Catabolism and bioenergetics: how do we make ATP Flashcards
What is the energy metabolism?
The process of using carbon and oxygen to make chemical energy in the form of ATP.
What happens in the catabolic pathways?
Carbon sources are broken down.
What do we need to do to have energy in our life?
Turn energy in a usable form.
Where is the current energy in our body?
In the cell.
In a molecule called adenosine triphosphate or ATP.
Where is chemical energy?
Locked in its phosphodiester bonds.
What happens when the phosphodiester bonds break down?
The energy released can be used to drive reactions.
Biosynthesis, mechanical work, transport.
Why is ATP important?
It allows reactions to occur that otherwise would be impossible.
Provides a link between energy consuming and energy producing reactions.
How much ATP does our heart need?
6kg/day.
700 mg/one time.
Efficient at making it and not stop for breath.
What do we need to do first to turn energy into a usable form of ATP?
Break down a carbon source, lipid, polysaccharide, protein into its parts.
Feed its parts in the energy producing pathways.
What do we break down in humans?
Starch and sugars from food.
Or glycogen stored in liver –> ribose + hexose sugars –> hydrolysed into 3 carbon sugars –> converted into pyruvate.
Where does the break down of starch and sugars occur in humans?
In the cytoplasm.
How does the break down of starch and sugars in humans called?
Glycolysis = sugar breakdown.
What is the result of the conversion of 3 carbon sugars into pyruvate?
The release of 1 molecule of ATP.
How many ATP molecules does hexose sugar, like glucose produce?
2 ATPs.
What do we need in order to generate ATP efficiently and avoid generating the by product lactate?
Mitochondria for oxidative phosphorylation.
How many ATP molecules can be produced by the oxidative phosphorylation where mitochondria are involved?
38 ATPs for every glucose molecule at the start of the process.
Which organisms need the efficiency to make enough ATP for their needs?
Complex organisms.
What happens at the process of oxidative phosphorylation?
Pyruvate enters –> mitochondria –> converted into acetyl coA –> fatty acids break down through beta oxidation –> produce acetyl coA –> used by mitochondria –> Acetyl coA joins Krebs cycle.
On what does the amount of coA production depend?
On the length of carbon chain.
What happens when the Acetyl coA joins the Krebs cycle?
Oxidation is produced.
Co factors are reduced –> fed into –> electron transfer chain.
What is the function of electron transfer chain (ETC)?
It hands electrons from one complex to the next.
And it generates ATP.
Which is the final electron acceptor in the ETC?
Oxygen.
What is the function of oxygen in ETC?
It reacts with H+ –> produces water.
We rely on oxygen.
Which are the three energy sources?
Fats.
Carbohydrates in glycogen form.
Amino acids.
What is glycolysis?
The initial process of carbohydrate metabolism.
Where does glycolysis occur?
In the cytoplasm.
What molecule is really stable on its own and we need to ‘get it going’ through the metabolic pathway?
Glucose.
What is the function of glucose?
It diffuses easily out of the cell.
Needs to held in place and prevented from escaping.
What is the first step of glycolysis pathway and the total glycolysis pathway?
The phosphorylation of glucose –> glucose 6 phosphate (G6P) –> fructose 6 phosphate –> phosphorylation –> fructose 1,6, bisphosphate.
What do the phosphorylation steps use?
ATP.
What is the purpose of the phosphorylation steps in the glycolysis pathway?
They change the ATP and hormone levels to regulate them.
Example: insulin turn on glycolysis.
Glucagon turns off glycolysis.
How many ATP molecules do we use in the start of the glycolysis pathway?
2 ATPs.
How many ATP molecules do we produce at the end of glycolysis pathway?
4 ATPs.
What is the net production of ATP in glycolysis for every glycose molecule?
2.
What are the advantages of glycolysis?
It can directly generate ATP without using oxygen.
It generates NADH to make more ATP.
The rate can be increased quickly.
Is ATP generation in the absence of O2 important?
Yes.
It is very important.
If blood supply is high in body areas.
During heavy exercise: sprinting, heart attack, stroke.
When we use glucose as a metabolic fuel, without what can we break it down in the cytoplasm in glycolysis?
Without oxygen.
Is the break down of glucose without oxygen in the cytoplasm in glycolysis efficient?
No.
It generates lactic acid.
From what are enzyme kinetics altered by?
By pH changes.
Where is pyruvate made and during which process?
In mitochondria, during glycolysis.
Is the pyruvate generation in the mitochondria during glycolysis more efficient process of Krebs cycle and why?
Yes.
It oxidizes carbon metabolites each step –> phosphorylation –> produces 38 ATPs for each glucose.
Underpins all complex life.
What does determine the next step in metabolism?
Oxygen levels.
How is the next step in metabolism determined by oxygen levels?
Pyruvate is removed.
Or glycolysis stops.
What happens when fatty acid metabolism joins glycolysis pathway?
Pyruvate –> converted into –> acetyl coA in mitochondria –> combined with oxygen –> make water + CO2 in Krebs cycle –> Greater ATP synthesis.
In what form does pyruvate can be converted to in yeast and some bacteria?
To ehanol.
What happens to pyruvate in humans when no oxygen is available?
It is converted to lactate.
What is the Lactate dehydrogenase?
An important enzyme.
What is the function of Lactate dehydrogenase enzyme?
