Glycolysis Flashcards
What are the two stages of Glycolysis?
Energy-investing reactions (consume ATP)
Energy-harvesting reactions (produce ATP)
Which stage of Glycolysis produces ATP?
stage 2- energy-harvesting raactions
what is the purpose of Glycolysis?
Convert 6-C Glucose –> two 3-C Pyruvate
What are the two steps in Parts 1 (reactions 1-5)
Glucose phosphorylated (add P) at C1 and C6
Glucose 6C ring is cleaved into 2 3C glyceraldheyde-3-phosphate
What are the four steps in Parts 1 (reactions 6-10)
Convert metabolic energy of GP3 –> ATP
4 new ATPS produced
2 ATPSs used in part 1
Net yeild = 2 ATPS
What is the first step of glycolysis? (enzyme and reaction)
Hexokianse
D-Glucose + ATP –> Glucose 6-phosphate + ADP
What is the second step of glycolysis? (enzyme and reaction)
Hexose Isomerease/ Phosphohexose Isomerase
Glucose-6-P <–> Fructose-6-P
What occurs in the 2nd step of glycolysis? (words)
Ring rearranges into 5-mememebred fructose ring 9moves carboynal group)
What is the third step of glycolysis? (enzyme and reaction)
Phosphofructokinase
F-6-P –> F1.6-bisphosphate + ADP
What occurs in the 3rd step of glycolysis? (words)
Adds second phosphate to ring
What steps of glycolysis are irreversible and why?
Steps 1-3, 5-6 and 10, due to negative Gibbs free energy (non-spontaneous).
What is the fourth step of glycolysis? (enzyme and reaction)
Aldolase A
F1,6-bisphosphate <–> dihydrochalcone phosphate + glyceraldehyde-3-p
What occurs in the 4th stage (words)?
Ring is opened and cleaved into two 3 carbon sugar phosphates
What are the two rings called that Aldolase A produces?
1 = dihydroxy-acetone phosphate
2= glyceraldehyde 3-phosopahte
What is the fifth step of glycolysis? (enzyme and reaction)
isomerase
DHAP –> G3P
What is the sixth step of of glycolysis? (enzyme and reaction)
(first energy harvesting)
Glyceraldehyde 3-phosphate dehydrogenase
G3P + Pi + NAD+ <–> 1,3 Bisphosphoglyceate + NADH2
What occurs in the 6th stage (words)?
Converts G3P into 1,3-PGA as well as NAD –> NADH2
Transfers free P to C1
What is the seventh step of of glycolysis? (enzyme and reaction)
3-Phosphoglycerate Kinase (subsrate level of phosphorylation)
1,3BPG + ADP <–> 3PG + ATP
What occurs in the 7th stage (words)?
Forms high energy P bonds where not previols
What is the eighth step of of glycolysis? (enzyme and reaction)
Phosphogoglycerate Mutase
3PG <–> 2PG
What occurs in the 8th stage (words)?
P moves from C2 to C3
What is the ninth step of of glycolysis? (enzyme and reaction)
Enolase
2PG <–> Phosphoenolyruvate (PEP) + H2O
What occurs in the 9th stage (words)?
Removes water from 3PG to make PEP
What is the tenth step of of glycolysis? (enzyme and reaction)
Pyruvate kinase
PEP + ADP <–> Pyruvate + ATP
What occurs in the 10th stage (words)?
Transfers phosphate from PEP to ADP
What is Substrate-level phosphorylation?
enzyme catalysed transfer of phosphate from donor molecules to ADP
for every mole of glucose that enters glycolosys, how many moles of pyruvate are produced?
2 Moles
in Energy-Investing steps, how much ATP tp glucose is hyrolysed?
hydrolysis of 2 ATP molecules per one glucose molecule
What do enegry releasing steps produce and how many?
two molecules of NADH
What occurs if O2 is present in glycolysis?
three stages of cell respiration = Pyruvate oxidation, citric acid cycle and respiratory chain/ATP synthesis
What is the overall reaction for glycolysis?
Glucose + 2NAD+ + 2P + 2ADP –> 2 Pyruvate + NADH + 4H + 2ATP + 2H2OWhich
What is the rhyme to remember glycolysis Steps?
Goodness Gracious, father Franklin, Did Go By Picking Pumpkins (to) Prepare Pies
What is the Rhyme for remembering Glycolysis Enzymes?
