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Microbiology > Chapter 11 > Flashcards

Chapter 11 Flashcards

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Biology 101 flashcards
1
Q

What are the four phases of metabolism?

A

Fueling: ATP, Reducing Power, Precursor Metabolites (entry, feeder pathways, central pathways).

Biosynthesis: Use products of fueling to generate building blocks.

Polymerization: DNA-RNA-Protein

Assembly: Cell Envelope.

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2
Q

What is the rationale for coordination?

A
  • Bacterial cells exposed to constantly changing conditions (many methods of regulation are required to adapt to this variation).
  • Regulation is important for efficient use of energy (making RNA and protein very energetically expensive).
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3
Q

What evidence shows that metabolic reactions are coordinated?

A
  1. Coordination in Biosynthesis
  2. Coordination in Fueling
  3. Coordination in Marcromolecular Composition
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4
Q

Coordination in Biosynthesis:

Experimental Media:

A

Radiolabeled glycerol as carbon source, unlabeled histidine. (no histidine in cell labeled)

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5
Q

What does the presence of any one compound in the medium do?

A

The presence of any one compound in the medium stops endogenous synthesis of that compound

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6
Q

Coordination of Fueling:

A

Cells adjust ratios of products of fueling to satisfy the needs of the cell. Therefore, cells must sense growth potential, respond.

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7
Q

Coordination in marcromolecular composition:

A

At the same growth rate, cells have the same macromolecular composition (proteins, DNA, lipids, carbohydrates).
Richness of medium affects growth rate.

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8
Q

How does richness of medium affect growth rate?

A
  1. Faster growth rate, richer in certain components, like RNA.
  2. Control rate of synthesis of each macromolecule to reflect richness of media and potential growth rate.
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9
Q

What are the three ways regulations refers to the regulation of enzymes?

A
  1. Changing enzyme activity.
  2. Changing amount of enzyme.
  3. Changing amount of substrate.
    (text- not much focus—changing the first 2 results
    in changes in substrates through biochemical
    pathways)
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10
Q

Why is controlling enzyme amounts more common in prokaryotes than in plant and animal cells?

A

Substrate limited
Coupled transcription and translation (adjust quickly)
mRNAs are short lived
Operons

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11
Q

Controlling enzyme activity:

A

Less common
Rates of metabolic reactions and to coordinate some cellular processes
Covalent modification (like phosphorylation)
Allostery (more common)

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12
Q

Covalent modification:

A

Examples: phosphorylation, adenylation

Not as common; important in some pathways, like chemotaxis.

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13
Q

Allosteric Interactions:

A

More common
Can be positive or negative, effect rate or substrate affinity
Binding of an effector to enzyme allosteric site
Not the same as competitive inhibition

Examples:
Biosynthesis- feedback common
Fueling- inhibition or activation dependent on allosteric effectors
Regulating RNAs

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14
Q

Feedback inhibition:

A

Nearly all building blocks control their own synthesis
by acting as negative allosteric effectors of the first
enzyme in their biosynthetic pathway

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15
Q

Regulatory sRNAs:

A
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16
Q

Regulatory Mechanisms of Protein Synthesis Diagram:

A
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17
Q

Regulatory Mechanisms:
1. DNA topology

A

Prevent or promote Sigma/RNAP binding the promoter
Supercoiling or packaging

18
Q

Regulatory Mechanisms:
2. Promoter Recognition

A

Interfere with promoter recognition.
Alternative sigma factors that direct RNAP to certain genes in the chromosome
Different Sigma factors expressed under different conditions.

19
Q

Regulatory Mechanisms:
3, 4, and 5: Transcriptional repression, activation, and enhancement

A

DNA control regions (like operators) are in, near, or far away from promoters.
Regulatory proteins bind control regions.

20
Q

Enhancers:

A

Long distance control DNA sequence, bending of DNA- enhancer-binding proteins.

21
Q

Activators:

A

Positive regulator (protein)- increase reaction.

22
Q

Repressors:

A

negative regulator (protein), decrease reaction.

23
Q

Where are most protein coding genes?

A

In operons.

24
Q

Most protein regulation is based on what?

A

Operon regulation.

25
Q

What is an operon?

A

Group of co-localized genes (cistronic), same promoter, same transcript (mRNA).
-Polycistronic

26
Q

What are the five parts of the Lac operon?

A
  1. Promoter
  2. Genes
  3. Transcription terminator
  4. Operator
  5. Regulatory gene
27
Q

What are the three things the lac operon has taught us?

A
  1. Initiation of transcription from the promoter of an operon can be a site of regulation
  2. Initiation of transcription can be controlled by allosteric proteins
  3. Increase in the expression of an operon can be triggered by relief of a negative control
28
Q

Transcription termination: Attenuation

A

Transcription prevented, because translation can occur.
Prevents cell from making tryptophan if trp is present.
High trp in cell, ribosome translation moves through trp codons in leader sequence (stem loop transcription terminator)
Low trp in cell, ribosome stalls on trp codons- different stem-loop, allows reaction.

29
Q

sRNAs:
Some RNAs are regulatory, what do they do?

A
  • Mimic Open Complex and bind RNAP-Sigma70
    holoenzyme
  • Binds to Promoter DNA
  • Termination loop formation on mRNA that
    stops RNAP elongation
30
Q

mRNA stability:

A

Some mRNAs have a shorter or longer life span.

31
Q

What does sRNA bind to and do?

A

Bind and trigger degradation of target mRNA molecules

32
Q

Translational control:

A

Regulation of initiation of translation. Too much protein present in cell- will not be translated.
Binding to mRNA- sRNA, metabolites, or r-proteins.

33
Q

Proteolysis:

A

Degradation of protein following translation.
-regulated
often for regulatory proteins (like Sigma factors)

34
Q

Regulons:

A

Frequently; multiple operons, simultaneously
regulated by same proteins

35
Q

Modulons:

A

Group of regulons.

36
Q

What are the two system types of modulons?

A
  • Catabolite Repression System
  • Stringent Response System
37
Q

When is glucose used in catabolite repression?

A

First, it’s a better energy source.

38
Q

When glucose is gone, what happens?

A

When gone: increases frequency of
transcription initiation for operons that
control expression of genes involved in
catabolism of other substrates

39
Q

What is the stringent response system a response to?

A

Starvation.

40
Q

Why regulate both protein activity and amounts?

A
  • Save energy
  • Fast response
  • Metabolic coordination
41
Q
A

Microbiology (22 decks)

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