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Microbiology > Microbial Metabolism > Flashcards

Microbial Metabolism Flashcards

1
Q

What is metabolism?

A

The sum of all chemical reactions taking place in cells

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2
Q

What is Catabolism?

A

Breakdown of large, complex molecules into smaller, simpler molecules; this process generally releases energy (which can be used to support anabolism

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3
Q

What is anabolism? example?

A

Building of larger, more complex molecules from smaller, simpler “building blocks”

AA’s used to make proteins; this process generally requires energy

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4
Q

What is ATP? How is it created?

A

Adenosine triphosphate. It is the energy “currency” of all cells. Energy that is released by catabolism is captured by adding a high-energy phosphate group to ADP, thus creating ATP, an energy-carrying molecule.

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5
Q

What is ATP used for?

A

It is carried to anabolic pathways for use during biosynthesis; this potential energy could also be used for transport functions, morality, etc.

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6
Q

What are enzymes?

A

Chemically, Proteins. The biological catalysts that provide the ability to lower the activation energy required for reactions to proceed. Enzymes make many reactions go forward that may not spontaneously do so otherwise.

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7
Q

Many vitamins act as…

A

coenzymes

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8
Q

What is a prothetic group?

A

A firmly bound, large organic molecule that activates the enzyme. Ie Haeme group in haemoglobin.

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9
Q

What is an apoenzyme?

A

If cofactor/coenzyme/prosthetic group is needed, the protein part of the enzyme is an apoenzyme.

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10
Q

What is a holoenzyme?

A

The fully functional enzyme, with all components in place

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11
Q

What is the active site?

A

A site where enzymes possess a surface on which the reaction that the enzyme catalyzes takes place.

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12
Q

What is a substrate?

A

The substance on which the enzyme acts.

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13
Q

What is an enzyme-substrate complex?

A

Where the enzyme has been bound to the substrate. When this happens, chemical bonds are weakened; the overall shape of the substrate is altered. It is released from the enzyme as the product of the reaction.

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14
Q

What is the “lock and key” mechanism?

A

Enzymes show a high degree of SPECIFICITY; each enzyme acts on one substrate and catalyzes one reaction. This specificity is due to the shape and charge status of the enzyme molecule, esp. at the active site

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15
Q

Enzymes can be denatured, what does this mean?

A

Due to their protein nature, any change in the 3o or 4o structure will alter the enzymes shape and therefore its activity. Any influence on proteins can influence enzymes.

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16
Q

Enzymes can be inhibited, what does this mean?

A

This allows for coordinated control of their activity by the cell itself. It also provides a route by which external influences can alter cellular metabolism.

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17
Q

Competitive inhibition is effected by….

A

a non-substratre molecules that is similar to the substrate in shape, an therefore binds to the enzymes active site. The inhibitor can have its binding to the enzyme revered by increasing substrate.

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18
Q

What are Sulpha drugs?

A

they compete with PABA (para-aminobenzoic acid) for binding to the enzyme that normally converts PABA to folic acid. When the drug is present, the microbe cannot manufacture folic acid.

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19
Q

Non-competitive inhibition is ….

A

The inhibitor binds to a second site, called an allosteric site, on the enzyme.
The inhibitor alters the shape of the enzyme in a way that the shape of the active site is affected. The normal substrate cannot bind to the active site. Some allosteric inhibitors bind reversibly and irreversibly. Increase in substrate has no influence.

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20
Q

What is feedback inhibition?

A

reversible, non-competitive inhibition. The product of a biochemical/metabolic pathway can, at high enough [ ]’s, “feedback” by binding to the initial enzyme in the pathway and inhibiting it. This is a method for controlling against the over-production of certain substances.

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21
Q

What is glycolysis?

A

Also known as the Embden-Meyerhoff pathway.
Common to autotrophs and heterotrophs, aerobes and anaerobes.
The initial metabolic breakdown of glucose.
DOES NOT REQUIRE OXYGEN

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22
Q

Important features of glycolysis?

A
  1. Start with one molecule of GLUCOSE
    1 mole (6.023 X 1023 molecules) = 686,000 calories (or 686 kcal)
  2. Multiple reaction steps occur, each catalyzed by a specific enzyme
  3. End product is two molecules of pyruvate/pyruvic acid
  4. Requires 2 molecules of ATP be used per molecule of glucose
  5. 2 molecules of ATP are produced per each molecule of phosphoglyceraldehyde (PGAL) that is converted to pyruvate; therefore, 4 molecules of ATP are produced in total
  6. Therefore, there is a net production of 2 ATP
  7. 2 molecules of NADH are created; these are shunted to the electron transport chain to produce more ATP
  8. Pyruvate can be further metabolized in a variety of ways
    I.e. fermentation, aerobic respiration, anaerobic respiration
    This supports efficiency and metabolic diversity at the same time
  9. Many carbohydrates (not just glucose!) can “feed” glycolysis
    This is done by catalyzing longer, more complex CHOs into glucose itself or into one of the intermediates in the glycolysis pathway
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23
Q

What is aerobic respiration?

