of proteins.

<p>True</p> Signup and view all the answers

Secondary structural elements in proteins do not include alpha-helices and beta-sheets.

<p>False</p> Signup and view all the answers

Glycogen is a homopolymer of glucose, branched every 12-14 residues using $eta 1-4$ and $eta 1-6$ glycosidic bonds.

<p>False</p> Signup and view all the answers

Cellulose is composed of long straight chains of glucose connected by $eta1-4$ glycosidic bonds.

<p>True</p> Signup and view all the answers

Amylose, one of the components of starch, has a branched structure and connects glucose units with $eta 1-4$ glycosidic bonds.

<p>False</p> Signup and view all the answers

Fatty acids contain a hydrophilic head and a hydrophobic tail, making them soluble in water.

<p>False</p> Signup and view all the answers

Chitin is a polysaccharide that is a homopolymer of n-acetyl-glucosamine and serves structural roles in invertebrates.

<p>True</p> Signup and view all the answers

Prostaglandins and leukotrienes are classified as charged lipids within the lipid classification.

<p>False</p> Signup and view all the answers

Steroids are a type of lipid that do not contain glycerol in their structure.

<p>True</p> Signup and view all the answers

Lipopolysaccharides are composed entirely of lipids and have no carbohydrate component.

<p>False</p> Signup and view all the answers

Arachidonic acid is classified as an -3 fatty acid.

<p>False</p> Signup and view all the answers

Cholesterol is a major precursor for the synthesis of bile acids.

<p>True</p> Signup and view all the answers

Leukotrienes are synthesized via cyclooxygenase (COX).

<p>False</p> Signup and view all the answers

Triglycerides are primarily stored in adipose tissue as the main energy reserve.

<p>True</p> Signup and view all the answers

Essential fatty acids can be synthesized by the human body.

<p>False</p> Signup and view all the answers

Prostaglandins have a longer half-life than leukotrienes.

<p>False</p> Signup and view all the answers

The characteristic ring system of steroids is composed of four fused carbon rings.

<p>True</p> Signup and view all the answers

Monoacyl glycerol is a major component of cell membranes.

<p>False</p> Signup and view all the answers

Arachidonic acid has 4 double bonds located between carbons 11-12 and 14-15.

<p>False</p> Signup and view all the answers

Sphingolipids are classified as triglycerides.

<p>False</p> Signup and view all the answers

Acylation involves the addition of a sugar group to proteins.

<p>False</p> Signup and view all the answers

Glycoproteins are formed from the linkage of many monosaccharides.

<p>False</p> Signup and view all the answers

Nitrosylation adds a nitric oxide group to proteins.

<p>True</p> Signup and view all the answers

Disaccharides consist of three to ten monosaccharides linked together.

<p>False</p> Signup and view all the answers

Monosaccharides can exist as either aldoses or ketoses.

<p>True</p> Signup and view all the answers

Amyloid is formed solely from a single protein type.

<p>False</p> Signup and view all the answers

Ubiquitination serves as a signal for cell division.

<p>False</p> Signup and view all the answers

Polysaccharides are composed of many linked oligosaccharides.

<p>False</p> Signup and view all the answers

The presence of amyloid fibrils in tissues is indicative of certain diseases.

<p>True</p> Signup and view all the answers

The empirical formula for monosaccharides is (C6H12O6).

<p>False</p> Signup and view all the answers

Fructose is an example of a hexose sugar.

<p>True</p> Signup and view all the answers

Cyclisation of monosaccharides results in a linear structure.

<p>False</p> Signup and view all the answers

A beta glycosidic bond has the -OH group in an upward position.

<p>True</p> Signup and view all the answers

Alzheimer's disease is linked to the deposition of misfolded proteins in the heart.

<p>False</p> Signup and view all the answers

Triose is a monosaccharide that contains a three-carbon chain.

<p>True</p> Signup and view all the answers

The primary structure of a protein is related to its amino acid sequence linked by glycosidic bonds.

<p>False</p> Signup and view all the answers

Hydrophilic amino acids are typically found on the inside of globular proteins.

<p>False</p> Signup and view all the answers

Cholesterol is known to have 27 carbons and plays a crucial role in the structure of cellular membranes.

<p>True</p> Signup and view all the answers

Cysteine and methionine are the only amino acids that contain sulfur.

<p>True</p> Signup and view all the answers

A triglyceride consists of three molecules of fatty acids and a single molecule of glycerol.

