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 C 6 H 12 O 6 All carbohydrates we consume are eventually converted into glucose

Catabolism of Glucose C 6 H 12 O 6 + 6O 2  6CO 2 + 6H 2 O + energy Transfer energy from glucose to ATP Most energy lost as heat Glucose

Catabolism of Glucose Occurs as a series of steps…. Major Pathways Glycolysis (does not require O 2 ) -glucose split into 2 parts, generating 2 ATP Aerobic Respiration (requires O 2 ) - 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 O 2 Occurs in cytoplasm Provides energy during strenuous exercise All I need is Glycolysis…And my Jenny.

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 Key Steps in Glycolysis

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 B 2 ) FAD + 2H  FADH 2 Temporary carriers of energy

4.Coenzyme NAD + collects hydrogen Key Steps in Glycolysis

5. Create 4 ATP by substrate-level phosphorylation Key Steps in Glycolysis

Substrate-level Phosphorylation

6. Create 2 Pyruvate molecules Key Steps in Glycolysis

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 2 TCA ATP Produced

Aerobic vs. Anaerobic Respiration Kreb’s Cycle Electron Transport Chain So What Happens to Pyruvate?

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 FADH 2 Membrane Reactions (Electron Transport Chain) Occurs within the inner mitochondrial membrane NADH & FADH 2 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. CO 2 removed from Pyruvate and several intermediate molecules C 6 H 12 O 6 + 6O 2  6CO 2 + 6H 2 O + energy CO 2 is a metabolic waste product Glucose

2.Hydrogen removed from intermediate molecules Picked up by NAD + and FAD coenzymes Major Steps of the TCA Cycle

Summary of Krebs Cycle 2 pyruvate + 6 H 2 O  6 CO 2 2 ADP + 2 P i  2 ATP 8 NAD H 2  8 NADH + 8 H + 2 FAD + 2 H 2  2 FADH 2 Carbon from Pyruvate converted to CO 2 and exhaled Energy has been lost (as heat) or stored in 2 ATP, 8 NADH, and 2 FADH 2.

Kreb’s Cycle Animation Do not worry about the following: Names of Intermediate carbon molecules What GTP is (it is an ATP precursor) Focus on the following: CO 2 production Action of coenzymes NAD & FAD Creation of ATP Animation

To the Inner Mitochondrial Membrane! 22 TCA

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 FADH 2 Membrane Reactions (Electron Transport Chain) Occurs within the inner mitochondrial membrane NADH & FADH 2 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 FADH 2 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 AnimationAnimation

Summary of Glucose Catabolism TCA