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Questions and Answers
Which of the following statements about glucose is true?
Fructose is classified as a polysaccharide.
False
What bond is formed when two monosaccharides combine to create a disaccharide?
glycosidic bond
A __________ is a substance formed from the combination of many monomers.
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Match the following types of carbohydrates with their descriptions:
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What two monosaccharides are produced when sucrose is hydrolysed?
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Starch and glycogen are soluble polysaccharides.
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What types of molecules are triglycerides and how are they formed?
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The _______ bond is broken when water is added to sucrose during hydrolysis.
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Match the polysaccharides with their primary characteristics:
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What is the primary function of globular proteins in the body?
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Fibrous proteins have a complex tertiary structure and are soluble in water.
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Name one example of a conjugated protein.
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Collagen forms a triple helix known as __________.
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Match the following features with their corresponding protein type:
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Which amino acid is most commonly found in collagen?
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Collagen is a soluble fibrous protein found only in skin.
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What type of bond primarily holds the polypeptide chains in collagen together?
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What is the primary role of phospholipids in a cell?
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Phospholipids are hydrophobic substances that do not interact with water.
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How do saturated and unsaturated fatty acid tails affect the fluidity of cell membranes?
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The central carbon atom in an amino acid is bonded to an amine group, a carboxylic acid group, a hydrogen atom, and an ______.
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Match the following proteins with their functions:
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Which type of interaction helps control the orientation of membrane proteins?
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There are 20 types of amino acids commonly found in proteins across all living organisms.
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Name one immunoprotein mentioned in the context of proteins.
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Which type of bond is formed between cysteine amino acids?
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Ionic bonds are the weakest bonds in tertiary structured proteins.
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What is the three-dimensional configuration of a protein called?
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The bonds that help stabilize proteins, which are known as __________ bridges, are formed between cysteine R groups.
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Match the following types of bonds with their characteristics:
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What type of interactions are primarily responsible for the folding of a polypeptide chain into its tertiary structure?
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Quaternary structure involves more than one polypeptide chain working together.
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What occurs when disulphide bonds are broken?
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Study Notes
Carbohydrates
- Carbohydrates are polymers that are made of monomers called monosaccharides
- They contain carbon, hydrogen and oxygen atoms, with a general formula of Cx(H2O)y
- Monosaccharides are single sugar molecules that dissolve readily.
- Disaccharides are made of two monosaccharides joined by glycosidic bonds.
- Polysaccharides are long chains of many monosaccharides joined together.
- The formation of a glycosidic bond is a condensation reaction where a molecule of water is removed.
- The breakage of a glycosidic bond is a hydrolysis reaction where a molecule of water is added.
Reducing Sugars
- Glucose, fructose and maltose are reducing sugars, meaning they can donate electrons to other molecules.
- Sucrose is a non-reducing sugar, because it can't donate electrons.
- This is because the glycosidic bond is formed between the anomeric carbons of the two monosaccharides, preventing the free aldehyde or ketone group needed for reducing ability.
Polysaccharides
- Polysaccharides are complex carbohydrates made up of many monosaccharide units.
- These include starch, glycogen, and cellulose.
- They are formed by condensation reactions.
- Their structure is related to their function.
Starch
- Starch is a storage polysaccharide found in plants.
- It forms granules in plastids.
- Starch exists in two forms, amylose and amylopectin.
- Amylose is unbranched and helical.
- Amylopectin is branched and more compact.
- These structures make starch ideal for storing energy.
Glycogen
- Glycogen is a storage polysaccharide found in animals.
- It forms granules in the cytoplasm.
- Glycogen is highly branched, making it even more compact than amylopectin.
- This structure allows for rapid release of glucose when needed.
Cellulose
- Cellulose is a structural polysaccharide found in plant cell walls.
- It forms long, straight chains of β-glucose molecules.
- The chains are linked together by hydrogen bonds, creating strong, rigid fibers.
- This structure provides support and rigidity to plant cells.
Lipids
- All lipids are hydrophobic and non-polar.
- They are important for energy storage, insulation, and other functions.
- Triglycerides are a type of lipid that is most common in organisms.
Triglycerides
- Triglycerides are composed of a glycerol molecule and three fatty acids.
- Fatty acids are long hydrocarbon chains with a carboxyl group at one end.
- They can be saturated or unsaturated.
- Saturated fats are solid at room temperature because they have only single bonds between carbon atoms.
