Glycolysis Flashcards
General Results for Glycolysis
6 carbon glucose molecule to two 3 carbon molecules (each called pyruvate) Needs 2 ATPS to make 4 ATPs = 2 net ATPs produced Anaerobic, does not need oxygen
First irreversible rxn
take glucose, and using hexokinase we take a phosphate from that ATP to make it ADP and use that phosphate to make Glucose 6 Phosphate
Second irreversible rxn
It happens after we use Phosphoglucose isomerase to turn our Glucose-6-phosphate to Fructose 6-Phosphate. We take another phosphate from another ATP (this is our second ATP for investment) and do the above step again to make the complex have 2 phosphates. This time it is done via PK-1 or Phosphofructokinase-1.
Final Irreversible rxn
Phosphoglycerate mutase followed by Enolase turn our 3-PGs to phosphoenolpyruvates (PP), which are acted on by Pyruvate Kinase to turn our PPs into Pyruvates (the last irreversible rxn of glycolysis), in the process generating 2 ATPs from 2 ADPs (remember everything is X2)
Draw out the iireversible tautomerization reaction that turns our enol pyruvate to a pyruvate in keto form
Draw glycerol
Draw glyceraldehyde
Draw glyceric acid
Draw glycerate
Draw Acetone
Draw Hydroxy-Acetone
Draw di-hydroxy acetone
Why are certain glycolysis steps irreversible?
Making these irreversible is great for fast energy production, but these steps must be bypassed during gluconeogenesis in the liver.
How does glucose enter the cell?
Passive transport via GLUT4
What are the 3 irreversible steps in glycolysis
Step 1: Glucose to G6P
Step 3: F6P to F16BP
Step 10: PEP to pyruvate
What steps produce ATP
Step 7: 13BPG to 3-phosphoglycerate
Step 10: PEP to pyruvate
What does glucokinase have a high Km
A high Km (aka low affinity) means that glucose uptake in the liver is restricted to when blood glucose is very high
Unlike hexokinase, glucokinase is not inhibited by its products and continues to function until blood glucose levels drop to normal level
What is the major product of digestion of carbohydrates?
Glucose, but some galactose and fructose are also produced
Pentose Phosphate Pathway
G6P used to make NADPH (which is used in the biosynthesis of fatty acids) and ribose-5-phosphate (nucleotide production)
What is a carbohydrate?
Compounds that contain at least three carbons, a number of hydroxyl groups, and usually an aldehyde or ketone group
Where can glucose and fructiose be phosphorylated?
On carbons 1 and 6
Common dissarcharides
Maltose, Lactose, and Sucrose
I DIe watching soccer (MLS)
What happens to RBCs when they are exposed to high levels of blood glucose?
The glycosylated fraction of hemoglobin (normally 4-6%) increases
Measuring this is helpful when determining glycemic control for individuals with diabetes
Proteoglycans
Found in the EM or ground substance of connective tissue, synovial fluid, virteous humor, secretions of mucus-producing cells, and in cartilage
Glycoproteins
Serve as enzymes, hormones, antibodies, and structural proteins
Found in the extracellular fluid and in lysosomes
Involved in cell-cell interactions
What are the major dietary carbohydrates?
Strach, sucrose, and lactose
What is glycogen?
The major storage form of carbohydrate in animals
What does glycogen degradation produce?
glucose-1-phosphate, but free glucose is also formed
What controls glycogen breakdown in the liver?
Glucagon and epinephrine via cAMP
What controls muscle glycogen breakdown?
Epinephrine via cAMP
Glycogen synthesis
Glucose enters the cell and is phosphorylated to G6P
Phosphoglucomutase converts G6P to G1P
G1P reacts with UTP, forming UDP-glucose (catalyzed by UDP-glucose pyrophosphorylase)
What is the key regulatory enzyme for glycogen synthesis
Glycogen synthase (transfers glucose residues from UDP-glucose to the nonreducing ends of a glycogen primer)
What is the key regulatory enzyme for glycogen degradation?
Glycogen phosphorylase: removes glucose residues, one at a time, from the nonreducing ends of glycogen molecules
Produces G1P
Regulation of glycogen degradation
Glucagon (liver cells) and epinephrine (live and muscle) activate adenylate cyclase, which converts ATP to cAMP
cAMP activates protein kinase A
protein kinase A phosphorylates glycogen synthase (less active) and phorphorylase kinase
Phosphorylase kinase phsophorylates phosphorylase b, converting it to its active from, phosphorylase a (good luck)
phosphorylase a cleaves glusose residues, producing G1P
What activates phosphorylase b?
AMP (occurs during muscle contraction)
What activates phosphorylase kinase?
Calcium (released from SR)
Insulinomas
Leads to hypoglycemia
Stimulaion of glucose transport into the muscle and fat cells
Glucagonomas
Leads to hyperglycemia, as the liver is instructed to release glucose via glycogenolysis and gluconeogenesis in the presence of glucagon
GLUT1 deficiency
The GLUT1 transporter translocates glucose across the blood-brain barrier
When one allele is defective, the rate of glucose entry into the nervous system is insufficent for the cells’ needs, leading to seizures, developmental delays, and microcephaly
Deficiency of pyruvate kinase
Leads to decreased production of ATP from glycolysis
RBCs have insufficient ATP for their membrane pumps, and a hemolytic anemia results (oxygen delivery to tissues is not necessarily affected)
Why does pyruvate kinase deficiency not necessarily lead to decreased oxygen delivery?
As phosphoenolpyruvate accumulates, it is converted to 2PG, which leads to increased levels of 2,3BPG in the RBCs
Elevated levels of 2,3BPG promote oxygen release from hemoglobin
Major sites of regulation in skeletal muscle
Hexokinase and PFK1
Major sites of regulation in the liver
Glucokinase, PFK1, and pyruvate kinase
What determines if pyruvate is converted to lactate or acetyl-CoA
The activity of pyruvate dehydrogenase
