Chapter 16- Glycolysis Flashcards
What are the 3 stages of the generation of energy from food?
- Large molecules in food are broken down into smaller molecules in the process of digestion
- Many small molecules are processed into key molecules of metabolism (acetyl CoA)
3 ATP is produced from the complete oxidation of the acetyl component of acetyl CoA
Slide 2
What is starch glycogen and cellulose?
What are they converted to and by what?
Why can’t we digest cellulose? (Difference between cellulose and starch/glycogen)
Starch and glycogen are degraded to glucose, maltose and oligosaccharides by salivary and pancreatic amylases
In ruminants, cellulose is converted to glucose by cellulase
Can’t digest cellulose because it has beta 1-4 linkages while starch and glycogen have alpha 1-4 link
What are the 3 main sugars in the small intestine?
What are they converted to and by what?
- Lactose (milk sugar)- converted to glucose and galactose by lactase (β-galactosidase)
- Sucrose (common sugar)- converted to glucose and fructose by sucrase (invertase)
- Maltose- converted to glucose by maltase
Galactose and fructose can be further converted to glucose if not converted in small intestine they go to liver to be metabolized
These monosaccharides are then transported into the cells and then to bloodstream
Difference between glycogen and starch?
Glycogen is highly branched compared to starch
What is glucose?
What is glucose transporter GLUT2?
Glucose is main source of energy for us
GLUT2 is found in liver and pancreatic β cells
In the pancreas it regulates insulin
In the liver, it removes excess glucose from the blood
Memorize the possible pathway of glucose on slide 5.
Glucose
2 pyruvate
2 ethanol + 2CO2, 2 acetyl CoA, 2 lactate
4CO2 + 4H2O
What enzyme traps glucose in the cell and begins glycolysis?
What are the types in muscle and liver?
Hexokinase
Phosphorylates hexoses in various tissues
Muscle uses hexokinase I and liver uses hexokinase IV (glucokinase)
Slide 7 picture slide 8 lists
What is the isomerization of glucose 6 phosphate (G6P) to fructose 6-phosphate (F6P) on slide 9?
What enzyme catalyzes this reaction?
Look on slide 9
Catalyzed by phosphoglucose isomerase
How is fructose 6-phosphate (F6P) then converted to Fructose 1,6- bisphosphate (F16BP)?
What enzyme catalyzes this?
Look on slide 10
Catalyzed by phosphofructokinase catalyzes this reaction
Look at graph on slide 11
How is fructose 1,6-bisphosphate (F16BP) then converted to dihydroxyacetone (DHAP) and Glyceraldehyde 3-phosphate (GAP)?
What enzyme catalyzes this reaction?
Look at diagram on slide 12
Aldolase catalyzes this reaction
How is dibydroxyacetone phosphate (DHAP) converted to glyceraldehyde 3-phosphate (GAP)?
What enzyme catalyzes this?
Look on slide 13
Triose phosphate isomerase catalyzes this reaction
How is glyceraldehyde 3-phosphate (GAP) converted to 1,3-biphosphoglycerate (13BPG)?
What enzyme catalyzes this?
Look at slide 14
Glyceraldehyde 3-phosphate dehydrogenase catalyzes this reaction
Slide 15 example of reaction
How is 1,3-biphosphoglycerate (13BPG) converted to 3-phosphoglycerate?
What enzyme catalyzes this reaction?
Look at slide 16
Catalyzed by phosphoglycerate kinase
How is 3-phosphoglycerate converted to 2-phosphoglycerate?
What enzyme catalyzes this?
Look at slide 17
Phosphoglycerate mutase catalyzes this
How is 2-phosphoglycerate converted to phosphenolpyruvate then to pyruvate and what enzymes do this?
Slide 17!
Enolase converts 2PG to phophenolpyruvate
Pyruvate kinase converts phosphenolpyruvate to pyruvate
What is the net reaction for glycolysis? How much atp molecules are produced?
