Nitrogenous Bases and Nucleotides

Questions and Answers

What distinguishes structural isomers from other types of isomers?

They exhibit the same chemical properties.

They have different molecular formulas.

They involve the same atoms in different arrangements. (correct)

They have different functional groups.

What is a defining characteristic of geometric isomers?

They have the same covalent arrangements but different spatial orientations. (correct)

They do not contain double bonds.

They differ in the number of atoms.

They involve mirror image arrangements of atoms.

Which statement about enantiomers is true?

Both enantiomers exhibit the same biological activity.

They can have identical physical properties.

They must contain a carbon atom with four different substituents. (correct)

One enantiomer is always more stable than the other.

Why are fats considered hydrophobic substances?

They are made primarily of long hydrocarbon tails. Signup and view all the answers

In the biochemistry of vision, what happens to rhodopsin?

It undergoes a structural change from one geometric isomer to another. Signup and view all the answers

What was the effect of one enantiomer of the drug thalidomide?

It reduced morning sickness safely. Signup and view all the answers

Which type of isomer involves mirror images?

Enantiomers Signup and view all the answers

What is the primary element that serves as the backbone of biological molecules?

Carbon Signup and view all the answers

Which of the following compounds is an example of structural isomerism?

Butane and isobutane Signup and view all the answers

Which of the following best describes organic chemistry?

The study of carbon compounds Signup and view all the answers

What element is commonly found bonded to carbon in biological molecules?

Sulfur Signup and view all the answers

Why are organic compounds able to form a vast variety of molecules?

Because of carbon's versatility in bonding Signup and view all the answers

How do variations in organic molecules relate to living things?

They can distinguish even between individuals of a single species. Signup and view all the answers

What is the composition of the majority of biological molecules?

Primarily carbon with hydrogen, oxygen, nitrogen, sulfur, and phosphorus Signup and view all the answers

What did early organic chemists initially focus on?

Purifying and improving the yield of products from organisms Signup and view all the answers

Which of the following compounds represents a simple organic molecule?

CH4 Signup and view all the answers

What is the primary function of fats in organisms?

Energy storage Signup and view all the answers

How do animals benefit from storing energy as fats instead of polysaccharides?

Fats offer a more compact fuel reservoir Signup and view all the answers

What component of phospholipids is typically responsible for their hydrophilic nature?

Phosphate group Signup and view all the answers

What structural arrangement do phospholipids form when they are added to water?

Micelles Signup and view all the answers

What role does adipose tissue play in addition to energy storage?

Cushioning vital organs Signup and view all the answers

Which of the following best describes how phospholipids are arranged at the cell membrane?

Hydrophobic tails point inward and hydrophilic heads are outward Signup and view all the answers

Why do plants use oils instead of starch for energy storage in seeds?

Oils are more compact for dispersal and storage Signup and view all the answers

What is a key characteristic of the fatty acid tails in phospholipids?

They are hydrophobic and repel water Signup and view all the answers

Which of the following nitrogenous bases is a pyrimidine?

Cytosine Signup and view all the answers

What is the key difference between ribose and deoxyribose?

Deoxyribose lacks an oxygen atom on carbon two. Signup and view all the answers

What forms the backbone of a polynucleotide?

Sugar-phosphate units linked by phosphodiester linkages Signup and view all the answers

What does the 5' end of a nucleic acid molecule contain?

A phosphate group Signup and view all the answers

How are adjacent nucleotides in a polynucleotide chain joined?

Through covalent bonds known as phosphodiester linkages Signup and view all the answers

What is a nucleoside composed of?

A nitrogenous base and a pentose sugar Signup and view all the answers

What determines the primary structure of a protein?

The order of bases in a DNA or mRNA polymer Signup and view all the answers

Which of the following statements about RNA is true?

RNA is a single polynucleotide chain. Signup and view all the answers

What typically causes proteins to denature when transferred to an organic solvent?

