Biology Exam Review Test Part One - Macromolecules

The four main categories of large biological molecules present in living systems are proteins, nucleic acids, polysaccharides, and lipids. Proteins are involved in various cellular functions and are made up of amino acids. Nucleic acids, such as DNA and RNA, store and transmit genetic information. Polysaccharides are complex carbohydrates that serve as energy storage molecules and structural components. Lipids are hydrophobic molecules that function as energy storage, insulation, and components of cell membranes.

Plant walls consist mainly of cellulose, which is a complex carbohydrate that provides structural support and rigidity to plant cells. Cellulose is a major component of the cell wall, forming a strong network of fibers that give plants their shape and help them withstand external pressures. Chitin is a polysaccharide found in the exoskeleton of arthropods and peptidoglycan is a component of bacterial cell walls, neither of which are present in plant walls. Therefore, the correct answer is cellulose.

Nucleic acids are composed of smaller units called nucleotides. These nucleotides consist of a sugar molecule, a phosphate group, and a nitrogenous base. DNA and RNA are examples of nucleic acids, and they are made up of long chains of nucleotides. Fatty acids are not the building blocks of nucleic acids, and polysaccharides are carbohydrates, not nucleic acids. Therefore, the correct answer is nucleotides.

A dehydration reaction is actually the process in which water molecules are removed or eliminated from a compound or a reaction. It is not about water molecules being attracted to each other. This reaction is commonly used in organic chemistry to form larger molecules by removing water molecules from smaller molecules.

Nucleotides are molecules that consist of three components: a nitrogenous base, a phosphate group, and a pentose sugar. The nitrogenous base can be either a purine or a pyrimidine. The phosphate group is responsible for providing the negative charge to the molecule, while the pentose sugar forms the backbone of the nucleotide. Therefore, the correct answer is "a nitrogenous base, a phosphate group, and a pentose sugar."

The flow of genetic information in a cell is a fundamental process known as the central dogma of molecular biology. It starts with DNA, which contains the genetic instructions for making proteins. These instructions are transcribed into RNA molecules through a process called transcription. The RNA molecules then undergo translation, where they are used as templates to synthesize proteins. Therefore, the correct answer is true.

RNA molecules play a crucial role in the synthesis of proteins. They act as messengers between DNA and the ribosomes, where proteins are synthesized. RNA molecules carry the genetic information from DNA to the ribosomes and serve as templates for protein synthesis. Through a process called translation, the information encoded in RNA is converted into a specific sequence of amino acids, which are the building blocks of proteins. Therefore, the correct answer is that RNA molecules function in the synthesis of proteins.

The characteristic that all lipids have in common is that they are all made of fatty acids and glycerol. Lipids are organic molecules characterized by their hydrophobic (water-repelling) nature, and they consist of various types of fatty acids and glycerol molecules. This structure is a fundamental characteristic shared by all lipids.

The correct answer is cytosine and uracil. Both cytosine and uracil are nitrogenous bases of the pyrimidine type. Pyrimidines are one of the two types of nitrogenous bases found in nucleic acids, the other being purines. Cytosine is found in both DNA and RNA, while uracil is found only in RNA. Ribose and deoxyribose, on the other hand, are sugars that are components of nucleotides, but they are not nitrogenous bases. Adenine and thymine are nitrogenous bases of the purine type.

The correct answer is guanine and adenine. Nitrogenous bases are the building blocks of nucleic acids, and there are two types: purines and pyrimidines. Adenine and guanine are examples of purine bases, while thymine, cytosine, and uracil are pyrimidine bases. Therefore, adenine and guanine are the nitrogenous bases of the purine type.