Lecture 16 Flashcards
metabolic pathways
series of chemical rxns whereby the products of onercn are the substrates for the next rxn etc.. till the end product is generated
catabolism vs anabolism
cata= breakdown, release of E ana= build up, net input of E
cata/ana steps
cata= complex–> simple (ADP+ Pi —> ATP)
ana = simple –> complex (ATP —>ADP+ Pi )
catabolism order of steps
1- proteins, NA, polysac, complex lipid
2- Monomers- AA, Nuctides, Sugars, FA, glycerol
3- Metabolic intermediates- pyruvate, Acetyl-coa, CAC int
4- net output- energy+ small molecules- h2o, co2, nh3
anabolism order of steps
1- net input- energy+ small molecules- h2o, co2, nh3
2- Metabolic intermediates- pyruvate, Acetyl-coa, CAC int
3- Monomers- AA, Nuctides, Sugars, FA, glycerol
4-proteins, NA, polysac, complex lipid
Cellular respiration
is the liberation of energy through the oxidation of food.
how many oxidation states of carbon?
9
Formal charge #
the higher the ox # the more oxidizied
-1 for each bond to hydrogen
0 for each bond to carbon
+1 for each bond to O, N or S
alkane ox #
-4 –> most reduced
alcohol ox #
-2
aldehyde ox #
0
carboxylic acid ox #
+2
CO2 ox #
+4 –> most oxidized
molecules with more reduced carbons yield more energy upon oxidation
methane= most reduced= most energy
why CO2 can’t be burned–> end product
Why is ATP
the most widely used energy
currency of the cell?
• Hydrolysis yields lots of energy: – ATP + H2O ADP + Pi – ∆G0’= -30.5 kJ/mol (-7.3 kcal/mol) – Phosphoryl group has high transfer potential – Hydrolysis of ATP is favored because • Relief of charge repulsion • Resonance stabilization • Ionization and Solvation of ADP
hydrolysis of ATP
ATP4- + H2O —> ADP3- + P2-i + H+
NADH is the most widely
used electron carrier in cells
reducing power
Importance of coupling reactions:
• Problem: Virtually all synthetic reactions are
endergonic and cannot proceed as written.
(endergonic– need E to go to the right)
• Solution: Couple an endergonic reaction to an
exergonic reaction such that the overall reaction is
exergonic.
Coupling Reactions
The overall ∆G of a coupled series
of reactions = sum of the ∆G’s for the individual
reactions.
∆G of Pi + glucose —> glucose-6-P + H2O
+13.8
endergonic
∆G of ATP + H2O —> ADP + Pi
-30.5
exergonic
Coupling reactions to synthesize Glucose-6-
Phosphate from glucose and ATP
overall = ATP + glucose —> ADP + glucose-6-P
+13.8 - 30.5 = -16.7
What is Glycolysis?
• Uses Glucose:
– Corn syrup, sucrose, starch, glycogen
– Primary source of energy for the brain
– Fuels quick bursts of activity in muscle
• 10 reactions
• Takes place in the cytoplasm of a cell.
• The oxidation of glucose to pyruvate, NADH
and ATP.
Source of energy during a sprint:
- Pre-existing ATP
- Phosphocreatine via creatine
kinase - Glucose via glycolysis
- Glucose via glycolysis and
respiration
Creatine Kinase
PCr + ADP Cr + ATP
Glucose gets into cells via glucose transporters
Facilitated Diffusion
GLUT 1
ubiquitous– high affinity for glucose
GLUT 2
liver and pancreatic β-cells – low affinity, high
capacity for glucose, These organs need to “sense” glucose levels.
GLUT4
skeletal muscle and fat, responsive to insulin
Glucose + 2 Pi + 2 ADP + 2 NAD+ —–>
2 pyruvates + 2 ATP + 2 NADH + 2 H+ + 2 H2O
Hexokinase
first step in Glycolysis— Hexokinase activates glucose and keeps it in the cell.
Types of hexokinases
Types I and II: brain, skeletal muscle, fat. High affinity for glucose
Type IV: “Glucokinase” in liver and pancreas. Theses organs need to “sense” glucose levels. Low affinity for glucose
“Induced Fit” mechanism
The binding of glucose to Hexokinase induces a conformational change that helps the glucose bind and facilitates phosphorylation of the glucose.
glycolysis
1st step in the catabolism of carbs- glucose broken down -> 2 pyruvate
net prod of ATP and red of 2 NAD+ to NADH
citric acid cycle
takes place in the mitochondrial matrix–
oxidation of acetyl units to CO2 w/ prod of red equiv and ATP