<p>True</p> Signup and view all the answers

All amino acids can be classified based on the properties of their R groups, including polarity and charge.

<p>True</p> Signup and view all the answers

Amino acids that cannot be synthesized in the body must be obtained through diet and are called non-essential amino acids.

<p>False</p> Signup and view all the answers

Eicosanoids are primarily derived from linoleic acid, which has a 20 carbon chain.

<p>False</p> Signup and view all the answers

The quaternary structure of a protein is characterized by the interaction of multiple polypeptide chains.

<p>True</p> Signup and view all the answers

Proline is considered an essential amino acid because it can only be obtained through dietary sources.

<p>False</p> Signup and view all the answers

Post-translational modifications play no role in the function of proteins.

<p>False</p> Signup and view all the answers

The stability of a protein's structure is influenced solely by ionic bonds.

<p>False</p> Signup and view all the answers

Fatty acids can only have an even number of carbon atoms.

<p>False</p> Signup and view all the answers

Monosaccharides are the building blocks of both polysaccharides and disaccharides.

<p>True</p> Signup and view all the answers

Study Notes

Amino Acids

  • The basic building blocks of proteins
  • Contain an amino group (NH2), a carboxyl group (COOH), a hydrogen atom (H), and a side chain (R group)
  • Side chains determine chemical properties
  • Side chain properties include polarity, hydrophobic/hydrophilic, acidic/basic
  • Amino acid properties determine how they behave within a polypeptide chain

Amino Acid Properties

  • Non-polar hydrophobic (water-hating): glycine, alanine, valine, leucine, isoleucine, methionine, proline, phenylalanine, tryptophan
  • Polar hydrophilic (water-loving): serine, threonine, tyrosine, cysteine, asparagine, glutamine
  • Basic (positive charge): lysine, arginine, histidine
  • Acidic (negative charge): aspartic acid (aspartate), glutamic acid (glutamate)

Additional Amino Acid Characteristics

  • Small amino acids: glycine and alanine
  • Branched amino acids: valine, leucine, isoleucine
  • Sulfur-containing amino acids: cysteine and methionine
  • Amino acid found at a bend in a protein: proline
  • Amino acids that can be phosphorylated: serine, threonine, tyrosine
  • Amino acids that can be glycosylated: asparagine, serine, threonine
  • Amino acid that can be nitrosylated: cysteine

Essential vs. Non-essential Amino Acids

  • Essential amino acids cannot be synthesized in the body and must come from the diet: methionine, arginine, threonine, tryptophan, valine, isoleucine, leucine, phenylalanine, histidine
  • Non-essential amino acids can be synthesized by the body: alanine, aspartic acid, asparagine, cysteine, glutamic acid, glycine, proline, serine, tyrosine, lysine, glutamine

Protein Structure

  • Four levels: primary, secondary, tertiary, quaternary

Primary Structure

  • Linear sequence of amino acids linked by peptide bonds
  • Peptide bonds are formed between the carboxyl group of one amino acid and the amino group of the next.
  • Chain has direction: amino terminus (N terminus) to carboxyl terminus (C terminus)

Secondary Structure

  • Regular, repetitive folding pattern stabilized by hydrogen bonds
  • Two main types: alpha helix and beta pleated sheet
  • Examples: alpha helix - collagen, keratin (hair), beta sheet - silk

Tertiary Structure

  • Further folding of the polypeptide chain to form a globular structure.
  • Stabilized by various bonds and interactions between side chains: disulfide bonds, hydrophobic interactions, ionic bonds, hydrogen bonds
  • Determines the unique 3D structure and biological function of the protein

Quaternary Structure

  • Arrangement of multiple polypeptide chains (subunits) in a multi-meric protein
  • Subunits can be identical or different
  • Held together by non-covalent interactions, inter-chain disulfide bonds
  • Example: Hemoglobin

Native Conformation

  • The functional, fully folded three-dimensional structure of a protein
  • Determined by primary, secondary, tertiary, and sometimes quaternary structure
  • Determines biological function: catalysis, protection, regulation, signal transduction, storage, transport

Denaturation

  • Loss of the native conformation of a protein, leading to loss of function
  • Can be caused by heat, pH changes, detergents, or heavy metals

Post-translational Modifications (PTM)

  • Chemical modification of a protein after translation
  • Involved in increasing protein diversity and function
  • Examples: phosphorylation (addition of phosphate), glycosylation (addition of sugar), acylation (addition of fatty acid), ubiquitination (addition of ubiquitin), nitrosylation (addition of nitric oxide)

