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Biology > 6A > Flashcards

6A Flashcards

1
Q

what are the resources microorganisms need to grow

A
  • nutrients
  • oxygen ( anaerobic organisms require the absence of oxygen)
  • optimum pH
  • favorable temperature
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2
Q

describe the process of binary fission

A
  • the single circular DNA molecule starts to replicate
  • any plasmid will undergo DNA replication
  • the parent cell will divide into tow daughter cell which the cytoplasm will be halved roughly
  • the two daughter cells have one copy of circular DNA and variable copies of plasmids
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3
Q

describe the 4 phases in the population growth of microorganisms

A
  • Lag phase: the population number increases slowly since microorganisms are adjusting to the new environment
  • Exponential (log) phase: as there are a high availability of nutrients and space the population doubles with each division
  • Stationary phase: the population reaches its maximum due to the lack of access to nutrients and space the no. of death = no. of microorganisms produced then growth curve levels off
  • Death (decline phase): due to the lack of nutrients and build up of toxic waste and the population starts to decline
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4
Q

what is the difference between prokaryotes and eukaryotic

A
  • prokaryotes lack membrane-bound organelles
  • Ribosomes that are smaller (70 S) than those found in eukaryotic cells (80 S)
  • prokaryotes have no nucleus but have a circular DNA material
  • prokaryotes have cell wall that contain glycoprotein murein ( peptidoglycan)
  • some prokaryotes have
    . have loops of DNA known as plasmids
    . capsules help cells to prevent from drying out and attacks from cells
    . Flagella enables the prokaryotic to move
    pili involved in gene transfer ( conjugation )
    . folds known as mesosomes where respiration occurs
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5
Q

Describe the structure of viruses

A
  • viruses are non-cellular particles
  • A nucleic acid core: their genome can be either DNA or RNA
  • have a protein coat called a capsid
  • they do not possess a cytoplasm, plasma membrane or ribosomes
  • some viruses have an outer layer of membrane-phospholipid called an envelope
  • some contain protein in their capsid
  • they contain virus attachments particles eg.glycoproteins
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6
Q

how are viruses classified

A
  • DNA viruses
  • RNA viruses
  • Retroviruses
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7
Q

what are DNA viruses

A
  • they contain DNA as a genetic material
  • viral DNA acts a direct template for producing new viral DNA and mRNA for the viral proteins
  • Ex.: smallpox, adenoviruses, and bacteriophages
  • Bacteriophages are viruses that infect bacteria, such as the λ (lambda) phage
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8
Q

what are RNA viruses

A
  • they contain RNA genetic material
    do not produce DNA
  • mutation are more likely to occur in RNA viruses than in DNA viruses
    EX: tobacco mosaic virus (TMV), Ebola virus
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9
Q

what are Retroviruses

A
  • special type of RNA viruses
  • viral RNA controls the production of enzyme reverse transcriptase which produces viral DNA from the RNA strand and the new viral DNA is incorporated into the host DNA where it produces viral proteins and DNA
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10
Q

how can viruses enter the host cell

A

-Lysogenic
-Lytic

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11
Q

how do viruses use lysogenic pathway

A
  • provirus inserts itself into the host cell which has a viral gene that is coded for repressor protein that prevents the viral DNA from being transcribed
  • every time the host DNA copies itself the viral DNA is also copied this stage is called ( a latent stage) the virus may activate and enter the lytic pathway
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12
Q

How do viruses use lytic pathway

A

-The genetic material is injected into the host cell via endocytosis
- the genetic material is translated and transcribed to produce new viral component which assembles into mature viruses then more viruses are produced until the host cell bursts (lysis)

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13
Q

what is tuberculosis

A

it is a disease which is caused by the bacteria Mycobacterium tuberculosis also known as TB
- the bacteria is engulfed by phagocytes in the lungs and will survive ad reproduce inside the phagocyte this is called the primary infection. Individuals with healthy immune system will not develop TB
- infected phagocytes will become encased in structure called tubercles in the lungs which will remain inactive for a period of time

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14
Q

when does the active phase of TB will occur

A

when the individual becomes infected with HIV and their immune system is compromised

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15
Q

what are the symptoms of TB

A
  • fever
  • fatigue
  • coughing
  • lung inflammation
  • if left untreated the bacteria might cause respiratory failure and lead to organ failure
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16
Q

what is HIV

A

HIV is (human immunodeficiency virus)
- HIV contain RNA and is a retrovirus
- HIV is transmitted by body fluids by:
_ sexual intercourse
_ by blood donation
_ by sharing of needles by intravenous drug users
_ from mother to child across placenta
_ through breast feeding

