Biological Molecules

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Questions and Answers

Describe the difference between $\alpha$-glucose and $\beta$-glucose, and how this difference affects the structure of the polysaccharides they form.

$\alpha$-glucose has the -OH group on the bottom of carbon 1, while $\beta$-glucose has it on the top. This difference leads to different glycosidic bonds and thus different polysaccharide structures; $\alpha$-glucose forms starch and glycogen (coiled or branched), while $\beta$-glucose forms cellulose (straight chains).

Explain how a condensation reaction leads to the formation of a glycosidic bond between two monosaccharides. What molecule is released as a byproduct of this reaction?

A condensation reaction involves the removal of a water molecule (H₂O) when two monosaccharides join together. The removal of -OH from one monosaccharide and -H from the other allows a glycosidic bond to form. Water is the byproduct.

Compare and contrast the structures of amylose and amylopectin, highlighting the types of glycosidic bonds present in each and how these differences affect their overall shape.

Amylose has only 1-4 glycosidic bonds, forming a straight chain that coils into a helix. Amylopectin has both 1-4 and 1-6 glycosidic bonds, resulting in a branched structure.

Explain why polysaccharides, such as starch and cellulose, do not significantly affect the water potential of a cell.

Polysaccharides are large, insoluble molecules. Their size prevents them from dissolving in the cytoplasm. Because of the polysaccharide's insolubility, it does not affect the water potential. Signup and view all the answers

Describe the structure of a triglyceride molecule, and explain how it is formed through condensation reactions.

A triglyceride consists of a glycerol molecule and three fatty acid chains. It is formed by three condensation reactions, each creating an ester bond between the glycerol and a fatty acid, and releasing a water molecule. Signup and view all the answers

Distinguish between saturated and unsaturated fatty acids, and explain how this difference in structure affects their physical properties.

Saturated fatty acids have only single bonds between carbon atoms, allowing them to pack tightly together, making them solid at room temperature. Unsaturated fatty acids have at least one double bond, creating kinks in the chain, preventing tight packing, and making them liquid at room temperature. Signup and view all the answers

Explain why triglycerides are considered efficient energy stores and a source of metabolic water.

Triglycerides have a high ratio of energy-storing carbon-hydrogen bonds, making them efficient energy stores. They also have a high hydrogen-to-oxygen ratio, which releases water when metabolized, acting as a source of metabolic water. Signup and view all the answers

Describe the structure of a phospholipid molecule, highlighting the hydrophilic and hydrophobic regions and how these properties contribute to the formation of a lipid bilayer.

A phospholipid consists of a glycerol molecule, two fatty acid chains (hydrophobic tails), and a phosphate group (hydrophilic head). In water, phospholipids form a bilayer with the heads facing outward (towards water) and the tails facing inward (away from water). Signup and view all the answers

Describe the general structure of an amino acid, and explain what makes each of the 20 different amino acids unique.

An amino acid consists of a central carbon atom bonded to a hydrogen atom, an amino group (NH₂), a carboxyl group (COOH), and a variable R group. The R group is unique for each of the 20 different amino acids. Signup and view all the answers

Explain how a peptide bond is formed, and what type of reaction is involved in the formation of a dipeptide from two amino acids.

A peptide bond is formed via a condensation reaction between the carboxyl group of one amino acid and the amino group of another, releasing a water molecule. The formation of a dipeptide involves this process. Signup and view all the answers

Describe the primary structure of a protein, and explain its significance in determining the higher levels of protein structure.

The primary structure is the sequence of amino acids in a polypeptide chain. The order of amino acids determines the locations and types of bonds that can form in the secondary, tertiary, and quaternary structures, influencing the protein's overall shape and function. Signup and view all the answers

Describe the secondary structure of a protein, naming the two main types and explaining how they are stabilized.

