Biological Molecules - Chapter 2 Outcomes

A test to identify the presence of non-reducing sugars involves acid hydrolysis and Benedict's solution. The acid hydrolysis breaks down the non-reducing sugar into its constituent monosaccharides. Benedict's solution is then used to test for the presence of reducing sugar.

Triglycerides are composed of a glycerol molecule and three fatty acids. The glycerol molecule has three hydroxyl groups, each of which is attached to a fatty acid through an ester bond. Saturated fatty acids possess single bonds between carbon atoms in their hydrocarbon tails, while unsaturated fatty acids have one or more double bonds between carbons. The presence of double bonds in unsaturated fatty acids results in a kinked structure, contributing to their lower melting points compared to saturated fatty acids.

Phospholipids are composed of a glycerol molecule, two fatty acid tails, and a phosphate group. The phosphate group, attached to one end of the glycerol molecule, is hydrophilic (attracted to water) due to its polar nature. The fatty acid tails, on the other hand, are hydrophobic (repelled by water) due to their non-polar structure. This dual nature of phospholipids makes them essential components of cell membranes, allowing them to create a barrier between the intracellular and extracellular environments.

<p>Globular proteins are generally water-soluble, adopting compact, folded structures. They primarily perform physiological roles, often functioning as enzymes, hormones, or transport carriers. In contrast, fibrous proteins have elongated, thread-like structures. Due to their extensive interactions within the structure, they are generally insoluble in water and are responsible for providing structural support in organisms, such as in hair, skin, and connective tissues.</p> Signup and view all the answers

<p>Hemoglobin is a globular protein composed of four polypeptide chains: two alpha (a) chains and two beta (β) chains. Each chain is associated with a non-protein component called a heme group, which contains an iron atom. The heme group binds reversibly to oxygen molecules. The four chains interact through a variety of bonds, including hydrogen bonds and hydrophobic interactions, resulting in a compact, spherical quaternary structure. This quaternary structure is critical for hemoglobin's function as an oxygen transporter.</p> Signup and view all the answers

<p>Hemoglobin's quaternary structure, with its multiple polypeptide chains and heme groups, enables a cooperative binding of oxygen molecules. When one oxygen molecule binds to the heme group of one chain, it induces a conformational change that makes it easier for other oxygen molecules to bind to the remaining heme groups. This cooperativity allows for efficient oxygen uptake in the lungs, where oxygen concentration is high, and release in tissues where oxygen concentration is low. The iron atom within the heme group is essential for oxygen binding. It acts as a central site for the reversible binding of oxygen molecules, ensuring that oxygen can be transported to the body's cells and released when needed.</p> Signup and view all the answers

<p>Water molecules are polar, with a partial positive charge on the hydrogen atoms and a partial negative charge on the oxygen atom. This polarity allows for the formation of hydrogen bonds between adjacent water molecules. Hydrogen bonds are responsible for water's high specific heat capacity, meaning that it takes a lot of heat to raise or lower its temperature. This feature contributes to the stability of the internal temperature of organisms. Due to its polar nature, water is also an excellent solvent, allowing dissolved substances to be transported throughout the organism. The high latent heat of vaporization requires a significant amount of heat to change liquid water into vapor, thus making it an effective coolant in processes such as sweating.</p> Signup and view all the answers

<p>Collagen is a fibrous protein composed of three polypeptide chains that are wound around each other, forming a triple helix structure. Each chain is approximately 1000 amino acids long. Hydrogen bonds between these chains and covalent bonds between the R groups of different collagen molecules contribute to the formation of collagen fibrils. Collagen fibrils further associate with each other to form thicker collagen fibers, providing strength and flexibility.</p> Signup and view all the answers

<p>Collagen's triple helix structure, a result of the interweaving of three polypeptide chains, contributes to its high tensile strength and elasticity. The formation of collagen fibrils, where individual molecules are tightly packed together, further amplifies these properties. This robust structure is essential for providing structural support and elasticity to various tissues in the body, including skin, bone, tendons, and ligaments.</p> Signup and view all the answers

<p>Proteins have a wide range of functions, playing crucial roles in virtually all biological processes. Some of their key functions include catalyzing metabolic reactions (enzymes), providing structural support (collagen), transporting molecules (hemoglobin), regulating cellular processes (hormones), and defending the body against foreign invaders (antibodies).</p> Signup and view all the answers

<p>An amino acid is composed of a central carbon atom bonded to four different groups: an amino group (-NH2), a carboxyl group (-COOH), a hydrogen atom (-H), and a side chain (R group). The R group varies between different amino acids, determining their unique properties and characteristics.</p> Signup and view all the answers

