Lecture 12 Flashcards
What is an extremely common strategy to modify enzymes and protein activity?
– covalent modifications
T or F, covalent modifications are often reversible and are done by enzymes which are themselves subjected to regulation
True
Describe phosphorylation by kinases and dephosphorylation by phosphatases.
– utilize an ATP that adds a PO4 to a specific amino acid on an enzyme –> phosphorylation
– dephosphorylation is removal of phosphate by phosphotases
What are zymogens?
– inactive forms of enzymes aka proenzymes
How does regulation with zymogens work?
– zymogens are activated into enzymes by proteolytic cleavage (protease activation)
– Synthesized in pancreas and secreted into duodenum in small intestine
- enter as inactive forms and get converted to active proteases in small intestine
- ensures active enzymes are only in lumen and not in pancreatic cells
T or F, trypsin is a common activator of many zymogens
True
What is trypsin?
– a common activator of multiple zymogens for enzymes involved in protein degradation and more generally in digestive functions
T or F, zymogens activation by trypsin provides strong and synchronized commitment to digestion of proteins
True
Why are good inhibitors needed for trypsin?
– because zymogen activation is irreversible, good inhibitors are needed to block key activators such as trypsin
Ex: Pancreatic trypsin inhibitor regulate trypsin activity
How does trypsin active chymotrypsin?
– It cleaves at the 15/16 site that results in the formation of the pi chymotrypsin.
– This further cleaves to form a triad by the release of two dipeptides.
– This results in the alpha chymotrypsin, the most active chymotrypsin, and results in a A, B and ,C chain that contain the serine residue, histidine, and Aspartate amino acid.
What are other important biological cascades involving zymogens?
- Blood clotting
- Caspases: enzymes involved in cell apoptosis
- Protein hormones: Insulin is derived from pro-insulin
- Collagen is derived from procollagen
What are the general functions of carbohydrates?
- They act as cellular protection,
- generate and store biological energy, – serve as molecular recognition analogs, – cell signaling
- cell adhesion
- biological lubrication
- control of protein trafficking, and – maintenance of biological structure.
What is the general molecule formula for carbohydrates?
(CH2O)n
T or F, elemental analysis of carbohydrate yield one H2O molecule for every C atom
True
T or F, carbohydrates have a very large structural diversity
True
What are monosaccharides typically used for?
as fuel and as building blocks for synthesis of complex molecules like dna, glycoproteins, storage molecules
What’s the difference between an aldose and ketose sugar?
an aldose sugar has a sugar with the 1 carbon containing an aldehyde group. A ketose sugar has a ketone group somewhere along its chain. This ketone group is not carbon 1.
What is the most common form of stereoisomer of sugars in living organisms?
D sugars
True or false. Monosaccharides with 3 carbons or more contain 1 or more chiral carbons.
True
How do we assign D/L isomers for carbohydrates?
– the position of the last chiral carbon from the carbonyl group.
– If the last chiral carbon contains the OH to the right, it is a d sugar.
– If the last chiral carbon contains an OH to the left, it is an L sugar.
True or false.
At equilibrium, carbohydrates are typically in their cyclic form
True
True or false.
Furan are 5-membered sugar sings that result from the 4C alcohol attacking the 1C carbonyl group
True
True or false?
Pyranose is made from the attack of the C5 sugar on the C1 carbonyl to give a 6 membered sugar ring.
True
Which carbon in a sugar is considered the anomeric carbon?
C1
