Lecture #20-Intro to Metabolism-29 (2019)...
Transcript of Lecture #20-Intro to Metabolism-29 (2019)...
CH2210 Introduction to Metabolism Cell Structure and Function
Introduction to Metabolism Cell Structure and Function
Cells can be divided into two primary types
prokaryotes - Almost all prokaryotes are bacteria
eukaryotes - Eukaryotes include all cells of multicellular organisms, and many single-celled organisms such as the yeasts and the protists.
Introduction to Metabolism - Cell Structure and Function
Anatomy of a Typical Eukaryotic Cell
The d i f f e re nce s be t w e e n p r o k a r y o t e s a n d eukaryotes l ie in their internal organization and modes of reproduction.
In eukaryotic cells, many of the cellular macromolecules a r e p a c k a g e d i n t o o r g a n e l l e s , s u b c e l l u l a r structures surrounded by their o w n m e m b r a n e s . P r o k a r y o t e s l a c k t h i s internal organization.
Introduction to Metabolism - Cell Structure and Function
General Functions of Metabolism
Obtain energy in a chemical form by degradation of nutrients
Convert a wide variety of nutrient molecules into the central precursor molecules needed to build proteins,
carbohydrates, nucleic acids, and lipids
Synthesize cell molecules.
Modify and repair the biomolecules necessary for specific functions in specialized cells or both.
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Catabolism vs Anabolism
Catabolism Biochemical Degradation of Energy-Containing Compounds
1 Capture of the Energy in New Chemical Forms
(ATP, GTP, NADH, NADPH, FADH2) 2
Conversion of Energy-Containing Compounds into a small number of simple molecules
(Pyruvate, Acetate, Krebs Cycle Intermediates)
Catabolism vs Anabolism
Anabolism
Synthesis and Repair of Biomolecules 1
Glucose → Other Monosaccharides and Polysaccharides 2
Acetate → Fatty Acids 3
Glycerol + Fatty Acids → Triglycerides 4
Lipids + Polar Components → Cell Membranes 5
Amino acids → Proteins, Hormones, Neurotransmitters 6
Nucleotides → ATP, Coenzymes, Nucleic Acids
Transport of Substances Across Membranes
Stages of Catabolism for Energy Production
Nutrient molecules are degraded to lower-molecular mass components.
The products of stage 1 are converted into one simple molecule: Accetyl-S-Coenzyme A (Acetyl-S-CoA).
Acetyl-S-coenzyme A is oxidized to CO2 and H2O by the Citric Acid Cycle.
Reduced coenzymes are oxidized through the Electron Transport Chain to yield ATP.
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Stages of Catabolism
Amino AcidsGlucoseand
Other Sugars
Fatty acids and Glycerol
Stages of Catabolism FOOD
Fats Carbohydrates ProteinsStage 1
Bulk food is digested in the stomach and
small intestine to yield small molecules.
Digestion
Stages of Catabolism
Stage 2
Small sugar, fatty acid, and amino acid
molecules are degraded in cells to yield
Acetyl-CoA.
Glycolysis β-Oxidation Pathway
Amino AcidCatabolism
Amino Acids
Glucoseand
Other SugarsFatty acids
and Glycerol
Acetyl CoA Production
CH3 C
O
CoA
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Stages of Catabolism
Nutrients New Forms of Energy
During the second and third stages of catabolism, important “high energy” compounds are formed that fuel anabolism:
Adenosine triphosphate (ATP) Carrier of energy.
