Chapter 5&6 lecture flashcards Preview

Microbiology > Chapter 5&6 lecture flashcards > Flashcards

Flashcards in Chapter 5&6 lecture flashcards Deck (97):
1

Cells must accomplish 2 fundamental tasks to grow

1. Synthesize new components = ANABOLISM
- Biosynthesis
2. Harvest energy = CATABOLISM

2

The sum total of chemical reactions of biosynthesis and energy-harvesting is termed?

Metabolism

3

Metabolism has 2 components

1) Catabolism
– Degradative reactions
– Produce energy from breaking down molecules
2) Anabolism
– Synthesis of cell components
– Require energy input
* Anabolic reactions utilize the energy produced from catabolic reactions

4

Metabolic pathways occur in sequence of chemical reactions

* Starting compound is converted to intermediate molecules and end products.
- Intermediates and end products can be used as precursor metabolites
* Metabolic pathways employ critical components to complete processes:
 Enzymes
 ATP
 Chemical energy source
 Electron carriers
 Precursor metabolites

5

What is the role of enzymes?

– Enzymes facilitate each step of metabolic pathway
– They are generally proteins and act as catalysts
* Favors (does not accelerate) conversion of substrate to product
– Catalyze reactions by lowering activation energy
* Energy required to initiate a chemical reaction

6

Enzyme inhibitors

– Competitive inhibitors bind active site
– Allosteric inhibitors bind elsewhere causing shape of enzyme to change

7

Role of ATP

– Adenosine triphosphate (ATP)
* Energy currency of cell
– Negatively charged phosphate groups attached to
adenosine molecule
* Negative charges of phosphate repel each other & create unstable bond that is easily broken releasing energy
– ATP created by 3 mechanisms:
 Substrate phosphorylation
 Oxidative phosphorylation
 Photophosphorylation

8

Substrate phosphorylation uses?

Chemical energy to add phosphate ion to molecule of ADP

9

Oxidative phosphorylation uses?

Energy from proton motive force to add phosphate ion to ADP

10

Photophosphorylation ultilizes?

Radiant energy from sun to convert ADP to ATP

11

Role of chemical energy source

- Energy source: Compound broken down to release energy, variety of compounds available, glucose most common organic molecule

12

Harvesting energy requires series of couples reactions

Oxidation-reduction reactions

13

Oxidation-reduction reactions

– Electrons transferred from one substance to another
* Compounds that LOSE electrons are oxidized (termed electron donor)
* Compounds that GAIN electrons are reduced (termed electron carrier)
– In reactions, electrons are removed
* Protons often follow, generally in the form of H+ ion
– H+ ion has one proton and no electron

14

Three different types of electron carriers

1) Nicotinamide adenine dinucleotide (NAD+)
2) Flavin adenine dinucleotide (FAD)
3) Nicotinamide adenine dinucleotide phosphate (NADP+)

15

Reduced forms of electron carriers represents?

Reducing power.
- due to usable energy in bonds
Reduced forms are:
– NADH
– FADH2
– NADPH

16

Precursor metabolites are?

– Intermediate products produced in catabolic pathways
– Used in anabolic pathways
* Serve as raw materials for construction of macromolecules

17

The key central metabolic pathways are?

– Glycolysis
– Tricarboxylic acid cycle (TCA)
– Electron Transport Chain
– Fermentation
– Pentose phosphate pathway

18

Central (metabolic) pathways are amphibolic and provide?

– Energy (ATP)
– Reducing power
– Precursor metabolites

19

Electrons move from one carrier to another, eventually to a?

Terminal e- acceptor

20

This chain (electron transport chain) allows protons to be pumped across the cell membrane of prokaryotes, a?

PROTON GRADIENT

21

Proton gradient provides energy to?

Phosphorylate ADP -> ATP

22

Respiration generates a?

Proton gradient
– Produces ATP by oxidative phosphorylation
– Used to power flagella and some active transport

23

Aerobic respiration

– Final electron acceptor is O2 (yields H2O)
– Uses Krebs (TCA) cycle
– More ATP generated = most effective

24

Anaerobic respiration

Anaerobic respiration
– Final electron acceptor is not Oxygen
– Uses modified Krebs (TCA) cycle, generating less reducing power
– Less ATP generated = less effective

25

Fermentation is?

1) For cells that cannot respire
2) Do not oxidize glucose completely
3) Produces less ATP than either form of respiration
4) Uses pyruvate, or other organic molecule as terminal electron acceptor
5) Process may produce acids, alcohols, and gases

26

The pentose phosphate pathway is?

