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Biology: Unit 4 > Topic 6 > Flashcards

Topic 6 Flashcards

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1
Q

What is a virus

A

Smallest microorganisms
Arrangement of genetic material and protein
Obligate intracellular parasites (can only exist and reproduce in the cells of other organisms

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2
Q

Structure of viruses

What is the capsid?

A

Protein coat

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3
Q

What makes up the capsid

A

Capsomere

Repeating protein units

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4
Q

What is the point of repeating units in the capsid

A

Minimise the amount of genetic material needed to code for coat production

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5
Q

Some viruses have an envelope in their structure what is the purpose of this and what is it made up of

A

Lipid derived membrane
Presence makes it easier for the virus to pass from cell to cell
However it makes it vulnerable to substances such as Ethers which dissolve lipids

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6
Q

Structure of a virus what is contained in the nucleic acid

A

Viral genetic material can be RNA or DNA and the nucleic acid is sometimes double-stranded and sometimes single

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7
Q

What is viral DNA used for

A

Acts as a template for both new viral DNA and for the mRNAs needed to induce synthesis of viral proteins

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8
Q

Give examples of DNA viruses

A

Smallpox virus

Adenoviruses (which causes colds etc)

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9
Q

What are bacteriophages

A

Viruses that infect bacteria

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10
Q

What is a viral RNA used for

A

Synthesis of enzyme called reverse transcriptase which proceeds to make DNA molecules corresponding to the viral genome
This DNA is used as a template for new viral proteins

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11
Q

Give examples of RNA viruses

A

Tobacco mosaic virus

Human immunodeficiency virus

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12
Q

How do viruses attach to their host cells

A

By antigens which target proteins in the host cell surface membrane

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13
Q

What two ways can viruses infect a cell

A

Lysogenic pathway

Lytic pathway

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14
Q

Describe the life cycle of a retrovirus

A

Viral RNA translated into DNA by reverse transcriptase in the cytoplasm
Viral DNA enters nucleus where it is inserted into the host cell
Host makes viral genome RNA, mRNA and coat proteins
Virus particles assemble and leave by exocytosis
Viral DNA remains in the nucleus the cell continues to act as a virus factory

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15
Q

What can viral infections be specific to

A

Particular tissues

E.G Adenoviruses viruses which cause colds affect the tissues of the respiratory tract

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16
Q

What is the specificity due to

A

The presence or absence of cell markers on the surface of host cells
Each type of cell has its own recognition markers and different types of virus can only bind to particular markers

The presence or absence of these markers can affect vulnerability

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17
Q

What are angiosperm and Gymnosperms

A 
Flowering Plants (vulnerable)
Conifers (not vulnerable)
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18
Q

Describe the lysogenic pathway

A

Bacteriophages attacks bacterium

Phage DNA injects viral dna into host cell synthesis of viral enzymes

Viral DNA is incorporated into host cell DNA
Viral DNA is replicated each time the bacterium divides without causing any damage

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19
Q

Describe the Lytic pathway

A

Phage DNA inactivates the host DNA and takes over the cell

Phage DNA is replicated

New Phage Particles are assembled as new protein coats are made around phage DNA
the enzyme lysozyme is synthesised or released

Lysis- the bacterial cell bursts due to the action of the lysozyme releasing up to 1000 phages to infect other bacteria

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20
Q

Are the contents of bacteria hypertonic hypotonic or isotonic?

A

Hypertonic this results in more water moving in By osmosis

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21
Q

State the main features in bacteria

A 
Cell-surface membrane 
Cell wall
Circular DNA
 photosynthetic membrane*
Capsule or slime layer*
Flagellum 
Small ribosomes
Glycogen granules, lipid droplets
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22
Q

What is the purpose of a cell wall in bacteria

A

Prevents the swelling and bursting
Maintain shape and support
Protection

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23
Q

Where is the site of respiration in bacterial cells

A

Bacterial cells have no mitochondria so cell membrane is the site of respiratory enzymes

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24
Q

Some bacterial cells have a slime capsule, why?

A

Formed from starch gelatin protein

protects bacteria from phagocytosis by covering cell markers

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25
Q

flagellum????

