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Metabolism
All  living  things  require  energy

Metabolism


Metabolism  is  the  process  through  which  
living  systems  acquire  and  use  free  energy  
to  carry  out  functions

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Metabolism
Metabolism  performs  4  functions:
1
...
  Convert  nutrients  into  macromolecules
3
...
  Degrade  macromolecules  as  required  for  
biological  function

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Metabolism  

Definitions

Metabolism: network  of  chemical  reactions  carried  out  by  
living  cells  –  two  phases  catabolism  &  
anabolism
Metabolite: ‘small’  molecules  that  are  intermediates  in  the  
degradation  and  biosynthesis  of  more  complex  
molecules
Catabolism: Degrade  molecules  to  yield  smaller  molecules  
and  energy
Anabolism: Synthesis  of  more  complex  molecules  from  
simpler  molecules  –  requires  energy
Pathway:

A  series  of  connected  chemical  reactions  e
...
-­‐‑
                                   Aà  Bà  Cà  …  Z

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Energy  Relationship  Between  
Catabolism  and  Anabolism

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Biomolecules
Biomolecules  are  largely  composed  of  
carbon,  hydrogen,  oxygen  and  nitrogen
...
 Energy  and  Carbon
Autotrophs  –  Self  feeding
...
 These  are  self  sufficient  cells  
that  utilize  CO2  from  the  atmosphere  as  the  
carbon  source

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I
...
 Energy  and  Carbon
Heterotrophs  –  Feeding  on  others
v Heterotrophs  obtain  energy  by  oxidation  
of  organic  compounds  (carbohydrates,  
lipids,  or  proteins)
v Heterotrophs  obtain  carbon  from  glucose,  
proteins  and  lipids
...
 Energy  and  Carbon
Plant  cells  are  two  types:

1
...
 heterotrophic  –  root  
cells  

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II
...
 They  
used  oxygen  to  oxidize  organic  nutrients

Anaerobes  –  live  in  the  absence  of  oxygen
...
 Oxygen  
Obligate  anaerobes  –  are  poisoned  by  
oxygen

Facultative  –  some  organisms  can  life  in  
either  aerobic  or  anaerobic  conditions
...
g
...
 coli

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III
...
 Most  
animals  obtain  nitrogen  from  amino  acids
...
 Nitrogen
N2  

v   Major  gas  component  of  our  atmosphere  (80%)
...

v All  living  organism  depends  on  these  N2  fixing  
microbs  [cyanobacteria  &  blue-­‐‑green  algae]
v Many  N2  fixing  bacteria  lives  in  soil,  some  lives  
symbiotically  in  the  nodules  of  the  roots  of  
plants
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III
...


The  substrates  of  these  enzymes  –  
metabolites

Metabolic  pathway  –  sequence  of  chemical  
reactions  in  which  each  reaction  is  catalyzed  
by  a  specific  enzyme,  and  the  product  of  one  
reaction  is  the  substrate  for  the  next
...
 

The  catabolic  pathways  and  anabolic  
pathways
...

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Metabolic  Pathway
Catabolic  pathways  lead  to  the  disassembly  
of  complex  molecules  to  form  simpler  
products
...
  Make  available  raw  materials  which  
other  molecules  can  synthesized
2
...


Anabolic  pathways  are  energy-­‐‑requiring  
and  utilize  chemical  energy  released  by  the  
exergonic  catabolic  pathways
...
 
The  degradation  of  NADP+  à  NADPH  or  by  
coupling  exergonic  reactions  to  synthesize  ATP

Anabolism
Complex  biomolecules  are  synthesized  from  
simple  precursor
...
 This  
process  requires  the  free  energy  of  ATP  hydrolysis,  
ATPàADP  +  Pi  or  NADHàNAD+
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Metabolic  Pathway
Glycolysis

A  catabolic  pathway  for  the  breakdown  of  glucose  or  fructose  to  
pyruvate,  producing  ATP,  NADH  and  smaller  3-­‐‑carbon  building  
blocks


Tricarboxylic  acid  (TCA)  cycle

Amphibolic  pathway,  for  oxidation  of  acetyl  groups  (e
...
 from  
glycolysis  or  the  oxidation  of  fahy  acids)  to  CO2,  producing  
NADH,  FADH2  &  ATP


Oxidative  phosphorylation

A  catabolic  pathway  but  provides  ATP  to  drive  anabolic  
processes
...

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Metabolic  Pathway  
The  four  principles

1
...
 
Consequently  if  two  metabolites  
are  interconvertible,  the  
pathway  from  the  first  to  the  
second  must  be  different  that  
the  pathway  of  the  second  back  
to  the  first
...
  Every  metabolic  pathway  has  a  first  
commited  step
Most  of  the  reactions  in  a  metabolic  
pathway  are  close  to  equilibrium,  but  
every  pathway  has  an  irreversible  highly  
exergonic  reaction  that  commits  the  
intermediate  it  produces  to  continue  
down  the  pathway

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The  four  principles
3
...
  Metabolic  pathway  in  eukaryotes  occur  
is  specific  cellular  locations
                       What  does  this  means???

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Eukaryotes  use  organelles  to  

compartmentalize  metabolic  
pathways  allowing  different  
metabolic  pathways  to  occur  in  
specific  locations
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Compartmentalized  of  Metabolic  
Pathways
Mitochondrian Citric  acid  cylcle,  oxidative  
phosphorylatio,  amino  acid  
catabolism
Cytosol
Glycolisis,  pentose  phosphate  
pathway,  fahy  acid  biosynthesis,  
gluconeogenesis
Nucleus
DNA  replication,  RNA  transcription,  
RNA  processing
Lysosomes
Enzymatic  digestion  of  cellular  
components
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Compartmentalized  of  Metabolic  
Pathways
Golgi  Apparatus Post  translational  modification  of  
membrane  and  secretory  proteins,  
formation  of  plasma  membranes  and  
secretory  vesicles
Rough  
Endoplasmic  
Reticulum

Synthesis  of  membrane-­‐‑bound  and  
secretory  proteins

Smooth  
Endoplasmic  
Reticulum

Lipid  and  steroid  biosynthesis


Perixosomes

Oxidative  reactions  invoving  amino  acid  
oxidases  and  catalase,  glyoxylate  cycle  
reactions  in  plants

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What  about  multicellular  
organisms???

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In  multicellular  organisms  
compartmentation  is  carried  a  step  
further  to  the  level  of  tissues  and  organs
...
g

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