Metabolic Pathways and Energy Production

Metabolism and ATP Energy

Important Coenzymes

Glycolysis

Metabolism

All the chemical reactions that occur in the cells of our bodies.

Catabolic reactions• Break down large molecules • Provide energy for ATP

Anabolic reactions• Use small molecules to build large ones• Require energy

catabolic

anabolic

Cell Structure

Typical animal cell• Nucleus• Chromosomes in the nucleus

contain genetic material• Cytoplasm is material

between nucleus and cell membrane

• Mitochondria are where energy-producing reactions occur

ATP

• Energy is released as food is oxidized• Used to form ATP from ADP and Pi

ADP + Pi + Energy ATP • In cells, energy is provided by the hydrolysis

of ATP

ATP ADP + Pi + Energy

Structure of ATP

O

OH OH

N

N

N

N

NH2

CH2OPOPOPO-

O O O

O- O- O-

adenine

ribose

adenosine triphosphate ATP

ADP

adenosine diphosphate

Digestion of Foods

Digestion is the first step of catabolism

• Carbohydrates glucose, fructose, galactose

• Proteins amino acids

• Lipids glycerol fatty acids

Coenzymes

• Substances that connect metabolic pathways• In reduction, coenzymes accept H atoms• In oxidation, coenzymes remove H atoms

FAD (flavin adenine dinucleotide)

FAD + -CH2-CH2- FADH2 + -CH=CH-

NAD+ (nicotinamide adenine dinucleotide)

NAD+ + -CH-OH NADH + H+ + -C=O

Glycolysis: Oxidation of Glucose

2ATP2 NAD+

2ADP 2NADH + 2H+

4 ADP

4 ATP

Glucose

two Glyceraldehyde-3-PO4

two Pyruvate

Glycolysis: Oxidation of Glucose

2 glyceraldehyde-3-phosphate

O

CH2HO

OH

OH

OH

OH PO4O

CH2O

OH

CH2 O PP

OHHO

glucosefructose-1,6-diphosphate

CHO

C OHH

CH2O P

2

Glycolysis: Oxidation of Glucose

2 NAD+ 2 NADH + 2 H+

2 glyceraldehyde-3-phosphate

CHO

C OHH

CH2O P

2 2

CHO

CH O

CH3

2 pyruvate

2 ADP + 2 Pi 2 ATP

Glycolysis: Oxidation of Glucose

Glycolysis generates 2 ATP molecules and 2 NADH + 2 H+

Two ATP used in adding phosphate groups to glucose and fructose-6-phosphate (- 2 ATP)

Four ATP generated in direct transfer to ADP by two 3-C molecules (+ 4 ATP)

Glucose + 2 ADP + 2 Pi + 2 NAD+ 2pyruvate + 2 ATP + 2 NADH + 2 H+

Pathways for Pyruvate

Aerobic conditions O

||

CH3–C –COO- + NAD+ + CoA

pyruvate

O

||

CH3–C –CoA + CO2 + NADH + H+

acetyl CoA

Pathways for Pyruvate

Anaerobic conditions (No O2 available)

Reduce to lactate to replenish NAD+ for glycolysis

O OH

|| |

CH3–C –COO- + NADH + H+ CH3–CH –COO- + NAD+

pyruvate lactate

enzyme: lactate dehydrogenase

Lactate in Muscles

• Strenuous exercise leads to anaerobic conditions

• Oxygen in muscles is depleted• Lactate builds up as glycolysis continues• Muscles tire and become painful• Breathing rate increases• Rest repays oxygen debt • Lactate re-forms pyruvate in liver

Learning Check

Match the following with the terms below:

(1) Catabolic reactions (2) Coenzymes

(3) Glycolysis (4) Lactate

A. Produced during anaerobic conditions

B. Reactions that convert glucose to pyruvate

C. Metabolic reactions that break down large molecules to smaller molecules + energy

D. Substances that remove or add H atoms in oxidation and reduction reactions

Solution

Match the following with the terms below:(1) Catabolic reactions (2) Coenzymes(3) Glycolysis (4) Lactate

A. 4 Produced during anaerobic conditionsB. 3 Reactions that convert glucose to pyruvateC. 1 Metabolic reactions that break down large

molecules to smaller molecules + energyD. 2 Substances that remove or add H atoms in oxidation and reduction reactions