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17
Q

state the steps of HIV replications

A

1- virus infects helper T cells
2- gradually the virus reduces the number of T cells in the immunity system where:
- B cells are no longer activated
- no antibodies are produced
- the patient begins to suffer from HIV-related symptoms
3- because of the lack of T cells the body will be on the final stage which is advanced AIDS ( Acquired immune deficiency syndrome)

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18
Q

what are the symptoms of AIDS

A

1- mild flu-like symptoms
2- after several months or years the viral DNA replicated by HIV particles will become active and will become AIDS
3-the individual will suffer from a range of more
serious opportunistic infections since the number of T cells is low and the opportunistic will cause this individual to die

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19
Q

what are the factors that affect how quickly HIV will progress into AIDS

A
  • the number of existing infections
  • the strain of HIV the person is infected with
  • their age
  • access to healthcare
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20
Q

what are the major routes pathogens may take when entering a body

A

vectors:
- insects that carry around pathogens and transmit them between hosts
inhalation:
- the airway provides a entry point when the pathogens in the air droplets are inhaled by people
ingestion:
-these pathogens are present in undercooked food and can enter the lining of gut when an individual ingest the food\
indirect contact:
- when an individual touch object that has pathogens on it
Direct contact
- these pathogen transmit from hist to host when they touch each other
- pathogens that use this route can pass through the mucous membrane
Inoculation:
- when pathogens enter into a broken skin

21
Q

what are the barriers to pathogenic entry

A

skin: prevents entry by the blood clotting mechanism when the skin is damaged
Microorganisms of the guts: these harmless pathogens are known as the gut or skin flora(non-pathogenic)
- they compete for resources therefore limiting their numbers and ability to infect the body
Stomach acid:
- the hydrochloric acid is acidic which causes an acidic environment which is unfavorable to pathogens
Lysozyme:
- secretions of mucosal surfaces ex. tears, saliva and mucus contains an enzyme which damages the cell wall of pathogens then they lyse is called lysozyme

22
Q

what are the two types of immune response in the body

A
  • Non-specific: this response produces the same antibodies regardless of the pathogen
  • Specific: this response produces specific antibodies for this pathogen by recognizing the antigens of the pathogen ( glycoproteins ) which identify the pathogen
23
Q

what happens when a pathogen invades the body

A

The NON-SPECIFIC immune response begins:
- inflammation
- interferons
- phagocytosis

24
Q

how does inflammation form

A
  • mast cells (body cells) that respond to damaged tissues by secreting a chemical signalling molecule called histamine which stimulates vasodilation ( the widening of a blood vessel) increases blood flow through capillaries
  • capillaries become more permeable, allowing fluid to enter the tissues which creates swelling
  • phagocytes leave the capillaries to engulf foreign particles
  • cells release cytokines which is a chemical signalling molecule that triggers the immune response in the infected area
25
Q

how does Interferon works for immune response

A
  • cells produce anti-viral protein called interferon which prevent the replication of the virus by inhibiting the production of viral proteins and activate white blood cells with specific immune response to destroy the infected cell
  • they increase the non-specific immune response by inflammation
26
Q

how does phagocytosis

A
  • phagocytes are white blood cells that engulf and digest dead cells or invasive microorganisms this process is known as phagocytosis
  • phagocytes are released in large numbers and they can squeeze themselves through capillary walls
  • Mode of action:
  • histamine and chemicals released by pathogens attracts phagocytes
  • they bind to the antigens of the pathogen and recognize the pathogen as a non-self (does not belong to the body)
  • the phagocyte extends its membrane and engulfs the pathogen by trapping within a phagocytic vacuole this is part of endocytosis
  • lysosome fuses with the phagocyte to release digestive enzymes (exocytosis) which include lysozyme and digest the pathogen
  • the phagocyte will present the antigen of the pathogen to initiate the specific immune response
27
Q

what are antigens

A
  • they are markers on the cell membrane that identify the cell if self or non-self
  • self antigens do not stimulate the immune response while non-self do
28
Q

how does the immune system is activated by the antigen presenting cell such as macrophages

A

macrophages are a type of phagocytic withe blood cell
- when white blood cells known as lymphocytes bind to the antigens on the membrane with specific receptors

29
Q

describe the structure of the antibody and where does it come from

A
  • antibodies are secreted by a white blood cell called plasma cell
  • antibodies are Y-shaped molecules immunoglobulins
  • antibodies consist of 4 polypeptide chains consist of two long chains attached by disulfide to two short chains
  • each polypeptide chain has a constant region and variable region
  • the amino acid sequences in the variable region are different for each antibody
  • the variable region is where antibody binds with epitope of an antigen to form antibody-antigen complex
  • the hinge region is where the disulfide bonds join long bonds which gives the flexibility to the antibody
    antibodies can be membrane-bound or secreted directly into the blood and membrane-bound antibodies are attached to the surface of lymphocytes
30
Q

