Integration of Metabolism Flashcards
What is the link between Pyruvate/TCA cycle intermediates and amino acids?
Pyruvate and the TCA cycle intermediates can be converted into amino acids and vice versa.
What glycolysis product (not pyruvate) can be used to form nucleotides and how?
Glucose-6-phosphate via the pentose phosphate pathway.
The pentose phosphate pathway generates a lot of what?
NADPH needed for anabolic pathways (e.g. cholesterol synthesis).
Describe the metabolic requirements of the brain.
Requires a continuous supply of glucose.
It cannot metabolize anything but glucose though it can use ketone bodies as a partial substitute.
What can hypoglycaemia result in?
Faintness and coma.
What can hyperglycaemia result in (in the brain)?
Irreversible damage.
Although only making up 2% of total body weight, what percentage of the body’s metabolism is due to the brain and nervous tissue?
20%
Describe the metabolic requirements of skeletal muscles.
It can use fat and carbohydrates mainly but can also use ketone bodies.
ATP requirements vary depending on the exercise undertaken.
For light contractions, how are skeletal muscle energy requirements met?
Oxidative phosphorylation, using glucose and other substrates as fuels.
Why do muscles need ATP?
For muscle actomyosin ATPase and cation balance.
How do muscles meet increased demands for glucose?
An increase in the number of glucose transporters on the membranes of muscle cells.
How does adrenalin help muscles meet the demands for ATP?
Increases the rate of glycolysis in muscle, increases the rate of gluconeogenesis by the liver, increases the release of fatty acids from adipocytes.
For vigorous contractions, how are skeletal muscle energy requirements met?
O2 becomes a limiting factor leading to the abandoning of the TCA cycle/OP and instead lactate is formed and sent to the liver.
Glycogen is also broken down as glucose supply can no longer meet demands.
What is the breakdown of glycogen known as?
Glycogenolysis.
What does the liver do to pyruvate?
Pyruvate is converted to lactate by LDH (lactate dehydrogenase) and can be later used to generate glucose via gluconeogenesis.
Describe the metabolic requirements of the heart.
The heart must constantly beat and so is very flexible with the types of energy sources it can use (fats, ketones, carbohydrates).
It is especially designed for aerobic metabolism and so is rich in mitochondria.
What happens when the heart receives a lack of oxygen?
Unlike other cells, anaerobic conditions are particularly devastating. It results in cell death and myocardial infarction which is made worse by the fact that most heart cells do not grow back.
Describe the metabolic features of the liver.
Highly metabolically active and undertakes a wide repertoire of metabolic processes.
It can interconvert nutrient types.
Mainly uses fatty acids for energy but can use glucose. too.
Cannot use ketone bodies for energy.
Plays a central role in maintaining blood glucose.
Involved in lipoprotein metabolism and transport of triglycerides and cholesterol.
What happens to excess glucose-6-phosphate in the liver?
Used to generate glycogen.
Deamination of all 20 amino acids gives rise to how many molecules?
Seven.
What are the molecules formed from the deamination of amino acids?
Pyruvate Acetyl CoA Acetoacetyl CoA Alpha-ketoglutarate Fumarate Oxaloacetate Succinyl CoA (Acronym: Proteins And Amino Acids Follow Our Sugars)
What are glucogenic amino acids?
Amino acids whose skeletons can give rise to glucose via gluconeogenesis.
What are ketogenic amino acids?
Amino acids whose skeletons cannot enter gluconeogenesis but can be used to synthesis fatty acids and ketone bodies.
What are triglycerides broken into?
Fatty acids and glycerol.
What is glycerol converted to before entering the gluconeogenic pathway?
DHAP
Why can’t fatty acids be converted into glucose?
Fatty acids end up as acetyl CoA through beta-oxidation (2 carbons). It combines with pre-existing oxaloacetate to form citrate and as the cycle progresses it loses two carbon atoms as CO2 before re-forming oxaloacetate. This regenerates the oxaloacetate we used at the start and the loss of the CO2 in the cycle means there is no net gain of carbon and so no net synthesis of oxaloacetate or pyruvate is possible from acetyl CoA.