A

The flagellum moves the bacterium by rapid rotations

26
Q

Describe genetic material found in bacteria cell

A

Single length of circular DNA lying free in the cytoplasm

27
Q

What makes up a bacterial cell wall

A

Consist of a layer of peptidoglycan

28
Q

Describe the structure of peptidoglycan

A

Many parallel polysaccharide chains with short peptide cross linkages
Net like structure

29
Q

What are the two types of cell walls

A

Gram-positive bacteria

Gram-negative bacteria

30
Q

What colour are gram-positive bacteria compared to gram-negative

A

+ve = purple

-ve= red

31
Q

State the key differences between the two types of cell walls

A

+ve
Thicker layer of peptidoglycan
Contains teichoic acid

-ve
Thinner layer of peptidoglycan
No teichoic acid

32
Q

Explain the colour differences

A

The crystal violet binds to the teichoic acid and resists decolourising, leaving the purple/blue colour

In negative, no teichoic acid to bind to so crystal violet decolourises and is replaced by red safranine, so cells appear red

33
Q

What other features can be used to classify bacteria

A

Shape

Respiratory requirements

34
Q

What 4 categorical shapes are there

A

Spherical (cocci)
Rod shape (bacci)
Twisted. (Spirilla)
Comma shape (vibrios)

35
Q

What’s is meant by:

Obligate aerobes

A

Need oxygen

36
Q

What’s is meant by:

Facultative anaerobes

A

Use oxygen if it is available but can manage without

37
Q

What’s is meant by:

Obligate anaerobes

A

Can only respire in the absence of oxygen

38
Q

2 ways infectious diseases be transmitted?

A

Transmitted from person to person by invading microorganisms

Natural flora getting out of control and becoming pathogenic

39
Q

What ways can bacteria reproduce

A 
asexual reproduction (binary fission)
Sexual reproduction
40
Q

Give 3 ways in which genetic material form one bacterium can be taken in and used as part of the DNA of another bacterium

A

Transformation
Transduction
Conjugation

41
Q

Explain transformation

A

Short piece of DNA is released by a donor and taken up by a recipient where it replaces a similar piece of DNA

42
Q

Explain transduction

A

DNA transferred by a bacteriophage

43
Q

Explain conjugation

A

Genetic material transferred by direct contact

Sex pilus, cytoplasmic bridge DNA. Transferred

44
Q

Typically where does bacteria grow

A

In localised areas, unless they get into the blood stream

45
Q

What two types of toxins are there

A

Endotoxins

Exotoxins

46
Q

What are exotoxins, what are they likely to cause?

A

Lipopolysaccharides- part of the outer layer of gram negative
Rarely fatal, tend to cause symptoms such as fever, vomiting or diarrhoea
E.g. Salmonella
E.coli

47
Q

What are exotoxins, what damage do they cause?

Example?

A

Soluble proteins produced/releases as bacteria metabolise and reproduce

Can damage cell membranes
(Cell breakdown, internal bleeding)
Poison cells

E.g meningitis

48
Q

Give 6 ways a pathogen can invade the body

A 
Fomites
Vectors
Direct contact 
Inhalation 
Ingestion 
Inoculation
49
Q

Explain how pathogens can enter by vectors (example?)

A

Living organism transmits infection from one host to another

E.g malaria, yellow fever

50
Q

Explain and give an example of how pathogens can invade the body by fomites

A

Fomites are inanimate objects that carry pathogens from one host to another

E.g. Hospital towels/bedding
Staphylococcus infections

51
Q

How can pathogens be spread by direct contact (examples)

A

Spreading skin diseases
Sexual diseases

E.g impetigo and herpes

52
Q

How can pathogens be spread by inhalation

A

Cough/sneeze droplets expelled carrying pathogens, water evaporates pathogens remain in air

Examples influenza and TB

53
Q

Describe how ingestion can cause pathogens to invade body

Examples

A

Gut diseases
Transmitted by contaminated food or drink
E.g. Salmonella, hepatitis a

54
Q

Explain inoculation

Examples

A

Pathogens enter body through breaks in the skin
Through injury, contaminated medical instrument or shared needles

HIV, tetanus, hepatitis B

55
Q

How is skin a barrier to infection

A

Natural flora- out compete
Impenetrable layer (toughened with keratin)
Sebum-> chemicals inhibit growth of microorganisms
Surfaces of tubes/ducts vulnerable so mucus containing lysozyme effective protection

56
Q

What is lysozyme

A

Enzyme which destroys microbial cell walls
Effective against gram positive
Present in tears and mucus

57
Q

What else is present on the epithelial surface

A

Phagocytic WBCs engulf and digest pathogens

58
Q

What are the four non-specific response to infection

A

Fever
Inflammation
Lysozymes
Phagocytosis

59
Q

What are the two main groups of white blood cells

A

Granulocytes

Agranulocytes

60
Q

Define phagocyte

A

General term used describe white blood cells which engulf and digest pathogens

61
Q

What are the two main types of phagocytes

A

Neutrophils
(Mostly granulocytes)

Macrophages
(Agranulocytes)

62
Q

What is pus

A

Accumulation of dead cells, mainly neutrophils but also macrophages which produce antibodies

Biology: Unit 4 (2 decks)

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