Carbohydrates

  • Molecules made up of carbon (C), hydrogen (H), and oxygen (O) atoms
  • Classified based on the number of monosaccharide units: monosaccharide (single unit), disaccharide (two units), oligosaccharide (few units), polysaccharide (many units)
  • Can be associated with proteins (glycoproteins) or lipids (glycolipids)

Monosaccharides

  • Simple sugar units with the empirical formula (CH2O)n, where n represents the number of carbon atoms.
  • Can be classified based on the number of carbon atoms: triose (3 carbons), pentose (5 carbons), hexose (6 carbons)
  • Polyhydroxy aldehydes (aldoses) or ketones (ketoses)
  • Examples of hexoses: glucose, fructose, galactose, mannose

Glucose

  • An aldose (aldehyde)
  • Major source of energy in the body
  • Found in fruit juices, starch, glycogen, lactose, maltose, and cane sugar

Fructose

  • A ketose (ketone)
  • Found in fruit juices, honey, and cane sugar

Monosaccharide Cyclisation

  • Monosaccharides tend to form ring structures
  • Cyclisation involves the reaction of the carbonyl group (C=O) with a hydroxyl group (OH) within the same molecule
  • In aldoses, the carbonyl carbon (C1) becomes the anomeric carbon after cyclisation
  • In ketoses, the carbonyl carbon (C2) becomes the anomeric carbon after cyclisation
  • Anomeric carbon has two possible configurations: alpha (α) and beta (β) based on the position of the hydroxyl group

Disaccharides

  • Two monosaccharide units linked together by a glycosidic bond

Glycosidic Bond

  • A covalent bond between monosaccharides
  • Formed via a condensation reaction involving the hydroxyl group of one monosaccharide and the anomeric carbon of another
  • Named based on the numbers of the connected carbons and the position of the anomeric hydroxyl group (α or β)
  • Example: Lactose - β-galactose + glucose, linked by a β(1→4) glycosidic bond

Polysaccharides

  • Polymers consisting of many monosaccharide units linked together by glycosidic bonds
  • Classified based on the type of glycosidic bond and branching patterns
  • Example: Amylopectin, a branched polysaccharide with α(1→4) and α(1→6) glycosidic bonds

Polysaccharide Functions

  • Storage: starch (in plants) and glycogen (in animals)
  • Structure: cellulose (in plants) and chitin (in invertebrates)

Lipids

  • A diverse group of water-insoluble (hydrophobic) organic molecules
  • Major source of energy, structural components of cells and organelles, involved in cellular signaling

Classification of Lipids

  • Fatty acids and their derivatives: prostaglandins, leukotrienes
  • Lipids containing glycerol: neutral lipids (mono-, di-, tri-acylglycerol or triglycerides), charged lipids (phospholipids)
  • Lipids not containing glycerol: steroids, sphingolipids, terpenoids
  • Lipoproteins and lipopolysaccharides

Fatty Acids

  • Long-chain carboxylic acids
  • Classified based on chain length, saturation (presence or absence of double bonds), and position of double bonds
  • Example: 18:1(Δ9) - oleic acid (18 carbons, one double bond at carbon 9 relative to the carboxyl carbon)

Acylglycerides (Triglycerides)

  • Esters of glycerol with one, two, or three fatty acids
  • Major form of energy storage in the body
  • Commonly known as fat

Phospholipids

  • Lipids with a phosphate group attached to a glycerol backbone
  • Important components of cell membranes

Sphingolipids

  • Lipids based on the sphingosine backbone
  • Found in cell membranes and involved in signal transduction

Steroids

  • Lipids with a characteristic four-ring structure
  • Examples: cholesterol, sex hormones, and corticosteroids

Lipoproteins

  • Complexes of lipids and proteins
  • Involved in the transport of lipids in the blood

Arachidonic Acid

  • Arachidonic acid is a 20-carbon chain fatty acid with four double bonds at carbons 5-6, 8-9, 11-12, and 14-15.
  • Classified as an omega-6 (ω-6) fatty acid due to the terminal double bond being located six bonds from the omega carbon.