what is the function of antibodies

A
  • antibodies act as anti-toxins by binding to the toxins
  • antibodies clump pathogens by a process called agglutination for phagocytes to engulf more numbers of pathogen
31
Q

what are the two types if lymphocytes

A
  • T cells
  • B cells
32
Q

what are T cells

A
  • T cells are produced in the bone marrow and mature in the Thymus
  • when the T cells are activated by macrophages they divide by mitosis to for identical daughter cells with the same receptors
  • T cells divide into three main type of cell:
  • helper T: release chemical signalling molecules to activate B cells
  • killer T: binds to the infected cell to destroy
  • memory T cells: enables a faster specific immune response for the same pathogen
33
Q

what are B cells

A
  • they are produced and mature in the Bone marrow
  • each B cell has different antibody receptor
  • when one of the B cells match the antigen of the pathogen it gets activated then this B cell will divide to daughter cell by mitosis to produce two types of daughter cell:
  • effector cell, which forms into plasma cell to produce antibodies
  • memory cell remain in the blood to allow faster immune response for the same pathogen
34
Q

what happens when the immune system encounters the antigen for the first time

A
  • the immune system will be activate which launches primary immune response where the number of T and B cells are low
  • they will take time to divide into daughter cell
  • when the immune system encounters the same pathogen it will launch a secondary immune response which is specific where it is faster and stronger with larger number of antibodies and more quickly
  • this will eliminate the pathogen
35
Q

what is active immunity

A

it is acquired when a pathogen enters the body
naturally or by vaccination which will result in long-term immunity

36
Q

what is passive immunity

A
  • it does not require immune system where antibodies are gained from other resource
  • antibodies can be passed:
    naturally: fetus receives antibodies through placenta or by breastfeeding
    Artificial: people can be given injection of antibodies where the antibodies had been collected from other organisms or people
  • no memory cells are produced through the process that enable a secondary response
37
Q

what are vaccines

A
  • a vaccine contains an antigen from of dead or weakened pathogens or a genetic material that codes for the antigen which would induce active immune response
  • vaccines are given through injection or mouth
  • when antigenic variation occurs the antigen in the vaccine must change
38
Q

what do antibiotics do when they enter an infected body

A
  • they are chemical substances that destroy the bacterial cells
  • antibiotics can be two types:
    bactericidal: they kill bacterial cells
    bacteriostatic: they inhibit bacterial growth process
39
Q

how do antibiotics interfere the growth or metabolism of the pathogen

A
  • inhibit bacterial enzyme they weaken the cell wall then it will burst due pressure of the water
  • binding to the ribosomes where stops protein synthesis to produce enzyme
  • damaging the membrane which leads to loss of metabolisms or uncontrolled water entry
  • preventing bacterial DNA to form rings where it no longer fits
  • eukaryotic cells are not damaged because they have different ribosome, enzyme and no cell wall
40
Q

why are viruses not affected by the antibiotics

A
  • they do not have cell wall, cell membrane, ribosomes nor enzymes
41
Q

why do patients get HAI’s (hospital acquired infections) in the hospital

A
  • because of y poor hygiene
    . people are not washing their hands regularly
    . coughing or sneezing
    . failing to disinfect the tools after use
42
Q

what is an evolutionary race

A

where organisms have evolved their immune system to deal with a wide range of pathogens and pathogens had also evolved different ways to evade their host’s immunity

43
Q

what is evasion mechanism of HIV

A

1- kills helper T cells
2- HIV shows antigenic variability due to high mutation rates which will result in memory cells not recognise

44
Q

what is the evasion mechanism of Mycobacterium tuberculosis TB

A
  • once engulfed by phagocytes the bacteria will produce a chemical that prevents lysosome from fusing with phagocytic vacuole
  • the bacteria can disrupt the antigen presentation in an infected phagocyte with the presence of HIV.
45
Q

how are HAI’s created

A
  • they are caused by antibiotic resistant bacteria
  • they are difficult to treat as they do not respond to regular antibiotics
  • antibiotics act as a selection pressure
46
Q

how to reduce the risk of antibiotic resistant HAIs

A
  • no antibiotics prescriptions for minor infections or viral diseases
  • no use of antibiotics against infection
  • prescriptions of narrow-spectrum antibiotics to treat the infection
47
Q

how to measure the growth of microorganisms using dilution plating

A
  • a single cell will reproduce by cloning itself to produce a mass of identical cells called colony
  • it will be difficult to identify individual colonies therefore using serial dilution it will reduce the number of individual microbial
48
Q

how to measure the growth of fungi using area and mass

A
  • measure the diameter of individual areas of the mycelia the resulting areas of fungal mycelia are then measured
  • this can be used to compare with different temperatures, the larger the diameter the greater the rate of growth
  • testing the dry mass of fungi is another effective way, the greater the mass the higher rate of of fungal growth

Biology (7 decks)

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