The secondary structure is the folding or twisting of the primary structure into alpha helices or beta-pleated sheets. Hydrogen bonds between amino acids in the polypeptide chain stabilize these structures. Signup and view all the answers

Explain the tertiary structure of a protein, naming the different types of bonds involved in maintaining this structure.

The tertiary structure is the further folding of the secondary structure into a unique 3D shape. Ionic, hydrogen, and disulfide bonds hold the tertiary structure in place. Signup and view all the answers

Describe the quaternary structure of a protein, and explain when a protein exhibits this level of structure.

The quaternary structure is the unique 3D shape of a protein made of more than one polypeptide chain. It is held together by ionic, hydrogen, and disulfide bonds. Only proteins with multiple polypeptide chains exhibit quaternary structure. Signup and view all the answers

Explain how the primary structure of a protein determines its tertiary structure.

The sequence of amino acids in the primary structure dictates where specific interactions such as ionic, hydrogen, and disulfide bonds can occur along the polypeptide chain. These interactions cause the protein to fold into its unique 3D tertiary structure. Signup and view all the answers

Explain why enzymes are specific to one reaction, relating this specificity to the structure of the enzyme's active site.

Enzymes are specific to one reaction because the active site has a unique shape complementary to a specific substrate. Only that substrate can bind effectively, allowing the enzyme to catalyze the reaction. Signup and view all the answers

Describe the induced fit model of enzyme action, and explain how it differs from the lock-and-key model.

In the induced fit model, the enzyme's active site slightly changes shape to mold around the substrate, putting strain on the substrate's bonds and reducing activation energy. Unlike the lock-and-key model, the active site is not a rigid shape. Signup and view all the answers

Explain how temperature affects the rate of enzyme-controlled reactions, including the effects of both low and high temperatures.

Lower temperatures reduce kinetic energy, resulting in fewer successful collisions and fewer enzyme-substrate complexes, thus slowing the rate. High temperatures above the optimum break bonds, causing the enzyme to lose its shape and denature, thus stopping the reaction. Signup and view all the answers

Explain how pH affects the rate of enzyme-controlled reactions, relating pH changes to the structure of the enzyme.

pH levels outside the optimum interfere with charges in amino acids (specifically in the R-groups), breaking ionic and hydrogen bonds and causing denaturation. The change in shape denatures the enzyme. Signup and view all the answers

Explain how increasing substrate concentration affects the rate of an enzyme-catalyzed reaction up to the point of saturation.

Increasing substrate concentration increases the rate of reaction until the enzyme's active sites are saturated. Beyond this point, adding more substrate does not increase the rate because all available enzyme molecules are already working at their maximum capacity. Signup and view all the answers

Describe how a competitive inhibitor affects enzyme activity, and explain how this type of inhibition can be overcome.

A competitive inhibitor binds to the active site, preventing substrate binding and slowing the rate of reaction. Increasing substrate concentration can overcome competitive inhibition by outcompeting the inhibitor for the active site. Signup and view all the answers

Describe how a non-competitive inhibitor affects enzyme activity, and explain why increasing substrate concentration cannot overcome this type of inhibition.

A non-competitive inhibitor binds to the allosteric site, changing the shape of the active site and making it unable to bind to the substrate. Increasing substrate concentration cannot overcome this because the active site's shape remains altered. Signup and view all the answers

Describe the biochemical test for starch, including the reagents used and the expected result for a positive test.

Add iodine to the sample. A positive result is a color change from orangey-brown to blue-black. Signup and view all the answers

Describe the biochemical test for reducing sugars, including the reagents used and the expected result for a positive test. How does the result change with different concentrations of reducing sugar?

Add Benedict's reagent and heat. A positive result is a color change from blue to green, yellow, orange, or brick red. The color change intensity indicates the concentration of reducing sugar; brick red indicates the highest concentration. Signup and view all the answers

Describe the biochemical test for non-reducing sugars, including the steps required and the expected result for a positive test.

