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AS Biology Term 3 Flashcards

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1
Q

Describe the structure of the human gas exchange system

A
  • As air enters through the mouth or nose, it moves into the trachea which lead from the throat to the lungs.
  • The lungs are found in the thoracic cavity surrounded by pleural membranes, which enclose an airtight space. This space contains fluid to allow for frictionless movement of diaphragm and ribs.
  • The trachea branches out into bronchi which subdivide forming the bronchial ‘tree’ in each lung.
  • Each of the two bronchi branch to form bronchioles.
  • Terminal bronchioles divide to form respiratory bronchioles that end with the alveoli.
  • The alveoli are tiny, collectively have a large surface area, and are the surface for gas exchange in humans.
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2
Q

Describe the distribution of cartilage, goblet cells, smooth muscle, ciliated epithelium, and squamous epithelium in the structures of the gas exchange system

A

Trachea: C-shaped rings of cartilage, goblet cells and smooth muscle present, lining is ciliated epithelium.

Bronchus: Irregular blocks of cartilage, goblet cells and smooth muscle present, lining is ciliated epithelium.

Bronchiole: No cartilage or goblet cells, Terminal has smooth muscle and respiratory does not, lining is ciliated epithelium.

Alveoli: No cartilage, goblet cells or smooth muscle. Lining is squamous epithelium.

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3
Q

Describe the functions of cartilage and smooth muscle in the airways

A

Cartilage: Keeps airways open and air resistance low. Prevents airways from collapsing or bursting as air pressures change.

Smooth muscle: Used in bronchioles to adjust diameter of airways by contracting or relaxing (e.g. during exercise they open wider to allow greater air flow). Absence of cartilage allows such adjustments.

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4
Q

Describe the function of cilia, goblet cells and mucus

A
  • All used in the warming and cleaning of air

Mucus:

  • Particles larger than 5-10 micrometers are caught in the mucus lining the nasal passages and other airways.
  • Mucus is a slimy solution of mucin that consists of many glcyoproteins with many carbohydrate chains making it sticky.

Goblet Cells:

  • Produce mucus as the upper part swells with mucin droplets which have been secreted by the cell.
  • Mucus also made by mucous glands beneath epithelium.

Cilia:

  • Hair like structures found on epithelium of trachea, bronchi and bronchioles.
  • Continual beating of cilia carries carpet of mucus upwards towards the larynx.
  • As mucus is swallowed, the pathogens are destroyed by the acid in the stomach.
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5
Q

List and explain the adaptations of alveoli for gas exchange

A
  • Contain elastic fibres: Allow alveolar walls to stretch during inspiration and recoil during expiration to help force out air. Also allows alveoli to expand according to volume of air breathed in.
  • Have extremely thin walls (no more than 0.5 micrometers thick): Made of squamous epithelial cells meaning the distance for diffusion of gases is very small, increasing efficiency.
  • Surrounded by blood capillaries: Again, decreases diffusion distance and ensures continuous fresh blood supply, maintaining concentration gradient, maintaining efficient gas exchange. Breathing also ensures fresh supply of air, also maintaining concentration gradient.

Large surface area: Large number of alveoli mean collective surface area is very large, increasing the area over which diffusion can take place.

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6
Q

Describe the effect smoking has on chronic bronchitis

A
  • Chronic bronchitis is a chronic obstructive pulmonary disorder (COPD) in which the airways become damaged and obstructed.
  • Tar from cigarette smoke stimulates goblet cells and mucous glands to enlarge and secrete more mucus.
  • Tar also inhibits the cleaning action of the ciliated epithelium, causing the destruction of most cilia and weakening the sweeping action of the remaining cilia.
  • This causes mucus to accumulate in the bronchioles, causing obstruction.
  • Dirt, bacteria and viruses collect stimulating ‘smoker’s cough’.
  • Damaged epithelia are replaced with scar tissue , and smooth muscle surrounding airways get thicker, making the airways narrow making it difficult to breathe.
  • When there are other infections, such as pneumonia, the linings become inflamed, further narrowing the airways.
  • Sufferers have a severe cough, producing large quantities of phlegm.
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7
Q

