VL 2 (Petra Wendler) Flashcards
Name the three Steps of energy extraction.
1. Step : digestion of
- fat –> fatty acids and glycerin
- Polysaccheride –> Glucose and diffrent Sugars
- Proteins –> amino acid
2. Step: Production of Acetyl-CoA
3.Step: complete oxidation of Acetyl-group to Co2
Acetyl-Coa –> Krebs cycle –8e—> oxidative phosphorylierung –> ATP
Explain catabolism and anabolism
Catabolism:
- breakdown of complex molecules into simpler substances, to release energy and provide building blocks for anabolism.
- Key Processes: Glycolysis, Krebs Cycle, Fatty Acid Oxidation, Protein Degradation.
(Example: Digesting food to produce energy)
Anabolism:
- synthesis of complex molecules from simpler substances, to build and maintain structures in cells and tissues.
- Key Processes: Protein Synthesis, DNA Replication, Photosynthesis, Cell Division.
(Example: Creating new proteins or forming glucose in photosynthesis)
What is the diffrence between phototrophic organisms and chemotrophic organisms?
Phototrophic organisms: get energy from sunlight
Chemotrophic organisms: get energy through oxidation of nutrients
Properties of metabolic reactions:
- Many metabolic reactions are near-equilibrium reactions (ΔG ≈ 0).
- Irreversible metabolic reactions take place far away from equilibrium (ΔG «_space;0).
- Enzymes accelerate adjustment of the equilibration without changing its position.
Thermodynamik pricipal in metabolism
- Many metabolic reactions are near-equilibrium reactions (ΔG ≈ 0).
- Irreversible metabolic reactions take place far away from equilibrium (ΔG «_space;0).
- Enzymes accelerate adjustment of the equilibration without changing its position.
Properties of metabolic pathways:
1. Metabolic pathways consist of sever
Gibbs free Energy
- Gibbs free energy is determined by concentration of reaction partners
What is an exergonic and endergonic reaction?
exergonic: If ΔG < 0, direction of reaction is A + B → C + D (right)
–> concentration of reaction partners > 1 ([A][B] < [C][D])
endergonic: If ΔG > 0, direction of reaction is C + D → A + B (order increases) (left)
–> concentration of reaction partners < 1 ([A][B]> [C][D])
equilibrium: If ΔG = 0, the reaction is in equilibrium
–> concentration of reaction partners = 1 ([A][B]= [C][D])
How is the high phosphorylation potential of ATP achieved?
- Resonance stabilization of ADP and Pi
- Electrostatic repulsion of the 4 negative charges at ATP
- Stabilisation through hydration of ADP and Pi
- Gain in entropy
ATP + H20 <–> ADP + Pi
ΔG0‘ = -30,6 kJ/mol
Wjat is the active carrier of C2-Fragments?
Coenzyme A
Acetyl-CoA + H2O Acetat <–> CoA + H+
ΔG0‘ = -31,4 kJ/mol
Unlike oxygen esters, thioesters are not stabiliized by resonance structures
–> high acetyl group transfer potential
Activated electron carrier for oxidation?
NAD+ Nicotinamideadeninedinucleotide
What is the actrivated electron carrier for oxidation?
FAD Flavineadeninedinucleotide
What is the activated electron carrier for reductive biosynthesis?
NADPH Nicotineamideadeninedinucleotidephosphat
Carrier molecules in metabolism
- In the absence of catalysts, carriers are kinetically very stable.
This allows enzymes to control the flow of free energy. - The exchange of activated groups is carried out by a small set of carrier molecules in metabolism.
