Microbial Metabolism

advertisement
5-a
Microbial Metabolism
pp. 115-138; 144-148
1
Chapter 5 Overview
• Metabolism
• Enzymes
• Common energy pathways used by
microbes
– Fermentation
– Aerobic respiration
– Anaerobic respiration
• Metabolic diversity among organisms
2
Metabolism
Energy-Balancing Process
• Release energy
– Catabolism
– Breakdown of
molecules
• Sugar  CO2 + H20
– Provides ‘building
blocks’ for anabolism
– Provides energy for
anabolism
• ATP  ADP + energy
• Requires energy
– Anabolism
– Synthesis of
molecules
• Amino acids  protein
– Provides molecules for
catabolism
– Provides ATP for
catabolism
• ADP + energy  ATP
Molecule breakdown coupled with molecules synthesized
3
Enzymes
…Enable Energy-Balancing Process
•
•
•
•
•
•
•
Are a catalyst = speed up reaction
Increase the reaction rate
Lower the energy of activation
Are not altered in the reaction
Are highly specific
Each acts on a specific substance, the substrate
Each catalyzes only one reaction
4
Enzymes
• Provide a structure, a framework
– To allow collisions to occur
– And the chemical reaction to occur
AB  A + B
Substrate
Products
5
Energy Requirements - Chemical Reaction
The reaction is: AB  A + B
Fig. 5.2
6
Mechanism of Enzymatic Action:
Fig. 5.4a
When an enzyme and substrate combine:
– The substrate is transformed, to products
– And the enzyme is recovered, unaltered
Turnover number ~ 1-10,000 molecules per second
7
Naming enzymes:
• Names usually end in –ase
Enzyme classification:
• Based on the type of chemical reaction they
catalyze
– Example: oxidoreductases (ox-redox rxns)
• Within each class, named for the specific
reaction
– If remove hydrogen, called dehydrogenases
8
Enzyme classification (6 classes):
9
Enzyme Components
• Some enzymes consist only of protein
• Most consist of both a protein and a nonprotein component
– The protein called an apoenzyme
– The non-protein part called a cofactor
• Cofactors are
– Ions of iron, zinc, magnesium, calcium etc*
– If a cofactor is an organic molecule, it is called a:
• Coenzyme
* p. 119
10
• Apoenzymes are inactive by themselves
– They must be activated by cofactors
• Apoenzymes + cofactors form a
– Holoenzyme
+
Fig. 5.3
11
Enzyme & Cofactors
NAD+
NADP+
FMN, FAD
Coenzyme A
Nicotinamide adenine dinucleotide
Nicotinamide adenine dinucleotide phosphate
Flavin mononucleotide, Flavin adenine dinucleotide
Important in the Krebs cycle
12
Fig. 5.4b
Enzymes are characterized by specificity
– Specificity is a function of their active sites
(see ‘groove’)
– Enzyme + substrate = slight shape change
* Animation: Enzyme–Substrate Interactions. The Microbiology Place.
13
Organisms - Metabolic Diversity
• Chemotrophs
– Oxidation-reduction reactions of organic or
inorganic compounds for energy
• Phototrophs
– Use light as primary source of energy
• Autotrophs
– Use CO2 for principal carbon source
• Heterotrophs
– Use organic carbon source
14
Combine Energy & Carbon
• Photoautotrophs
– Energy = light; carbon = CO2
• Photoheterotrophs
– Energy = light; carbon = organic source
• Chemoautotrophs
– Energy = organic or inorganic compounds;
carbon = CO2
• Chemoheterotrophs*
– Energy = organic or inorganic compounds;
carbon = organic source
15
Nutritional Classification of Organisms
Fig. 5.27
16
Q’s
1. All of the following are enzymes
except:
a.
b.
c.
d.
Threonine deamainase
Acetyl
Peroxidase
Urease
2. Enzymes work most effectively at
their optimal temperature and pH.
a. True
b. False
17
Q’s
1. Beggiatoa bacteria use carbon
dioxide for their carbon source and
hydrogen sulfide as an energy source.
This organism is a:
a.
b.
c.
d.
Photoheterotroph
Chemoheterotroph
Photoautotroph
Chemoautotroph
Hint: Fig. 5.27
18
Q’s
In the figure shown, what is the small
organic molecule called that is needed to
activate the apoenzyme?
A. Holoenzyme B. Enzyme C. Coenzyme
D. Substrate E. Reactant
19
Q’s
1. A dehydrogenase is an example of a/an
_____________?
2. Nitrobacter bacteria use CO2 for their
carbon source and nitrate ions as an
energy source. This organism is a:
A. Chemoautotroph
B. Chemoheterotroph
C. Photoheterotroph
D. Photoautotroph
Hint: Fig. 5.27
20
Q’s
1. A coenzyme assists an enzyme by
accepting or donating matter. What does
NAD+ transfer?
A. CoA
B. Electrons
C. Acetyl groups
D. ATP
Hint: Table 5.2
21
Q’s
1. Organisms that use carbon dioxide as a
carbon source and energy sources such
as ammonia or hydrogen sulfide are
called:
A. Photoautotrophs
B. Photoheterotrophs
C. Chemoheterotrophs
D. Chemoautotrophs
Hint: Fig. 5.27
22
Q’s
Fill in the blanks:
Organism
Carbon
Source
Energy
Source
Photoautotroph
Photoheterotroph
Chemoautotroph
Chemoheterotroph
23
Download