E3 Module 9 Flashcards
Distinguish between the chemical structures of glucose and fructose
both simple sugars with 6 carbons
glucose, 6-membered ring, has an aldehyde group, fructose, 5-membered ring, has a ketone group
Simple sugars are metabolites that feed into the ____________ pathway, such as _________ sugars like glucose and __________ sugars like fructose
glycolytic
aldose
ketose
define the difference between aldose and ketose sugars; provide examples
Demonstrate the cyclization of linear glucose to cyclic glucopyranose.
Explain the significance of Benedict’s test
test uses an alkaline solution of copper as a mild oxidizing agent to detect the presence of reducing. The reduction of Cu2+ to Cu+ changes the color from blue to red because of a copper oxide precipitate.
*reduction of sugar turns it red
lactose
sucrose
trehalose
Differentiate between reducing and non-reducing sugars
demonstrate the difference between α-1,4 and β-1,4 linkages
List the 10 enzymes of glycolysis
- hexokinase
- phosphoglucoisomerase
- phosphofructokinase-1
- aldolase
- triose phosphate isomerase
- glyceraldehyde-3-phosphate dehydrogenase
- phosphoglycerate kinase
- phosphoglycerate mutase
- enolase
- pyruvate kinase
What is the overall net reaction of glycolysis?
Glucose + 2NAD+ + 2ADP + 2Pi ——–> 2 pyruvate + 2NADH + 2H+ +. 2ATP + 2H20
distinguish between the ATP investment and ATP earnings stages
Define substrate level phosphorylation
describe the two enzymatic reactions in glycolysis that result in ATP synthesis
Explain how the conversion of phosphofructokinase-1 between the T and R state is allosterically controlled by ATP, ADP and AMP
List three ways in which substrate availability and enzyme activity levels control flux through the glycolytic pathway
Compare and contrast Hexokinase I and glucokinase (hexokinase IV)
hexokinase I
-high affinity for substrate (low Km ~0.1mM)
-expressed in all tissues, not specific
-phosphorylates a variety of hexose sugars
-inhibited by the product of the rxn, glucose-6-P
Glucokinase
-low affinity for substrate (1000x higher Km ~10mM)
-highly specific for glucose
-expressed primarily in liver and pancreatic cells
-not inhibited by glucose-6-P
List the cell signaling steps of going from glucose to insulin signaling (in pancreatic beta cells) using glucokinase (glucose sensor)
- Stimulation of glucokinase enzyme levels
- Increased ATP synthesis
- ATP inhibits K+ channel
- Membrane depolarization
- Activation of voltage-gated Ca2+ channel
- Ca2+ stimulates insulin vesicles to fuse with plasma membrane
- Insulin signaling
Explain why glucokinase is a molecular sensor and the molecular basis for lactose intolerance and for fructose intolerance
List the potential metabolic fates of pyruvate and explain why, under anaerobic conditions, pyruvate must be metabolized to either lactate or ethanol
1) anaerobic - production of lactate
2) anaerobic - production of CO2 + ethanol
3) aerobic - production of CO2 + H20
What does glycolysis accomplish for the cell?
-generates 2 ATP which is critical under anaerobic conditions (no O2)
-generates pyruvate, a precursor to acetyl CoA, lactate, and ethanol (in yeast)
What are the key regulated enzymes in glycolysis?
Hexokinase, Phosphofructokinase-1, pyruvate kinase
What are examples of glycolysis in everyday biochemistry?
-sole source of ATP under anaerobic conditions which can occur in animal muscle tissue during intense exercise
-Fermentation, used to make alcoholic beverages when yeast cells are provided with glucose without oxygen
Draw out the structures for Stage 1: Investment of glycolysis
Draw out the structures for Stage 2: ATP earnings
what is metabolic flux and what does it depend on?
the rate at which metabolites go through a pathway
depends on substrate concentration
*NOT equilibrium
For the rxn Glucose-6-P —-> Fructose-6-P (deltaG^degree’ = +1.7kJ/mol)
What is the effect on deltaG if [Glucose-6P] increases 100 fold to 8.3 mM in the cell (up from 83uM) i.e., what is the new value for delta G?
