Download Carbohydrate Metabolism

Carbohydrate
Metabolism
Turning Sugar
into Energy
Outline
• What is Metabolism?
• Glycolysis
• TCA Cycle
• Electron Transport System
What is Metabolism?
• Sum of all chemical reactions in the body
What is Metabolism?
• Sum of all chemical reactions in the body
• Creates energy (ATP)
Why do we need to make ATP?
• Power muscular contraction
• Active Transport
• Homeostasis
• Synthesis of macromolecules
ATP is short-term energy storage
• ATP consumed < 1 minute from synthesis
Types of Metabolic Reactions
• Anabolic reactions
– Building macromolecules in the body
Types of Metabolic Reactions
• Anabolic reactions
– Building macromolecules in the body
• Catabolic reactions
– Hydrolysis of foods in GI tract
– Chemical breakdown releases energy
Types of Metabolic Reactions
• Anabolic reactions
– Building macromolecules in the body
• Catabolic reactions
– Hydrolysis of foods in GI tract
– Chemical breakdown releases energy
• Where does the energy come from?
Fuel Up with Slyders!
Our Fuel Sources
• Carbohydrates
– Sugars and starches
– First choice of metabolic fuel
• Fats
• Protein
Glucose: Our Primary Fuel
C6H12O6
All carbohydrates we consume are eventually
converted into glucose
Catabolism of Glucose
C6H12O6 + 6O2  6CO2 + 6H2O + energy
Glucose
• Transfer energy from glucose to ATP
• Most energy lost as heat
Catabolism of Glucose
• Occurs as a series of steps….
• Major Pathways
Glycolysis (does not require O2)
- glucose split into 2 parts, generating 2 ATP
Aerobic Respiration (requires O2)
- catabolizes the products of glycolysis and generates
more than 30 ATP
Where is Glucose Broken Down?
TCA
Glycolysis (Sugar Splitting)
• Occurs in presence and absence of O2
• Occurs in cytoplasm
• Provides energy during strenuous exercise
All I need is
Glycolysis…And
my Jenny.
Key Steps in Glycolysis
1. Glucose enters cell by facilitated diffusion
Key Steps in Glycolysis
2. Glucose is Phosphorylated by ATP
Key Steps in Glycolysis
3. Glucose split into two 3-carbon molecules
Key Steps in Glycolysis
4. Coenzyme NAD+ collects hydrogen
Coenzymes in Metabolism
• Collect electrons (hydrogen atoms) during
catabolism of glucose
– Transfer 2H+ and 2 e- at a time to
coenzymes NAD+ and FAD
– NAD+ (made from niacin)
NAD+ + 2H  NADH + H+
– FAD (made from vitamin B2)
FAD + 2H  FADH2
• Temporary carriers of energy
Key Steps in Glycolysis
4. Coenzyme NAD+ collects hydrogen
Key Steps in Glycolysis
5. Create 4 ATP by substrate-level
phosphorylation
Substrate-level Phosphorylation
Key Steps in Glycolysis
6. Create 2 Pyruvate molecules
Final Products of Glycolysis
2 molecules of Pyruvate
2 molecules of NADH + H+
4 gross ATP molecules, but only 2 net ATP
Quick Energy….but, not very much ATP
Glycolysis Animation
Some Cells Stop at Glycolysis
• Red Blood Cells
• Skeletal Muscle
(during exercise)
Much Energy Remains in Pyruvate
TCA
ATP Produced
2
So What Happens to Pyruvate?
• Aerobic vs. Anaerobic Respiration
• Kreb’s Cycle
• Electron Transport Chain
Most ATP is Generated in Mitochondria
• Two principal steps:
Matrix Reactions (Krebs Cycle)
• occurs in matrix of mitochondria
• Pyruvate is oxidized and electrons are transferred to
NAD+ and FAD, forming NADH +H and FADH2
Membrane Reactions (Electron Transport Chain)
• Occurs within the inner mitochondrial membrane
• NADH & FADH2 are oxidized, transferring energy to ATP
and regenerating NAD+ and FAD
Mitochondria: The Cell Powerhouse
The Krebs Cycle
Also known as….
Tricarboxylic Acid Cycle
TCA Cycle
Citric Acid Cycle
Major Steps of the TCA Cycle
1. CO2 removed from Pyruvate and several
intermediate molecules
C6Glucose
H12O6 + 6O2  6CO2 + 6H2O + energy
• CO2 is a metabolic waste product
Major Steps of the TCA Cycle
2. Hydrogen removed from intermediate
molecules
Picked up by NAD+ and FAD coenzymes
Summary of Krebs Cycle
2 pyruvate + 6 H2O  6 CO2
2 ADP + 2 Pi  2 ATP
8 NAD+ + 8 H2  8 NADH + 8 H+
2 FAD + 2 H2  2 FADH2
• Carbon from Pyruvate converted to CO2 and
exhaled
• Energy has been lost (as heat) or stored in
2 ATP, 8 NADH, and 2 FADH2.
Kreb’s Cycle Animation
Animation
Do not worry about the following:
Names of Intermediate carbon molecules
What GTP is (it is an ATP precursor)
Focus on the following:
CO2 production
Action of coenzymes NAD & FAD
Creation of ATP
To the Inner Mitochondrial Membrane!
TCA
2
2
So what happens to all of the
NADH and FADH?
Most ATP is Generated in Mitochondria
• Two principal steps:
Matrix Reactions (Krebs Cycle)
• occurs in matrix of mitochondria
• Pyruvate is oxidized and electrons are transferred to
NAD+ and FAD, forming NADH +H and FADH2
Membrane Reactions (Electron Transport Chain)
• Occurs within the inner mitochondrial membrane
• NADH & FADH2 are oxidized, transferring energy to ATP
and regenerating NAD+ and FAD
Electron Transport System (ETS)
• Occurs on Inner mitochondrial membrane
• Requires oxygen
ETS Makes Lots of ATP
Electron Transport System
1) NADH and FADH2
release hydrogen
atoms
Splitting of Hydrogen
2) Electrons passed along
electron transport system
Protons (H+) pumped out
of mitochondrial matrix
Flow of electrons powers
active transport of H+
ATP Synthase Creates ATP
3) H+ diffuse into matrix
through ATP Synthase
Flow of H+ powers
anabolism of ATP
Electron Transport System Payoff
• Produce ~34 ATP
• Efficiency of 40%
• Rest is body heat
Electron Transport System
Electron Transport Animation
Summary of Glucose Catabolism
TCA