Introduction to Metabolism Cell Structure and Function
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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 - Origin of Eukaryotes
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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2
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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
Biosynthesis of Molecules from Simple Components 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
Nutrient molecules are degraded to lower-molecular mass components.
The products of stage 1 are converted into one simple molecule: 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
Stages of Catabolism
Stages of Catabolism
Stages of Catabolism
Stages of Catabolism Acetyl-CoA
Citric Acid Cycle
ATP Production
Stages of Catabolism
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2
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2
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4
Stages of Catabolism
Nutrients New Forms of Energy
During the second and third stages of catabolism, important 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
NAD(P) +
ATP
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
ADP
AMP
PO43-
PO43-
Energy
Energy
H2O
H2O
Energy is used to Fuel Anabolic Processes: Biosynthesis Active transport Muscle contraction Transcription, translation
Use of ATP
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 are better described 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
Reduction and Oxidation of Nicotinamide Cofactors
+ H +
NAD+ serves as an oxidant by accepting a hydride ion (H:-) from a reductant to form NADH.
NAD+
NADH/H+
H:- , H+
H+
H
This reduced form is later reoxidized by passing its electrons to molecular oxygen through the electron transport chain in the mitochondria.
+ H+
Reduction and Oxidation of Nicotinamide Cofactors
NAD+ serves as an oxidant by accepting a hydride ion (H:-) and a H+ from a reductant to form NADH.
This reduced form is later reoxidized by passing its electrons to m o l e c u l a r o x y g e n through the electron transport chain in the mitochondria.
Reduction and Oxidation of Flavin Cofactors
FADH2
--
OHCH2
FAD
H H,
FAD serves as an oxidant by accepting two hydrogen atoms from a reductant to form FADH2.
This reduced form is later reoxidized by passing its electrons to molecular oxygen through the electron transport chain in the
mitochondria
H H,
Reduction and Oxidation of Flavin Cofactors
FAD serves as an oxidant by accepting two hydrogen atoms from a reductant to form FADH2.
This reduced form is later reoxidized by passing its
electrons to molecular oxygen through the electron
transport chain in the mitochondria
C CH CH C
H H O
O
O
O
C CH CH C
O
O
O
O
FAD FADH2
Succinate
Fumaratesuccinate
dehydrogenase
The Electron Transport System
pyruvate
Acetyl CoA
glycerolderivatives
fats carbohydrates proteins
DIETARY CARBON
fatty acids monosaccharides amino acids
TCA CYCLE
CO2
CO2
NADH/H+
FADH2
ATP
ATP
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