Bacterial Metabolism - PowerPoint PPT Presentation

1 / 46
About This Presentation
Title:

Bacterial Metabolism

Description:

Can they interact with many different kinds of molecules? ... Gluconeogenesis. Working backward and up through glycolysis is called gluconeogenesis ... – PowerPoint PPT presentation

Number of Views:685
Avg rating:3.0/5.0
Slides: 47
Provided by: J771
Category:

less

Transcript and Presenter's Notes

Title: Bacterial Metabolism


1
Chapter 6
  • Bacterial Metabolism

2
Do You Remember??
  • Laws of Thermodynamics
  • Dissecting a Chemical Reaction
  • Endergonic /Exergonic reactions
  • What Is Metabolism?
  • Anabolic/Catabolic Reactions
  • Coupling these reactions

3
Enzymes and Energy in Metabolism
  • What Are Enzymes?
  • Enzymes Catalyze All Cellular Reactions
  • (What is a catalyst?)
  • Are made of?
  • Are used up?
  • Can they interact with many different kinds of
    molecules?
  • Enzymes catalyze chemical reactions by?

4
More About How Enzymes Work
  • Old Model Lock and Key Model
  • Newer Model Induced Fit

5
  • Enzymes lower the activation energy so a reaction
    is more likely to occur
  • Enzymes weaken chemical bonds in the substrate

Figure 6.3, page 165
6
Naming Enzymes
  • Enzymes can be named in one of two ways
  • By their function
  • By the substrate on which they act
  • Examples
  • Sucrase
  • Lipase
  • Oxidase
  • Hydrolase

7
Some Enzymes Require Cofactors
  • Some enzymes are made entirely of protein
  • Other enzymes require the addition of a
    complementing substance a cofactor

8
Cofactors An Example
  • Carbonic Anhydrase
  • The gray sphere is zinc (a metal) acting as a
    cofactor

9
Coenzymes
  • Coenzymes
  • a subclass of cofactors that are organic
    molecules (but not proteins)

10
  • Enzymes Often Team Up in Biochemical Pathways
  • A metabolic pathway is a sequence of chemical
    reactions working in step-wise fashion to produce
    a final product
  • each reaction is catalyzed by a different enzyme
  • the product of one reaction serves as the
    substrate for the next

Figure 6.4, page 166
11
How Enzymes Work In a Cell
  • All enzymes working at the same time would cause
    chaos in a cell
  • Therefore, enzymes must be turned on off in the
    cell
  • Enzyme Inhibition
  • Competitive Inhibition
  • Non-Competitive Inhibition
  • Enzyme Activation

12
An Entire Biochemical Pathway Can Also Be
Inhibited
  • Feedback Inhibition

13
ATP
  • Energy in the Form of ATP is Required for
    Metabolism
  • ATP (adenosine triphosphate) is the cellular
    energy currency, providing energy for
  • Movement
  • Cell division
  • Protein synthesis
  • Etc.

14
  • Energy is released from ATP when the bond holding
    the last phosphate group on the molecule is
    broken, producing
  • adenosine diphosphate (ADP)
  • a free phosphate group high-energy electrons
  • Energy will be acquired by molecule that bonds
    the phophate group

15
  • Adding a phosphate group to a molecule is called
    phosphorylation
  • Enzymes that transfer a phosphate from one
    molecule to another are called kinases
  • ATP cannot be stored because it is relatively
    unstable
  • energy must be stored in more stable forms like
    glycogen, starch or lipids (in prokaryotes),
    which can then be used to form ATP

16
CATABOLIC PATHWAYS
  • Major catabolic pathways break organic molecules
    down Use harvested potential energy to form ATP
  • Formation of ATP in a cell Respiration
  • 2 major pathways Fermentation and Aerobic
    Respiration
  • Both start with Glycolysis

17
Catabolic Pathways An Overview
  • Glycolysis
  • A 10 step pathway
  • Aerobic resp. and ferm. both start here
  • All steps are catalyzed by enzymes
  • Does not require O2 or specialized membranes
  • Occurs in the cytoplasm
  • All cells do this
  • Because of last 3 items, is viewed as an ancient
    pathway

18
Catabolic Pathways Overview, cont.
  • Aerobic Respiration
  • Is comprised of 2 pathways
  • Krebs Citric Acid Cycle
  • An Electron Transport System
  • It follows glycolysis
  • Requires O2, Special Membranes, Special Electron
    Transporting Proteins
  • Because of last 2 items, is viewed as a more
    recent pathway

19
Step 1 in Aerobic Respiration or Fermentation
Glycolysis
  • Glycolysis splits 1 glucose molecule into 2
    pyruvate molecules
  • Steps 1-3 Energy Requiring Reactions
  • Step 4 Molecule Breaks in Half
  • Steps 5-10Energy Harvesting Reactions
  • Net yield for glycolysis is 2 ATP 2 NADH

20
(No Transcript)
21
Glycolysis Can Run Backward Gluconeogenesis
  • Working backward and up through glycolysis is
    called gluconeogenesis
  • Steps 1, 3 and 10 in glycolysis are irreversible
  • (Would this be an anabolic or a catabolic
    pathway?)

