Biochem Tb Chapter 1

The four most common elements in the human body are hydrogen, oxygen, carbon, and nitrogen. These elements are essential for various biological processes and make up a significant portion of the body's composition. Hydrogen is found in water and many organic compounds, while oxygen is necessary for cellular respiration. Carbon is the building block of organic molecules, and nitrogen is a crucial component of proteins and nucleic acids. Together, these elements play vital roles in maintaining the structure and function of the human body.

The mitochondria is responsible for the bulk of energy production in the form of ATP. It is often referred to as the "powerhouse" of the cell because it carries out cellular respiration, a process that converts nutrients into ATP. This organelle contains enzymes and other molecules necessary for the production of ATP through processes like the Krebs cycle and oxidative phosphorylation. The chloroplast, on the other hand, is responsible for photosynthesis and the production of glucose, not ATP. The other organelles listed, such as the olgi apparatus, lysosome, and endoplasmic reticulum, have different functions unrelated to energy production.

Carbon is such an abundant element in biomolecules because it can form stable covalent bonds by sharing its electrons. This allows carbon to easily bond with other elements, forming the backbone of many organic compounds. Carbon's ability to form multiple bonds also contributes to its versatility in creating complex and diverse biomolecules.

Rough ER is characterized by the presence of ribosomes on its surface, which give it a "studded" appearance. Ribosomes are responsible for protein synthesis, and their presence on the rough ER indicates that this organelle is involved in the production and processing of proteins. Therefore, the correct answer is ribosomes.

Living organisms are relatively simple is the correct answer because it contradicts the other statements. The other statements highlight the characteristics of living systems such as the role of biological structures, the flow of energy, the high organization, and the active engagement in energy transformation. However, the statement that living organisms are relatively simple suggests that living systems are not complex, which goes against the understanding that living systems are intricate and composed of various complex components and processes.

Supramolecular complexes are assemblies of multiple components that are held together by non-covalent interactions such as van der Waals forces, hydrogen bonds, hydrophobic interactions, and ionic interactions. Covalent bonds, on the other hand, involve the sharing of electrons between atoms and are much stronger than non-covalent interactions. Therefore, the structural integrity of supramolecular complexes is not dependent on covalent bonds, making it the correct answer.

The question is asking for the internal membrane specialized structures of animal cells, and the correct answer is chloroplast. Chloroplasts are actually found in plant cells, not animal cells. Lysosomes, nucleus, endoplasmic reticulum, and mitochondria are all internal membrane specialized structures that are present in animal cells.

Conformation refers to the specific three-dimensional arrangement of atoms in a molecule. Macromolecules, despite having simple building blocks, have complex and organized structures. This organization is referred to as conformation, which determines the molecule's function and properties. The other options, such as configuration, sequence, Lewis structure, and structural maturation, do not accurately describe the intricate three-dimensional architecture of macromolecules.

The correct answer is C. cytoskeleton. The cytoskeleton is a network of protein filaments in eukaryotic cells that provides structural support and helps the cell maintain its shape. It is also involved in cell movement, as it can generate forces that allow the cell to change shape and move. The other options, such as lysosome, plasma membrane, smooth endoplasmic reticulum, and Golgi body, are all cellular structures with different functions and do not directly contribute to the cell's shape and movement.

Structural complementarity refers to the matching shapes and chemical properties between a biological macromolecule and its ligand, allowing them to interact and bind together. This interaction is mediated by weak chemical forces, such as hydrogen bonds and van der Waals forces. It is the basis of many biological functions and is crucial for recognition in bimolecular interactions. However, it does not necessarily produce strong irreversible interactions, as the binding between the macromolecule and ligand can be reversible.

Complex biomolecules are made from smaller building blocks. Metabolites are small molecules that are involved in metabolic reactions and serve as precursors for building blocks. Building blocks are the basic units that are used to construct macromolecules. Macromolecules are large molecules made up of smaller units, such as proteins, nucleic acids, and carbohydrates. Finally, supramolecular complexes are formed when macromolecules interact with each other or with other molecules. Therefore, the correct sequence is metabolites, building blocks, macromolecules, supramolecular complexes.

