Proteins, Carbohydrates, and Lipids

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Questions and Answers

Explain the role of noncovalent forces in maintaining the structure of large assemblies of lipids.

Noncovalent forces, such as van der Waals forces, hydrogen bonds, and hydrophobic interactions, collectively maintain the structure of lipid assemblies without forming strong chemical bonds. This allows for flexibility and self-assembly.

Describe how the R-groups of amino acids contribute to a protein's surface chemistry and overall function.

Exposed R-groups dictate the protein's chemical interactions like ionic, hydrophobic, or hydrogen bonding. This surface chemistry enables the protein to bind specific molecules and perform biological functions.

Provide an example of how a change in pH can affect the structure and function of a protein.

Changes in pH can alter the ionization state of amino acid R groups. It causes disruptions in ionic and hydrogen bonds, leading to conformational changes that affect the protein's ability to bind ligands or catalyze reactions.

Describe how a disulfide bridge contributes to a protein's tertiary structure, and identify the amino acid involved in forming these bridges.

A disulfide bridge is a covalent bond between two cysteine residues that stabilizes the tertiary structure of a protein by cross-linking different parts of the polypeptide chain. Signup and view all the answers

Contrast the structural characteristics of amylose and cellulose, and explain how these differences relate to their distinct functions in plants.

Amylose has α-1,4-glycosidic bonds resulting in a helical, digestible structure for energy storage. Cellulose has β-1,4-glycosidic bonds forming long, straight chains for structural support which is indigestible to most organisms. Signup and view all the answers

Predict the consequences of a mutation that replaces a hydrophobic amino acid with a hydrophilic amino acid in the interior of a protein.

Introducing a hydrophilic amino acid to the hydrophobic core disrupts the protein's folding pattern. It can lead to instability, misfolding, aggregation, or loss of function as the protein attempts to minimize exposure of the polar residue to the nonpolar environment. Signup and view all the answers

Describe the role of chaperones in protein folding and predict the consequence of their dysfunction.

Chaperones assist in proper folding and prevent aggregation. Dysfunction leads to misfolded proteins, cellular stress, and diseases. Signup and view all the answers

Explain how the presence of double bonds in unsaturated fatty acids affects their packing and state at room temperature.

Double bonds introduce kinks in the hydrocarbon chain, reducing their ability to pack tightly. This results in lower melting points, causing them to be liquid at room temperature. Signup and view all the answers

Describe quaternary protein structure and explain why all proteins do not have this level of structure.

Quaternary structure involves the arrangement of multiple polypeptide subunits into a functional protein complex. It occurs only in proteins with more than one polypeptide chain. Signup and view all the answers

Explain how the amphipathic nature of phospholipids contributes to the formation of cellular membranes.

The amphipathic nature—having both hydrophilic and hydrophobic regions—drives phospholipids to form bilayers in aqueous solutions. Their hydrophobic tails cluster inward, away from water, while hydrophilic heads face outward, interacting with water, forming the basic structure of cell membranes. Signup and view all the answers

Explain the role of the phosphate group in nucleotides and how it contributes to the molecule's function.

The phosphate group provides a negative charge, contributing to the molecule's overall polarity, and it is involved in forming phosphodiester bonds that link nucleotides together in DNA and RNA. Also, carries energy in molecules like ATP. Signup and view all the answers

Describe how glycogen's branched structure affects its function as a storage molecule.

Branching increases the number of non-reducing ends, allowing for rapid glucose release or addition. This is important for quick energy mobilization. Signup and view all the answers

Describe the process of protein denaturation and provide two factors that can cause a protein to denature.

Denaturation is the unfolding of a protein, disrupting its native conformation and function. Factors: heat and strong acids. Signup and view all the answers

What are the four major biochemical roles of carbohydrates, and what common structural feature underlies these roles?

The four major roles are energy storage, energy transport, carbon skeletons, and structural components. A common structural feature is their ability to form polymers of sugar monomers. Signup and view all the answers

How do structural isomers of monosaccharides, such as glucose and fructose, have distinct biochemical properties?

Despite having the same chemical formula, their different arrangement of atoms affects the shape of the molecule. It impacts its interactions with enzymes and other molecules. For example, fructose tastes sweeter because of its configuration. Signup and view all the answers

Why are fats more efficient at storing energy compared to carbohydrates?