Hydrophobic regions facing outward Signup and view all the answers

Which factor can lead to the denaturation of proteins, potentially causing high fevers to be fatal?

Disruption of weak interactions by heat Signup and view all the answers

What role do chaperonins play in protein folding?

They isolate and protect polypeptides during spontaneous folding. Signup and view all the answers

What technique is commonly used to determine the conformation of a protein?

X-ray crystallography Signup and view all the answers

Which statement about the prediction of protein conformation is true?

It is still difficult to predict conformation solely from primary structure. Signup and view all the answers

What is the primary difference between RNA and DNA?

RNA contains uracil while DNA contains thymine. Signup and view all the answers

What is the significance of understanding a protein’s sequence in biochemistry?

It provides the information for its amino acid sequence and potential function. Signup and view all the answers

Which of the following statements about protein folding is correct?

Many proteins go through several intermediate stages during folding. Signup and view all the answers

Study Notes

Nitrogenous Bases and Their Structure

Three pyrimidines: cytosine (C), thymine (T), uracil (U).
Two purines: adenine (A), guanine (G); has a six-membered ring fused to a five-membered ring.
RNA contains ribose sugar; DNA contains deoxyribose, differing by one oxygen atom at carbon two.
Sugar atoms in nucleotides are labeled with a prime notation (e.g., 2' for the second carbon).
Nucleoside formed by the combination of a nitrogenous base and a pentose sugar.
Nucleotide formed when a phosphate group is added to a nucleoside.

Polynucleotides and Gene Information

Polynucleotides linked by phosphodiester bonds between the 3’ hydroxyl group of one nucleotide and the 5’ phosphate of another.
A sugar-phosphate backbone with nitrogenous base appendages forms the structure of DNA and RNA.
DNA and RNA have distinct ends: 5’ end with a phosphate group and 3’ end with a hydroxyl group.
Unique sequences of bases in DNA/mRNA dictate the primary structure of proteins and determine their function.

Carbon and Molecular Diversity of Life

Cells are primarily composed of carbon-based compounds, despite being 70-95% water.
Carbon's ability to bond with various elements enables the creation of diverse biological molecules, including proteins and nucleic acids.
Major elements: carbon (C), hydrogen (H), oxygen (O), nitrogen (N), sulfur (S), phosphorus (P).

Organic Chemistry and Structural Variations

Organic chemistry focuses on carbon compounds, which range from simple molecules like CO2 to complex proteins.
Isomers have the same molecular formula but different structures, affecting their chemical properties.
Structural isomers differ in covalent arrangements; geometric isomers differ in spatial arrangements around double bonds.
Enantiomers are mirror images and may have different biological activities, one often being active and the other inactive.

Function and Storage of Fats

Fats serve mainly for energy storage; they store more energy per gram than carbohydrates.
Adipose tissue cushions organs and provides insulation; humans store long-term energy in adipose cells.
Phospholipids are crucial components of cell membranes, composed of two fatty acids, glycerol, and a phosphate group.

Membrane Structure

Phospholipids naturally self-assemble in water, forming micelles with hydrophobic tails inward and hydrophilic heads outward.
In cell membranes, phospholipids arrange as a bilayer, providing a barrier to the external environment.

Protein Structure and Function

Proteins may denature due to harsh conditions (like heat), affecting their functionalities.
Chaperonin proteins assist in correct folding of polypeptides, not specifying final structures but protecting and segregating them.
X-ray crystallography and nuclear magnetic resonance (NMR) spectroscopy are methods used to determine protein structures.

Nucleic Acids and Heredity

DNA is the hereditary material and encodes the amino acid sequence of proteins through genes.
Two nucleic acid types: RNA (a single polynucleotide chain) and DNA (double helix structure).

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Description

Explore the structure and function of nitrogenous bases, including pyrimidines and purines. Understand the formation of nucleosides and nucleotides, as well as the significance of polynucleotides and their roles in DNA and RNA structure. This quiz will cover key concepts essential for grasping molecular biology.