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Questions and Answers
What is the main element that consists in living matter?
Carbon
Which organic molecules consist only of carbon and hydrogen?
Monosaccharides are reducing sugars.
True
Cellulose is made up of long chains of __________ molecules linked together by beta-1,4 glycosidic bonds.
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Match the following organic compounds with their descriptions:
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What is the primary sugar monomer found in cellulose?
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Hemicellulose contains a diverse array of sugar units, including pentoses and hexoses.
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What is the primary component of pectin?
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Chitin is a major component of cell walls and exoskeletons in ___________ and some algae.
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Match the following carbohydrates with their respective tests:
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Study Notes
Carbon Atom
- Atomic number: 6
- Electron configuration: 2, 4
- Carbon atom has 4 valence electrons
- Can form 4 covalent bonds with C, H, O, and N atoms
- Forms molecules with straight chains, branched chains, and ring/cyclic structures
Organic Compounds
- Chemical compounds that consist of carbon
- Examples: hydrocarbons (molecules consisting only of carbon and hydrogen)
- Carbon and hydrogen atoms have similar electronegativity, making simple hydrocarbons nonpolar
- Functional groups can attach to hydrocarbons, making them polar
Biological Macromolecules
- Simple molecules combine to form large molecules (macromolecules)
- Often polymers
- Monomer: repeating unit that serves as the building block for polymer synthesis
- Polymer: giant molecule consisting of many similar repeating subunits linked by covalent bonds
- Examples: carbohydrates, proteins, nucleic acids
Synthesis and Breakdown of Polymers
- Monomers connect through dehydration reactions, releasing water molecules
- Each monomer contributes part of the water molecule released during the reaction
- Every time a bond forms between monomers, a water molecule is removed
- Hydrolysis: reverse reaction, adding water to break bonds and disassemble macromolecules
Carbohydrates
- Macromolecules containing C, H, and O
- Molar ratio of H:O is 2:1
- Empirical formula: Cx(H2O)y
- Classified into 3 categories: monosaccharides, disaccharides, and polysaccharides
Monosaccharides
- Simplest carbohydrates
- Contain carbonyl group (C=O) and multiple hydroxyl groups (-OH)
- Formula: (CH2O)n
- All monosaccharides are reducing sugars
- Classified by:
- Number of carbon atoms (trioses, tetroses, pentoses, hexoses, heptoses)
- Placement of carbonyl group (aldose or ketose sugar)
- Chiral handedness (L-sugars or D-sugars)
Hexoses
- Monosaccharides with 6 carbon atoms
- Examples: glucose, galactose, fructose
- Glucose is a major nutrient for cells
- Ring structure forms in aqueous solutions
Functions of Monosaccharides
- Primary source of energy for living organisms
- Substrate for biosynthesis
- Involved in cell-cell recognition and signaling
Disaccharides
- Composed of two sugar molecules
- Examples: sucrose, lactose
- Can be hydrolyzed into subunits
- All are reducing sugars (except sucrose)
Polysaccharides
- Composed of many sugar molecules
- Examples: starch, glycogen, cellulose
- Classified into:
- Starch: mixture of amylose and amylopectin
- Glycogen: similar to starch, but more branched
- Cellulose: complex carbohydrate, provides structural support in plant cell walls
- Functions:
- Energy storage
- Structural support
- Cellular communication
Derivatives of Carbohydrates
- Chitin: complex carbohydrate in exoskeletons of arthropods
- Hemicellulose: mixture of sugar monomers, serves as a structural component in plant cell walls
- Pectin: complex polysaccharide found in plant cell walls, particularly in fruits
Identification Tests for Carbohydrates
- Molisch's test
- Benedict's test
- Fehling's test
- Seliwanoff's test
- Barfoed's test
- Iodine test for starch
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Description
Learn about the importance of carbon atoms in living matter, their electron configuration, and how they form covalent bonds with other atoms to create various molecules.