Metabolic Pathways And Energy Production

Metabolic Pathways and Energy Production Metabolism and ATP Energy Important Coenzymes Glycolysis

1

Metabolism All the chemical reactions that occur in the cells of our bodies. Catabolic reactions • Break down large molecules • Provide energy for ATP

catabolic

anabolic

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

2

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 3

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 4

Structure of ATP adenosine diphosphate ADP O -

O

O

O

-

O

N

O

N

P O P O P O CH2 -

NH2

-

O

N

adenine

N

O ribose

OH

OH

adenosine triphosphate ATP 5

Digestion of Foods Digestion is the first step of catabolism • Carbohydrates

glucose, fructose, galactose

• Proteins

amino acids

• Lipids

glycerol fatty acids 6

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 7

Glycolysis: Oxidation of Glucose Glucose 2ATP 2 NAD+ 2ADP

two Glyceraldehyde-3-PO4

2NADH + 2H+ 4 ADP

two Pyruvate

4 ATP 8

Glycolysis: Oxidation of Glucose P O CH 2

HO CH2 O OH

OH

CH 2 O P

O

PO4

HO

OH OH glucose

OH

OH fructose-1,6-diphosphate CHO 2

H C OH CH 2O P

2 glyceraldehyde-3-phosphate

9

Glycolysis: Oxidation of Glucose 2 ADP + 2 Pi

2 ATP CHO

CHO 2

2

H C OH

H C O CH3

CH 2O P 2 glyceraldehyde-3-phosphate 2 NAD+

2 pyruvate

2 NADH + 2 H+ 10

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 3C molecules (+ 4 ATP) Glucose + 2 ADP + 2 Pi + 2 NAD+ 2pyruvate + 2 ATP + 2 NADH + 2 H+ 11

Pathways for Pyruvate Aerobic conditions O || CH3–C –COO- + NAD+ + CoA pyruvate O || CH3–C –CoA + CO2 + NADH + H+ acetyl CoA 12

Pathways for Pyruvate Anaerobic conditions (No O2 available) Reduce to lactate to replenish NAD+ for glycolysis O || CH3–C –COO- + NADH + H+

OH | CH3–CH –COO- + NAD+

pyruvate enzyme: lactate dehydrogenase

lactate

13

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 14

Learning Check M1 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 15

Solution M1 Match the following with the terms below: (1) Catabolic reactions (2) Coenzymes (3) Glycolysis (4) Lactate A. 4 Produced during anaerobic conditions B. 3 Reactions that convert glucose to pyruvate C. 1 Metabolic reactions that break down large molecules to smaller molecules + energy D. 2 Substances that remove or add H atoms in oxidation and reduction reactions 16