Organelles are specialized structures within a cell that perform specific functions. They are found only in eukaryotic cells, which have a membrane-bound nucleus. Organelles are also membrane-bound structures and have a dedicated set of tasks, meaning they carry out specific functions within the cell. This distinguishes them from prokaryotic cells, which lack membrane-bound organelles and have a different organization. Therefore, the correct answer is "Only in eukaryotic cells, membrane bound, have a dedicated set of tasks."

Metabolism refers to the chemical processes that occur within living organisms to maintain life. It involves various reactions and pathways that enable the breakdown of complex molecules (catabolism) to release energy and the synthesis of new molecules (anabolism). This statement correctly states that metabolism has two components: anabolism and catabolism, which work together to regulate the flow of energy and nutrients in an organism.

All the statements given in the options are true for prokaryotic cells. Prokaryotic cells can have flagella for movement, they have a simple plasma or cell membrane, they possess a distinct nuclear area called nucleoid which contains genetic material but no true nucleus, and they have ribosomes for protein synthesis but lack mitochondria. Therefore, the correct answer is that all the statements are true for prokaryotic cells.

Weak forces such as hydrogen bonds, van der Waals forces, ionic interactions, and hydrophobic interactions play a crucial role in creating and maintaining stability in biological structures. These forces are constantly forming and breaking at physiological temperatures, but their cumulative effect imparts stability. Covalent bonds, on the other hand, are strong chemical bonds that involve the sharing of electrons between atoms. While they are important for forming and stabilizing specific molecular structures, they do not contribute to the constantly forming and breaking interactions that create stability in biological structures.

The statement "The more linear the bond, the stronger the interaction" is true because hydrogen bonds are strongest when the hydrogen atom is linearly aligned between the donor and acceptor atoms. This alignment allows for maximum electrostatic attraction between the partial positive charge on the hydrogen atom and the partial negative charge on the acceptor atom. As the bond becomes more linear, the distance between the hydrogen and acceptor decreases, increasing the strength of the interaction.

Membrane structures are primarily maintained by hydrophobic interactions. These interactions occur between nonpolar molecules or regions of molecules, where the hydrophobic parts tend to cluster together and exclude water. This drives the formation and stability of membrane structures, such as lipid bilayers. Covalent bonds, hydrogen bonds, ionic interactions, and non-spontaneous assembly may also contribute to membrane structure, but hydrophobic interactions play a key role in organizing and maintaining the integrity of these structures.

Supramolecular complexes of nucleic acid encapsulated in a protein coat, and in some instances, surrounded by a membrane envelope are called viruses. This is because viruses are infectious agents that consist of genetic material (nucleic acid) enclosed in a protein coat. They can also have a lipid envelope derived from the host cell's membrane. Viruses are distinct from plasmids, which are small, circular DNA molecules found in bacteria. Nucleosomes are structures formed by DNA wrapped around histone proteins, and ribosomes are cellular structures involved in protein synthesis. Therefore, the correct answer is viruses.

When viral genetic elements are integrated into the host chromosome and become quiescent, it is referred to as lysogeny. Lysogeny is a process in which a bacteriophage (a virus that infects bacteria) inserts its genetic material into the DNA of its host bacterium. The viral DNA becomes dormant and is replicated along with the host DNA during cell division. This allows the virus to persist within the host cell without causing immediate harm.

All of the activities listed in the options - osmoregulation, biosynthesis, movement of muscles, and light emission - require energy. ATP and NADPH are both energy molecules that are used in various cellular processes, including the ones mentioned. Therefore, none of the activities listed can occur without the presence of ATP or NADPH.

All of the given options (nitrate and dinitrogen, water, carbon dioxide, ammonium ion) are major precursors for the formation of biomolecules. This means that they are all necessary components in the synthesis of biomolecules such as proteins, carbohydrates, and nucleic acids. Therefore, the correct answer is that none of them are excluded as major precursors.

Viruses are acellular, meaning they do not have cells. However, they rely on host cells to reproduce. They enter a host cell, take over its machinery, and use it to replicate their genetic material and produce more viruses. This process allows viruses to reproduce and spread to other cells or organisms. The other options, such as protecting themselves, growing in size, and gaining genetic information, may be important for some viruses, but the primary purpose of their cellular parasitism is to reproduce.

Hydrogen bonds, ionic bonds, and hydrophobic interactions exhibit a certain level of specificity because they involve specific interactions between particular functional groups or molecules. On the other hand, van der Waals interactions are induced by temporary fluctuations in electron density and do not rely on specific functional groups. Therefore, the statement that hydrogen bonds, ionic bonds, and hydrophobic interactions carry a degree of specificity while van der Waals interactions are induced is true.