Nicotinamide adenine dinucleotide (NADH) Carrier of reducing power
Nicotinamide adenine dinucleotide phosphate (NADPH) Carrier of reducing power
Flavin adenine dinucleotide (FAD) Carrier of reducing power
Flavin adenine mononucleotide (FMN) Carrier of reducing power
Synthesis of ATP
Adenosine-O--P--P Adenosine-O--P--P--P
R--PNutrients
Substrate level phosphorylation: Direct transfer of a phosphate group from a high energy phosphate
compound to adenosine diphosphate
Synthesis of ATP
Adenosine-O--P--P Adenosine-O--P--P--P
PEnergy
High energy electrons
Oxidative phosphorylation: Direct addition of inorganic phosphate to ADP during the simultaneous oxidation of reduced
cofactors by the electron transport chain
ATP
N
NN
N
NH2
O
OHOH
HHH
CH2
H
OP
O
O
O-
P
O
O-
O-
P
O
-O
O-
Energy is used to Fuel Anabolic Processes:
Biosynthesis Active transport
Muscle contraction Transcription, translation
N
NN
N
NH2
O
OHOH
HHH
CH2
H
OP
O
O
O-
P
O
O-
O-
P
O
-O
O- ATP
N
NN
N
NH2
O
OHOH
HHH
CH2
H
OP
O
O
O-
P
O
-O
O-
ATP
ADP
AMP
PO43-
PO43-
Energy
Energy
H2O
H2O
ADP
N
NN
N
NH2
O
OHOH
HHH
CH2
H
OP
O
-O
O-
ATP
ADP
AMP
PO43-
PO43-
Energy
Energy
H2O
H2O
AMP
Utilization of ATP
N
N
N
NH2
N
O
OH
HHH
CH2
HOH
PO
O
O
O
PO
O
O
N
O
OH
H HH
H2C
HOH
C
O
NH2
H
NAD+
+ N
C
O
NH2
H H
NADH,H+
Reduction and Oxidation of Coenzymes
N
N
N
NH2
N
O
OH
HHH
CH2
HOH
PO
O
O
O
PO
O
O
CH2CCCCH2
OHOHOH
HHH
N N
N
NO
OH
N N
N
NO
OH
H
H
FADH2FAD
Forms of Hydrogen in Oxidation/Reduction Reactions
H H
H H
H H+-
hydrogen molecule
hydrogen atoms
hydrogen ionhydride ion
The carriers of energy in oxidation-reduction reactions are actually the electrons, but the
hydrogens tell us where the electrons are.
Reduction and Oxidation of Coenzymes
Certain cofactors link metabolic oxidations to metabolic reductions. These oxidations and reductions can be visualized as dehydrogenations and hydrogenations, the removal and addition of hydrogen ions and electrons.
Coenzyme(oxidized)
Coenzyme-H2(oxidized)
BH2
BA
AH2
( reduced )
Metabolic intermediates
Metabolic intermediates
Coenzyme(oxidized)
Coenzyme-H2(oxidized)
BH2
BA
AH2
Coenzyme As an oxidizing agent As a reducing agent
Nicotinamide adenine dinucleotide NAD+ NADH/H+
Nicotinamide adenine dinucleotide phosphate NADP+ NADPH/H+
Flavin adenine dinucleotide FAD FADH2
Flavin adenine mononucleotide FMN FMNH2
Reduction and Oxidation of Coenzymes
( reduced )
Metabolic intermediates
Metabolic intermediates
+ H+N
C
O
NH2
H H
NADH,H+
Reduction and Oxidation of Nicotinamide Cofactors
( H-, H+ )
N
N
N
NH2
N
O
OH
HHH
CH2
HOH
PO
O
O
O
PO
O
O
N
O
OH
H HH
H2C
HOH
C
O
NH2
H
NAD+
This reduced form is later reoxidized by passing its electrons to molecular o x y g e n t h r o u g h t h e electron transport chain in the mitochondria.
N
N
N
NH2
N
O
OH
HHH
CH2
HOH
PO
O
O
O
PO
O
O
CH2CCCCH2
OHOHOH
HHH
N N
N
NO
OH
Reduction and Oxidation of Flavin Cofactors
H H,FAD
C CH CH C
H H O
O
O
O
C CH CH C
O
O
O
O
FAD FADH2
Succinate
Fumaratesuccinate
dehydrogenase
This reduced form is later reoxidized by passing its electrons to molecular
oxygen through the electron transport chain in the mitochondria
N N
N
NO
OH
H
H
FADH2
Stages of Catabolism
Digestion
Acetyl CoA Production
Stages of Catabolism
Citric Acid Cycle
ATP Production
2 H+ + ½ O2 H2O
NADH,H+ FADH2
electrons electrons
ATP synthase
Electron Transport System
ADP + Pi ATP
pyruvate
Acetyl CoA
glycerolderivatives
fats carbohydrates proteins
DIETARY CARBON
fatty acids monosaccharides amino acids
TCACYCLE
CO2
CO2
NADH/H+
FADH2
ATPATP
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“N”