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Biology Edexcel B > Microbiology and Pathogens > Flashcards

Microbiology and Pathogens Flashcards

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1
Q

What is the structure of DNA?

A

Double helix composed of nucleotides containing a phosphate group, a sugar, and a nitrogenous base.

The four nitrogenous bases are adenine, thymine, cytosine, and guanine.

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2
Q

Describe the process of DNA replication.

A

The double helix unwinds, DNA polymerase synthesizes new strands by adding complementary nucleotides.

This process is semi-conservative, meaning each new DNA molecule consists of one old and one new strand.

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3
Q

List three features of prokaryotic cells.

A
  • Lack membrane-bound organelles
  • Single-celled organisms
  • Circular DNA structure

Prokaryotic cells include bacteria and archaea.

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4
Q

Describe the structure of the HIV virus.

A

HIV is an enveloped virus with a cone-shaped core containing RNA and reverse transcriptase.

The envelope is derived from the host cell membrane and contains glycoproteins.

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5
Q

List three disaccharides and their monomers.

A
  • Sucrose: glucose + fructose
  • Lactose: glucose + galactose
  • Maltose: glucose + glucose

Disaccharides are formed by glycosidic bonds between monosaccharides.

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6
Q

Compare and contrast two types of lipids.

A
  • Saturated lipids: no double bonds, solid at room temperature
  • Unsaturated lipids: one or more double bonds, liquid at room temperature

Saturated fats are typically found in animal products, while unsaturated fats are found in plants and fish.

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7
Q

Explain how the structure of glycogen relates to its function.

A

Glycogen is highly branched, allowing rapid release of glucose when needed.

It serves as a primary energy storage molecule in animals.

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8
Q

Why are electron microscopes used to see organelles in more detail?

A

They use electrons instead of light, providing higher resolution and magnification.

This allows visualization of structures at the nanometer scale.

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9
Q

List the order of taxa in the classification system.

A
  • Domain
  • Kingdom
  • Phylum
  • Class
  • Order
  • Family
  • Genus
  • Species

This hierarchy is used to categorize and identify organisms.

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10
Q

Compare and contrast allopatric and sympatric speciation.

A
  • Allopatric: speciation due to geographic isolation
  • Sympatric: speciation occurring in the same geographic area due to ecological or behavioral differences

Allopatric speciation often involves barriers like mountains or rivers.

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11
Q

What is aseptic technique?

A

Methods used to prevent contamination during microbial culture.

It includes sterilization, disinfection, and maintaining a sterile environment.

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12
Q

What are the essential requirements for culturing microorganisms?

A
  • Oxygen
  • Warm temperature
  • Nutrients
  • pH

These factors are crucial for optimal growth conditions.

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13
Q

What is an autoclave?

A

A machine that uses steam under pressure to kill harmful microorganisms.

It is commonly used for sterilizing laboratory equipment.

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14
Q

What are broth cultures?

A

Liquid cultures used to grow microorganisms.

They provide a nutrient-rich environment for growth.

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15
Q

What are agar cultures?

A

Solid cultures used to grow microorganisms on a gel-like medium.

Agar allows for easy visualization and isolation of individual colonies.

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16
Q

What is selective medium?

A

A culture medium that contains specific chemicals to support the growth of certain microorganisms.

It is used to isolate particular species from a mixture.

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17
Q

What is batch culture?

A

A method where bacteria are inoculated into a fixed volume of growth medium.

Growth rates may decline as nutrients are depleted.

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18
Q

What is continuous culture?

A

A method where growth medium is continuously added and waste is removed.

This allows for sustained growth and nutrient availability.

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19
Q

What is inoculation?

A

The process of adding bacteria to a nutrient medium.

It is crucial for initiating microbial growth in cultures.

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20
Q

What is the streak plate method?

A

A technique used to isolate a pure culture from a mixed sample.

It involves spreading bacteria across an agar plate in a specific pattern.

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21
Q

What are the four phases of growth curves?

A
  • Lag phase
  • Exponential phase
  • Stationary phase
  • Death phase

Each phase represents different growth dynamics and nutrient availability.

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22
Q

What does turbidity mean in microbiology?

A

A measure of how clear a liquid is, indicating microbial growth.

Higher turbidity suggests a higher concentration of microorganisms.

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23
Q

What is the purpose of a haemocytometer?

A

A device used to count cells in a liquid culture.

It allows for estimation of cell concentration in a sample.

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24
Q

What is dry mass measurement?

A

A method of measuring the biomass of microorganisms by weighing dried cells.

This technique provides an estimate of the total mass of cells in a culture.

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25
Q

What are the advantages of measuring bacterial growth using turbidimetry?

A
  • Quick assessment
  • Non-destructive

However, it cannot differentiate between live and dead cells.

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26
Q

What are the disadvantages of using dilution plating?

A
  • Time-consuming
  • Requires serial dilutions

It may also underestimate viable counts if cells are clumped together.