Perform Benedict's test first; if negative (blue), add acid and boil (hydrolyzing any non-reducing sugars into reducing sugars). Cool and neutralize the solution, then heat with Benedict's reagent again. A positive result is a color change from blue to green, yellow, orange, or brick red. Signup and view all the answers

Describe the biochemical test for proteins, including the reagents used and the expected result for a positive test.

Add Biuret reagent, which is blue. A positive result is a change to purple. Signup and view all the answers

Describe the biochemical test for lipids, including the steps required and the expected result for a positive test.

Dissolve the sample in ethanol by shaking, then add distilled water. A positive result is a white emulsion. Signup and view all the answers

Describe the structure of a DNA nucleotide, including its three main components.

A DNA nucleotide consists of a phosphate group, deoxyribose sugar, and a nitrogenous base (adenine, guanine, cytosine, or thymine). Signup and view all the answers

Name the four nitrogenous bases found in DNA, and explain which bases pair together.

The four nitrogenous bases in DNA are guanine, cytosine, adenine, and thymine. Cytosine pairs with guanine (C-G), and adenine pairs with thymine (A-T). Signup and view all the answers

Explain how polynucleotides are formed from individual nucleotides, naming the type of bond that links the nucleotides together.

Polynucleotides are formed by condensation reactions, creating phosphodiester bonds between the deoxyribose sugar of one nucleotide and the phosphate group of the next. Signup and view all the answers

Describe three key differences between DNA and RNA.

DNA contains deoxyribose sugar, while RNA contains ribose. DNA contains thymine, while RNA contains uracil. DNA is typically double-stranded, while RNA is typically single-stranded. Signup and view all the answers

Explain what is meant by the term 'semi-conservative replication' of DNA.

Semi-conservative replication means that each new DNA molecule contains one original strand and one newly synthesized strand. This ensures that genetic information is accurately passed on to daughter cells. Signup and view all the answers

Describe the role of DNA helicase in DNA replication.

DNA helicase breaks hydrogen bonds between base pairs, unwinding the double helix and separating the two strands of DNA. Signup and view all the answers

Describe the role of DNA polymerase in DNA replication.

DNA polymerase joins adjacent nucleotides together, creating phosphodiester bonds and forming the new DNA strand. It also ensures that the correct base pairings are happening by proofreading along the strand. Signup and view all the answers

Describe the structure of an ATP molecule, including its three main components.

ATP (adenosine triphosphate) consists of ribose, adenine, and three phosphate groups. Signup and view all the answers

Explain how ATP releases energy, and name the enzyme that catalyzes this reaction.

ATP releases energy when hydrolyzed to ADP and inorganic phosphate (Pi), breaking the bond between the second and third phosphate groups. This reaction is catalyzed by ATP hydrolase. Signup and view all the answers

Explain the process of phosphorylation and its significance in cellular processes.

Phosphorylation is when ATP transfers a phosphate group to another compound, making it more reactive. This increases the potential energy of the phosphorylated molecule and enables it to participate in various cellular processes. Signup and view all the answers

Explain why water is considered a polar molecule.

Water has a slight negative charge on oxygen and a slight positive charge on hydrogen due to the unequal sharing of electrons in the covalent bonds. This unequal sharing of electrons makes water polar/dipolar. Signup and view all the answers

Describe the role of water as a metabolite in biological reactions, giving specific examples.

Water is involved in condensation reactions (where it is removed to form larger molecules) and hydrolysis reactions (where it is added to break down larger molecules). It is also involved in photosynthesis. Signup and view all the answers

Explain why water is considered a good solvent, and how this property is important for transport in living organisms.

Water is a good solvent because its polarity allows it to dissolve solutes easily. This enables easy transport of substances around the body in blood and other fluids. Signup and view all the answers

Explain how water's high heat capacity helps to buffer temperature changes in living organisms.

Water has a high heat capacity, meaning it can absorb or release a large amount of heat without a significant change in its own temperature. This helps to stabilize internal temperatures and prevent enzyme denaturation. Signup and view all the answers

Explain how water's large latent heat of vaporization provides a cooling effect through evaporation.