A

REQUIRES OXYGEN

Produces more ATP (36) than glycolysis alone (2) (metabolic advantage)

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24
Q

What are the two stages in aerobic respiration?

A 
Krebs cycle (or citric acid cycle)
Electron transport chain (oxidative phosphorylation)
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25
Q

What is the Kreb’s Cycle?

A
  1. Two 3-carbon molecules (pyruvate) from glycolysis enter the Krebs cycle
  2. Pyruvate is first converted to acetyl CoA; this step produces 2 NADH (one per pyruvate molecule), which goes off to ETC
  3. Acetyl CoA is then converted to citric acid by adding oxaloacetic acid (a 4-C molecule) to acetyl CoA (a 2-C molecule)
  4. CO2 is released in the conversion of pyruvate to acetyl CoA
  5. 2 more ATPs are produced during the Krebs cycle (one ATP per molecule of pyruvate entering cycle)
  6. The Krebs cycle also produces 4 NADH and 1 FADH2 (per molecule of pyruvate) that will ultimately be shunted to the ETC and result in the production of more ATPs
  7. A wide variety of “fuels” can feed Krebs cycle due to large variety of intermediates in pathway; fats, proteins can each be metabolized to some of these intermediates, thus serving as fuel for Krebs and ETC
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26
Q

What is oxidative Phosphorylation; ETC?

A

This is a series of reactions linked to one another by the transfer of electrons from one molecule to another in the pathway.

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27
Q

The steps of oxidative Phosphorylation; ETC?

A
  1. As electrons are transferred from one carrier to another, they lose some energy
  2. That energy can be used to join a phosphate to ADP (to make ATP) OR to reduce coenzymes NAD+ (to NADH) and FAD2+ (to FADH2)
  3. Some of the released energy can also be used to “drive” protons (H+) out of the cell via a mechanism known as a proton motive force
  4. Protons build up outside of the cell (so do + charges; inside is then becoming more –ve) and begin to “flow” back into cell through protein channel that contains an ATP synthetase enzyme
  5. As protons flow through, they cause a shape change in the enzyme such that a phosphate is bonded to ADP (both are bound to the enzyme already) to make ATP
  6. The final electron acceptor in the pathway is oxygen. At the same time, it accepts 2 protons from the cytoplasm of the cell and becomes H2O
  7. If no oxygen is present? The entire process halts.
  8. ETC’s chemiosmosis (use of energy provided by electrons flowing back into cell via osmosis to add P to ADP to make ATP) requires intact plasma membrane to function
28
Q

What can halt ETC and kill cell?

A

Any agent that alters plasma membrane structure/function.

29
Q

Glycolysis and Krebs comparison

A

Glycolysis: 2 ATP directly; 2 NADH, which are used in ETC to produce 6 more ATP indirectly
Krebs: 2 ATP directly; 8 NADH, which are used in ETC to produce 24 more ATP indirectly; 2 FADH2, which are used in ETC to produce 4 more ATP indirectly

30
Q

Why would it use Fermentation?

A

If O2 is not available.

It is possible to switch to fermentation to metabolize glucose and other carbohydrates.

31
Q

The final electron acceptor in the process fermentation is..

A

an organic molecule, not oxygen.

32
Q

Which is more productive? Fermentation of aerobic respiration?

A

Aerobic respiration.

33
Q

how can Klebsiella pneumonia be differentiated from other Enterobacter members?

A

The presence of acetone. Voges-proskauer test

34
Q

Clostridium perfringens causes….

A

gas gangrene. The tissue damage is due to the production of an exotoxin by the microbe that produces myonecrosis, and gases (a mixture of hydrogen, o2, CO2, N2) that facilitate further invasion of the tissue by the microbe. Probably needs amputation

35
Q

What is homolactic fermentation?

A

Produces lactic acid as only metabolic by-product; NO GAS is made
Used in cheese making
Simplest fermentative pathway
Used by members of Lactobacillus, Stretococcus & human muscle tissue when no O2

36
Q

What is Mixed-Acid Fermentation?

A

Variety of metabolic by-products, but all are organic acids.

Gasses also made

37
Q

Alcoholic Fermentation

A

Rare in bacteria, common in yeast
Only acid produced is ethanol; gas produced is CO2
Used to make beer, wine

38
Q

What is Butanediol Fermentation?

A

Results in production of butanediol as acid, CO2 as gas

39
Q

what is Butyric-Butylic fermentation?

A

Produces butyric acid, butanol, isopropyl alcohol or acetone as acid; gas produced is CO2.

40
Q

What is Anaerobic Respiration?

A

This is a pathway that is used by some anaerobes.
Parts of the Krebs and ETC are used but O2 is NOT the final electron acceptor, and fewer ATP are produced.
Instead, and inorganic oxygen-carrying molecule is used as the final electron acceptor.

41
Q

What is the preferred fuel for glycolysis?

A

Glucose

or sucrose can be broken down into glucose and fructose via action of enzyme sucrase

42
Q

What are proteases?