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27
Q

What is the difference between gram-positive and gram-negative bacteria?

A

Gram-positive bacteria have a thick peptidoglycan layer, while gram-negative bacteria have a thin peptidoglycan layer and an outer lipid membrane.

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28
Q

What is meant by a pathogen?

A

A pathogen is an organism that causes disease.

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29
Q

Where does transcription happen and what is produced?

A

Transcription happens in the nucleus and produces mRNA.

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30
Q

Where does translation happen and what is produced?

A

Translation happens in the cytoplasm and produces proteins.

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31
Q

Name three examples of aseptic technique.

A
  • Sterilizing equipment
  • Using gloves
  • Working near a flame
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32
Q

What is turbidity?

A

Turbidity is a measure of the cloudiness or haziness of a liquid caused by large numbers of tiny particles.

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33
Q

How can a mutation lead to a non-functional enzyme being produced?

A

A mutation can alter the amino acid sequence of a protein, affecting its structure and function.

34
Q

What is the general structure of bacterial cells?

A

Bacterial cells typically have a cell wall, cell membrane, cytoplasm, and genetic material (DNA).

35
Q

How do bacteria damage cells?

A

Bacteria can damage cells by producing toxins, invading tissues, and triggering inflammatory responses.

36
Q

What are endotoxins and which type of bacteria produce them?

A

Endotoxins are components of the outer membrane of gram-negative bacteria, released when the bacteria die.

37
Q

What are exotoxins?

A

Exotoxins are proteins released by both gram-positive and gram-negative bacteria that can cause damage to the host.

38
Q

What is the role of O antigen in endotoxins?

A

O antigen allows the production of antibodies against bacteria.

39
Q

What is the core component of endotoxins?

A

The core component is a polysaccharide.

40
Q

What is Lipid A in the context of endotoxins?

A

Lipid A is the toxic part of the endotoxin structure.

41
Q

True or False: Exotoxins have a more localized effect compared to endotoxins.

A

False. Exotoxins have a more widespread effect.

42
Q

What are haemolysins?

A

Haemolysins are proteins that create pores in cell membranes, leading to cell lysis.

43
Q

What are superantigens?

A

Superantigens are proteins that stimulate the immune system and can lead to toxic shock syndrome.

44
Q

What happens to macrophages during tuberculosis infection?

A

Macrophages engulf the bacterium and become sealed in tubercles with a thick waxy coat.

45
Q

What is meant by the term ‘dormant’ when referring to TB?

A

Dormant refers to the state when the bacteria are inactive and not causing disease.

46
Q

Fill in the blank: Endotoxins are produced by _______ bacteria.

A

[gram-negative]

47
Q

Fill in the blank: Exotoxins are released into the _______ and can have widespread effects.

A

[blood and bodily fluids]

48
Q

What are the two types of toxins produced by bacteria?

A
  • Endotoxins
  • Exotoxins
49
Q

Name an example of a bacterium that produces exotoxins.

A

Staphylococcus

50
Q

Explain why a person with HIV may be more likely to develop TB if exposed.

A

A weakened immune system allows bacteria to become active and cause disease.

51
Q

Compare and contrast Endotoxins and Exotoxins

A

-Endotoxins have the structure of a lipopolysaccharide while Exotoxins have a prottein structure.

-Endotoxins results to delayed symptoms response after infection while Exotoxins results to immediate symptoms after infection.

-Endotoxins cannot be denatured by boiling while Exotoxins can be denatured by boiling.

-Endotoxins are released when bacterial cell membrane/wall is damaged while Exotoxins are released anytime outside the bacterial cell.

52
Q

What type of toxin is produced by Salmonella?

A

Endotoxins

53
Q

What type of toxin does Staphylococcus produce?

A

Exotoxins

54
Q

Example of Staphylococcus exotoxins

A

Haemolysins and Superantigens

55
Q

Describe the invasion of host tissue by “Mycobacterium tuberculosis”

A

Phagocytes in lungs engulf the bacterium, then other immune cells (T cells) surround the infected macrophages. They become sealed in tubercules with a thick waxy coat and infection remains dormant for years, but become active if immune system become weakened.

56
Q

Name two types of bacteria and give an example of each.

A

Gram-positive (e.g., Staphylococcus aureus)
Gram-negative (e.g., Escherichia coli)

Gram-positive bacteria have thick cell walls, while gram-negative bacteria have thinner walls and an outer membrane.

57
Q

Compare the structures of Gram-positive and Gram-negative bacteria.

A

Gram-positive: thick peptidoglycan layer
Gram-negative: thin peptidoglycan layer with an outer membrane

The structural differences affect their response to antibiotics.

58
Q

Name two types of toxins and which bacteria they come from.

A

Exotoxins (e.g., produced by Clostridium botulinum)
Endotoxins (e.g., found in Escherichia coli)

Exotoxins are secreted by bacteria, while endotoxins are part of the bacterial cell wall.