Water requires a large amount of energy to change from a liquid to a gas. When water evaporates from a surface (like sweat from skin), it absorbs heat, providing a cooling effect. Signup and view all the answers

Explain how water's strong cohesion, due to hydrogen bonds, allows for continuous columns of water in xylem tissue of plants.

Water molecules are cohesive due to hydrogen bonds, creating a strong attraction between them. This strong attraction enables continuous columns of water to be drawn up the xylem from the roots to the leaves. Signup and view all the answers

Explain how hydrogen ions (H+) are important for enzyme activity, hemoglobin function, and chemiosmosis.

Hydrogen ions (H+) affect pH, which is crucial for maintaining the correct shape and activity of enzymes. They also influence the binding of oxygen to hemoglobin and are essential for generating a proton gradient in chemiosmosis to produce ATP. Signup and view all the answers

Explain the role of iron ions (Fe2+) in oxygen transport within living organisms.

Iron ions (Fe2+) are a component of hemoglobin, the protein found in red blood cells that binds and carries oxygen throughout the body. Signup and view all the answers

Describe the role of sodium ions (Na+) in the co-transport of glucose and amino acids across cell membranes.

Sodium ions (Na+) are involved in the co-transport of glucose and amino acids. The movement of sodium ions down their concentration gradient provides the energy needed to transport glucose and amino acids against their concentration gradients. Signup and view all the answers

Describe the role of phosphate ions (PO43-) in the formation of phosphodiester bonds in DNA and RNA.

Phosphate ions (PO₄³⁻) are essential for forming phosphodiester bonds, which link nucleotides together to create the DNA and RNA backbone. Signup and view all the answers

How do the structural differences between amylose and amylopectin affect their respective functions in plant cells?

Amylose's tightly coiled, unbranched structure is ideal for compact storage. Amylopectin's branched structure provides a larger surface area for faster enzyme-mediated glucose release. Signup and view all the answers

Explain how the arrangement of phospholipids in a cell membrane contributes to its function as a barrier.

Phospholipids form a bilayer with hydrophobic tails facing inwards and hydrophilic heads facing outwards. This creates a barrier to water-soluble substances while allowing lipid-soluble molecules to pass through. Signup and view all the answers

Describe how the primary structure of a protein influences its final three-dimensional conformation and function.

The primary structure (amino acid sequence) dictates how the polypeptide chain will fold and interact, determining the placement of hydrogen, ionic, and disulfide bonds. This folding dictates the protein’s unique 3D shape, thus its function. Signup and view all the answers

How does the induced fit model of enzyme action explain the specificity of enzymes for their substrates?

The induced fit model suggests the active site molds around the substrate, optimizing the fit. This precise interaction ensures the enzyme only binds to substrates with a complementary shape and chemical properties. Signup and view all the answers

Explain how varying pH levels can disrupt enzyme activity, referencing the bonds involved in maintaining enzyme structure.

Extreme pH levels disrupt ionic and hydrogen bonds within the enzyme's structure, particularly at the active site. This alters the enzyme's shape, including the active site, preventing substrate binding and denaturing it. Signup and view all the answers

How do competitive and non-competitive inhibitors differ in their mechanisms of action, and how can their effects on enzyme activity be distinguished?

Competitive inhibitors bind to the active site, blocking substrate binding, while non-competitive inhibitors bind to an allosteric site, altering the active site's shape. Competitive inhibition can be overcome by increasing substrate concentration, while non-competitive inhibition cannot. Signup and view all the answers

Describe the expected results of the biochemical tests for starch and reducing sugars when testing a sample of potato.

The starch test (iodine) would yield a blue-black color change, indicating the presence of starch. The reducing sugars test (Benedict's reagent with heat) would show a positive result, likely turning green or yellow, indicating the presence of reducing sugars like glucose. Signup and view all the answers

Explain the significance of semi-conservative replication in maintaining genetic continuity during cell division.

