1. METABOLISME SEL

2. Microbial Metabolism: The Chemical Crossroads of Life Chapter 8

3. Metabolism
The sum total of all chemical reactions & physical workings occurring in a cell

4. 2 types of metabolism Anabolism - biosynthesis
building complex molecules from simple ones
requires energy (ATP)
Catabolism - degradation
breaking down complex molecules into simple ones
generates energy (ATP)

8. Enzyme structure Simple enzymes – consist of protein alone
Conjugated enzymes or holoenzymes – contain protein and nonprotein molecules
apoenzyme –protein portion
cofactors – nonprotein portion
metallic cofactors – iron, copper, magnesium
coenzymes -organic molecules - vitamins

10. Enzyme-substrate interactions

11. Exoenzymes – transported extracellularly, where they break down large food molecules or harmful chemicals; cellulase, amylase, penicillinase
Endoenzymes – retained intracellularly & function there

13. Constitutive enzymes – always present, always produced in equal amounts or at equal rates, regardless of amount of substrate; enzymes involved in glucose metabolism
Induced enzymes – not constantly present, produced only when substrate is present, prevents cell from wasting resources

15. Synthesis or condensation reactions – anabolic reactions to form covalent bonds between smaller substrate molecules, require ATP, release one molecule of water for each bond
Hydrolysis reactions– catabolic reactions that break down substrates into small molecules, requires the input of water

17. Transfer reactions by enzymes
Oxidation-reduction reactions – transfer of electrons
Aminotransferases – convert one type of amino acid to another by transferring an amino group
Phosphotransferases – transfer phosphate groups, involved in energy transfer
Methyltransferases – move methyl groups from one molecule to another
Decarboxylases – remove carbon dioxide from organic acids

18. Metabolic pathways

19. Control of enzyme activity
Competitive inhibition – substance that resembles normal substrate competes with substrate for active site
Feedback inhibition – concentration of product at the end of a pathway blocks the action of a key enzyme
Feedback repression – inhibits at the genetic level by controlling synthesis of key enzymes
Enzyme induction – enzymes are made only when suitable substrates are present

20. Competitive inhibition

21. Energy –capacity to do work or cause change
Endergonic reactions – consume energy
Exergonic reactions – release energy

22. Redox reactions always occur in pairs
There is an electron donor and electron acceptor which constitute a redox pair
The process salvages electrons & their energy.
released energy can be captured to phosphorylate ADP or another compound

23. Electron carriers
resemble shuttles that are loaded and unloaded with electrons and hydrogen
most carriers are coenzymes, NAD, FAD, NADP, coenzyme A & compounds of the respiratory chain

24. NAD reduction

25. Electron carriers

26. ATP 3 part molecule consisting of
adenine – a nitrogenous base
ribose – a 5-carbon sugar
3 phosphate groups
Removal of the terminal phosphate releases energy

27. ATP

28. Phosphorylation of glucose by ATP

29. Formation of ATP substrate-level phosphorylation
oxidative phosphorylation
photophosphorylation

30. substrate-level phosphorylation

31. Catabolism of glucose Glycolysis
Tricarboxylic acid cycle, Kreb’s cycle
Respiratory chain, electron transport

32. Metabolic strategies Pathways involved Final e- acceptor ATP yield
Aerobic respiration
Glycolysis, TCA, ET O2 38
Anaerobic respiration
NO3-, So4-2, CO3-3
variable
Fermentation
Glycolysis
Organic molecules 2

33. Overview of aerobic respiration

34. Overview of aerobic respiration
Glycolysis – glucose (6C) is oxidized and split into 2 molecules of pyruvic acid (3C)
TCA – processes pyruvic acid and generates 3 CO2 molecules
Electron transport chain – accepts electrons NADH & FADH, generates energy through sequential redox reactions called oxidative phosphorylation

35. Glycolysis

36. TCA cycle

37. Electron transport system

38. Chemiosmosis

39. Fermentation
Incomplete oxidation of glucose or other carbohydrates in the absence of oxygen
Uses organic compounds as terminal electron acceptors
Yields a small amount of ATP
Production of ethyl alcohol by yeasts acting on glucose
Formation of acid, gas & other products by the action of various bacteria on pyruvic acid

40. Fermentation

41. Products of fermentation

42. Many pathways of metabolism are bi-directional or amphibolic
Metabolites can serve as building blocks or sources of energy
Pyruvic acid can be converted into amino acids through amination
Amino acids can be converted into energy sources through deamination
Glyceraldehyde-3-phosphate can be converted into precursors for amino acids, carbohydrates and fats