It reversibly converts pyruvate to lactate and vice versa.
On what does the function of Lactate dehydrogenase enzyme depend on?
On how much pyruvate and lactate is present.
Why is the function of Lactate dehydrogenase enzyme important?
It maintains glycolysis.
It removes final product of glycolysis.
What happens to our bodies if lactate levels build up?
We end up with local acidosis.
Causes cramps.
What must happen to lactate when oxygen becomes available again?
It needs to be ‘burned off’.
It is turned back into pyruvate by lactate dehydrogenase.
And enters mitochondria.
And enters Krebs cycle.
What is the Krebs cycle?
A pathway.
Glycolysis –> Pyruvate –> used.
Pyruvate –> generates –> NADH + FADH.
NADH +FADH –> used in ETC.
What happens in the presence of oxygen?
Pyruvate –> in mitochondria –> converted to key metabolic intermediate: acetyl coA.
Acetyl coA uses CoASH and NAD+.
Carboxyl group is removed from pyruvate –> releases CO2, NAD+ –> reduced to NADH.
Acetyl group –> transferred to co enzyme A.
In what do the products of various steps in Krebs cycle pathways be used?
In biosynthesis steps: use carbon backbone.
From what do amino acids can be made?
From alpha ketoglutaric acid + oxaloacetic acid.
From what do porphyrins can be made?
From succinate.
Where is succinate used?
For haemoglobin biosynthesis.
From what can glycose be resynthesized?
From malic acid.
What is Acetyl CoA?
A key metabolic intermediate.
Where do glycolysis and free fatty acid oxidation lead on?
On acetyl-CoA.
From what are ketone bodies made?
From acetyl co-A.
When does acetyl co-A makes ketone bodies?
When blood glucose is low.
What else can the Krebs cycle generate?
The precursors for haem biosynthesis.
Why is Acetyl co-A also a precursor of steroid hormones?
Because it is used to make cholesterol from the derived steroids.
Where does fatty acid breakdown lead to?
Acetyl coA –> feeds in TCA cycle.
To what are triacyl glycerides hydrolysed?
Glycerol + fatty acids.
What happens under tight hormonal control from insulin and other hormones when they are involved in energy balance regulation?
Triacyl glycerides are stored in the adipocytes.
How is the process of fatty acid breakdown called?
Beta oxidation.
When does beta oxidation occur?
In the mitochondria.
How does Beta oxidation start?
With an activation phase.
What does the activation phase in Beta oxidation involve?
An energizing step.
An ATP consuming reaction.
CoA –> forms acyl Co A.
With what does the energizing step in Beta oxidation similar with?
Glycolysis.
What happens in the second step of Beta oxidation?
FAD –> reduced to –> FADH2.
Double bond is inserted.
ATP is produced.
How many ATPs are made from 1 fatty acid?
1.5 ATPs.
How many ATPs are made from 2 fatty acids?
3 ATPs.
What happens in the third step of Beta oxidation?
A hydroxyl group is added.
What happens in the fourth step of Beta oxidation?
NAD is further reduced to –> NADH.
NADH –> used –> makes –> more ATP.
How many carbons are lost from the carbon chain at each turn of the pathway of Beta oxidation?
2 carbons.
What happens to the carbon chain at each turn of the beta oxidation pathway?
It gets shorter each time.
What does each cycle of the Beta oxidation pathway produces?
An acetyl coA with 3 carbons.
How many ATPs can each acetyl coA make per turn of the Krebs cycle?
10 ATPs.
What does the oxidation at each step of Beta oxidation do?
It reduces the length of carbon chain.
An it produces acetyl coA.
Acetyl coA –> enters TCA cycle.
Where does the number of acetyl co A molecules made depend on?
On the length of the fatty acid chain.
When does Beta oxidation work with fatty acids??
When the number of carbons is optimal.
What does Beta oxidation generate?
NADH + FADH2.
Where do NADH + FADH2 which are generated by Beta oxidation pathway, used?
They are used by ETC.
What do NADH + FADH2 make, when they are generated by Beta oxidation pathway and used by ETC?
They make ATP.
Where does amino acid metabolism occur?
In the cytoplasm.
How are amino acids derived?
From the break down of proteins.
Where can amino acids enter?
In the metabolic pathway.
What can amino acids do once they enter the metabolic pathway?
Converted to pyruvate.
Or Converted to acetyl coA.
Or feed into the Krebs cycle.
What does the break down of amino acids produces?
Nitrogen waste products.
As what do nitrogen waste products present in humans?
As urea, excreted as urine.
How many amino acids are turned over by a 70Kg person per day?
400g.
How can we replace our loss of nitrogen?
By ingesting essential amino acids.
What actually happens in amino acid metabolism?
Proteins from muscle or diet –> break down into –> amino acids.
Transamination moves –> amine group of amino acids.
Amine group –> catalysed by aminotransferase specific for amino acid substrate.
Amine group –> stripped off –> leave just carbon skeleton.
Carbon skeleton –> enters metabolic pathway
Example = amine group from alanine –> removed –> produces –> pyruvate.
On what does the entrance of carbon skeleton in metabolic pathway depend?
On its structure.
To what are gluconeogenic amino acids converted?
To pyruvate.
To what are ketogenic amino-acids converted?
To acetyl-CoA.
