Biological Chemistry Metabolism
-
Upload
shannon-maguire-estrada -
Category
Documents
-
view
216 -
download
0
Transcript of Biological Chemistry Metabolism
8/13/2019 Biological Chemistry Metabolism
http://slidepdf.com/reader/full/biological-chemistry-metabolism 1/37
Adenosine 5’-triphosphate(ATP)
8/13/2019 Biological Chemistry Metabolism
http://slidepdf.com/reader/full/biological-chemistry-metabolism 2/37
Metabolic Pathways
Metabolism: the sum total of all reactions that take place in aliving cell or organism
Metabolic pathway: sequence of enzymatic reactions in which the product of one reaction is the substrate for the
next
8/13/2019 Biological Chemistry Metabolism
http://slidepdf.com/reader/full/biological-chemistry-metabolism 3/37
Metabolism Metabolism is generally divided into 2 parts:
Catabolism: larger compounds are broken into smallercompounds; this process usually generates energy (ATPis generated)
Anabolism: larger compounds are synthesized fromsmaller ones; this process usually requires energy (ATPis hydrolyzed)
Compounds that are used, directly or indirectly, to releaseenergy (also called activated carrier molecules) are centralto metabolism and include: ATP, GTP, NAD+, NADP+, FAD,acetyl-CoA
8/13/2019 Biological Chemistry Metabolism
http://slidepdf.com/reader/full/biological-chemistry-metabolism 4/37
Metabolism: the Usual Suspects
8/13/2019 Biological Chemistry Metabolism
http://slidepdf.com/reader/full/biological-chemistry-metabolism 5/37
Metabolism: the Usual Suspects II
8/13/2019 Biological Chemistry Metabolism
http://slidepdf.com/reader/full/biological-chemistry-metabolism 6/37
The Eukaryotic Cell
8/13/2019 Biological Chemistry Metabolism
http://slidepdf.com/reader/full/biological-chemistry-metabolism 7/37
Catabolism
Most catabolic pathways occur in a sausage-shapedorganelle enclosed by 2 separate membranes called themitochondrion: citric acid cycle, electron transport chain, fattyacid oxidation, amino acid catabolism, oxidativephosphorylation
Only glycolysis takes place in the cytoplasm of the cell
8/13/2019 Biological Chemistry Metabolism
http://slidepdf.com/reader/full/biological-chemistry-metabolism 8/37
8/13/2019 Biological Chemistry Metabolism
http://slidepdf.com/reader/full/biological-chemistry-metabolism 9/37
Catabolism I: Digestion
When food is ingested the first stage of catabolism is todigest it, or to break the large biopolymers into theirrespective monomer units
This occurs primarily in the stomach and intestinesthrough both hydrolytic and enzymatic processes
8/13/2019 Biological Chemistry Metabolism
http://slidepdf.com/reader/full/biological-chemistry-metabolism 10/37
8/13/2019 Biological Chemistry Metabolism
http://slidepdf.com/reader/full/biological-chemistry-metabolism 11/37
8/13/2019 Biological Chemistry Metabolism
http://slidepdf.com/reader/full/biological-chemistry-metabolism 12/37
8/13/2019 Biological Chemistry Metabolism
http://slidepdf.com/reader/full/biological-chemistry-metabolism 13/37
ΔG and Coupled Reactions
Recall for a reaction to be spontaneous ΔG< 0 Coupled reactions: nonspontaneous reactions (ΔG>0) can
be made to occur if coupled with a spontaneous reaction sothat the total ΔG (both steps) < 0
Fructose 6-phosphate + Pi fructose 1,6-bisphosphate + H2OΔG= 3.9 kcal
ATP + H2O ADP + Pi ΔG= -7.3 kcal
•Is the conversion of F-6-P into F-1,6-bP spontaneous ornonspontaneous in absence of ATP?
• Write the net coupled reaction and calculate the net ΔG for the
overall reaction.