1) Necessary for production of NADPH and certain precursor metabolites
2) NADPH is a coenzyme needed for synthesis of nucleotides and fats
3) Required for the production of nucleotides, glucose (via photosynthesis), and some amino acids

27

Photosynthetic metabolism in a nutshell

1) Generate chemical energy (ATP) from absorbing light
– Utilizes an electron transport chain
– Yields O2
2) Calvin Cycle (most common pathway of carbon fixation)
– “Fixes” atmospheric CO2 to generate organic compounds
– Use ATP to provide energy to cycle
– Yields sugar (fructose)

28

Prokaryotes divided based on oxygen requirements

1) Obligate aerobes
2) Obligate anaerobes
3) Facultative anaerobes
4) Microaerophiles
5) Aerotolerant anaerobes

29

Obligate aerobes (2 main points)

– Absolute requirement for oxygen
– Need oxygen to produce energy

30

Obligate anaerobes (2 main points)

– No multiplication in presence of oxygen
– May cause death

31

Facultative anaerobes (2 main points)

– Grow better with oxygen
– Use fermentation in absence of oxygen

32

Microaerophiles (2 main points)

– Require oxygen in lower concentrations
– Higher concentration inhibitory

33

Aerotolerant anaerobes (2 main points)

– Indifferent to oxygen, grow with or without
– Do not use oxygen to produce energy

34

Optimum temperature -5°C to 15°C
– Found in Arctic and Antarctic regions

Psychrophile

35

Temperatures in 20°C to 30°C range
* Important in food spoilage

Psychrotroph

36

Temperatures in 25°C to 45°C range
* More common
* Disease causing

Mesophile

37

Temperatures in 45°C to 70°C range
* Common in hot springs

Thermophiles

38

Temperatures in 70°C to 110°C range
* Usually members of Archaea
* Found in hydrothermal vents

Hyperthermophiles

39

Do not cause disease in humans because they cannot survive at body temps; some do cause food spoilage in refrigerators

Psychrophiles

40

Because normal body temp. is around 37 Degrees C, human pathogens are?

Mesophiles

41

Mesophiles that can survive brief periods at higher temps.

Thermoduric organisms.

42

Thermophiles & hyperthermophiles stabilize their proteins with extra?

Hydrogen & covalent bonds between amino acids

43

Heat-loving organisms do not cause disease because?

They "freeze" at body temps.

44

Organisms are sensitive to changes in acidity because hydrogen ions and hydroxyl ions interfere with hydrogen bonding w/in proteins and nucleic acids; as a result organisms have ranges of?

Acidity that they prefer & can tolerate

45

A pH below 7.0 is _______; the lower the pH value, the more ______ a substance is

Acidic

46

Alkaline pH values are?

Higher (basic) than 7.0

47

Most bacteria & protozoa, including most pathogens, grow best in what type of pH?

A narrow range around a neutral pH between 6.5 and 7.5. Such microbes are thus called neutrophiles

48

Some bacteria & many fungi are acidophiles which are?

Organisms that grow best in acidic habitats

49

Obligate acidophiles require an acidic environment & die if the pH approaches

7.0

50

The low pH of some cheeses act as what?

Preservative by preventing any further microbial growth. Other acidic foods, such as sauerkraut and dill pickles are also kept from spoiling because most organisms cannot tolerate their low pH

51

Multiply between pH of 5 to 8
– Maintain optimum near neutral

Neutrophiles

52

Thrive at pH below 5.5
– Maintains neutral internal pH, pumping out protons (H+)

Acidophiles

53

Grow at pH above 8.5
– Maintain neutral internal pH through sodium ion exchange
– Exchange sodium ion for external protons

Alkalophiles

54

Pumping of hydrogen ions in the electron transport chain generates what?

The gradient used by the ATP synthase complex to synthesis ATP

55

In addition to the protein complexes in the electron transport chain are?

Two mobile carries:
1) Ubiquinone
2) Cytochrome c

56

At the start of the electron chain ___ electrons are passed from?

2 electrons are passed from NADH into the NADH dehydrogenase protein complex. Coupled with this transfer is the pumping of one hydrogen ion for each electron

57

After the beginning of the electron transport chain where NADH passes 2 electrons and the pumping of one hydrogen ion for each electron what happens?

The two electrons are transferred to ubiquinone which moves the electrons to the next protein complex (cytochrome b-c1). Each electron is then passed from the complex (cytochrome b-c1) to the mobile cytochrome c which accepts one electron at a time. One hydrogen ion is pumped through the complex as each electron is transferred

58

Osmotolerant bacteria tolerate what?

high salt environments

59

Bacteria that require high salt for cell growth termed?

halophiles

60

All microorganisms require water for? not available in all environments

Water

61

In high salt environments bacteria increase?

internal solute concentration. Synthesize small organic molecules

62

Growth of prokaryotes depends on nutritional factors as well as physical environment.
Main factors to be considered are:

–Required elements
– Growth factors
– Energy sources
– Nutritional diversity

63

Required elements. Major elements

Carbon, oxygen, hydrogen, nitrogen, sulfur, phosphorus, potassium, magnesium, calcium and iron.
– Essential components for macromolecules

64

Organisms classified based on carbon usage

1) Heterotrophs– Use organic carbon as nutrient source
2) Autotrophs– Use inorganic carbon (CO2) as carbon source

65

Trace elements

Cobalt, zinc, copper, molybdenum and manganese.
– Required in minute amounts

66

Culture media can be liquid or solid

1) Liquid is broth media used for growing large numbers of bacteria
2) Solid media is broth media with addition of agar
- Agar marine algae extract
- Liquefies at temperatures above 95°C
- Solidifies at 45°C
- Remains solid at room temperature and body temperature

67

Bacteria grow in colonies on?