22
Aerobic Respiration, ContKREBS CITRIC ACID
CYCLE
  • The Krebs Cycle extracts additional energy from
    pyruvate following glycolysis
  • Synthesizes building block molecules
  • Before entering Krebs Cycle, pyruvate molecules
    coming from glycolysis must pass through an
    intermediate step

23
The Intermediate Step
  • Before entering the Krebs cycle, enzymes
  • remove a carbon from each pyruvate molecule to
    form acetate
  • combine the carbon with coenzyme A (CoA) to form
    acetyl-CoA
  • This releases 1 NADH and 1 CO2/pyruvate
  • Is also called the Grand Central Station Step
    because many building block molecules are
    synthesized at this step

24
The Intermediate Step
25
Krebs Citric Acid Cycle
  • For each two pyruvate molecules that enter the
    cycle, the following molecules are formed
  • 4 CO2
  • 2 ATP
  • 6 NADH
  • 2 FADH2

26
NADH and FADH2 Are Electron Carriers!These
molecules will carry electrons to an electron
transport system (if one is present)
  • The Krebs cycle functions like a constantly
    turning wheel
  • picking up pyruvate molecules from glycolysis
  • spitting out CO2, and transferring electrons to
    ATP, NADH, and FADH2
  • Note the ATP made at the bottom of the cycle

27
  • OXIDATIVE PHOSPHORYLATION
  • The Big Gun
  • Pairs of electrons are passed from one chemical
    substance to another (electron transport),
    releasing energy
  • The energy released is used to pump H ions
    across a membrane
  • NADH and FADH2 provide the source electrons for
    oxidative phosphorylation
  • Oxygen bonds with the electron pair at the end of
    the chain, acquires 2 protons, which forms water

28
Oxidative Phosphorylation
29
Oxidative Phosphorylation Occurs on an Electron
Transport Chain
  • Electrons moving through the protein electron
    carriers provide the energy to pump protons
    across a membrane (chemiosmosis)
  • Forms a concentration gradient of protons on one
    side of the membrane
  • As the protons flow through ATP synthase, the
    energy (proton motive force) is used to
    phosphorylate ADP and form ATP

30
  • Fermentation
  • Produces ATP Using an Organic Final Electron
    Receptor
  • Fermentation is used
  • when oxygen and other alternative electron
    acceptors are unavailable
  • When electron transport carrier proteins are not
    available (the organism doesn't have the genetic
    code for these carriers)
  • No functional specialized H membrane is present

31
Fermentation Reforms NAD
  • NADH ? NAD Electron pair H
  • Electron pair and H will be donated to an
    organic molecule
  • NAD must be reformed so that glycolysis step 5
    can occur (NAD oxidizes glyceraldehyde-3-phospha
    te)

32
Two Common Fermentation Pathways
  • Pyruvate ? lactate
  • In our muscle cells
  • Pyruvate? CO2 ethanol
  • In yeast cells
  • Used commercially to produce risen bread and
    alcoholic beverages

33
Prokaryotes Have Many Different Fermentation
Pathways A Way We Identify Species
34
Bioremediation
35
Other Aspects of Catabolism
  • Other Nutrients Represent Potential Energy
    Sources
  • Many mono-, di-, and polysaccharides can be
    energy sources for prokaryotes
  • They must all be prepared before being processed
    by
  • Glycolysis
  • the Krebs cycle
  • oxidative phosphorylation

Figure 6.12, page 179
36
  • Catabolism of Fats
  • Pathway is known as b-oxidation
  • C-H bonds in fats store large amounts of energy,
    making fats good energy sources
  • See board for chemical reactions
  • Catabolism of Proteins
  • Cells use proteins for energy when fats and
    carbohydrates are lacking
  • Deamination is the replacement of the amino group
    in a protein with a carbonyl group in protein
    breakdown
  • See board for chemical reactions

37
  • Anaerobic Respiration Produces ATP Using Final
    Electron Acceptors Other Than Oxygen
  • In anaerobic respiration, anaerobes use molecules
    other than O2 as the final e- receptor on the ETC
  • For example NO2, NO3, H2So2, etc.
  • Anaerobic respiration produces less ATP than
    aerobic respiration
  • We will talk more about this in lab

38
ANABOLIC PATHWAYS
  • Carbohydrate Synthesis Lipid Synthesis
  • Protein Synthesis
  • DNA Synthesis

39
6.4 The Anabolism of Carbohydrates
  • Photosynthesis Is a Process to Acquire Chemical
    Energy
  • In photosynthesis, light energy is converted to
    chemical energy, which is stored as an organic
    compound
  • In prokaryotes, it is carried out in the cell
    membrane or thylakoid lamella, in eukaryotes in
    organelles called chloroplasts
  • The green pigment chlorophyll a absorbs light
    energy
  • Some bacteria use other pigments, such as
    bacteriochlorophylls
  • some archaea use bacteriorhodopsin

Figure 6.15, page 183
40
Some Prokaryotes Harvest Electrons and Protons
from H2S Some from H2O
41
Photosynthesis
  • Photosynthesis is divided into two sets of
    reactions
  • energy-fixing reactions
  • carbon-fixing reactions

42
The Carbon-Fixing Reaction The Calvin Cycle
43
Stromatolites Examples of Early Oxygenic
Photosynthesis
44
Oxygenic Photosynthesis and the Great Oxidation
Event
45
Patterns of Metabolism
  • Autotrophs and Heterotrophs Acquire Their Carbon
    in Different Ways
  • Autotrophs synthesize their own foods from simple
    carbon sources like CO or CO2 Self Eaters
  • Photoautotrophs use light as their energy source
  • Chemoautotrophs use inorganic compounds as their
    energy source

46
  • Heterotrophs acquire carbon from large organic
    molecules Other Eaters
  • Photoheterotrophs use light as their energy
    source and organic compounds as their source of
    carbon
  • Chemoheterotrophs use organic compounds both for
    energy and carbon sources
  • Saprobes feed exclusively on dead organic matter
  • Parasites feed on living organic matter
Write a Comment
User Comments (0)
About PowerShow.com