8/13/2019 Biological Chemistry Metabolism
http://slidepdf.com/reader/full/biological-chemistry-metabolism 14/37
8/13/2019 Biological Chemistry Metabolism
http://slidepdf.com/reader/full/biological-chemistry-metabolism 15/37
Multiple Paths for Pyruvate I
In yeast, pyruvate undergoes alcoholic fermentation is firstsplit into acetaldehyde and CO2, followed by the reductionof acetaldehyde to ethanol
The reduction of acetaldehyde occurs with concomitant
oxidation of NADH to produce NAD+ to go back intoglycolysis
8/13/2019 Biological Chemistry Metabolism
http://slidepdf.com/reader/full/biological-chemistry-metabolism 16/37
8/13/2019 Biological Chemistry Metabolism
http://slidepdf.com/reader/full/biological-chemistry-metabolism 17/37
Multiple Paths for Pyruvate III
In humans, when oxygen is sufficient (aerobic conditions)pyruvate is converted into acetyl-CoA, ready for the firststep in the CAC
This occurs in the mitochondria where CAC will begin
8/13/2019 Biological Chemistry Metabolism
http://slidepdf.com/reader/full/biological-chemistry-metabolism 18/37
Gluconeogenesis
Gluconeogenesis: a linear anabolic pathway in whichglucose is synthesized from noncarbohydrate sources i.e.glycerol, lactate, and amino acids
This cycle goes into effect during periods of fasting or early
starvation when diet glucose and glycogen have beendepleted
This cycle is necessary for the protection of brain cells whose sole source of energy is glucose
This cycle converts small non-carbohydrate molecules intoglucose in a cycle resembling the reverse of glycolysis
8/13/2019 Biological Chemistry Metabolism
http://slidepdf.com/reader/full/biological-chemistry-metabolism 19/37
Occurs primarily in the liverand to some extent in thekidneys
8/13/2019 Biological Chemistry Metabolism
http://slidepdf.com/reader/full/biological-chemistry-metabolism 20/37
Glycogen Metabolism
Glycogen is a highly branched homopolymer of glucose[α(14) and α(16)] that is an immediately available formof glucose between meals and during activity
The main glycogen stores are in the liver and skeletalmuscle
Glycogenolysis Glycogenesis
8/13/2019 Biological Chemistry Metabolism
http://slidepdf.com/reader/full/biological-chemistry-metabolism 21/37
Glycogenolysis Reaction
n residues
8/13/2019 Biological Chemistry Metabolism
http://slidepdf.com/reader/full/biological-chemistry-metabolism 22/37
Glycogenesis Reaction
8/13/2019 Biological Chemistry Metabolism
http://slidepdf.com/reader/full/biological-chemistry-metabolism 23/37
Covalent Modification
Many enzymes including those involved in glycogenmetabolism are controlled through reversiblephosphorylation
Glycogen synthesis is closely coordinated with itsdegradation, thus when glycogen phosphorylase is on,glycogen synthase is off and vice versa
Phosphorylase b phosphorylase a(usually inactive) (active)
8/13/2019 Biological Chemistry Metabolism
http://slidepdf.com/reader/full/biological-chemistry-metabolism 24/37
Citric Acid Cycle
Glycolysis yields 2 ATP, 2 NADH, and 2 pyruvate
Pyruvate can be converted into acetyl-CoA and be furthercatabolized by the Citric Acid Cycle
CAC is a circular cycle that takes place in the mitochondriaand yields: 3 NADH, 1 FADH2, and 1 GTP
Net Reaction:
Acetyl-CoA + 3 NAD+
+ FAD + GDP + Pi 2CO2 + CoA + 3 NADH + FADH2 + GTP ΔG= -11 kcal
8/13/2019 Biological Chemistry Metabolism
http://slidepdf.com/reader/full/biological-chemistry-metabolism 25/37
8/13/2019 Biological Chemistry Metabolism
