What is the primary difference between how autotrophs and heterotrophs utilize carbon?
Heterotrophs obtain carbon by using organic carbon sources. In contrast, autotrophs can utilize inorganic carbon from molecules like CO2 and CaCO3 that do not contain C-H bonds.
What is the basic molecular structure shared by all amino acids?
All amino acids consist of a central carbon atom bonded to an amino group (−NH2), a carboxyl group (−COOH), a hydrogen atom, and a variable side group called an −R group. The specific identity of the −R group determines the unique chemical properties of each amino acid.
How do the terms “dipeptide,” “tripeptide,” and “protein” differ in terms of their composition?
A dipeptide is a chain consisting of exactly two amino acids, while a tripeptide contains three. A protein is a much longer chain, typically composed of 50 or more amino acids bonded together.
What role do proteins play when they function as enzymes or antibodies?
When proteins act as enzymes, their primary role is to catalyze or accelerate chemical reactions within the organism. As antibodies, proteins function as a defense mechanism against various pathogens.
What are the specific electron configuration characteristics of transition and inner transition elements?
For transition elements, the last electron enters a d orbital. In inner transition elements, the last electron enters an f orbital.
How does the chirality of amino acids used by Earth life differ from a general mixture?
Why is the amino acid glycine considered an exception to the rule of molecular chirality?
Earth life exhibits homochirality, meaning it primarily uses “one-handed” molecules. Specifically, life on Earth prefers L-type (left-handed) amino acids, with the exception of glycine, which is symmetric.
What is a codon, and what is its function in protein synthesis?
A codon is a three-letter sequence of bases found within RNA. Each codon represents a specific amino acid, effectively serving as the instruction set for building proteins.
Describe the structural components of the DNA “twisted ladder.”
The structure of DNA is a double helix, which resembles a twisted ladder. The “sides” of the ladder are made of a sugar-phosphate backbone, and the “rungs” consist of nitrogenous bases attached to that backbone.
What are the three main differences between RNA and DNA regarding strands, sugars, and bases?
RNA typically has one strand, uses ribose sugar, and contains the base uracil. DNA consists of two strands, uses deoxyribose sugar, and utilizes the base thymine instead of uracil.
Define carbohydrates and provide their general chemical formula.
Carbohydrates, commonly known as sugars, are molecules composed of carbon, hydrogen, and oxygen. Their general chemical formula is (CH2O)n
.
Why are sugars considered a good source of short-term energy for organisms?
Sugars are hydrophilic, meaning they “like” water, which prevents them from packing as efficiently as hydrophobic fats. Because they are not packed tightly, they are fast and easy for organisms to break down and use for immediate energy.
What is the chemical difference between ribose and deoxyribose?
The primary difference is the presence or absence of an −OH group. Deoxyribose lacks one oxygen atom compared to ribose, which is reflected in the “deoxy-“ prefix of the name.
What are the primary functions of lipids in biological organisms?
Lipids are essential for long-term energy storage because they pack very efficiently. Additionally, they serve as the main structural component of cell membranes.
Compare the physical properties and packing efficiency of saturated versus unsaturated fatty acids.
Saturated fatty acids have straight chains that pack tightly, often making them solid at room temperature (like butter). Unsaturated fatty acids have bent chains that do not pack tightly, usually resulting in a liquid state at room temperature (like olive oil).
How do the general chemical formulas for sugars and lipids differ?
Sugars follow the formula (CH2O)n, maintaining a specific ratio of carbon, hydrogen, and oxygen. Lipids (fatty acids) follow the formula CH3 (CH2)n COOH, characterized by long hydrocarbon chains and a carboxyl group.
What are the two major requirements for a substance to serve as a biological solvent?
First, bioessential molecules must be able to move through the solvent quickly enough to support chemical reactions. Second, the solvent should not destroy those bioessential molecules and must be amenable to the specific chemistry (such as carbon-based chemistry) of that life form.
List three advantages of water as a biological solvent.
Water possesses a strong dipole moment (polarity) and a high heat of vaporization. Furthermore, ice is less dense than liquid water, allowing it to float and trap warmer water underneath for organisms.
What are the potential disadvantages of water when it interacts with biological molecules?
Water can disrupt the hydrogen bonding between amino acids in proteins and serve as a medium for the reactive deamination of nucleobases. Additionally, the formation of some biological molecules actually requires dehydration, meaning water must be removed for the reaction to occur.
Describe the function and composition of hemoglobin.
Hemoglobin is an iron-rich protein molecule responsible for carrying oxygen and carbon dioxide throughout the bloodstream. It features a complicated quaternary structure formed from four distinct peptide subunits.
In a perspective drawing of a molecule, what do wedge-shaped lines and dashed lines signify regarding spatial orientation?
Wedges indicate bonds coming forward; dashes indicate bonds going backward.
In which orbital type does the last electron enter for transition elements?
The d orbital
In which orbital type does the last electron enter for inner transition elements?
the f orbital
What is the primary function of Sulfur within the electron transfer systems of cells?
It facilitates electron transfer within the cell.
The amino acid glycine is unique among standard amino acids because its side chain (−R group) is what?
a hydrogen atom