Electrostatic forces involve the interaction between negatively charged carboxyl groups and positively charged amino groups. These groups are oppositely charged and can attract each other, forming ionic interactions. This type of electrostatic force is commonly observed in molecules that contain carboxyl and amino groups, such as amino acids and proteins. The presence of these charged groups allows for specific interactions and plays a crucial role in various biological processes.

All of the above options involve molecular recognition mechanisms based upon structural complementarity. In each case, there is a specific interaction between molecules that is facilitated by their complementary shapes or structures. In the interaction of a protein with a metabolite, the protein recognizes and binds to the metabolite based on their complementary shapes. Similarly, in the association of a strand of DNA with its complementary strand, the base pairing between nucleotides relies on structural complementarity. The ability for a sperm cell to bind to an egg also involves recognition of specific molecules on the surface of the egg based on their complementary structures. Finally, the binding of a hormone to its receptor is also based on structural complementarity between the hormone and the receptor.

Covalent bonds are not a common interaction used in molecular recognition. Molecular recognition can occur between various types of molecules, not just protein molecules. Complementarity of the molecules is indeed required for molecular recognition to occur, as it involves specific interactions between complementary shapes, charges, and functional groups. Hydrogen bonds are actually effective mediators of molecular recognition, despite their relatively low strength. Therefore, the correct answer is that for molecular recognition to occur, complementarity of the molecules is required.

The correct answer is cell wall. The description of the structural feature, composed of peptidoglycan, a rigid framework of polysaccharide cross-linked by short peptide chains, matches the characteristics of a prokaryotic cell wall. The cell wall provides support and protection to the cell, maintaining its shape and preventing it from bursting under osmotic pressure. The presence of peptidoglycan is a key characteristic that distinguishes prokaryotic cell walls from eukaryotic cell walls.

Biological molecules, such as proteins and nucleic acids, have specific structures that are essential for their function. These structures can be disrupted or denatured by certain environmental conditions. A dramatic increase in temperature can cause denaturation by disrupting the weak interactions that stabilize the molecule. Changes in ionic strength can also disrupt these interactions. Addition of strong acid or base can alter the pH, which can disrupt the charges and hydrogen bonding within the molecule. However, refrigeration, which involves lowering the temperature, does not typically denature biological macromolecules.

An increased activity of an enzyme does not directly increase the amount of energy produced. Enzymes function by lowering the activation energy required for a reaction to occur, but they do not generate energy themselves. The amount of energy produced in a reaction is determined by the reactants and their energy content, not by the activity of the enzyme.

A carboxylic acid at pH 7.4 can exist in its ionized form, where the carboxyl group donates a proton to form a carboxylate ion. This carboxylate ion can form an ionic interaction with an amine, as the carboxylate ion is negatively charged and the amine is positively charged. Additionally, carboxylic acids can also form hydrogen bonds with alcohols, as the oxygen atom in the carboxyl group can act as a hydrogen bond acceptor and the hydrogen atom in the alcohol can act as a hydrogen bond donor. Therefore, both options a and c are correct.

Fatty acids are not generally incorporated into macromolecules. Macromolecules such as proteins are made up of amino acids, carbohydrates are made up of monosaccharides, and nucleic acids are made up of nucleotides. Fatty acids, on the other hand, are primarily used for energy storage and membrane structure. They are not typically incorporated into the structure of macromolecules.

The correct answer is "identical protein and lipid composition in the major organelles." This answer is the exception among the given options because membranes in major organelles can have different protein and lipid compositions depending on their specific functions and roles within the cell. Membranes are supramolecular assemblies that define the boundaries of cellular components and are formed through spontaneous assemblies resulting from hydrophobic interactions. Therefore, the other options are true properties of membranes.

Hydrophobic interactions do not involve hydrogen bonding between water and nonpolar molecules. Instead, they arise from the tendency of water molecules to form a network of hydrogen bonds with each other, which leads to the exclusion of nonpolar substances from the aqueous environment. This exclusion causes nonpolar molecules or groups to aggregate or cluster together, minimizing their contact with water. This phenomenon is responsible for the formation of hydrophobic interactions in biological systems and is crucial for protein folding, lipid bilayer assembly, and other macromolecular structures.

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