Fermentation And Regulation Of Glycolysis Flashcards
What are the two types of fermentation
Alcoholic
Lactic acid
What is fermentation
After pyruvate is formed from glycolysis, if the cell has no oxygen (anaerobic)
fermentation to form either ethanol or lactic acid occurs
Why does fermentation happen
To provide redox balance in the cell
In glycolysis, NADH is formed, in fermentation NAD+ gets formed As a balance
It keeps glycolysis happening under anaerobic conditions
What are the acceptors and donors of the electrons in fermentations
Organic compounds (not o2 because it’s not present)
Describe the process of alcoholic fermentation
Pyruvate decarboxylase turns pyruvate to acetaldhyde (also realese co2)
Acetaldehyde accepts electrons (gets reduced) from Nadh through the use of the enzymes alchohol dehydrogenase
This forms ethanol and NAD+
Doescribe the process of lactic acid fermentation
Pyruvate gets reduced by Nadh with the help of the enzyme lactate dehydrogenase
Lactate and NAD+ is formed
What are obligate anaerobes
Facultative anaerobes
Bacteria that cannot tolerate oxygen (can’t have o2 around them, ex clostridium botulinum)
Can function with or without O2 (yeast)
Slide 7
In I pad
What are the three steps in glycolysis where regulation can occur
At the irreversible steps:
Hexokinase
Phsophopructokinase
Pyruvate kinase
How does regulation happen in glycolysis
Allosteric effectors or covalent modification binds to one of the three enzymes to increase or decrease their activity
This regulation is tissue specific (it’s diff in muscle cells compare to liver cells)
How is the regulation of phosphofruktokinase done
It’s the most important regulation
It’s caused by allosteric inhibition of the enzyme by ATP (atp binds, inhibited) because the energy charge is high (atp/amp)
If there is high atp, we don’t need glycolysis as much so the activity of the enzyme decrease, opposite for low atp (where amp binds and increases activity)
How is the inhibition of phosphofructokinase reversed
Why not adp
AMP (mono phosphate) bind to the same site on the enzyme that atp does
Not adp because the. atp can be made from adp if it’s used up really quick
Amp acts as a counteracting molecule
How is regulation of Hexokinase done
It gets inhibited by its product glucose 6 phosphate
If at rest, more atp inhibits pfk. This causes more fructose 6 phosphate to be made.
the equilibrium shifts to make more glucose 6 phosphate which then inhibits Hexokinase through negative feedback inhibition.
This is good because glucose 6 phosphate is use for things other than glycolysis.
What is a commited step and what is the first one in glycolysis
Is the step that turns the substrate into something that has not choice but to proceeed into down a specific pathway
The conversion of fructose 6 phosphate and fructose 1,6 bi phosphate through the use of phosphofructokinase
How does the regulation of pyruvate kinase occur
Depends on the energy charge of the cell (atp/amp)
It gets allosterically inhibited by atp
If low atp in the cell, pfk gets activated by amp and makes fructose 1,6 biphosphate. This then does feed forward stimulation to activate pyruvate kinase
How does regulation in the muscle occur
When at rest
When activd
When at rest, inhibited glycolysis so Hexokinase is inhibits by negative feedback, atp inhibits pyruvate kinase and pfk
When active, more glycolysis so pyruvate kinase and pfk are stimulated by AMP binding to PFK
In muscle regulation what can also inhibit pfk
Low ph
Due to lactose acid formation
The liver has ______ than the muscle
More biochemical functions
How does the liver store glucose
Stores it in the blood as glycogen
Releases it as needed
How Is regulation in the liver done
Through biosynthesis where the power made from glucose is used to make building blocks for other macro molecules
How is regulation of phosphofructokinase done in the liver
The ph is less important (compared to muscle) so most regulation is due to atp
A high concentration of citrate and atp inhibits PFK and makes less glycolysis
A high concentration of fructose TWO,6 bisphospohate and amp, activate PFK and does feedforward stimulation to make more glycolysis
In the liver, when is fructose 2,6 bisphophate high
When does this mean
More of its is made in the liver when the glucose levels are high
F 26 p is concentration dependent
If in the liver there is higher glucose supply, but there is also atp inhibiting what happens
If there’s higher glucose, there higher F 26 p
Higher F 26 p means more glycolysis
If there’s higher amount of glucose, the inhibitions by atp is lowered, and there’s more glycolysis
How is Hexokinase regulated in the liver
Same a muscle cells, but the enzyme is now Hexokinase 4 (glucokinase)
Glucokianse is an isozyme of Hexokinase and can only get stimulated not inhibited (by g 6 p)
If glucose is high, glycolysis happens. If low, it leaves the glucose alone and lets of part of the body do glycolysis with it
Km for glucose is ____ that of Hexokinase
50 times out of
What are isozymes
They calatlyzs the same reaction
Have different kinetics/regulation, and primary structure
How is regulation of pyruvate kinase done in the liver
The pyruvate kinase in the liver is in the L isozyme. (Muscle is m isozyme)
The L form is inhibited by atp, alanine, and reversible phosphorylation
When glucose is low, the kinase is phosphorylated and its activity is decreased. This causes less glycolysis
How is glycolysis regulated by glucose transporters
These different transporters control the amount of available glucose in the cell for glycolysis
Glut 1 and 3 are always on
Glut 2 is only in when glucose is high
Glut 4 increases when more exercise