Semi-conservative replication ensures each new DNA molecule consists of one original strand and one newly synthesized strand. This minimizes the chance of errors and preserves the genetic information accurately. Signup and view all the answers

Outline the role of ATP in providing energy for cellular processes, including the process of phosphorylation.

ATP releases energy through hydrolysis, breaking the bond between phosphate groups. This released phosphate group can then be transferred to another molecule (phosphorylation), making that molecule more reactive and driving cellular work. Signup and view all the answers

Describe how the polar nature of water molecules contributes to its properties as a solvent and its role in biological systems.

Water's polarity allows it to form hydrogen bonds with other polar molecules and ions, dissolving them and facilitating transport. This solvent property is crucial for many biochemical reactions and the transport of substances in living organisms. Signup and view all the answers

Explain the role of inorganic phosphate in energy transfer and its importance in biological processes.

Inorganic phosphate is a component of ATP and, when released during ATP hydrolysis, can phosphorylate other molecules, increasing their reactivity. This energy transfer is critical for driving metabolic reactions and cellular signaling. Signup and view all the answers

How does the presence of double bonds in unsaturated fatty acids affect their physical properties and their arrangement in cell membranes?

Double bonds in unsaturated fatty acids create kinks in the hydrocarbon chain, preventing tight packing. This results in lower melting points and increased membrane fluidity compared to saturated fatty acids. Signup and view all the answers

Describe how the structure of cellulose contributes to its role in providing support to plant cell walls.

Cellulose consists of long, unbranched chains of beta glucose linked by 1-4 glycosidic bonds. These chains form hydrogen bonds with adjacent chains, creating strong microfibrils that provide tensile strength to plant cell walls. Signup and view all the answers

Explain the role of DNA helicase and DNA polymerase in the process of DNA replication.

DNA helicase unwinds the double helix by breaking hydrogen bonds between base pairs, separating the strands. DNA polymerase then adds complementary nucleotides to the template strand, forming phosphodiester bonds and creating the new strand. Signup and view all the answers

Contrast the composition and function of mRNA and rRNA in protein synthesis.

mRNA carries the genetic code transcribed from DNA, specifying the amino acid sequence. rRNA, along with proteins, forms ribosomes, which are the sites of protein synthesis, where mRNA is translated into a polypeptide chain. Signup and view all the answers

Explain why triglycerides are an efficient form of energy storage, with reference to their structure.

Triglycerides have a high proportion of energy-rich carbon-hydrogen bonds. Their hydrophobic nature also allows them to be stored without water, maximizing energy density. Signup and view all the answers

How do the properties of water contribute to temperature regulation in living organisms?

Water's high heat capacity allows it to absorb a large amount of heat without a significant temperature change, buffering against extreme temperature fluctuations. Its large latent heat of vaporization also allows organisms to cool down through evaporation. Signup and view all the answers

Explain how the glycosidic bonds in starch and cellulose differ, and how these differences affect their digestibility in humans.

Starch contains alpha 1-4 and 1-6 glycosidic bonds, which human enzymes can readily hydrolyze. Cellulose contains beta 1-4 glycosidic bonds, which humans lack the enzymes to digest. Signup and view all the answers

Describe how hydrogen bonds contribute to the structure of proteins at the secondary level.

Hydrogen bonds form between the amino acids in the polypeptide chain, causing it to fold into alpha helices or beta pleated sheets, which constitute the secondary structure of the protein. Signup and view all the answers

Explain how sodium ions are involved in the co-transport of glucose and amino acids across cell membranes.

Sodium ions are transported down their concentration gradient. This provides the energy for glucose and amino acids to be transported against their concentration gradients. In other words, the movement of Glucose and Amino acids are 'coupled' with the transport of sodium ions. Signup and view all the answers

Flashcards

Monomers

Small units that can join to form larger molecules.

Polymers

Large molecules made of many monomers bonded together.