Fats have a higher proportion of carbon-hydrogen bonds, which release more energy upon oxidation compared to the carbon-oxygen bonds prevalent in carbohydrates, allowing fats to store more energy per gram. Signup and view all the answers

Explain why enzymes are essential for the normal biochemical function of cells. Refer to specific impacts on reaction rates and cellular metabolism.

Enzymes act of catalysts, accelerating biochemical reactions by lowering activation energy. They are essential for regulating metabolic pathways, enabling reactions at physiological conditions and ensuring efficient energy utilization within cells. Signup and view all the answers

Contrast the properties of saturated and unsaturated fatty acids and explain how these differences influence membrane fluidity.

Saturated acids are straight and pack tightly, decreasing fluidity. Unsaturated ones have kinks, increasing fluidity. Signup and view all the answers

What distinguishes structural, geometric and optical isomers?

Structural differ in bonding, geometric in arrangement around a double bond, and optical are nonsuperimposable mirror images. Signup and view all the answers

Describe the role of hydrolysis in the breakdown of macromolecules, emphasizing its importance in releasing monomers for cellular use.

Hydrolysis is the process where water is used to break the bonds between monomers in a macromolecule, releasing them for cellular processes like energy production or building new structures. Signup and view all the answers

What function is determined by a protein's structure?

Binding, catalyzing or signaling function. Signup and view all the answers

Are lipids polymers?

No. Signup and view all the answers

What are proteins?

Polymers made up of 20 amino acids. Signup and view all the answers

What are carbohydrates formed from (or linked together by)?

monosaccharides Signup and view all the answers

What are nucleic acids formed from?

nucleotides Signup and view all the answers

What are the four kinds of molecules that are characteristic of living things?

Proteins, carbohydrates, lipids, and nucleic acids. Signup and view all the answers

What is the name of the most carboxyl group?

-COOH Signup and view all the answers

What is the name of the most basic amino group?

-NH2 Signup and view all the answers

What is the function of chitin?

Chitin gives rigidity to the structure and provides support. Signup and view all the answers

In what type of environment do lipids prefer to aggregate?

away from water Signup and view all the answers

Name two main properties of Amino acids

Acidic and basic Signup and view all the answers

What happens when water is added to polymers?

Polymers separate into monomers. Signup and view all the answers

What is the general formula for carbohydrates?

$C_n(H_2O)_m$ Signup and view all the answers

Describe the 3 special amino acids.

Cysteine: Can react to form a covalent bond. Glycine: Side chain is a single H allows for the protein to be flexible. Proline, an amino group is modified:lacks an H atom and covalently bonds to hydrocarbon side chain Signup and view all the answers

Describe what happens to a protein's structure if there is high concentration of a polar or nonpolar substance?

It denatures Signup and view all the answers

What is the main use of carbohydrates in organisms?

Stored energy Signup and view all the answers

What is the primary structure of a protein composed of?

Amino acids joined by peptide bonds Signup and view all the answers

Describe the shape and chemistry behind how proteins function.

Binding to their shape. Signup and view all the answers

Explain a difference between saturated and unsaturated fats.

Saturated fats = solid at room temperature. unsaturated fats = liquids at room temperature. Signup and view all the answers

How do proteins change shapes?

Through interaction, or covalent modification. Signup and view all the answers

How do changes in pH affect protein structure, specifically relating to the R groups of amino acids?

Changes in pH alter the ionization patterns of the carboxyl and amino groups in the R groups of amino acids. This causes polar groups to move towards the outside (water), and nonpolar groups move inside (away from water). Signup and view all the answers

Explain how a protein's shape and surface chemistry contribute to its function.

A protein's shape must allow a general 'fit' for a given molecule to bind. Surface chemistry, determined by exposed R groups, allows chemical reactions with other substances through ionic, hydrophobic, or hydrogen bonds. Signup and view all the answers

Describe the unique structural features of proline and how they influence protein structure.

Proline's amino group is modified into a ring structure that lacks an H atom and covalently bonds to the hydrocarbon side chain which limits hydrogen bonding capability and rotation around the alpha carbon. This often causes bends or loops in the protein. Signup and view all the answers

How does a denatured protein differ structurally from a native protein?

A denatured protein has a larger volume and can take many shapes, with exterior hydrogen bonds (to water). A native protein is compact with one preferred shape, stabilized by internal hydrogen bonds. Signup and view all the answers

How do the properties of the R-group side chains contribute to the overall three-dimensional structure of a protein?