<p>A peptide bond is formed through a condensation reaction between the carboxyl group of one amino acid and the amino group of another amino acid. This reaction releases a molecule of water. The peptide bond links amino acids together to form polypeptide chains. Peptide bond breakage occurs through hydrolysis, where a water molecule is added to the peptide bond, breaking it apart and releasing individual amino acids.</p> Signup and view all the answers

<p>The primary structure refers to the specific sequence of amino acids in a polypeptide chain. The secondary structure describes the local folding patterns of the polypeptide chain, often forming alpha helices or beta sheets. The tertiary structure represents the overall three-dimensional shape of a single polypeptide chain, determined by interactions between amino acids. The quaternary structure, only applicable to proteins composed of multiple polypeptide chains, describes the arrangement of these individual chains in space, forming a functional protein complex.</p> Signup and view all the answers

<p>Hydrophobic interactions arise from the tendency of non-polar amino acids to cluster together, minimizing their exposure to the aqueous environment. Hydrogen bonds form between polar amino acids that have partial charges on specific atoms. Ionic bonds occur between oppositely charged amino acids, while covalent bonds, including disulfide bonds, form strong connections between sulfur atoms within cysteine amino acid residues.</p> Signup and view all the answers

<p>The Biuret Test is used to detect the presence of peptide bonds in proteins. The test solution, which contains copper ions in alkaline conditions, reacts with peptide bonds, resulting in a color change from blue to purple. This color change indicates the presence of proteins.</p> Signup and view all the answers

<p>The emulsion test is a simple method for detecting the presence of lipids. The test involves dissolving the sample in ethanol, which readily dissolves lipids. When this ethanol solution is mixed with water, lipids, if present, will precipitate out, forming a cloudy or milky emulsion. The appearance of this emulsion is indicative of the presence of lipids.</p> Signup and view all the answers

<p>The iodine test is a specific test for the presence of starch. When iodine solution, which is typically orange-brown, is added to a substance containing starch, it reacts with the starch molecules to form a blue-black complex. This color change is a positive indication of the presence of starch.</p> Signup and view all the answers

<p>A prosthetic group is a non-protein component that is tightly bound to a protein molecule. It is essential for the protein's function and often contributes significant properties to the protein. Examples include the heme group in hemoglobin, which binds oxygen.</p> Signup and view all the answers

<p>Providing structural support</p> Signup and view all the answers

<p>The primary structure of a protein determines its shape, which in turn influences its function.</p> Signup and view all the answers

<p>Phosphodiester bonding</p> Signup and view all the answers

<p>False</p> Signup and view all the answers

<p>False</p> Signup and view all the answers

<p>Glycogen</p> Signup and view all the answers

<p>Cellulose</p> Signup and view all the answers

<p>Saturated fatty acids have only single bonds between carbon atoms in their hydrocarbon tails, whereas unsaturated fatty acids have one or more double bonds between carbons. The presence of double bonds in unsaturated fatty acids creates a kink in the structure, resulting in lower melting points and greater fluidity compared to saturated fatty acids.</p> Signup and view all the answers

<p>Sucrose</p> Signup and view all the answers

<p>Biuret Test</p> Signup and view all the answers

<p>Water's high specific heat capacity is due to the extensive hydrogen bonding between its molecules. Breaking these hydrogen bonds requires significant energy input, thus leading to a high specific heat capacity, which means a large amount of energy is required to raise or lower the temperature of water.</p> Signup and view all the answers

<p>Water's high latent heat of vaporization is also a consequence of hydrogen bonding. When water transitions from liquid to gas, these hydrogen bonds must be broken, requiring a significant amount of energy. This property makes water an effective coolant, as it absorbs substantial heat during the process of evaporation.</p> Signup and view all the answers

<p>Water is an effective solvent due to its polar nature. Its oxygen atom carries a partial negative charge, while its hydrogen atoms carry a partial positive charge. This polarity allows water molecules to interact with charged ions and polar molecules, effectively dissolving them and transporting them throughout the organism.</p> Signup and view all the answers

<p>Ice is less dense than water because of the hydrogen bonding structure. Water molecules in ice form a more open, crystalline structure, resulting in greater space between molecules and lower density. This property allows ice to float on water, forming an insulating layer on the surface of lakes and oceans. This layer prevents the water from freezing completely, protecting aquatic life underneath.</p> Signup and view all the answers

<p>A dipole is a separation of charge within a molecule, creating a partial positive and a partial negative end. Hydrogen bonds are a specific type of attraction between a partially positive hydrogen atom and a partially negative atom, typically oxygen or nitrogen, on another molecule. Hydrogen bonds are often formed between molecules that have dipoles.</p> Signup and view all the answers