Carbohydrates Flashcards
What kind of bond forms between monosaccharides to form disaccharides/polysaccharides?
Glycosidic bond
What differs between aldoses and ketoses?
Aldoses have an aldehyde (CHO) group, ketoses have a ketone (C=O) group.
Define enantiomer.
Enantiomer = stereoisomers that are mirror images of each other.
Are monosaccharides reducing or oxidising agents? Give an example of a test for the presence of these.
Monosaccharides are reducing agents and can be oxidised by relatively mild oxidising agents. Fehling’s reaction = semi-quantitative test for reducing sugars.
Describe the process of gluconeogenesis.
Pyruvate / lactate -> oxaloacetate in the citric acid cycle
-> Phosphoenolpyruvate -> Glucose 6-phosphate
Describe the process of glycolysis.
Glucose + 2ATP -> Fructose 1,6-bisphosphate
-> Glyceraldehyde 3-phosphate + 2 phosphate -> 1,3-bisphosphoglycerate
+ NAD+ + 2ADP -> 2 pyruvate (forming 2 ATP molecules)
How is Acetyl Co-A produced from pyruvate?
Pyruvate + CoA + NAD+ acetyl CoA + NADH + H+ + CO2
How is glycolysis allowed to continue under anaerobic conditions?
Lactate dehydrogenase catalyses formation of lactate from pyruvate, forming NAD+
How many molecules of ATP does complete oxidation of glucose produce?
32 molecules of ATP
What is the structure and function of starch?
Storage polysaccharide in plant cells - unbranched amylose and branched amylopectin chains.
What is the structure and function of glycogen?
Storage in animals (liver and muscle cells) - linear chain of alpha 1,4 and 1,6 linkages.
What are the adaptations of glycogen?
Extensively branched = broken down quickly.
More compact than starch.
What is the structure and function of cellulose?
Structural in plant cell walls - linear unbranched beta glucose chains.
List three functions of information-carrying poly/oligosaccharides.
- Provide communication between cells and their extracellular surroundings.
- Label proteins for transport to specific organelles or for destruction.
- Recognition sites for extracellular signalling molecules (e.g. growth factors/bacteria).
What are the functions of the glycocalyx?
Cell-cell recognition and adhesion, blood clotting, immune response, wound healing.
Describe proteoglycans.
Found on cell surface or in ECM.
Contain glycosaminoglycan chains attached to Ser residues.
Describe glycoproteins.
Found on cell surface or in ECM.
Contain oligosaccharides covalently-linked to Ser, Thr, or Asn residues.
Describe glycolipids.
Found on extracellular surface.
Plasma membrane lipids covalently linked to oligosaccharides.
Define lectin and state the role of these.
Lectins = proteins that bind carbohydrates.
Cell-cell recognition, signalling and adhesion.
Found on extracellular surface.
What are the actions of selectins?
Selectins = family of plasma membrane lectins.
Mediate cell-cell recognition and adhesion in processes, e.g. movement of leukocytes at sites of infection/inflammation.