- Unsaturated fats are liquid at room temperature because they have some double bonds between carbon atoms creating 'kinks' in the chain.
- The ester bond forms between the glycerol molecule and fatty acids through condensation reactions.
Phospholipids
- Phospholipids are similar to triglycerides but contain a phosphate group instead of one fatty acid.
- They are amphipathic, meaning they have both hydrophobic and hydrophilic parts.
- They are the primary molecule in the structure of cell membranes.
- The hydrophilic phosphate heads face the aqueous environment inside and outside the cell.
- The hydrophobic fatty acid tails form the inner core of the bilayer membrane, acting as a barrier to water-soluble molecules.
Proteins
- Proteins are polymers made of monomers called amino acids.
- There are 20 common amino acids in organisms.
- These amino acids can be linked in many different sequences, creating a wide variety of proteins.
- The sequence of amino acids in a protein determines its shape and function.
- Proteins play many vital roles in cells, including:
- Enzymes
- Cell membrane proteins
- Hormones
- Immunoglobulins
- Transport proteins
- Structural proteins
- Contractile proteins
Amino Acids
- Amino acids consist of a central carbon atom bonded to:
- An amino group (-NH2)
- A carboxyl group (-COOH)
- A hydrogen atom
- An R group (side chain) that varies between amino acids
- The R group differs between each amino acid, giving it unique properties.
- The amino and carboxyl groups form peptide bonds to join amino acids together.
Protein Structures
- The primary structure of a protein is its amino acid sequence.
- The secondary structure of a protein is formed by hydrogen bonding between amino acids in the polypeptide chain.
- This can result in an α-helix or β-pleated sheet.
- The tertiary structure of a protein is formed by interactions between the R groups of amino acids in the polypeptide chain.
- This can result in a variety of shapes, such as globular or fibrous.
- The quaternary structure of a protein is formed by the interaction of multiple polypeptide chains.
Bonds in Proteins
- Proteins are held together by various types of bonds:
- Peptide bonds: between amino acids (primary structure)
- Hydrogen bonds: contribute to the secondary and tertiary structures
- Disulphide bonds: between cysteine amino acids; stronger and help to stabilize the tertiary structure
- Ionic bonds: between charged R groups; stronger than hydrogen bonds but less common
- Hydrophobic interactions: between non-polar R groups; occur in the interior of the polypeptide chain
- Van der Waals forces: weak forces between non-polar R groups; contribute to protein stability
Fibrous Proteins
- Long, insoluble polypeptide chains
- Have a limited number of amino acids with a repetitive sequence
- Examples include keratin, collagen, and elastin
- Play structural roles in cells and tissues due to their strength and insolubility
- Keratin is found in hair, skin, and nails.
- Collagen is a major component of connective tissues such as tendons, ligaments, and cartilage.
Collagen
- The most common structural protein in vertebrates.
- Forms a triple helix structure.
- Contains many glycine, proline, and hydroxyproline amino acids.
- Glycine is critical because it allows the three strands to pack tightly.
- Provides strength and support to tissues due to its structure and cross-linking.
Globular Proteins
- Fold into compact, three-dimensional shapes.
- Have a more complex tertiary structure.
- Examples include enzymes, antibodies, and hormones.
- Involved in a wide range of functions, including catalysis, transport, and signaling.
Haemoglobin
- A globular protein that contains a prosthetic group called haem.
- Haem binds to oxygen molecules to transport oxygen throughout the body.
- Its quaternary structure and haem group allow for efficient oxygen binding.
- Consists of four polypeptide chains and four haem groups.
Enzymes
- Biological catalysts that speed up chemical reactions without being used up themselves.
- Highly specific for their substrates, the molecules they act upon.
- Have an active site that binds to the substrate.
- The shape and chemical properties of the active site determine the enzyme's specificity.
- Can be denatured by changes in temperature or pH.
Immunoglobulins (Antibodies)
- Part of the immune system.
- Recognize and bind to specific antigens (foreign molecules).
- This binding triggers a cascade of events that can neutralize or destroy the antigen.
- Their structure allows them to bind to specific antigens.
- Have a variable region that binds to the antigen and a constant region that interacts with other immune cells.
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Description
This quiz covers the structure and types of carbohydrates, including monosaccharides, disaccharides, and polysaccharides. It also explores the classification of reducing and non-reducing sugars, providing insights into their chemical properties. Test your understanding of these essential biomolecules!
