Respiratory system Flashcards
4 types of catabolic reactions
- production of ATP
- muscle contraction
- reducing equivalents
- biosynthetic precursors
2 types of anabolic reactions
- storage of energy
- production of macromolecules
Gibbs free energy of a reaction
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What R and T under standard conditions?
T - 310.15K
R - 8.314 J K-1 mol-1
How much energy is released on decomposition of ATP?
30.5 KJ mol-1
How much energy is released on decomposition of ADP?
45.6 KJ mol-1
Higher energy compounds can be
used to make ATP
Lower energy compounds can be
activated by ATP
How are the rings of sugars closed?
Addition of H to make alcohol on both ends, hemiacetyl, reversible reaction
What is a six membered ring called?
Pyranose
What is a five membered ring called
furanose
5 important things about glycogen
- the main storage polysaccharide in mammals
- composed entirely of glucose, with 1-4 and 1-6 bonds
How is glucose transported into cells?
- transport is mediated by a number of glucose transporters
GLUT 1&3
mediates basal glucose uptake and found in all cell types
GLUT 2
- Liver - takes up glucose to store as glycogen
- Pancreas - uptake triggers secretion of insulin, increases GLUT 4 in well-fed state
GLUT 4
Found in muscle and adipose tissue
GLUT 5
Transports dietary fructose from small intestine, which can be converted to glucose
What is glycolysis?
- 10 steps in 3 stages
1. activation and rearrangement
2. splitting and phosphorylated C3 sugars
3. conversion of C3 sugars into pyruvate - Takes place in cytosol
What is the yield of glycolysis?
2 x pyruvate
2 x ATP
2 x NADH
Summarise stage one of glycolysis
- 2 x ATP used to activate and form 2 x C3 sugars
- phosphorylation causes ring opening
Summarise stage two of glycolysis
- Aldolase breaks fructose-1,6-bisphosphate into dihydroxyacetone phosphate and glyceraldehyde-3-phosphate;
- Triose phosphate isomerase catalyses enol/keto tautomerisation.
Summarise stage three of glycolysis
Each step is repeated twice as two molecules
Products for stage 3 are 2 x NADH and 4 x ATP
What is anaerobic respiration?
- Without oxygen, pyruvate is reduced to R/D-lactate
- This oxidises NADH to NAD+ and allows glycolysis to continue;
What is the cori cycle?
- Recycles R-lactate to glucose;
- Lactate goes from muscle to liver, converts R-lactate to pyruvate
- Requires 6 x ATP per glucose molecule - 2 x ATP molecules from glycolysis.
What is gluconeogenesis?
- Occurs mostly in the liver
- 2 x pyruvates for each glucose
- 2 x ATP and 1 x NADH also required
What is the structure of mitochondria?
- Matrix contains the enzymes for the TCA cycle
- Membranes are required for electron transport system
What is the pyruvate dehydrogenase complex?
- Controls entry of pyruvate into the TCA cycle
- Pyruvate dehydrogenase (E1) â decarboxylates pyruvate
- Dihydrolipoyl transferase (E2) â makes CoA
- Dihydrolipoyl dehydrogenase (E3) â converts reduced lipoamide to disulfide
- Mammals have 30 x E1, 12 x E2 and 12 x E3
What is the pyruvate dehydrogenase complex reaction?
- TPP anion adds to pyruvate and CO2 is released
- Lipoamide disulfide is added to acetyl group and redox reaction occurs
What are the phases of the TCA cycle?
- Condensation and rearrangement (1 & 2)
- Decarboxylation (3 & 4)
- Formation of GTP using phosphate anhydride bond (5)
- Conversion of succinate to oxaloacetate (6-8)
What is amphibolic mean?
Used in catabolic and anabolic reactions
What are the products of the TCA cycle?
Acetyl-CoA is oxidised to 2 x CO2
3 x NADH and H+
1 x FADH2
1 x GTP
Summarise stage one of the TCA cycle
Citrate synthase catalyses condensation of acetyl-CoA and oxaloacetate
Hydrolysis of CoA ester makes reaction irreversible
Citrate rearranges to form isocitrate.
Summarise stage two of the TCA cycle
Isocitrate dehydrogenase uses NAD+ to produce a β-ketoacid;
β-ketoacid loses CO2
2-Oxoglutarate is converted to succinyl-CoA by a multi-enzyme complex
Summarise stage three of the TCA cycle
CoA is displaced by inorganic phosphate to produce an mixed acid anhydride
Produces ATP equivalent (GTP);
Phosphate is transferred to an active site His
Transfer of phosphate group onto GDP forms GTP
Summarise stage four of the TCA cycle
Produces reduced cosubstrates
Converts succinate into oxaloacetate in three steps
- Desaturation of C-C bond using FAD;
- Hydration of double bond. Anti-addition of H2O to obtain S-malate;
- NAD+-dependent oxidation to re-form oxaloacetate.
The last step is thermodynamically unfavourable and is driven by conversion of oxaloacetate to citrate, i.e. the availability of acetyl-CoA.
What is oxidative phosphorylation?
Takes place in mitochondria
Requires O2
Two parts
- Generation of a proton gradient;
- Production of ATP
Generates most ATP 26/30
Electrons move faster/slower through
Faster through vacuum
Slower through proteins
What is the chemi-osmotic hypothesis?
ATP synthesis is coupled to the proton gradient
ATP synthesis consists of:
1) proton transport to mitochondrial inter-membrane space
2) transport of protons through inner membrane by ATP synthase
How much ATP is received from degradation of glucose?
30 ATP
5 from glycolysis
5 from pyruvate oxidation
20 from acetyl-CoC oxidation
How are glycogen 1,4 bonds made?
Allows the extension of the glycogen polymer
Lone pair of electrons on oxygen forms double bond
How are glycogen 1,6 bonds made?
Branching enzyme transfers several terminal residues in a chain to a 6-position of an internal glucose residue;
How do glycogen 1,4 bonds degrade?
Degraded by glycogen phosphorylase
How does branched glycogen degrade?
Residues are removed by glycogen phosphorylase until three 1,4 residues are left next to the 1,6-glycosidic bond;