10 Questions
What are the four most abundant elements in living organisms, and what percentage of the mass of most cells do they make up?
Hydrogen, oxygen, nitrogen, and carbon, making up more than 99% of the mass of most cells.
What is the significance of carbon in the molecular machinery of cells?
Carbon's bonding versatility was a major factor in the selection of carbon compounds for the molecular machinery of cells during the origin and evolution of living organisms.
What is the main difference between prokaryotic and eukaryotic cells?
Prokaryotic cells lack a true nucleus and other membrane-bound organelles, whereas eukaryotic cells have a true nucleus and membrane-bound organelles.
What is the primary function of trace elements in the human body?
They are essential to the function of specific proteins, including many enzymes.
What is the significance of water in living organisms?
Water is an integral part of life and is essential for many biological processes.
What is the difference between hydrophilic and hydrophobic compounds?
Hydrophilic compounds have an affinity for water, whereas hydrophobic compounds repel water.
What is the significance of stereoisomers in biomolecules?
Stereoisomers have different three-dimensional structures, which can affect their function and properties.
What is the primary function of biomolecules?
Biomolecules are the molecular machinery of cells, and they perform a wide range of functions necessary for life.
What is the characteristic of carbon atoms that allows them to form a wide range of biomolecules?
Carbon atoms can form covalent bonds with each other and with other elements, allowing them to form a wide range of biomolecules with different sizes, shapes, and compositions.
What is the significance of the phylogenetic tree in understanding the evolution of life on Earth?
The phylogenetic tree shows the lines of descent of cellular life on Earth, indicating the relationships between different organisms.
Study Notes
Biomolecules
- Biomolecules contain a variety of functional groups, including alcohols, amines, aldehydes, ketones, and carboxylic acids.
- Many biomolecules are polyfunctional, containing two or more types of functional groups.
Biomolecules: Size
- Biomolecules can be classified into two categories: small molecules (Mr ≈ 100 to 500) and macromolecules (Mr > 500).
Weak Interactions
- Weak interactions play a critical role in macromolecular structure integrity.
- Types of weak interactions:
- Hydrogen bonds (ΔG ≈ -8 to -30 kJ/mol)
- Ionic bonds (ΔG ≈ -20 to -30 kJ/mol)
- Van der Waals force (ΔG ≈ -3 to -4 kJ/mol)
- Hydrophobic interactions
Macromolecules
- Proteins:
- Long polymers of amino acids
- Constitute the largest fraction (besides water) of cells
- Serve as enzymes, structural elements, signal receptors, or transporters
- Nucleic acids (DNA and RNA):
- Polymers of nucleotides
- Store and transmit genetic information
- Some RNA molecules have structural and catalytic roles
- Polysaccharides:
- Polymers of simple sugars such as glucose
- Have three major functions: energy-rich fuel stores, rigid structural components of cell walls, and extracellular recognition elements
- Lipids:
- Water-insoluble hydrocarbon derivatives
- Structural components of membranes, energy-rich fuel stores, pigments, and intracellular signals
- Individual lipid molecules are much smaller (Mr 750 to 1,500) and are not classified as macromolecules
Stereoisomerism
- Molecules with the same chemical structures/bonds but different stereochemistry are called stereoisomers.
- Types of stereoisomers:
- Conformational isomers (rotamers)
- Configurational isomers
Configurational Isomers
- Configuration is conferred by the presence of either:
- Double bonds (Geometric isomers or cis-trans isomers)
- Chiral centers (Optical isomers)
- Geometric isomers or cis-trans isomers:
- Differ in the arrangement of their substituent groups with respect to the non-rotating double bond
- Chiral centers:
- A carbon atom with four different substituent is called asymmetric
- One chiral carbon = two stereoisomers; two or more (n) chiral carbons = 2n stereoisomers
- Enantiomers:
- Pairs of stereoisomers that are mirror images of each other
- Rotate the plane of plane-polarized light in opposite directions
- Diastereomers:
- Pairs of stereoisomers that are not mirror images of each other
- Racemic mixture:
- An equimolar solution of two enantiomers that shows no optical rotation
Life and Its Components
- Water is an integral part of life
- Prokaryotic and eukaryotic cells:
- Prokaryotes: lack a true nucleus and other membrane-bound organelles
- Eukaryotes: have a true nucleus and other membrane-bound organelles
- Major elements in living organisms:
- Hydrogen
- Oxygen
- Nitrogen
- Carbon
- Trace elements:
- Essential to life, usually because they are essential to the function of specific proteins, including many enzymes
- Represent a minuscule fraction of the weight of the human body
Biomolecules: Carbon-Based Compounds
- The chemistry of living organisms is organized around carbon (>50% of the dry weight of cells)
- Carbon's bonding versatility was a major factor in the selection of carbon compounds for the molecular machinery of cells during the origin and evolution of living organisms
- Covalently linked carbon atoms in biomolecules can form linear chains, branched chains, and cyclic structures
This quiz covers the different types of functional groups found in biomolecules, including alcohols, amines, aldehydes, and carboxylic acids, as well as the classification of biomolecules by size.
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