Test Flashcards
What are carbohydrates
Carbohydrates are one of the four types of macromolecules. They are linked to proteins and lipids, playing structural roles in plant and bacterial cell walls.
Describe the structural features of monosaccharides.
Monosaccharides are small molecules with 3-9 carbon atoms. They can be either aldehydes or ketones with multiple hydroxyl groups
Examples of monosaccharides
Trioses containing dihydroxyacetone, D- and L-glyceraldehyde.
Explain the significance of D- and L- configurations in sugars like Glyceraldehyde.
D- and L- configurations represent stereoisomers in sugars like Glyceraldehyde, which has two asymmetric carbon atoms. The configuration furthest from the aldehyde or ketone determines if the sugar is D- or L-.
What is the role of Haworth projections in representing carbohydrates, using Fructose as an example?
Haworth projections represent the spatial arrangement of atoms in cyclic sugars. For example, in Fructose, the α designation indicates the hydroxyl group attached to C1 is on the opposite side of the ring from CH2OH, determining the D- or L- configuration
How are disaccharides formed, and what distinguishes reducing from non-reducing disaccharides?
Disaccharides result from two sugars joined by an O-glycosidic bond. Reducing disaccharides, like Maltose, have a free hemiacetal unit, while non-reducing disaccharides, like Sucrose, form acetal linkages between their anomeric centers.
What characterizes reducing sugars, and why is Glucose considered a reducing monosaccharide?
Reducing sugars have an aldehyde group or can form one through isomerism. Glucose is a reducing monosaccharide because it can be oxidized by mild oxidizing agents, such as Benedict’s and Fehling’s solutions.
Explain the role of Glycogen in storing glucose, including its structure and mobilization in animal cells
Glycogen is a large, branched polymer of glucose stored in animal cells. It serves as a mobilized form of glucose, mainly through α-1,4 glycosidic bonds. Stored in the liver and skeletal muscle, glycogen regulates blood glucose levels and provides a ready source of glucose between meals.
What is the structural and functional significance of Cellulose in plants?
Cellulose is a polysaccharide serving a structural role in plants. It forms unbranched polymers of glucose with β-1,4 linkages, creating long straight chains. The lack of cellulases in mammals prevents them from digesting cellulose.
Discuss the role of enzymes, such as phosphorylase, in glycogen synthesis and degradation.
Phosphorylase is involved in removing glucose from the non-reducing end of glycogen during glycogen degradation. It regulates glucose levels in blood and converts glucose-1-phosphate to glucose-6-phosphate.
How does the liver contribute to maintaining blood glucose levels, and what enzyme is involved in this process?
The liver maintains a constant level of glucose in blood by converting glucose-6-phosphate to glucose. The enzyme glucose-6-phosphate plays a crucial role in this process
What is the structural backbone of DNA and RNA, and how are the nucleotides linked in these macromolecules?
The structural backbone of DNA and RNA consists of sugars and phosphates, forming long linear polymers of linked nucleotides. The sugars are connected via phosphodiester bonds.
Differentiate between the sugar compositions of DNA and RNA and explain the significance of the 2’ carbon in their structures.
DNA contains deoxyribose, lacking an oxygen on the 2’ carbon, while RNA has ribose with an OH- group on the 2’ carbon. The 2’ carbon configuration influences the stability and functions of these nucleic acids.
Describe the features of the nucleic acid chain, including the 5’ and 3’ ends, and the formation of b-glycosidic bonds.
The nucleic acid chain has a 5’ end attached to a phosphoryl group and a 3’ end with a free -OH group. The b-glycosidic bonds are formed between the sugar and base, with the backbone being formed by 3’-to-5’ phosphodiester linkages
Explain the structure of DNA as a double helix, detailing the base pairs and the stabilizing forces
DNA exists as a double helix with two complementary strands. Adenine pairs with Thymine, and Cytosine pairs with Guanine, stabilized by hydrogen bonds. The helix has sugar-phosphate backbones on the outside and bases on the inside.
