Glycolysis Flashcards
what is CHO stand for?
Carbohydrates
Carbs are broken down into two categories, what are they?
simple and complex.
simple are broken down in the mouth whereas complex are broken down in the small intestine
what is the similarity between simple and complex carbs?
they both enter the blood stream as glucose
what happens to carbs once they are broken down into glucose?
must be used or stored
what is glucose stored as in muscles?
stored in large molecules called glycogen
what is the process of making glycogen called?
glycogenesis
the liver can directly and indirectly convert glucose to what?
it is directly converted to glycogen (straight from food)
it can indirectly make glycogen from other substrates such as lactate to glucose
why can glucose not be stored as glucose?
it is water soluble.
what happens to excess glucose?
it is stored as fat
what system uses glucose for energy?
all systems in the body
- nerves and brain uses large amounts of glucose
- high carb intakes, the liver will use glucose too
- important for movement (skeletal muscle uses glucose to produce rapid amounts of ATP)
what is the production of ATP from glucose called?
glycolysis - the breakdown of glucose
glucose turns into what which is then stored as fat?
aceto-co-a
breaksdown into triglycerides which is then stored as fat
what is the percentage of glucose used by the brain?
upwards of 60% from rest
what does the brain rely on if there is no glucose in the body?
fat (keto diet)
where does glycolysis occur?
cytosol of the cell
what enzyme is used to convert glucose?
hexokinase which uses an ATP (invested) to breakdown glucose
what is the primary role of glycolysis?
to rapidly create ATP
what is very important to glycolysis process?
the addition and removal of H+ ions
required nicotinamide adenine dinucleotide (NAD+) as this is an acceptor of H+
what is the final product of glycolysis?
2x pyruvate (some become lactate) 2x ATP
what is a co-enzyme?
they have more broad application (not lock and key)
what are the terms used to describe the addition or removal of hydrogen H+ ions?
oxidation and reduction
what is reduction?
when an H+ ion is added to a substrate (your reducing the desire for an electron with the addition of H+)
NAD+ +H+ = NADH
what is oxidised?
when an H+ ion is removed from a substrate
FADH2 = FADH+ + H+
what are the other yields from glycolysis?
2 NADH are released which are worth 3 ATP each
making the total energy production up to 8.
what is pyruvate?
3 carbon fate
what does pyruvate convert to?
some to lactate
some are used later in aerobic metabolism
how do you convert pyruvate to lactate? Which enzyme?
lactate dehyrogenase (ase meaning enzyme) LDH
what happens in a low Keq?
means there is more product to be made - bring it up to equilibrium
what happens in a high Keq
means there is less reactant and more product (reactions are happening quickly)
what happens with an accumulation of lactate and pyruvate?
slows glycolysis down
how do we remove or use lactate?
can be oxidised (removal of H+) - in muscle (same or other) - liver - in other organs (heart) converted back to glucose
what does it mean if there are lower levels of muscle glycogen?
earlier fatigue
how much glycogen is stored in the muscle and liver?
400g=1600kcal and 100g =400kcal
what are the two types of control?
feed-forward
feed-back
what is feed-forward
accumulcation of products stimulates forward movement
usually associated with glucose 6 phosphate
- hexokinase (glucose to G6P)
- events that increase G6P tend to increase the rate of glycolysis
what is feed - back?
determined by glycolysis by-products
most associated with phosphofructokinase (PfK)
most important regulatroy enzyme as it can speed up or slow down glycolysis
an exothermic reaction should be what?
negative
-7.3kcal
what are the several areas of glycolysis control?
PFK – Energy Charge – Thermodynamic – Lactate Removal – Pyruvate Removal – Redox State (NADH/NAD+ ) – Glycogenolysis
why is PFK important?
it is a key regulatory enzyme of glycolysis
it helps convert fructose 6 phosphate to fructose 1, 6-diphosphate
how is PFK stimulated?
ADP, Pi, AMP, decreasing pH, NH4+
these are the ATP pre-cursors which means our body recognises to generate more ATP
what can PFK be inhibited by?
ATP, PCr, and citrate (krebs cycle intermediate)
what is the energy charge in the cell?
it is the ratio between AMP, ATP & ADP in the cell.
how do you work out the energy charge?
there is a large equation but the closer the number is to 1, it has more ATP, if it is at 1, there is only ATP, if it is at 0, then it is all AMP. Usually resides around 0.8
what are the three steps in glycolysis involving exothermic reactions?
hexokinase
PFK
Pyruvate kinase
what does the conversion of pyruvate to acetyl coa result in?
the production of NADH
what is the redox state?
refers to the ratio of NADH to NAD+ in cytosol
NADH/NAD+
whata re the two processes that create NAD+
lactate production
aerobic metabolism
what are the changes in redox?
↑NADH/↓NAD+ = Increased redox and slower glycolysis ↓NADH/↑NAD+ = Decreased redox and faster glycolysis
what is the enzyme in control of glycogen?
phosphorylase
what does phosphorylase control by?
Pi - high levels of Pi stimulate glycogen breakdown
Ca2+ released during muscle contraction can increase glycogen breakdown
