TUT 1 Flashcards
(13 cards)
What is oxidative phosphorylation and how does it differ from substrate level phosphorylation?
- Oxidative phosphorylation is the process in which ATP is formed as a result of the transfer of electrons from NADH or FADH2 to O2 by a series of electron carriers. This process, which takes place in the inner mitochondrial membrane, is the major source of ATP in aerobic organisms (NOT A DIRECT PROCESS) –> Generates 36 ATP
- Substrate level phosphorylation: synthesis of ATP by the direct transfer of phosphate group from a substrate to a molecule of ADP (occurs in glycolysis and TCA cycle). –> ADP + P → ATP (IS A DIRECT PROCESS) –> Generates 2 ATP
What does fructose do in the human body when consumed at normal vs excess levels? How is it processed, and what disorders exist with regards to fructose metabolism?
- Fructose doesn’t go into glycolysis in normal concentrations. It is usually used for structural purposes in the body.
- Broken down in liver and turned into triglycerides
- Fructose –> Fructose-1-Phosphate –> Structural carbohydrates
- Regulates energy by promoting more pyruvate into the krebs cycle
- High fructose diet: high tryglycerides, insulin resistance(hyperinsulinemia), links to cancer, GIT issues
What does Adenylyl kinase (myokinase) do, and how is it significant in energy regulation?
Adenylyl kinase catalyses the reversible reaction:
2ADP ⇔ ATP + AMP
- Significant because it can make ATP from ADP
- Not practical in normal conditions –> emergency escape
- Adenylyl kinase will generate energy in an emergnecy
Glycogen can normally be used to increase blood glucose. Not in Muscle though. Why can Muscle glycogen not contribute to circulating blood glucose?
Muscle glycogen lacks the enzyme glucose-6-phosphate (the enzyme that catralyses glucose formation.
Therefore the glycogen cannot be turned into glucose and cannot contribute to blood glucose levels
What does the Glycerophosphate shuttle or Malate shuttle do? And what are the significant differences between these 2 shuttle systems. It may assist to draw a mitochondria while answering this question – especially in relation to why total ATP generation is different depending on the shuttle used.
The shuttles allow NADH to migrate into the inner mitchondrial membrane.
Most efficient: Malate shuttle
- Malate shuttle produces more ATP than the glycerophosphate shuttle
- 2.5 mol of ATP formed per oxygen atom consumed (present in more tissues)
Glycerophosphate shuttle
- 1.5 mol of ATP formed epr oxygen atom consumed
- Present in brain, white muscle and heart tissue
Everyone used both shuttles, certain organs use each one differently (ranges on the ATP outcome)
What is the purpose of the creatine phosphate shuttle
Creatine phosphate is a storage form of ATP
>Allows rapid transport of high energy phosphate from mitochondrial matrix into the cytosol. Feeds ADP back to ATP
What is the pentose phosphate pathway? Why is it important and what are its products used for?
Pentose phosphate pathway is a more complex pathway than glycolysis. Similarly to glycolysis, enzymes of the pathway are in the cytosol/ cytoplasm. DIFFERENCE is that the pentose phosphate pathway achieves oxidation by dehyrogenation using NADP+ not NAD+
Pathway has two phases (oxidative and non-oxidative phase)
Oxidative: -1 H20, 2NADPH, 1CO2
Non-Oxidative (reversible): Ribose-5-phosphate for DNA/RNA building (also produced in the oxidative pahse)
The two most important products from this process are the ribose-5-phosphate sugar used to make DNA and RNA,
Explain what Glutathione is structurally, what it does and how it is reformed after use. What is its relationship with the pentose phosphate pathway?
Glutathione: antioxidant that helps make proteins in the body
>Glutathione is a tripeptide comprised of three amino acids (cysteine, glutamic acid, and glycine) –> peptide bonds links Glu to Cys
Red blood cells generate a large amount of NADPH through the pentose phosphate pathway to use in the reduction of glutathione
What do Pyruvate dehydrogenase kinase and pyruvate dehydrogenase phosphatase do? Are these enzymes also regulated? If so, what affects their activity.
Pyruvate Dehydrogenase catalyses the irreversible reaction of Pyruvate –> Acetyl-Coa
PDH kinase(inactivates) and PDH Phosphatase(removes phosphates –> active form of PDH) help to regulate the amount of PDH
>If there in an excessive amount of Acetyl Coa, PDH kinase will add a phosphate to to PDH to turn it off
Pyruvate dehydrogenase is inhibited when one or more of the three following ratios are increased: ATP/ADP, NADH/NAD+ and acetyl-CoA/CoA.
Relating to the previous question, why does this system exist?
Acetyl-CoA is the major substrate for long chain-fatty acid synthesis (make acetyl-COA from fatty acids).
If you have too much Acetyl-CoA, too many ketone bodies are produced
What parts of the glycolysis pathway are different when the reverse process of gluconeogenesis is initiated. I.e. state the specific enzymes of Gluconeogenesis
Unique enzymes for gluconeogenesis
- Pyruvate carboxylase
- Phosphophenol Pyruvate carboxykinase
- Fructose 1,6-biphosphatase
- Glucose 6 phosphatase
How is Fructose 2,6 bi-phosphate formed – and what does it mean to a cell when levels of this molecule increase?
Fructose 2,6-biphosphate is formed by phosphorylation of fructose-6-phosphate with the help of the enyzme phosphofructokinase-2.
Fed State: Abundant supply of glucose, the concentration of fructose 2,6 biphosphate increases, stimulating glycolysis by activating phsophofructokinase-1 and inhibiting fructose 1,6-biphosphatase
Fasted State: Glucagon stimulations the production of cAMP, activating cAMP dependent protein kinase, which in turninactivates phosphofructokinase-2 and activates fructose 2,6-biphosphatase by phosphorylation. Hence glucneogenesis is stimulated by a decrease in the concentration of fructose 2,6-biphosphate, which inactivates phosophofructikinase-1 and relives the inhibition of fructose 1,6-biphosphatase
FYI: glycolysis occurs mainly in the muscle and brain, gluconeogensis occurs mainly in the liver
What does it mean to describe an amino acid as either glycogenic or ketogenic? Can an amino acid be both
A glucogenic amino acid is an amino acid that can be converted into glucose through gluconeogenesis
Ketogenic amino acids are converted into ketone bodies. The production of glucose from glucogenic amino acids involve these amino acids being converted to alpha keto acids and then to glucose, with both processes occuring in the liver. This mechanism predominates during catabolysis, rising as fasting and starvation increase in severity.