Essential Fatty Acids

  • Essential fatty acids (EFAs) cannot be synthesized by our bodies and must be obtained from the diet.
  • Linoleic acid (ω-6) is an EFA with the chemical formula CH3(CH2)4(CH=CHCH2)2(CH2)6COOH and is 18:2(n-6).
  • α-Linolenic acid (ω-3) is another EFA with the chemical formula CH3CH2(CH=CHCH2)3(CH2)6COOH and is 18:3(n-3).
  • EFA deficiency can lead to:
    • Scaly dermatitis (ichthyosis)
    • Visual and neurological abnormalities

Signaling Fatty Acids

  • Eicosanoids are a group of signaling molecules derived from 20-carbon polyunsaturated fatty acids (PUFAs).
  • Prostaglandins (PG) are an eicosanoid family synthesized from arachidonic acid via cyclooxygenase (COX).
    • Short half-life (seconds)
    • Involved in inflammation and platelet homeostasis.
  • Leukotrienes are another eicosanoid family synthesized from arachidonic acid via lipoxygenase (LOX).
    • Longer half-life (up to 4 hours)
    • Multiple roles, including inflammatory responses and neutrophil adhesion.

Monoacyl, Diacyl, and Triacylglycerols

  • Monoacylglycerol is a breakdown product of triacylglycerol (TAG) during fat digestion.
  • Diacylglycerol (DAG) is a potent intracellular signaling molecule involved in calcium mobilization.
  • Triacylglycerol (TAG) is the primary storage form of energy in the body.
    • Composed of three fatty acids and glycerol.
    • Stored in adipose tissue.

Phospholipids and Sphingolipids

  • Phospholipids, also known as phosphoglycerates, are major components of cell membranes.
    • Example: Lecithin

Steroids

  • Steroids contain a characteristic fused ring system with a hydroxyl or keto group on carbon 3.
  • Major steroid classes:
    • Cholesterol (27 carbons)
    • Bile acids (24 carbons)
    • Progesterone and adrenocortical steroids (21 carbons)
    • Androgens (19 carbons)
    • Estrogens (18 carbons)
  • Functions of cholesterol:
    • Metabolic precursor to:
      • Vitamin D
      • Bile acids
      • Steroid hormones.
    • Plays a vital role in membrane structure.
    • A constant supply of cholesterol is needed.

### Lipoproteins

  • Spherical particles found in plasma that transport lipids, including cholesterol.
  • Have a hydrophobic core of triacylglycerols and cholesteryl esters surrounded by a phospholipid layer.

Amino Acids & Protein Structure

  • The basic structure of an amino acid consists of a central carbon atom bound to an amino group, a carboxyl group, a hydrogen atom, and a side chain (R group).
  • R groups vary in composition and properties, affecting the amino acid's polarity, hydrophobicity/hydrophilicity, and charge at neutral pH.
  • Amino acid properties determine how they will behave within a polypeptide.

Amino Acid Characteristics

  • Non-polar, hydrophobic: Glycine, Alanine, Valine, Leucine, Isoleucine, Methionine, Proline, Phenylalanine, Tryptophan
  • Polar, hydrophilic: Serine, Threonine, Tyrosine, Asparagine, Glutamine, Cysteine
  • Basic, positively charged: Lysine, Arginine, Histidine
  • Acidic, negatively charged: Aspartic acid (Aspartate), Glutamic acid (Glutamate)

Essential vs. Non-Essential Amino Acids

  • Essential amino acids: Cannot be synthesized by the body and must be obtained from the diet (e.g., Methionine, Arginine, Threonine, Tryptophan, Valine, Isoleucine, Leucine, Phenylalanine, Histidine, Lysine).
  • Non-essential amino acids: Can be synthesized by the body (e.g., Alanine, Aspartic acid, Asparagine, Cysteine, Glutamic acid, Glycine, Proline, Serine, Tyrosine, Glutamine).

Protein Structure

  • Primary structure: Linear sequence of amino acids linked by peptide bonds.
  • Secondary structure: Regular, repetitive folding patterns stabilized by hydrogen bonds (e.g., alpha helix, beta pleated sheet).
  • Tertiary structure: Further folding of the polypeptide chain into a globular shape, stabilized by various bonds and interactions between side chains (e.g., disulfide bonds, hydrophobic interactions, ionic bonds, hydrogen bonds).
  • Quaternary structure: The arrangement of multiple polypeptide chains (subunits) in a multimeric protein, held together by non-covalent interactions and disulfide bonds.

