Brenda - Glycolysis Flashcards
Define glycolysis
(3)
Splitting of sugar
The universal pathway for glucose breakdown
Anaerobic
Why is glycolysis necessary?
(3)
To produce energy in the form of ATP
and NADH (energy carriers)
To convert glucose into pyruvate for the Krebs cycle
To generate precursors for other pathways e.g. serine synthesis
How many molecules of ATP are made by glycolysis?
4 ATP out
How many molecules of ATP are needed for glycolysis to occur?
2 ATP in
How many carbons are in glucose?
6C
What is NADH+ +H+ before collecting 2 electrons?
NAD+
How many molecules of NAD+ are needed for glycolysis?
2NAD+
What is the fate of the 2NADH and H+ produced by glycolysis?
It’s used to make ATP in the mitochondria
Overall, what is glucose broken into by glycolysis?
2 x Pyruvate (3C)
Where does glycolysis occur in eukaryotes?
In the cytosol
After glycolysis in the cytosol, where does further oxidation occur?
In the mitchondria
Write a note on reaction 1
(6)
Glucose is converted into Glucose 6 phosphate
Catalysed by hexokinase
Energy needed in the form of ATP (ATP -> ADP)
Mg2+ is required
Hexokinase is inhibited by G-6-P
Liver hexokinase is not inhibited by G-6-P which allows the liver to adjust the rate of glucose utilisation in response to blood glucose levels
What inhibits hexokinase?
G-6-P
What does liver hexokinase do?
Liver hexokinase is not inhibited by G-6-P which allows the liver to adjust the rate of glucose utilisation in response to blood glucose levels
Write a note on reaction 2
(3)
The isomerisation of G6P
Glucose-6-phosphate is converted into Fructose-6-phosphate
Catalysed by phosphoglucoisomerase
Write a note on reaction 3
(7)
Fructose-6-phosphate is converted into Fructose bisphosphate
Catalysed by phosphofructokinase (PFK)
Needs energy in ATP (ATP ->ADP)
Phosphorylation reaction
The first step at which glycolysis is regulated
PFK is an allosteric enzyme
Two phosphates are also made
Phosphofructokinase is an allosteric enzyme, what does this mean?
The enzyme has another site other than it’s active site
What is the enzyme for reaction 2?
phosphoglucoisomerase
What is the enzyme for reaction 3?
Phosphofructokinase (PFK)
Write a note on reaction 4
(3)
Fructose bis phosphate is converted to DHAP (Dihydroxyacetone phosphate) and G3P (glyceraldehyde-3-phosphate)
Catalysed by aldolase
Cleavage reaction
What does DHAP stand for?
Dihydroxyacetone phosphate
What does G3P stand for?
Glyceraldehyde-3-phosphate
Write a note on reaction 5
(3)
DHAP is converted into G3P
Catalysed by triose phosphate isomerase
An isomerization reaction
What is the enzyme for reaction 5?
Triose phosphate isomerase
Give the types of the first five reactions of glycolysis
1 = phosphorylation
2 = isomerization
3 = phosphorylation
4 = cleavage
5 = isomerisation
Write a note on reaction 6
(4)
Glyceraldehyde 3 phosphate is converted into bisphosphoglycerate
Catalysed by glyceraldehyde-3-phosphate dehydrogenase (G3PDH)
Generates two NADH
Oxidation and phosphorylation
What is the catalyst for reaction 6?
glyceraldehyde-3-phosphate dehydrogenase (G3PDH)
Write a note on reaction 7
(4)
Bisphosphoglycerate is converted to 3-phosphoglycerate
Catalysed by phosphoglycerate kinase
Produces 2 ATPs
Substrate level phosphorylation reaction
What is the enzyme for reaction 7?
Phosphoglycerate kinase
How many ATPs are produced by reaction 7?
2 ATP
Write a note on reaction 8
(3)
3 Phosphoglycerate is converted into 2 phosphoglycerate
Catalysed by phosphoglycerate mutase
Isomerisation reaction
What is the enzyme for reaction 8?
Phosphoglycerate mutase
Write a note on reaction 9
(4)
2 phosphoglycerate is converted into phosphoenolpyruvate (PEP)
Catalysed by enolase
PEP is a super high energy compound
Dehydration reaction
What is the enzyme for reaction 9?
Enolase
Write a note on reaction 10?
(4)
Phosphoenolpyruvate is converted into pyruvate
Catalysed by pyruvate kinase
Substrate-level phosphorylation
Produces 2 ATP
What does PEP stand for?
Phosphoenolpyruvate
How many ATP molecules are produced by step 10?
2 molecules of ATP
How is lactose broken down into pyruvate?
(3)
Lactose is a polysaccharide made of glucose and galactose
Lactase works on lactose to break it down to it’s monosaccharides
Glucose enters glycolysis as normal
Galactose is then isomerised to form Glucose-6-phosphate which joins the cycle at reaction 2
How is sucrose broken down into pyruvate?
(4)
Sucrose is a disaccharide made of glucose and fructose
Sucrase breaks sucrose down into it’s simple sugars
Glucose enters glycolysis as normal
Fructose is phosphorylated into fructose-6-phosphate which then joins the cycle at reaction 3
How is maltose broken down into pyruvate?
(2)
Maltose is made of two glucose units
Maltase acts on maltose breaking it down into the two glucose molecules which enter the cycle as normal
What happens to pyruvate?
Most will be converted to acetyl CoA and oxidised through the TCA cycle
What type of reaction is the conversion of pyruvate to acetyl-CoA?
Oxidative decarboxylation
What catalyses the oxidative decarboxylation of pyruvate to acetyl-co A?
PDH
At what steps is glycolysis regulated?
Reaction 1, 3, 10