Modular construction is economical and elegant. - Many carriers are based on watersoluble vitamins:
* FADH and FMN: Vitamin B2 (Riboflavin)
* NADH, NADPH: Vitamin B3 (Niacin)
* Coenzyme A: Vitamin B5 (Pantothenate) - NAD+/NADH+: in catabolic processes; NADP+/NADPH+: in anabolic processes
- ATP, NADH, CoA, FAD all contain an ADP
Glykolysis
- Glucose –> Hexokinase
- Glucose 6-phosphate –> Phosphohexose isomerase
- Fructose 6-phosphate –> Phospho fructokinase-1
- Fructose 1,6-bisposphate –> Aldolase
- Glyceraldehyd 3-phosphate + Dihydroxyacetone phosphate –> Triose phosphate isomerase
- Glyceraldehyd 3-phosphate –> Glyceraldehye 3-phosphate dehydrognease
- 1,3-Bisphosphoglycerate –> Phosphoglycerate kinase
- 3-phosphoglycerate –> Phosphoglycerarte mutase
- 2-Phosphoglycerate –> Enolase
- Phosphoenolpyruvat –> Pyruvate kinase
- Pyruvat
Glykolysis in general
- Thermodynamically open system: equilibrium
-
hexokinase,phosphofructokinase and pyruvate kinase have significantly negative ΔGphysiol
–> Speed-determining steps for steady state
–> Regulation of metabolic pathways at pacemaker reactions (allosteric) - Flow of intermediates is constant in steady state. Synthesis and degradation are in balance
What is Gluconeogenesis and where does it takes place?
- in liver and guts
- Formation of glucose from non carbohydrates (lactate, amino acids, glycerol) via pyruvate to keep blood sugar levels constant
- Relevant in periods of hunger
- The organism can not produce glucose from acetyl-co !!!
- Exergonic reactions of glycolysis are bypassed by other reactions
- Gluconeogenesis requires 3 cell compartments: cytosol, mitochondria, ER
- The path from pyruvate to glucose costs more energy than the pathway from glucose to pyruvate supplies
Glucolysis vs. Gluconeogensis
Glycolysis:
Glc + 2NAD+ + 2 ADP + 2Pi →
2 Pyruvate + 2 NADH + 2H+ + 2ATP + 2H2O
Glycolysis produces two molecules of pyruvate from one molecule of glucose, producing 2 ATP and 2 NADH.
Glyconeogenesis:
2 Pyruvate + 2 NADH + 4ATP + 2GTP + 6H2O → Glucose + 2NAD+ + 2H+ + 4ADP + 2GDP + 6Pi
Gluconeogenesis produces one molecule of glucose from two molecules of pyruvate, consuming two NADH, 4ATP and 2GTP. It is not just the reverse of glycolysis
What happens with Pyruvate?
- Pyruvate needs to be further processed to regenerated NAD+ and maintain redox balance
- Acetaldehyd –> Ethanol
- Lactat
- Acetyl-CoA
What is the: Pentose phosphate pathway?
- Takes place in all cells; serves changing cellular needs
- Supplies riboses for DNA and RNA
- Delivers NADPH/H+ as a hydrogen transporter for anabolic processes (fatty acid
biosynthesis, peroxide poisoning, glutathione regeneration, …) - A maximum of 10% of the glucose molecules go into pentose phosphate pathway
- Divided into 2 sections
The pentose phosphate pathway provides reduction equivalents for biosyntheses as NADPH and pentoses
NADH vs. NADPH
NADH:
* is used to produce ATP in the respiratory chain
* is predominantly oxidized (NAD +) as needed in glycolysis
NADPH:
* serves for reductive biosynthesis in
- Liver: biosynthesis of cholesterol and fatty acid
- Adipose tissue: fatty acid biosynthesis
- Breast tissue: biosynthesis of milk fats
- Adrenal Bark: Biosynthesis of Steroids from Cholesterol
- Testes / ovaries: production of sex organs from cholesterol
* Protects the erythrocyte membrane and liver cells from cell toxins
* is preferably present in the reduced form (NADPH / H +)
Acetyl-CoA: interface of ATP generation
- Smallest common product of degradation of amino acids, fatty acids and carbohydrates
- takes C2-molecules into Krebs cycle
- produced in mitochondrium
What is the Pyruvate-dehydrognease complex?
- Localised in mitochondrial matrix
- Catalyses the oxidative decarboxylation of pyruvate
to acetyl-CoA - is a multi enzyme complex:
–> 3 enzymes (E1, E2, E3)
–> 5 coenzymes: - Thiaminepyrophosphate (vitamine B1),
- Liponamide,
- Coenzyme A (vitamine B5),
- FAD (vitamine B2),
- NAD+ (vitamine B3)
What is the interim balance?
2x ATP glycolysis
2x ATP citric acid cycle
2x NADH/H+ glycolysis
2x NADH/H+ pyruvate dehydrogenase
6x NADH/H+ citric acid cycle
2x FADH2 citric acid cycle
1 glucose -> 6 CO2 + 4 ATP + 10 NADH/H+ + 2 FADH2
