Carbohydrates
What elements are commonly found in carbohydrates? What is the typical ratio?
Carbohydrates contain carbon, hydrogen, and oxygen (C, H, O), generally with hydrogen and oxygen in an approximately 2:1 ratio.
What elements are commonly found in lipids, and why are most lipids hydrophobic?
Lipids primarily contain C, H, and O. Their large non-polar hydrocarbon regions do not interact favourably with polar water molecules, making them hydrophobic.
Draw the general structure of an amino acid and identify the 3 parts.
Amino group — central carbon — carboxyl group
The central carbon is also attached to a hydrogen and an R group.
What is the monomer of a nucleic acid? Draw its general structure and identify its three components.
The monomer is a nucleotide, consisting of:
An unknown molecule contains glycerol and several long hydrocarbon chains. What class of macromolecule does it most likely belong to? What additional structural information would you need to determine its specific type?
It most likely belongs to the lipids. More information is needed about the number of fatty-acid chains and whether a phosphate-containing region is present. For example, glycerol + three fatty acids suggests a triglyceride, while glycerol + two fatty acids + a phosphate-containing region suggests a phospholipid.
Define monosaccharide, disaccharide, and polysaccharide and give an example of each.
Describe the structure of a triglyceride.
A triglyceride consists of one glycerol molecule bonded to three fatty acid chains.
Describe how two amino acids are joined together.
Two amino acids are joined through a dehydration/condensation reaction, producing a peptide bond between them.
Compare the structure of DNA and RNA.
Two unknown polymers are both composed of carbon, hydrogen and oxygen. One stores energy in animal cells while the other provides structural support in plants. Identify both and explain how molecules made from similar building blocks can perform different functions.
Both contain glucose, but differences in their glycosidic linkages (alpha for glycogen, beta for cellulose) and resulting structures produce different properties and functions.
Compare the biological roles of glucose, glycogen, starch, and cellulose.
Describe the structure of a phospholipid. How is it different from a triglyceride?
The phosphate-containing region gives the phospholipid a polar/hydrophilic region.
Describe the primary, secondary, tertiary, and quaternary levels of protein structure.
Describe the structure of ATP.
ATP contains adenine, a ribose sugar, and three phosphate groups.
A mutation changes one amino acid in a protein. Explain how a change at the primary level could potentially affect the protein's tertiary structure and function.
Changing one amino acid changes the protein's primary structure. Because amino acids have different R groups and chemical properties, the substitution may alter interactions involved in protein folding. This can change the tertiary structure, potentially changing the protein's shape and therefore its function.
What is an α-glycosidic linkage? How does it differ from a β-glycosidic linkage?
An α-glycosidic linkage joins monosaccharides in carbohydrates such as glycogen. A β-glycosidic linkage joins glucose units in cellulose. The different orientations of these bonds produce different overall structures.
Why are some fats solid at room temperature while others are liquid?
Saturated fatty-acid chains can pack together more closely and are typically solid at room temperature. Unsaturated chains contain double bonds that produce bends, preventing tight packing, so they are typically liquid at room temperature.
List at least four different functions proteins can perform in organisms.
Possible protein functions include:
How does ATP store and release usable energy?
ATP stores potential energy in its phosphate bonds. Energy is released when ATP is converted to ADP.
A cell suddenly loses the ability to produce functional phospholipids. Predict one major cellular structure that would be affected and explain why.
The cell membrane would be strongly affected because phospholipids spontaneously form the bilayer that is a major structural component of cell membranes.
A scientist discovers a large molecule in an animal cell that is used to store energy. What molecule would you predict it is? Explain its structure.
Glycogen. It is a polysaccharide composed of glucose units with many branches and is used for carbohydrate energy storage in animals.
What type of bond joins glycerol to fatty acids?
Ester bonds/linkages.
A protein is heated but its peptide bonds remain intact. Explain which level of protein structure would definitely remain unchanged and which levels could be disrupted.
The primary structure would remain unchanged because the peptide bonds and amino-acid sequence remain intact. Secondary, tertiary and/or quaternary structures could be disrupted by heat.
A molecule contains ribose, phosphate groups and nitrogenous bases. What additional evidence could you use to determine whether it is RNA or ATP?
ATP specifically consists of adenine + ribose + three phosphate groups, whereas RNA is a polymer of many nucleotides.
A scientist isolates a molecule that contains nitrogen and can fold into a complex three-dimensional shape. Explain why this information alone is not enough to conclusively identify the molecule as a protein. What additional evidence would you look for?
Nitrogen content and a three-dimensional shape alone are not enough to conclusively identify a protein. Scientists could determine whether the molecule is composed of amino acids joined by peptide bonds. Evidence of a polypeptide chain would support its identification as a protein.