Native Conformation & Post-Translational Modifications

  • Native conformation: The functional, fully folded protein structure with a unique 3D shape, determined by the primary, secondary, and tertiary (and sometimes quaternary) structure.
  • Post-translational modifications (PTMs): Chemical modifications of a protein after translation, resulting in a change in protein function (e.g., phosphorylation, glycosylation, acylation, ubiquitination, nitrosylation).

Abnormal Protein Aggregates and Disease

  • Misfolding of proteins can lead to the formation of amyloid fibrils.
  • Amyloid deposition in different tissues can cause diseases (e.g., Alzheimer's Disease).

Carbohydrates (Saccharides)

  • Molecules containing carbon, hydrogen, and oxygen atoms.
  • Monosaccharide: Single sugar unit (e.g., glucose, fructose, galactose).
  • Disaccharide: Two monosaccharides linked together (e.g., lactose, maltose).
  • Oligosaccharide: A few linked monosaccharides.
  • Polysaccharide: Many monosaccharides linked together (e.g., cellulose, glycogen).

Monosaccharide Properties

  • Empirical formula: (CH2O)n, where n = 3 (triose), 5 (pentose), or 6 (hexose).
  • Structural components: Polyhydroxy aldehydes (aldoses) or ketones (ketoses).

Hexoses (C6H12O6)

  • Isomers: Same chemical formula but different structures (e.g., glucose, fructose, galactose, mannose).
  • Dietary sources: Glucose (fruit juices, starch, glycogen, lactose, maltose, cane sugar), Fructose (fruit juices, honey, cane sugar), Galactose (milk), Mannose (plants and gums).

Cyclisation of Monosaccharides

  • Monosaccharides form rings in solution.
  • Anomeric carbon: The carbon involved in ring formation.
  • Alpha (α) configuration: The -OH group on the anomeric carbon is down (fish in the sea).
  • Beta (β) configuration: The -OH group on the anomeric carbon is up (bird in the sky).

Disaccharides & Glycosidic Bonds

  • Glycosidic bond: Covalent bond formed between two monosaccharides via a condensation reaction.
  • The name/type depends on the connected carbons and anomeric configuration (alpha or beta).
  • Example: Lactose = β-galactose + glucose, linked by a β(1→4) glycosidic bond.

Polysaccharides

  • Oligosaccharides: 3-12 monosaccharides.
  • Polysaccharides: Hundreds of monosaccharides.
  • Structure: Chain length, branching, and glycosidic bond variations.

Polysaccharide Functions

  • Storage: Glycogen (animals), Starch (plants).
  • Structure: Cellulose (plants), Chitin (invertebrates).

Lipids

  • Water-insoluble (hydrophobic) organic molecules.
  • Major source of energy, structural components of cells and organelles, involved in cellular signaling.

Classification of Lipids

  • Fatty acids and their derivatives: Prostaglandins, leukotrienes.
  • Lipids containing glycerol: Neutral lipids (mono-, di-, tri-acylglycerols), Charged lipids (phospholipids).
  • Lipids not containing glycerol: Steroids, sphingolipids, terpenoids.
  • Lipoproteins and lipopolysaccharides: Complexes of lipids and proteins or carbohydrates, respectively.

Fatty Acid Structure

  • Chain length: Number of carbons in the chain.
  • Double bonds: Number and positions of double bonds relative to the carboxyl carbon.

The Fed and Fasting States: Creating Energy

  • Lipids play a crucial role in energy production during both the fed and fasting states.
  • They are a major source of energy for the body.### Arachidonic Acid
  • 20 carbon chain with 4 double bonds between carbons 5-6, 8-9, 11-12, and 14-15
  • Classified as an ω-6 fatty acid because its terminal double bond is 6 carbons in from the ω carbon

Essential Fatty Acids (EFAs)

  • We cannot synthesize EFAs so they are nutritionally essential
  • Linoleic acid (ω-6)
    • Chemical formula: CH3(CH2)4(CH=CHCH2)2(CH2)6COOH
    • Shorthand notation: 18:2(n-6)
  • α-linolenic acid (ω-3)
    • Chemical formula: CH3CH2(CH=CHCH2)3(CH2)6COOH
    • Shorthand notation: 18:3(n-3)
  • EFA deficiency (rare)
    • Can cause scaly dermatitis (ichthyosis), visual, and neurologic abnormalities

