Metabolism
Metabolism What Do You Need To Know?
•Amino Acids Side chain properties: hydrophobic/hydrophilic, pKa, functional groups •Enzyme kinetics and thermodynamics Transition state stabilization, allostery •Organic chemistry Lewis acidity/basicity, nucleophiles and electrophiles, electrons and curly arrows •Carbohydrate chemistry Simple sugars: nomenclature and structure •Cell biology The structure of cells, organelles, membranes
1
The Component Parts of Complex Organisms Perform Different Functions and have Different Requirements
2
Functional Compartmentalization is Even More Apparent at the Cellular Level
3
Overview of Metabolism
Enzyme or enzyme complex. May participate in more than one pathway
GLUCONEOGENESIS liver and kidneys
glucose
glycogen
GLYCOLYSIS cytoplasm, all cells
amino acids fats
pyruvate
acetyl-CoA
O2 aerobic
CO2
NAD+
NAD+ NADH anaerobic
TCA CYCLE II
I
lactate
H+ III
NADH
IV
H+
OXIDATIVE PHOSPHORYLATION mitochondria, all cells
4
ADP
ATP mitochondrial membrane
Metabolism • The sum of the chemical changes that convert nutrients into energy and the chemically complex products of cells • Hundreds of enzyme reactions organized into discrete pathways • Substrates are transformed to products via many specific intermediates
A Common Set of Pathways • Organisms show marked similarities in their major metabolic pathways • Evidence that all life descended from a common ancestral form • But there is significant diversity – Autotrophs use CO2 – Phototrophs use light – Heterotrophs use organic carbon – Chemotrophs use sugars, inorganics and sulfur
The Sun is Energy for Life
• Phototrophs use light to drive synthesis of organic molecules • Heterotrophs use these organic molecules as building blocks • CO2, O2, and H2O are recycled 5
Metabolism • Catabolism: degradative pathways – usually energy-yielding! • Anabolism: biosynthetic pathways – energy-requiring! • Catabolic pathways converge to a few end products • Anabolic pathways diverge to synthesize many biomolecules • Some pathways serve both in catabolism and anabolism • Such pathways are said to be amphibolic
6
Metabolic Pathways • • • • •
Pathways consist of sequential steps The enzymes may be separate Or may form a multienzyme complex Or may be a membrane-bound system New research indicates that multienzyme complexes are more common than once thought
7
3 Stages of Catabolism
8
Metabolic Regulation metabolic regulation favors different pathways for oppositely directed metabolic sequences • Anabolic & catabolic pathways involving the same product are not the same although some steps may be common to both • Some steps must be different to ensure that each pathway is spontaneous • This also allows regulation mechanisms to turn one pathway on and the other off
Redox in Metabolism • Catabolism is oxidative - substrates lose reducing equivalents, usually H- (hydride) ions • NAD+ collects electrons released in catabolism and is reduced to NADH • Anabolism is reductive - NADPH provides the reducing power (electrons) for anabolic processes
9
NADH and NAD+, NADPH and NADP+ NAD+ is an Anabolic Oxidizing Agent • • •
H- transferred to the pyrimidine nucleotide NAD+ Dehydrogenase reactions AH2 + NAD+ A + NADH + H+ eg alcohol dehydrogenase
NADPH Provides the Reducing Power for Anabolism
10
•Amino Acids Side chain properties: hydrophobic/hydrophilic, pKa, functional groups •Enzyme kinetics and thermodynamics Transition state stabilization, allostery •Organic chemistry Lewis acidity/basicity, nucleophiles and electrophiles, electrons and curly arrows •Carbohydrate chemistry Simple sugars: nomenclature and structure •Cell biology The structure of cells, organelles, membranes
1
The Component Parts of Complex Organisms Perform Different Functions and have Different Requirements
2
Functional Compartmentalization is Even More Apparent at the Cellular Level
3
Overview of Metabolism
Enzyme or enzyme complex. May participate in more than one pathway
GLUCONEOGENESIS liver and kidneys
glucose
glycogen
GLYCOLYSIS cytoplasm, all cells
amino acids fats
pyruvate
acetyl-CoA
O2 aerobic
CO2
NAD+
NAD+ NADH anaerobic
TCA CYCLE II
I
lactate
H+ III
NADH
IV
H+
OXIDATIVE PHOSPHORYLATION mitochondria, all cells
4
ADP
ATP mitochondrial membrane
Metabolism • The sum of the chemical changes that convert nutrients into energy and the chemically complex products of cells • Hundreds of enzyme reactions organized into discrete pathways • Substrates are transformed to products via many specific intermediates
A Common Set of Pathways • Organisms show marked similarities in their major metabolic pathways • Evidence that all life descended from a common ancestral form • But there is significant diversity – Autotrophs use CO2 – Phototrophs use light – Heterotrophs use organic carbon – Chemotrophs use sugars, inorganics and sulfur
The Sun is Energy for Life
• Phototrophs use light to drive synthesis of organic molecules • Heterotrophs use these organic molecules as building blocks • CO2, O2, and H2O are recycled 5
Metabolism • Catabolism: degradative pathways – usually energy-yielding! • Anabolism: biosynthetic pathways – energy-requiring! • Catabolic pathways converge to a few end products • Anabolic pathways diverge to synthesize many biomolecules • Some pathways serve both in catabolism and anabolism • Such pathways are said to be amphibolic
6
Metabolic Pathways • • • • •
Pathways consist of sequential steps The enzymes may be separate Or may form a multienzyme complex Or may be a membrane-bound system New research indicates that multienzyme complexes are more common than once thought
7
3 Stages of Catabolism
8
Metabolic Regulation metabolic regulation favors different pathways for oppositely directed metabolic sequences • Anabolic & catabolic pathways involving the same product are not the same although some steps may be common to both • Some steps must be different to ensure that each pathway is spontaneous • This also allows regulation mechanisms to turn one pathway on and the other off
Redox in Metabolism • Catabolism is oxidative - substrates lose reducing equivalents, usually H- (hydride) ions • NAD+ collects electrons released in catabolism and is reduced to NADH • Anabolism is reductive - NADPH provides the reducing power (electrons) for anabolic processes
9
NADH and NAD+, NADPH and NADP+ NAD+ is an Anabolic Oxidizing Agent • • •
H- transferred to the pyrimidine nucleotide NAD+ Dehydrogenase reactions AH2 + NAD+ A + NADH + H+ eg alcohol dehydrogenase
NADPH Provides the Reducing Power for Anabolism
10
