Metabolism Metabolism Energy released during catabolic metabolism goes

Metabolism • Metabolism = • Energy released during catabolic metabolism goes to: • How is metabolism regulated?

Important in Metabolic Pathways • Oxidation/Reduction reactions • Substrate-level phosphorylations • Oxidative phosphorylation • Decarboxylations • Coupled reactions

Oxidation/Reduction NAD+ Glyceraldehyde 3 -phosphate NADH + H+ 3 -phosphoglycerate Pi Figure 4 -5

Substrate-level phosphorylation

Glycolysis (glyco = sugar; lysis = to break down) Where do reactions of glycolysis occur in the cell? Where does the glucose (or other sugar) come from? Do these reactions need oxygen to generate energy? What is the end-product of glycolysis? Figure 4 -13

Test Your Knowledge: • Put a next to any oxidation/reduction reaction • Put a next to any substrate-level phosphorylation reaction • Which reactions do you think have a DG that is negative (exergonic)? Label them with a • Which reactions do you think have a DG that is positive (endergonic)? Label them with a • How many ATP are made by the breakdown of one glucose to two pyruvate molecules? • How many ATP are utilized to break down one glucose molecule into two pyruvate molecules? • What do you think happens to the two pyruvate molecules generated? • What else is made in glycolysis that might eventually produce energy? Figure 4 -14

Energy Production in Glycolysis

Anaerobic vs. Aerobic Metabolism of Pyruvate From glycolysis Figure 4 -15

pyruvate Figure 4 -16

pyruvate CO 2 NAD+ NADH • What types of reactions do you see occurring frequently in this cycle? • Is oxygen required in this cycle? • How many ATP (or other high energy nucleotides) are generated from one pyruvate molecule? Figure 4 -16

High Energy Electrons carried by NADH and FADH 2 Go to the Electron Transport Chain TEST YOUR KNOWLEDGE Where is the electron transport chain located? What kind of biomolecules make up the electron transport chain? What are the important functions of these biomolecules? Is oxygen required for the electron transport chain to function? If so, what is its role? The electron transport chain is where oxidative phosphorylation occurs. Where does the oxidation occur? How about the phosphorylation?

High-energy electrons are carried by NADH +H+ or FADH 2 Electron transport proteins: two functions ATP synthase O 2 and H 2 O Figure 4 -17

Test Your Knowledge: Follow one glucose molecule through glycolysis, the Krebs cycle, and the electron transport chain. Calculate: 1. How many NADH + H+ molecules are generated 2. How many FADH 2 molecules are generated 3. How many ATPs are produced by substrate-level phosphorylation 4. How many ATPs are produced by oxidative phosphorylation 5. How many CO 2 molecules are produced 6. How many O 2 molecules are consumed (used) 7. How many H 2 O molecules are produced

Table 4 -5

What about sugars besides glucose? ADP ATP Fructose 6 -phosphate glycolysis hexokinase • galactose from milk sugar (lactose) to glucose-6 -phosphate (1 ATP used) • Mannose from polysaccharrides and glycoproteins to fructose-6 -phosphate to glucose-6 phosphate (1 ATP used)

Figure 4 -18

Figure 4 -19 a

Figure 4 -19 b

Figure 4 -19 c

Carbon skeleton determines the fate of the amino acid glucogenic vs. ketogenic Alanine pyruvate

One NADH and one FADH 2 made for each 2 -carbons cut from the chain in b oxidation Problem: If lipase cuts off a 16 -carbon fatty acid from a triglyceride, and it is metabolized completely, how many ATPs will be produced? Figure 4 -20

Figure 4 -21

Figure 4 -22 - Overview

Regulation of Metabolism • • • Major role is to regulate blood glucose Regulation in response to ATP/ADP ratio Regulation to adjust NAD+/NADH ratio Regulates to reduce loss of energy All regulation occurs through changes in enzyme activity

Which enzymes in glycolysis do you think might be regulated? For what reason? List at least 3 and the reason why you think they would need to be regulated.