The functional groups contained within the side chains, or R-groups, determine the structure and function of a protein. Signup and view all the answers

What is the role of hydrolysis in the context of macromolecules, and how does it relate to condensation reactions?

Hydrolysis breaks down macromolecules by consuming water to break the covalent bond between monomers. It is the reverse of condensation, which forms macromolecules by producing water as monomers are joined. Signup and view all the answers

Consider two proteins with very different amino acid sequences. What biophysical or biochemical analyses could you perform to determine if they share a similar function?

Compare the 3D structures using X-ray crystallography or NMR spectroscopy. Additionally, conduct binding assays to test their affinity for similar ligands or substrates, or enzyme assays if they are suspected to be catalysts. Signup and view all the answers

Explain the significance of disulfide bridges in protein structure.

Disulfide bridges, formed by the reaction of two cysteine -SH groups, are covalent bonds that stabilize protein structure. Signup and view all the answers

Contrast the properties of starch and cellulose, and relate these properties to their respective functions in plants.

Starch is branched, easily broken down, and serves as an energy storage compound. Cellulose is unbranched, has strong structural integrity, and is the main component of cell walls. Signup and view all the answers

Describe the role of motor proteins. Give an example of a process where motor proteins are essential.

Motor proteins cause movement of structures in the cell. Muscle contraction is an example of a process where motor proteins are essential. Signup and view all the answers

How do ionic bonds and hydrophobic interactions contribute to the structure of a protein?

Ionic bonds can form between charged R groups, stabilizing the protein's structure, while hydrophobic interactions cause nonpolar R groups to cluster together in the protein's interior, avoiding water and contributing to folding. Signup and view all the answers

Describe the general formula of a carbohydrate and explain why the water molecules are not intact.

The general formula is $C_n(H_2O)_m$, but the water molecules are not intact because the linked carbon atoms are bonded with hydrogen atoms (-H) and hydroxyl groups (-OH) Signup and view all the answers

What is the significance of a protein's quaternary structure, and in what types of proteins would you expect to find it?

Quaternary structure involves the assembly of two or more polypeptide subunits into a larger protein molecule. It is found in many functional proteins that require multiple subunits to work correctly. Signup and view all the answers

Explain the link between the order of amino acids in a protein and its final, functional three-dimensional shape.

The sequence of amino acids dictates how the polypeptide chain will fold, because different amino acids have different properties (hydrophobic, charged, etc.). The final shape is determined by the interactions between these amino acids. Signup and view all the answers

Distinguish between structural and geometric (cis-trans) isomers, providing an example of each.

Structural isomers differ in the arrangement of atoms and bonds (e.g., butane vs. isobutane). Geometric isomers (cis-trans) have the same bonding pattern but differ in the spatial arrangement around a double bond (e.g., cis-butene vs. trans-butene). Signup and view all the answers

Describe the composition of triglycerides and explain what determines whether they are solid or liquid at room temperature.

Triglycerides are composed of glycerol and three fatty acids. They are solid (fats) at room temperature if they are saturated due to the molecules packing tightly together. They are liquid (oils) at room temperature if they are unsaturated due to the double bonds causing kinks in the fatty acids. Signup and view all the answers

Compare and contrast the functions of fats and phospholipids in living organisms.

Fats (triglycerides) primarily store energy. Phospholipids are major components of cell membranes, providing structural support and controlling permeability. Signup and view all the answers

What does it mean for a molecule to be 'amphipathic', and how does this property relate to the structure and function of phospholipids?

Amphipathic molecules have both hydrophilic and hydrophobic regions. Phospholipids arrange into bilayers because their polar heads interact with water, while their nonpolar tails avoid water. Signup and view all the answers

How do structural differences between saturated and unsaturated fatty acids affect their physical properties and biological roles?

Saturated fatty acids are straight and pack tightly, leading to solid fats. Unsaturated fatty acids have kinks due to double bonds and pack loosely, resulting in liquid oils. This impacts membrane fluidity and energy storage efficiency. Signup and view all the answers

What are some biochemical roles associated with carbohydrates?

Carbohydrates are a source of stored energy. Additionally, they transport stored energy within complex organisms, serve as carbon skeletons and form extracellular assemblies. Signup and view all the answers

Flashcards

Functional groups

Small groups of atoms that occur frequently in biological molecules and confer specific chemical properties when attached to larger molecules.

Hydrolysis

A chemical process that breaks polymers by the addition of water.