High Profile People Act Too Glamorous, picture Posing Every Place
What is allosteric regulation?
mechanism of control: effector binds to regulator site and induces conformational change to influence activity.
What are isozymes?
2 genes that encode proteins with similar functions
What are the two isozymes of phosphofructokinase? What do they do?
Phosphofructokianse-1 (PFK-1) = catalyses reaction 3
Phosphofructokianse-2 (PFK-2) synthesises F-2,6BP (allosteric regulator of PFK-1)
Both control rate of glycolysis via allosteric regulation
What are allosteric inhibitor examles?
ATP and Citrate
What are allosteric activator examples?
F2,6BP, ADP and AMP =
What activates PFK1?
F2,6BP
What is the nature of the two binding sites on PFK1?
1- high affinity for F6P
2- low affinity for F6P
What are the three modes of regulation of glycolysis?
- Difference between hexokinase and glucokinase Km vales
- phosphofructokinase controls rate of glycolysis
- Pyruvate kinase: allosteric regulation
What happens to glyclosys at a HIGH ATP?
Glycolysis slows down. ATP binds to PFK1 and decreases it’s affinity for F6P.
What can AMP do to regulate glyclyosis?
Is an Allosteric activator:
can displace ATP and increase affinity (lower Km)
What is F2,6BP regulated by?
Insulin and glucagon
What is the effect of Insulin on PFK2, F2,6BP and glycolysis?
promotes PFK2 activity, increases F2,6BP and glycolysis levels
What is the effect of glucagon on PFK1, F2,6BP, glycolysis and F2,6Bpase?
increases F2,6Bpase activity, decreases F2,6BP, PFK1 and glycolysis levels.
How does Pyruvate Kinase provide allosteric regulation?
via allosteric effector and phosphorylation
Insulin = dephosphorylation = active
Glucagon = phosphorylation = inactive
What is one major structural difference between fructose and glucose?
Glucose = aldehyde group
Fructose= ketone group
Where is the major site of metabolism for Fructose?
The Kidneys
Where is lactase located?
in the brush border/microvilli of cells in the small intestine
what is lactase essential for?
complete digestion of milk
what are the three enzymes used in galactose breakdown?
Galactokinase (GALK)
Galactose-1-phosphate uridyltransferase
UDP-galactose-4’-epimerase
is NAD+ in an oxidised or reduced state?
oxidised
what happens to NAD+ in the 6th step?
it is reduced: adds a H ion and becomes NADH2
What type of reaction is step 6 (G3P Dehydrogenase)?
redox reaction
Which steps are regulated?
the irreversible ones
where do ADP and AMP come from?
ATP
What occurs if there is too much ADP and AMP?
As they are products of ATP, it indicates that there is not enough ATP in the body. Sends a message to the enzyme via a negative feedback loop to increase ATP synthesis.
Km decreases so moves in the forward direction (less substrate needed).
What is the role of insulin in hormonal control of phosphofructokinase-2?
increases the transcription of genes that make glucose. UP REGULATION
What is the role of glucagon in hormonal control of phosphofructokinase-2?
DOWN REGULATION
increases production of gene that makes glycogen in the liver.
How (generally) is glucose transported to tissues?
monosaccharides absorbed from the intestine after being digested in diet, enter the blood and then travel to tissue where can be metabolized.
what organs are involved in the metabolism of glucose?
kidney and liver
what occurs after glucose is transported to cells?
hexokianse phosphorylates glucose into glucose-6-phosphate. This can then enter three common processes:
a- glycolysis
b-pentose phosphate pathway
-glycogen synthesis
what is the major fate of glucose-6-phosphate in the body?
oxidation via glycolysis
what are the hormones of metabolic homeostasis?
insulin and glucagon
What is different from fructose metabolism versus glucose metabolism
Regulated reaction of Phosphofructokinase is avoided.
Excess fructose can exhaust Aldolase B and use ATP up.
same ATP and pyruvate yield.
what is dominanat in a fasted state?
g) Glycogen = gluconeogenesis, glycogenolysis and ketogenesis increased
How is galactose transported into a cell
facilitated by Na transporter
Glut1, glut2 and Glut12
What is the difference between glycogen and glucagon?
Glycogen is how glucose is stored in the body.
Glucagon is the hormone that triggers liver glycogen to convert back into glucose