Solid media surface.
- All cells in colony descend from single cell
- Approximately 1 million cells produce 1 visible colony

68

The Growth Curve
– Characterized by 4 distinct phases:

1) Lag
2) Log (exponential)
3) Stationary
4) Death

69

Growth can be calculated

Nt=N0x2n
* (Nt ) number of cells in population
* (N0 ) original number of cells in the population
* (n) number of divisions

70

Some bacteria cannot synthesize some cell constituents

These must be added to growth environment. Referred to as growth factors

71

Organisms can display wide variety of factor requirements

Some need very few while others require many. These termed fastidious

72

Complex media

– Contains a variety of ingredients
– There is no exact chemical formula for ingredients
- Can be highly variable
* Examples include:
1) Nutrient broth
2) Blood agar
3) Chocolate agar

73

Chemically defined media

– Composed of precise amounts of pure chemicals
– Generally not practical for routine laboratory use
- Invaluable in research
- Each batch is chemically identical
- Does not introduce experimental variable

74

Selective media

Inhibit the growth of unwanted organisms. Allow only sought after organisms to grow

75

Thayer-Martin agar– For isolation of N. gonorrhoeae is an example of?

Selective media

76

MacConkey agar–For isolation of Gram- negative bacteria is an example of?

Selective media

77

Contains substance that bacteria change in recognizable way

Differential media

78

Blood agar– Certain bacteria produce hemolysin to break down RBC. Hemolysis. This is an example of?

Differential media

79

MacConkey agar– Contains pH indicator to identify bacteria that produce acid. This is an example of?

Differential media

80

Culturing anaerobes

1) Some die in the presence of oxygen even if exposed for a short time
2) Incubated in anaerobe jar
- Chemical reaction converts atmospheric oxygen to water
- Organisms must be able to tolerate oxygen for brief period
3) Reducing agents in media achieve anaerobic environment
- Agents react with oxygen to eliminate it
- Sodium thioglycolate
4) Anaerobic chamber also used for cultivation

81

Streak-plate method

– Simplest and most commonly used in bacterial isolation
– Object is to reduce number of cells being spread
- Solid surface dilution
- Each successive spread decreases number of cells per streak

82

Measuring turbidity with a?

spectrophotometer.
– Measures light transmitted through sample
– Measure is inversely proportional to cell concentration
– Must be used in conjunction with other tests once to determine cell numbers

83

Reduction reactions are those in which electrons are added. The molecule that donates an electron is oxidized. If the electron is part of a hydrogen atom, an oxidation reaction is also called?

Dehydrogenation.

84

Apoenzymes are the portions of enzymes that may require one or more?

Cofactors such as inorganic ions or organic cofactors (also called coenzymes)

85

The combination of both apoenzyme and its cofactors is a?

Holoenzyme

86

Feedback inhibition (negative feedback) occurs when?

The final product of a series of reactions is an allosteric inhibitor of some previous step in the series. Thus, accumulation of the end-product "feeds-back" into the series a signal that stops the process

87

The pentose phosphate and Entner-Doudoroff pathways are alternative means for the catabolism of glucose that yield fewer ATP molecules than does glycolysis. However, they produce?

Precursor metabolites not produced in glycolysis

88

Two carbons from pyruvic acid join coenzyme A to form acetylcoenzyme A (acetyl-CoA), which then enters the Krebs cycle, a series of 8 enzymatic steps that transfer electrons from?

Acetyl-CoA to coenzymes NAD+ & FAD

89

Aerobes use oxygen atoms as final electron acceptors in their electron transport chains in a process known as aerobic respiration, whereas anaerobes use?

Other inorganic molecules (such as N03-, SO42-, and CO32-), or rarely an externally acquired organic molecule as the final electron acceptor in anaerobic respiration

90

A proton gradient is an electrochemical gradient of?

Hydrogen ions across a membrane. It has potential energy known as a proton motive force

91

Oxidative phosphorylation and photophosphorylation use?

Chemiosmosis

92

Catabolic process in which enzymes split pairs of hydrogenated carbon atoms from a fatty acid & join them to coenzyme A to form acetyl-CoA

Beta-oxidation

93

Secreted by microorganisms to digest proteins outside the microbes cell walls. The resulting amino acids are moved into the cell & used in anabolism, or deaminated and catabolized for energy

Proteases

94

Metabolic reactions that are reversible- they can operate catabolically or anabolically

Amphibolic reactions

95

Some cells are able to synthesis glucose from amino acids, glycerol, & fatty acids via a process called

Gluconeogenesis

96

Reactions involving adding an amine group from ammonia to a metabolite to make an amino acid.

Amination

97

Occurs when an amine group is transferred from one amino acid to another

Transamination