59
Q

Describe the structure of an endotoxin.

A

Lipid A component of lipopolysaccharide (LPS)

Endotoxins are found in the outer membrane of Gram-negative bacteria.

60
Q

Give three differences between exotoxins and endotoxins.

A
  • Exotoxins are secreted; endotoxins are part of the cell wall
  • Exotoxins are typically more potent
  • Exotoxins can be neutralized by antibodies; endotoxins cannot

These differences impact their role in disease.

61
Q

What is meant by the term ‘dormant’ when referring to TB?

A

The bacteria are inactive but can reactivate later

Dormancy is a key factor in the persistence of tuberculosis infection.

62
Q

Explain why a person with HIV may be more likely to develop TB if exposed.

A

HIV weakens the immune system, making it less effective at controlling TB bacteria

Individuals with compromised immune systems are at higher risk for opportunistic infections.

63
Q

Explain how starch is adapted to carry out its function.

A

Starch is a polysaccharide, providing energy storage in plants due to its insolubility and compact structure

Starch consists of amylose and amylopectin, which enhance its storage capability.

64
Q

Describe the process of translocation in plants.

A

Movement of sugars and nutrients through the phloem from sources to sinks

Translocation is essential for plant growth and development.

65
Q

What are two types of antibiotics?

A
  • Bactericidal
  • Bacteriostatic

Bactericidal antibiotics kill bacteria, while bacteriostatic antibiotics inhibit bacterial growth.

66
Q

Name examples of antibiotics you may have been given.

A
  • Amoxicillin
  • Doxycycline
  • Penicillin
  • Ciprofloxacin
  • Clindamycin
  • Metronidazole
  • Streptomycin
  • Trimethoprim

These antibiotics target various bacterial infections.

67
Q

What does it indicate about antibiotics if they are effective against different bacteria?

A

They have varying mechanisms of action and target different bacterial structures

This variability is important for treating specific infections.

68
Q

Why can you not assume that an antibiotic effective on one bacteria would be effective on another?

A

Different bacteria have unique structures and resistance mechanisms

Understanding the specific targets of antibiotics is crucial for effective treatment.

69
Q

What is the difference between broad-spectrum and narrow-spectrum antibiotics?

A
  • Broad-spectrum: kill a wide range of bacteria
  • Narrow-spectrum: kill a limited number of bacteria

The choice of antibiotic spectrum is important for minimizing disruption to normal flora.

70
Q

What do bactericidal antibiotics do?

A

Destroy the cell wall of bacteria by inhibiting cross-linking in peptidoglycan

This action leads to bacterial lysis.

71
Q

Are the effects of bactericidal antibiotics reversible or irreversible?

A

Irreversible

Bacteria are killed, leading to permanent loss.

72
Q

Which type of bacteria would be most affected by bactericidal antibiotics?

A

Gram-positive bacteria

Their thick cell walls are particularly vulnerable to destruction.

73
Q

What do bacteriostatic antibiotics do?

A

Prevent protein synthesis and nucleic acid production

They halt bacterial growth rather than killing bacteria outright.

74
Q

Are the effects of bacteriostatic antibiotics reversible or irreversible?

A

Reversible

Bacteria can resume normal functions if the antibiotic is removed.

75
Q

Why is it useful that tetracycline doesn’t get transported into eukaryotic cells?

A

It selectively targets bacteria without affecting human cells

This selectivity minimizes side effects.

76
Q

Name two methods of action of antibiotics.

A
  • Inhibiting cell wall synthesis
  • Preventing protein synthesis

Different antibiotics utilize various mechanisms to combat bacterial infections.

77
Q

Describe how penicillin treats bacterial infections.

A

Inhibits the synthesis of the bacterial cell wall, leading to lysis

Penicillin is effective against Gram-positive bacteria.

78
Q

Describe the mechanisms by which bacteriostatic antibiotics work.

A
  • Inhibit protein synthesis (e.g., tetracycline, erythromycin)
  • Prevent nucleic acid synthesis (e.g., sulfonamides)

Bacteriostatic antibiotics halt growth without killing bacteria directly.

79
Q

Why are there more types of antibiotics discovered in the past than more recently?

A

Early discoveries led to a variety of derivatives; later discoveries face more resistance and regulatory challenges

The evolution of bacterial resistance complicates antibiotic development.

80
Q

Why can rapidly acting bactericidal antibiotics against non-typhoidal Salmonella enterica sometimes lead to symptoms?

A

They can cause a rapid release of endotoxins as bacteria die

This can lead to systemic inflammatory responses.

81
Q

Explain why the administration of bacteriostatic antibiotics usually lasts longer than that of bactericidal antibiotics.

A

Bacteriostatic antibiotics allow the immune system to clear the infection, while bactericidal antibiotics kill bacteria quickly

This difference in action can influence treatment duration.

Biology Edexcel B (4 decks)

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