Microbial Metabolism (Enzymes) Flashcards
1
Q
What is metabolism?
A
The sum of chemical reactions within a living organism
2
Q
Why do we need to know about microbial metabolism?
A
- Metabolism is the basis of all life
- Not just microbes
- “is the set of chemical reactions that occur in living organisms to maintain life”
- it is the chemistry of breaking down things for energy AND building or making things for cellular life
- catobolism + anabolism = metabolism
- metabolism forms the basis of all forms of microbiology, from environmental microbiology to medical microbiology
- Knowledge of metabolism forms the basis of antibiotic therapy. Many antibiotics interfere with metabolic reactions
3
Q
Catabolism is
A
- the breakdown of complex organic molecules into simpler molecules
- generally hydrolytic (water molecules get used)
- Exergonic (produce energy)- energy stored in chemical bonds is released
4
Q
Anabolism is
A
- the synthesis of complex organic molecules from simpler molecules
- Generally dehydration synthesis reactions (release water)
- Endergonic (consumes energy)
5
Q
Enzymes are:
A
- Biological catalyst that speed up chemical reactions but is not consumed in the reaction
- Specific for a particular substrate and reaction
- Has a unique shape to recognize substrates
- Very efficient- can increase the rate of a chemical reaction 10^8- 10^10 times
- Enable metabolic reactions to proceed at a speed compatible with life
6
Q
Enzyme Substrate Interaction
A
Enzymes have a unique active site which fits only a particular substrate
7
Q
Turnover number:
A
- Enzymes participate in chemical reactions but are not consumed by them (can function over and over again)
- An enzyme’s speed (turnover number) is the maximum number of substrate molecules an enzyme molecule can convert to produce each second
- Examples:
- DNA polymerase (DNA synthesis)–> 250
- Catalase (breakdown of H202–> 20,000
8
Q
Enzyme components
A
- Made entirely of protein
- Conjugated enzymes consist of;
- Apoenzyme: the protein component
- Cofactor- non-protein component (Mg^2+ or Ca^2+ ions)
- Apoenzyme + Cofactor = Holoenzyme
- Without cofactor - apoenzyme is not active
- Ex. DNA polymerase III
9
Q
Coenzyme is
A
an organic molecule that is a cofactor
10
Q
Naming Enzymes:
A
Enzyme names usually end in -ase
11
Q
Factors affecting enzymatic activity:
A
- Rate of chemical reactions increases with temperature
- elevation above a certain temperature leads to enzyme denaturation
- Most enzymes have a pH optimum
- Extreme pH can result in enzyme denaturation
- High substrate concentration leads maximal enzyme activity, the enzyme is said to be saturated
- Under normal conditions, enzymes are not saturated
12
Q
Metabolic pathways
A
- Metabolic pathways usually contain many steps, each with an enzyme
- Multienzyme systems
- Different patterns seen
- Linear
- Cyclic (TCAI)
- Branched
- At the level of the enzymes:
- Mess up the enzymes, pathways will not move forward
- Control of enzyme action - competitive vs non-competitive
- Control of synthesis - feedback loops of repression or induction
- Enzymes activity can be controlled by inhibitors
- controlling a microbe’s enzymes is also a good way to control growth. Why?
- Enzyme inhibitors can be classified as
- Competitive inhibitors
- Non-competitive inhibitors (allosteric inhibitors)
13
Q
Competitive Inhibitors
A
- Fill the active site and compete with substrate
- Similar in shape and chemical structure to the substrate
- Does not undergo any reaction to form products
*** Inhibition of folic acid synthesis by sulfanilamide - competes with para-aminobenzoic acid (PABA) for enzymes active site
14
Q
Non-Competitive Inhibitors
A
- Interact with a site other than the active site
- Binding of the inhibitor causes a change in the shape of the active site, making it non-functional
- May bind reversibly or irreversibly
15
Q
Feedback inhibition
A
- The end product of a metabolic pathway is often a non-competitive inhibitor of that pathway
- The end product inhibits one the enzymes in the pathway (often the first enzyme)j
- Prevents the cell from wasting energy