Signalling Fatty Acids

  • Prostaglandins (PGs) and Leukotrienes are part of the eicosanoid family synthesized from 20-carbon polyunsaturated fatty acids (PUFAs)
  • Eicosanoid synthesis:
    • Prostaglandins: synthesized from arachidonic acid via cyclooxygenase (COX)
      • Short half-life (seconds)
      • Multiple roles, including inflammation and platelet homeostasis
    • Leukotrienes: synthesized from arachidonic acid via lipoxygenase (LOX)
      • Longer half-life (up to 4 hours)
      • Multiple roles, including inflammation and neutrophil adhesion

Monoacyl, Diacyl, and Triacylglycerol

  • Monoacylglycerol
    • Breakdown product of triacylglycerol (TAG) during fat digestion
  • Diacylglycerol (DAG)
    • Potent intracellular signaling molecule
    • Involved in mobilization of calcium
  • Triglycerides (Triacylglycerols: TAG)
    • Composed of 3 fatty acids and glycerol
    • The primary storage form of energy in the body
    • Stored in adipose tissue

Phospholipids (Phosphoglycerates) and Sphingolipids

  • Glycerophospholipids
    • A major component of cell membranes
    • Example: Lecithin

Steroids

  • Characterized by a fused ring system with a hydroxyl or keto group on carbon 3
  • Major steroid classes:
    • Cholesterol: (27 carbons)
    • Bile acids: (24 carbons)
    • Progesterone and adrenocortical steroids: (21 carbons)
    • Androgens: (19 carbons)
    • Estrogens: (18 carbons)

Cholesterol Functions

  • Metabolic precursor of vitamin D, bile acids, and steroid hormones
  • Plays a vital role in maintaining membrane structure
  • The body requires a constant supply of cholesterol

Lipoproteins

  • Spherical particles found in plasma that transport lipids, including cholesterol
  • Contain a hydrophobic core of triacylglycerols and cholesteryl esters
  • A phospholipid layer surrounds the core

Amino Acid Classification

  • The chemical properties of amino acids depend on the nature of their side chain (R group).
  • R groups can be:
    • Polar
    • Hydrophobic/philic (water hating/loving)
    • Acidic (H+ Donor) -ve at neutral pH
    • Basic (H+ Acceptor) +ve at neutral pH
  • Amino acid properties determine their behaviour in a polypeptide.

Amino Acid Side Chain Properties

  • Non-polar (hydrophobic) - Aliphatic (hydrocarbon chain) or Aromatic (ring structure)
    • Glycine
    • Alanine
    • Valine
    • Leucine
    • Isoleucine
    • Methionine
    • Proline
    • Phenylalanine
    • Tryptophan
  • Polar (hydrophilic) - Neutral, Basic (positive charge), Acidic (negative charge)
    • Serine
    • Threonine
    • Asparagine
    • Glutamine
    • Tyrosine
    • Cysteine
    • Lysine
    • Arginine
    • Histidine
    • Aspartic acid (Aspartate)
    • Glutamic acid (Glutamate)

More Amino Acid Characteristics

  • 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 - Amino acids cannot be synthesised in the body and must come from the diet.
    • Methionine
    • Arginine*
    • Threonine
    • Tryptophan
    • Valine
    • Isoleucine
    • Leucine
    • Phenylalanine
    • Histidine
    • Lysine
  • Non-essential Amino Acids - Amino acids that can be synthesised from other amino acids or precursors.
    • Alanine
    • Aspartic acid
    • Asparagine
    • Cysteine
    • Glutamic acid
    • Glycine
    • Proline
    • Serine
    • Tyrosine
    • Glutamine*
    • *Conditionally essential in children

Levels of Protein Structure

  • Primary Structure - Amino acids formed into a polypeptide chain.
    • Amino acids linked together with peptide bonds.
    • Peptide bond is formed between the carboxyl group of one amino acid and the amino group of the next amino acid.
    • Peptide bond = C(O) - NH
    • Chain has direction:
      • Start = amino terminus = N terminus
      • End = carboxyl terminus = C terminus
  • Secondary Structure - Regular repetitive folding pattern controlled by amino acid sequence.
    • Stabilised by hydrogen bonds.
    • Examples:
      • Alpha (a) helix: collagen, keratin in hair
      • Beta (b) pleated sheet: silk
  • Tertiary Structure - Further folding of the polypeptide chain into a globular form.
    • Compact folded structure:
      • Hydrophobic AAs (amino acids) on the inside
      • Hydrophilic AAs on the outside
    • Stabilised by interactions between side chains of amino acids:
      • Disulphide bonds (between 2 cysteines)
      • Hydrophobic interactions
      • Ionic bonds
      • Hydrogen bonds
  • Quaternary Structure - Arrangement of protein subunits in a multi-meric protein.
    • 3D arrangement of more than one tertiary polypeptide.
    • Consist of 2 or more polypeptide chains - may be the same or different.
    • Held together by:
      • Non-covalent interactions
      • Inter-chain disulphide bonds
    • Example: Hemoglobin

