Carbohydrates 3 Flashcards
Define glycolysis
A series of cellular reactions, not requirin oxygen, that splits glucose, glycogen or other carbohydrates into pyruvic or lactic acid while storing energy in ATP molecules.
Why is glycolysis important?
Its the only way ATP can be made when lacking oxygen (e.g. during strenuous exercise) or in cells lacking mitochondria (RBCs)
How many stages/steps are involed in glycolysis?
2 stages
The preparatory phase has 5 steps
The payoff phase has 5 steps
Why cant glycolysis be easily reversed?
It has an overall -delta G making it spontaneous and thermodynamically impossible to reverse. This applies mainly to 3 steps that are very spontaneous.
What happens overall in the preparatory phase?
Glucose is converted to two Glucose-3-phosphates at the cost of 2 ATP
What occurs in step one of the preparatory phase?
Glc is converted to G-6-P by hexokinase at the cost of 1 ATP
What occurs in step 3 of the preparatory phase?
F-6-P is phosphorylated to F-1,6-bisP by phosphofructokinase-1 (PFK-1) at the cost of 1 ATP
Why is Step 3 of the preparatory phase especially importnat?
It is the first commited step of glycoslysis because it has a very -deltaG so is irreversible.
What happens overall in the payoff phase?
Two G-3-P molecules are converted to two pyruvates. This produces 4 ATP and 2 NADH.
What occurs at step 6 of glycolysis (step one of payoff phase)?
Two G-3-P are converted to 1,3-Bisphosphoglycerate (1,3-bisPG) producing two NADH
What happens in step 7?
Phosphate is transfered form the two 1,3-bisPG molecules to ADP to form two ATP and 3-phosphoglycerate
What occurs in step 10?
Phosphate transferred from two PEP to ADP to form two ATP and two Pyruvate.
What is different between substrate level and respiration-linked phosphorylation?
Substrate level phosphorylation needs soluble enzymes and chemical intermediates
Respiration linked phosphorylation requires membrane bound enzymes, oxygen and gradients of protons.
How is NAD+ replenished?
By converting pyruvate to Lactace (or other intermediates e.g. ethanol & CO2) which has a by-product of using up NADH.
What term is used to describe the constant use and replenishment of NAD+?
A redox Balance