Glucose + 2Pi + 2ADP + 2NAD+ —-> 2 pyruvate + 2 ATP + 2NADH + 2H+ + 2H2O
2 molecules of ATP produced in conversion of glucose to pyruvate
What are the 6 types of reactions in glycolysis?
- Phosphoryl transfer - kinases (phosphoryl group is transferred from ATP to a glycolytic intermediate or vice versa)
- Phosphoryl shift- mutase (shift from one oxygen to another)
- Isomerization- isomerases (conversion between ketone and aldose)
- Dehydration- enolase (removal of water molecule)
- Aldol cleavage- aldolase (split of C-C bond)
- Dehydrogenation- dehydrogenase (oxidation reduction)
What are the 3 characteristics of the phosphorlyated intermediates?
- Phosphate groups are completely ionized at physiological pH (7) gives intermediates negative charge impermeable to membranes
- Phosphate groups are essential for formation of atp from adp
- Phosphate groups serve as recognition for proper fit of intermediates to active sites of corresponding enzymes
What are fermentation’s? (Pyruvate to ethanol)
Fermentation’s are ATP generating pathways in which electrons are removed from one organic compound and passed to another
Pyruvate to ethanol generates NAD+
Pyruvate to acetaldehyde is catalyzed by pyruvate decarboxylase (needs vitamin thiamine)
Acetaldehyde to ethanol is catalyzed by alcohol dehydrogenase
Slide 22
Memorize the structures of thiamine pyrophosphate (TPP) and hydroxyethyl thiamine pyrophosphate on slides 23-24
Okay
How is pyruvate converted to lactate?
What enzyme catalyzes this?
What is the net reaction lactic acid formation?
Slide 25
NADH can also be oxidized by converting Pyruvate to lactAte
This reaction is catalyzed by the enzyme lactate dehydrogenase
Glucose + 2Pi + 2ADP -> 2 lactate + 2 ATP + 2H2O
^ lactic acid formation
Study the chart of the metabolism of galactose and fructose on slide 26
Where is galactose metabolized?
How is fructose metabolized?
Galactose metabolized in liver
Fructose can go straight to glucose 6 phosphate and can go to liver but goes through a few reactions then ends with two end products
What are the two intermediates of the glycolytic pathway?
How are these two made?
Dihydroxyacetone phosphate
Glyceraldehyde 3 phosphate
Fructose is converted to fructose 1 phosphate by fructokinase
Then fructose 1 phosphate is converted to Glyceraldehyde and dihydroxyacetone (one is phosphorylated and one is not) by fructose 1 phosphate aldose
Then Glyceraldehyde can be converted to Glyceraldehyde 3 phosphate by triose kinase
SLIDE 27
How is galactose converted to galactose 1 phosphate?
What enzyme does this?
Slide 28
This reaction is catalyzed by the enzyme galactokinase
Study what happens once galactose 1 phosphate is made up to UDP-glucose on slide 29
Okay
How is glucose 1-P converted to glucose 6-P (what enzyme)?
Phosphoglucomutase
It is converted to this because it can enter the glycolytic pathway
What is galactosemia?
What is classical galactosemia?
Aldose reductase catalyze oxidation reduction reactions
Lactose is made of glucose and galactose and children rely on milk so this deficiency is common in children
Cataracts forms from accumulating galactose is converted to galactitol which causes water to diffuse into lens
CLASSICAL GALACTOSEMIA IS A DEFICIENCY OF TRANSFERASE
Non classical is enzymes other than transferase
What is lactose intolerance?
Hypolactasia occurs from lack of enzyme to degrade lactose
Study regulation at rest and during exercise on slide 33
What are the two activators?
AMP activates phosphofructokinase 1
Fructose 2,6-biphosphate activates as well
What activates and inhibits Hexokinase, PFK 1, and pyr. Kinase?
Hexokinase- inhibited by glucose 6-P PFK-1- activates by AMP, F-2,6-P Inhibited by ATP, citrate Pyr. Kinase- activates by F 1,6-P2 Inhibited by ATP, Acetyl-CoA, fatty acids