Native Conformation

  • Functional fully folded protein structure.
  • Unique three-dimensional structure determined by:
    • Primary structure
    • Secondary structure
    • Tertiary structure
    • Sometimes quaternary structure
  • Determines the biological function of the protein:
    • Catalysis
    • Protection
    • Regulation
    • Signal transduction
    • Storage
    • Transport

Denaturation and Post-Translational Modifications (PTM)

  • Denaturation - Loss of protein shape and function due to environmental changes like:
    • Heat
    • pH change
    • Chemicals
  • Post-Translational Modifications (PTM) - Chemical modification of a protein after translation.
    • Functional group is attached to an amino acid.
    • Results in a change in protein function.
  • Some Common PTM of Proteins:
    • Phosphorylation: + phosphate on serine and/or threonine or tyrosine residue = phosphoprotein
    • Glycosylation: + sugar group on asparagine or serine or threonine residues = glycoprotein
    • Acylation: + fatty acid
    • Ubiquitination: + ubiquitin = death signal
    • Nitrosylation: + NO (nitric oxide)

Abnormal Protein Aggregates and Disease

  • Misfolded proteins can aggregate into fibrils (amyloid).
  • Over 20 different proteins can form amyloid.
  • Amyloid deposition in different tissues is associated with disease.
  • Presence of misfolded proteins in the brain is linked to Alzheimer's Disease.

Carbohydrates

  • Molecules that contain Carbon (C), Hydrogen (H), and Oxygen (O) atoms.
  • Monosaccharide: Single saccharide unit
  • Disaccharide: 2 linked monosaccharides
  • Oligosaccharide: A few linked monosaccharides - can be associated with proteins (glycoproteins) or lipids (glycolipids).
  • Polysaccharides: Consists of many monosaccharides linked together, examples:
    • Cellulose
    • Glycogen

Monosaccharides

  • Simple sugar units.
  • Empirical formula = (CH2O)n where n = 3 - 7 carbons.
    • n = 3 carbons: triose
    • n = 5 carbons: pentose
    • n = 6 carbons: hexose
  • They are poly-hydroxy aldehydes (aldose) or ketones (ketose).

Hexoses (C6H12O6)

  • Isomers: Same chemical formula but different structures.
    • Examples:
      • Glucose: Aldo group - Fruit juices, starch, glycogen, lactose, maltose, cane sugar
      • Fructose: Keto group - Fruit juices, honey, cane sugar
      • Galactose: Found in milk (lactose)
      • Mannose: Found in plants and gums

Monosaccharide Cyclisation

  • Aldoses: Cyclisation happens at carbon 1 (C1). C1 in a cyclised aldose = anomeric carbon.
  • Ketoses: Cyclisation happens at carbon 2 (C2).
  • Alpha (a) anomeric carbon: OH group is down (fish in the sea)
  • Beta (b) anomeric carbon: OH group is up (bird in the sky)

Disaccharides & Glycosidic Bonds

  • Bond between 2 sugars.
  • Bond type depends on:
    • Connected carbon numbers
    • Position of the anomeric hydroxyl group
  • Alpha (a) bond: OH group is in the alpha configuration.
  • Beta (b) bond: OH group is in the beta configuration.
  • Example: Lactose = b-galactose + glucose
    • Bond is between carbon 1 of b-galactose and carbon 4 of glucose: condensation event
    • Bond (linkage) is b (1→ 4) glycosidic bond

Polysaccharides

  • Oligosaccharides: n = 3-12 monosaccharides
  • Polysaccharides: n > 12 - hundreds of monosaccharides.
  • Variations in chain structure can occur:
    • Monosaccharides
    • Glycosidic bonds
    • Branch points
    • Structure
  • Example: Amylopectin
    • Branched every 24-30 residues
    • (1-4, 1-6)