A

Enzymes that break peptide bonds to release individual AA’s. AA’s are then deaminated (amine group is removed) the resulting molecules can enter glycolysis, Kreb’s, or fermentation

43
Q

Excess CHO’s are converted to

A

fat in bacteria and humans.

44
Q

What are fats hydrolyzed (broken down) into?

A

glycerol + 3 fatty acids via lipase enzymes

45
Q

What is Photoautotrophy?

A

Anabolic. Organisms using this pathway obtain energy from light
The energy is captured in the bonds of the CHO’s formed by using CO2 as a C source during photosynthesis

46
Q

There are two photosynthetic types. What are they?

A 
Algae, cyanobacteria, green plants:
Possess chlorophyll
energy from light excites pigment molecules to higher energy state that is used to split H2O; e- from this used in forming NADPH (which used to make ATP)
process releases O2
     Green and purple bacteria:
use older system that evolved in an environment with lots of H2 in atmosphere but no O2.
Bacteriophylls are used.
process does not release O2
47
Q

What is chemoautotrophy and chemosynthesis?

A

Not able to carry out photosynthesis
instead, oxidize inorganic substances to generate energy and then use this energy, plus CO2 as a C source, to synthesis CHOs, AAs, Fats, ETC. via chemosynthesis

48
Q

What is Protein Synthesis?

A

Performed in nearly identical way by all living organisms
Use DNA as informational template (“blueprint”
Information in DNA is used to produce RNA; Transcription
Information in RNA is used to produce proteins; Translation
The absence of a single enzyme can block the entire pathway

49
Q

What does RNA polymerase do?

A

“reads” DNA. the information in the DNA is used to specify the sequence of nucleotides in the RNA molecule; the enzyme is responsible for constructing that RNA

50
Q

Three types of RNA are made, what are they and what is their purpose?

A

mRNA; messenger RNA; carries information to specify sequence of AA’s in protein to be made
tRNA; physically ‘carries’ each individual AA to site of protein synthesis on ribosome
rRNA; forms part of structure of ribosome

51
Q

How does transcription in prokaryotes (bacteria) differ from that in eukaryotes (humans)?

A

Two ways:

  1. There are no intervening sequences (introns) in the genome of a bacteria and there is no post-transcriptional modification of the mRNA.
  2. There is no nuclear membrane. Transcription and translation occur simultaneously in the cytoplasm and the newly constructed mRNA can begin to the translated even before it is finished being constructed. This speeds up the entire process.
52
Q

Where is protein made during translation?

A

Takes place on ribosome

53
Q

How does translation when making protein work?

A

Information in mRNA is “read” in form of base triplets, to specify each individual AA to be added to growing polypeptide chain
The “codon” on mRNA is complementary to “anticodon” on tRNA (which allows a specific tRNA, carrying a specific AA, to bind to the appropriate spot on the ribosome to facilitate adding that AA to the chain)
A peptide bond forms between the incoming AA and the most recently added AA on the growing polypeptide chain
Now the empty tRNA leaves the ribosome and the cycle repeats

54
Q

How is translation when making proteins controlled?

A

Via action of several types of genes that are grouped into a unction unit known as an OPERON model. This is unique to bacteria.

55
Q

What are the types of genes in a bacterial operon?

A

Structural gene
Operator gene
Repressor gene
promotor region

56
Q

What is a structural gene?

A

specifies structure of protein to be produced (protein is often an enzyme required to metabolize a needed nutrient)

57
Q

What id an Operator gene?

A

found physically adjacent to structural gene; stimulates and controls the expression of the structural gene

58
Q

What is a repressor gene?

A

found further away from structural gene; controls the activity of the operator gene via production of repressor protein, which (in the absence of a needed nutrient) will bind to the operator gene and promotor region, effectively blocking them and turning the gene “off”

59
Q

What is a promotor region?

A

lies next to operator gene

60
Q

What is an Inducer?

A

A nutrient that is a substrate for the enzyme produced by the gene. This molecule binds to and inactivates the repressor protein, thereby allowing RNA polymerase to transcribe the structural gene.

61
Q

What is membrane transport?

A

Energy may be used for active transport of various substances across the plasma membrane. This allow for the accumulation of nutrients inside the cell, which will likely lead to more efficient metabolism.

62
Q

What is the phosphotransferase system (PTS)?

A

uses permeases (sugar-specific enzyme complexes) to form a transport system through the plasma membrane for carbohydrates

63
Q

What happens in Gram negative organisms only during the PTS?

A

Two membranes need to be traversed; outer membrane and the plasma membrane.

64
Q

What are Porins?

A

Transmembrane proteins that form channels through the outer membrane and operate via facilitated diffusion to bring substances into periplasmic place.

65
Q

What is movement?

A

Movement can occur using flagella, gliding motion, creeping motion.

66
Q

What is gliding movement?

A

accomplished by secretion of surfactant, which lowers the surface tension at the bacteria’s posterior end; this difference in surface tension between the front (where ST is high) and the rear (where ST is low) of the bacterium causes gliding movement to be possible

Microbiology (2 decks)

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