Week 5 - Glycolysis Flashcards
What is glycolysis
A series of enzyme-catalysed reactions by which glucose is oxidised to 2 molecules of pyruvate (C3) in the cytosol.
*This is an anaerobic process
What is the overall reaction of glycolysis
What does glycolysis link to
Links to the citric acid cycle
Where does Glycolysis occur
Cytosol (region of cytoplasm outside organelles)
What are the 3 main staged of Glycolysis
- Investment Stage (Step 1-3)
- Cleavage Stage (Step 4-5)
- Harvesting Stage (Step 6-10)
What does the investment stage mean
Where energy is invested in so that the molecule of glucose becomes unstable and is able to be broken down
What does the cleavage stage mean
Breaking apart the C6 sugar into 2 C3 units
What does the harvesting stage mean
Harvesting energy which will be either ATP or NADH
*What is Step 1 in glycolysis
The investment of ATP; Phosphorylation of glucose
Catalyse = Hexokinase
Cofactor = Mg+2
The phosphorylation is endergonic (+ve delta G) which is coubled with the hydrolysis of ATP (large -vg delta G) hence an overall exergonic (spontaneous) reaction>.
What is Step 2 in Glycolysis
Isomerization of glucose 6-phosphate
*What is Step 3 in glycolysis
Investment of ATP: phosphorylation of F-6-P
*This is the RATE LIMITING STEP
Catalyst = Phosphofructokinase
Cofactor = Mg+2
- which is allosterically inhibited by ATP, citrate and activated by AMP
What is step 4 in glycolysis
Cleavage of fructose1, 6-bisphosphate to 2 triose phosphates
What is step 5 of glycolysis
Isomerization of DHAP to G3P, required as G3P is the substrate for the next step
*What is step 6 of glycolysis
Harvest: NADH
From oxidation of the -CHO of GAP
- contains the high energy phosphoester bond
Why is step 6 of glycolysis important
*This is a crunch step for the whole glycolysis pathway as without the production of NADH every other reaction after cannot occur
What is step 7 of glycolysis
Transfer of a phosphate group from 1,3-bisphosphoglycerate to ADP
*HARVESTING ATP
What is step 8 of glycolysis
Isomerization of 3-phosphoglycerate to 2-phosphoglycerate
What is step 9 of glycolysis
Dehydration of 2-phosphoglycerate to form PEP
*What is step 10 of glycolysis
Phosphate transfer to ADP
HARVEST ATP
Catalyst = pyruvate kinase
CoFactor= Mg+2
What step is the RDS
Step 3
phosphorylation of F-3-P
At what steps is ATP invested
Step 1 and 3
At what steps is ATP harvested
Step 7 and 10
During exercise and rest conditions which steps are allosterically controlled
Step 1 - hexokinase
Step 3 - phosphofructokinase
Step10 - pyruvate kinase
What is the enzyme in step 1
hexokinase
with Mg+2 cofactor
What is the enzyme in step 3
phosphofructokinase
with Mg+2 cofactor
What is the enzyme in step 10
pyruvate kinase
with Mg+2 cofactor
How is step 3 phosphofructokinase inhibited
By high concentration of ATP activated by AMP
High concentrations of AMP will increase the rate of step 3
Low concentrations of AMP and high conentration of ATP will decrease the rate of step 3
How is step 10 allosterically controlled
Feedforward activated by FBP
High concentrations of FBP (Fructose 1,6-bisphosphate) in step 4 will increase the rate of step 10
High concentration of ATP will inhibit step 10
What are the 2 pathways the product pyruvate can go after glycolysis
- Aerobic conditions, forms Acetyl CoA and goes tot he Citric Acid Cycle
- Anaerobic conditions and forms Lactate and NAD+
What is the lactic acid fermentation pathway
Pathway which occurs during anerobic conditions and is where the enzyme lactate dehydrogenase reduces pyruvate to lactate. NADH is the reducing agent for this process, and as pyruvate is reduced, NADH is oxidized and NAD+ is again available, permitting glycolysis to continue
What is the equation of step 11
What is the enzyme that catalyses step 11 of glycolysis
lactate dehydrogenase
What is acidogenicity
Ability of bacteria to produce acid
comes from cariogenic bacteria e.g. MS
What is the reaction of anaerobic glycolysis
What are fermentable carbohydrates
a sugar that allows reaction 11 (lactate fermentation) in anaerobic glycolysis to proceed for bacteria in the oral cavity
All carbohydrates which can serve as a energy supply for cariogenic microorganisms
Example of fermentable carbohydrates
- glucose
- fructose
- sucrose
- lactose
- starch
Example of non fermentable carbohydrates
- xylitol
- splenda
What are homofermentative bacteria
Microorganisms that primarily produce a single fermentation product from a substrate, typically lactic acid.
They can produce acids from fermentable carbohydrates via an alternative pathway to glycolysis (phosphoketose pathway)
What’s an examples of a homofermentative bacteria
Strep mutans
What are heterofermentative bacteria
Microorganisms that primarily produce a mixture of metabolities
What is the phosphoketose pathway (PPK)
A major route of glucose catabolism in heterofermentative lactic acid producing bacteria e.g. lactobacillus
An alternative pathway for the production of ATP from glucose done by microorganisms
How much ATP is produced from glycolysis
overall gain of 6 ATP (invest 2ATP, harvest 8)
Draw glucose (in solution and out)
Draw pyruvate
Draw a-D-Fructose 1,6-biphosphate
What type of bacteria is streptococci mutans
Facultative anaerobic bacterium
cariogenic microorganism
What does streptococci mutans do in the oral cavity
- Produces acid rapidly from fermentable carbohydrates
- Homofermentative bacteria which means that it follows the lactic acid fermentation pathway (reaction 11)
What type of bacteria undergoes anaerobic glycolysis pathway to lactic acid
Homofermentative cariogenic bacteria e.g. Strep Mutants
What type of bacteria undergoes the phosphoketose pathway to lactic acid
Heterofermentative bacteria e.g. lactobacilli
Is glycolysis anerobic or aerobic
Anerobic
What are the parts of the mitochondria
- matrix
-inner membrane - intermembrane space
How much energy does the hydrolysis of ATP produce in kcal/mol
7.3 kcal/mol
How much energy does the hydrolysis of ATP produce in kJ/mol
30.5 kJ/mol
What is the equation for the hydrolysis of ATP to ADP
What is the reaction for the phosphorylation of ADP to ATP
What is the redox equation for the reduction of NAD+
How is enolase related to dentistry
Fluoride has shown to inhibit enolase which leads to a diminished production of ATP and the lactate end product in anerobic glycolysis
What is the phosphoketose pathway
A major route of glucose catabolism in heterofermentative lactic-acid producing bacteria such as Lactobacillus
What is the reaction of the phosphoketose pathway
What is the name of the key cleavage enzyme in the phosphoketose pathway
phosphoketolase