Polysaccharide Functions

  • Storage in animals:
    • Glycogen: A homopolymer of glucose. Branched every 12-14 residues (1-4, 1-6)
  • Storage in plants:
    • Starch: A homopolymer of glucose:
      • Amylopectin (80-85%): Branched every 24-30 residues (1-4, 1-6)
      • Amylose (15-20%): Non-branched helical structure (1-4)
  • Structure in plants:
    • Cellulose: Homopolymer of glucose. Long straight chains (β1-4)
  • Structure in invertebrates:
    • Chitin: Homopolymer of n-acetyl-glucosamine

Lipids - General Properties

  • Heterogeneous group of water-insoluble (hydrophobic) organic molecules.
  • Functions:
    • Major source of energy in the body
    • Structural components of cells and organelles
    • Involved in cellular signaling events, e.g. steroids, prostaglandins, leukotrienes

Lipid Classification

  • Fatty Acids and their Derivatives:
    • Prostaglandins
    • Leukotrienes
  • Lipids containing glycerol:
    • Neutral lipids: mono-, di-, tri-acylglycerol (triglycerides)
    • Charged lipids: Phospholipids
  • Lipids Not containing glycerol:
    • Steroids
    • Sphingolipids
    • Terpenoids
  • Lipoproteins and lipopolysaccharides

Fatty Acid Chain Lengths

  • Number before colon: Number of carbons in chain
  • Number after colon: Numbers and positions of double bonds relative to carboxyl carbon
  • Example:
    • 18:2 - 18 carbon chain with 2 double bonds
    • 16:0 - 16 carbon chain with 0 double bonds### Arachidonic Acid
  • A 20-carbon chain fatty acid with 4 double bonds.
  • Classified as an omega-6 fatty acid due to its terminal double bond being 6 bonds away from the omega carbon

Essential Fatty Acids (EFAs)

  • Cannot be synthesized by the body, so they are essential for human health
  • Linoleic acid (omega-6): 18:2(n-6); plays a key role in various bodily functions, including cell growth and development.
  • Alpha-linolenic acid (omega-3): 18:3(n-3); crutial for brain function, vision, and cardiovascular health.
  • EFA deficiency is rare but can lead to symptoms like scaly dermatitis and visual and neurological abnormalities.

Signalling Fatty Acids

  • Prostaglandins (PG):
    • Part of the eicosanoid family synthesized from arachidonic acid.
    • Synthesized via cyclooxygenase (COX).
    • Short half-life (seconds)
    • Involved in inflammation, platelet homeostasis, and other important functions.
  • Leukotrienes:
    • Also part of the eicosanoid family, synthesized from arachidonic acid.
    • Synthesized via lipoxygenase (LOX).
    • Longer half-life (up to 4 hours).
    • Play a variety of roles, including mediating inflammation and neutrophil adhesion.

Monoacyl, Diacyl, and Triacyl Glycerol

  • Monoacyl glycerol:
    • A breakdown product of triglycerides during fat digestion.
  • Diacylglycerol (DAG):
    • A potent intracellular signaling molecule involved in the mobilization of calcium.
  • Triglycerides (Triacylglycerols: TAG):
    • Composed of three fatty acids and a glycerol molecule.
    • The primary form of energy storage in the body.
    • Stored in adipose tissue.

Phospholipids

  • Major components of cell membranes.
  • Glycerophospholipids:
    • A type of phospholipid, with lecithin being a common example.

Sphingolipids

  • A class of lipids that play a role in cell signaling and membrane structure.

Steroids

  • Characterized by a fused ring system with a hydroxyl or keto group on carbon 3.
  • Major steroid classes:
    • Cholesterol:
      • Contains 27 carbon atoms.
      • Plays a crucial role in membrane structure and acts as a metabolic precursor for vitamin D, bile acids, and steroid hormones.
    • Bile acids:
      • Contain 24 carbons.
    • Progesterone and adrenocortical steroids:
      • Contains 21 carbons.
    • Androgens:
      • Contains 19 carbons.
    • Estrogens:
      • Contains 18 carbons.

Lipoproteins

  • Spherical particles found in plasma that transport lipids, including cholesterol.
  • Have a hydrophobic core of triacylglycerols and cholesteryl esters.
  • A phospholipid layer surrounds the core and is associated with proteins.

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Explore the fundamental building blocks of proteins through this quiz on amino acids. Learn about their structures, properties, and classifications, including polar, non-polar, acidic, and basic amino acids. This quiz will test your knowledge on the various characteristics and functions of amino acids in polypeptides.

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