http://slidepdf.com/reader/full/biological-chemistry-metabolism 26/37
From 1 Glucose…
For a total of: 4 ATP, 10 NADH, 2 FADH2
El t T t Ch i d O id ti
8/13/2019 Biological Chemistry Metabolism
http://slidepdf.com/reader/full/biological-chemistry-metabolism 27/37
Electron Transport Chain and Oxidative
Phosphorylation: Aerobic Respiration The ETC is a group of proteins embedded in the inner
mitochondrial membrane ETC/OP use the electrons from NADH and FADH2 to
ultimately generate the majority of the ATP in an organism
On Average:1 NADH= 2.5 ATP1 FADH2= 1.5 ATP
8/13/2019 Biological Chemistry Metabolism
http://slidepdf.com/reader/full/biological-chemistry-metabolism 28/37
8/13/2019 Biological Chemistry Metabolism
http://slidepdf.com/reader/full/biological-chemistry-metabolism 29/37
Shuttle Systems
The 2 NADH generated
by glycolysis in the
cytoplasm cannot enter
ETC directly b/c theycannot cross the inner
mitochondrial
Membrane
They must enterindirectly through 1 of 2
shuttle systems
8/13/2019 Biological Chemistry Metabolism
http://slidepdf.com/reader/full/biological-chemistry-metabolism 30/37
8/13/2019 Biological Chemistry Metabolism
http://slidepdf.com/reader/full/biological-chemistry-metabolism 31/37
Lipid Metabolism Triglycerides are concentrated stores of metabolic energy
When hydrolyzed, triglycerides form 3 fatty acids and 1molecule of glycerol
glycerol
Dihydroyacetoneglycolysis
8/13/2019 Biological Chemistry Metabolism
http://slidepdf.com/reader/full/biological-chemistry-metabolism 32/37
Fatty Acid Catabolism
β-oxidation
A Spiral Cycle
Each turn of the cycle produces: 1 NADH, 1 FADH2, and acetyl-CoA
8/13/2019 Biological Chemistry Metabolism
http://slidepdf.com/reader/full/biological-chemistry-metabolism 33/37
8/13/2019 Biological Chemistry Metabolism
http://slidepdf.com/reader/full/biological-chemistry-metabolism 34/37
Problem1. Beginning with hexanoic acid, how many passes
through the oxidation spiral will take place?2. From your answer to part a, what is the net change in
NADH, FADH2, acetyl-CoA, and ATP, when onlyactivation and the passes through the oxidation spiral
are considered?3. From the answer to the previous questions, what will be
the total yield of ATP once all of the acetyl-CoA hasmoved through the citric acid cycle and all of thereduced coenzymes produced (including those from thecitric acid cycle) have been used for electron transportand oxidative phosphorylation?
4. How does the total yield of ATP obtainable from onehexanoic acid molecule compare with that from one
glucose molecule?
8/13/2019 Biological Chemistry Metabolism
http://slidepdf.com/reader/full/biological-chemistry-metabolism 35/37
Ketone Bodies
During fasting or uncontrolled diabetes, acetyl-CoA buildsup b/c there is limited oxaloacetate for it to condense within the step 1 of the citric acid cycle (oxaloacetate will beused in gluconeogenesis to synthesize glucose)
Excess acetyl-CoA is therefore used to generate 3compounds known as ketone bodies: acetoacetate, 3-hydroxybutyrate, and acetone
Acetoacetate is a major fuel source in some cells (heart and
renal cortex) and under starvation conditions, brain cellsderive 75% of their energy from it
8/13/2019 Biological Chemistry Metabolism
http://slidepdf.com/reader/full/biological-chemistry-metabolism 36/37
8/13/2019 Biological Chemistry Metabolism
http://slidepdf.com/reader/full/biological-chemistry-metabolism 37/37
Congratulations…The End!