Describe emphysema

A
  • The inflammation of the constantly infected lungs, which can result from chronic bronchitis, causes phagocytes to leave the blood and line the airways.
  • To reach lining of lungs from capillaries, phagocytes release elastase which destroys elastin in the walls of the alveoli, making a pathway for the phagocytes.
  • This means alveoli do not stretch and recoil and as a result, the bronchioles collapse during expiration, trapping air in the alveoli, often causing them to burst.
  • This reduces number of capillaries and surface area for gas exchange.
  • As air remains in the lungs after breathing out, together with the reduced surface area for gas exchange, people with emphysema do not oxygenate their blood well and have a rapid breathing rate.
  • As lung function deteriorates, wheezing and breathlessness becomes progressively worse.
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8
Q

Describe the effect of emphysema on the cardiovascular system

A

As emphysema progresses, blood vessels in the lungs become more resistant to the flow of blood. To compensate for this increased resistance, blood pressure in the pulmonary artery increases, and over time, the right side of the heart enlarges.

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9
Q

Explain how smoking can lead to lung cancer

A
  • Tar in tobacco smoke contains many carcinogens which react with DNA in epithelial cells to produce mutations.
  • Tumours form and spread through bronchial epithelium. Metastasis occurs if tumour is malignant.
  • Coughing up blood, chest pain, and difficulty breathing are symptoms of lung cancer.
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10
Q

Describe the effect of nicotine on the body

A
  • It is a drug found in tobacco
  • It stimulates nervous system to reduce diameter of arterioles and to release adrenaline.
  • This causes heart rate and blood pressure to increase, and blood flow to extremities to decrease. Also increases the risk of blood clotting.
  • Stimulates nerve endings in the brain to release dopamine which is associated with reinforcing pleasurable experiences.
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11
Q

Describe the effect of carbon monoxide on the body

A
  • Forms stable compound with haemoglobin, carboxyhaemoglobin. Means haemoglobin does not become fully oxygenated.
  • May also damage lining of arteries.
  • Means the blood of smokers has less oxygen than non-smokers as cigarettes contain CO.
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12
Q

Describe the short term effects of smoking on the cardiovascular system

A
  • Damage of artery walls may lead to build-up of fatty tissue and reduction of blood flow.
  • Coronary heart disease (CHD) and stroke may be the result.
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13
Q

Define a disease, infectious disease, and non-infectious disease

A

Disease: An illness or disorder of the body or mind that leads to poor health.

Infectious Disease: Diseases caused by pathogens that can pass between organisms, from infected to uninfected people.

Non-infectious Disease: Long term, degenerative diseases. Can be genetic or inherited.

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14
Q

State the causative agent of cholera

A

Vibrio cholerae, Bacteria

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15
Q

Explain how cholera is treated and how transmission is prevented

A

Treatment:

  • Can be controlled cheaply by solution of salts and glucose given intravenously.
  • Can be given oral rehydration therapy.
  • Intake of fluid must equal fluid loss to maintain osmotic balance of blood and tissue fluid.

Prevention:

  • Ensure drainage and supply of clean water.
  • Can be done using efficient sewer plants
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16
Q

Describe the transmission of malaria

A
  • As a female Anopheles mosquito feeds on human blood, in order to gain protein to develop their eggs, if the person they bite is infected with Plasmodium, they will take up the parasite’s gametes.
  • The gametes fuse in the mosquito forming infective stages.
  • When mosquito feeds again, she injects anticoagulant, and the infective stage flow into the human’s blood from the mosquito’s salivary glands.
  • The parasites multiply within the human body.
  • The female Anopheles mosquito is a vector of malaria as she passes the infective stages from an infected person to an uninfected person.
  • Can also be passed during blood transfusion and across placenta from mother to fetus.
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17
Q

State the causative agent of malaria

A

Plasmodium falciparum, P. vivax, P. ovale, P. malariae, Protoctist

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18
Q

Describe the transmission of cholera

A
  • Disease is water-borne meaning it occurs where people do not have access to proper sanitation and uncontaminated food.
  • Bacteria passed out through faeces, which can contaminate water supplies.
  • Can also be transmitted if infected people handle food or cooking utensils without washing their hands.
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19
Q

Explain how malaria is treated

A
  • Anti-malarial drugs such as quinine and chloroquinine are used.
  • Prophylactic (preventative) drugs which stop an infection from occuring if bitten are also used.
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20
Q

Describe how malaria can be prevented

A
  1. Reduce number of mosquitoes
  2. Avoid being bitten by mosquitoes
  3. Use drugs to prevent parasite from infecting
  • Mosquitoes can be killed by placing oil on top of water bodies, or draining water bodies as mosquitoes lay their eggs in water.
  • Using insect nets and insect repellents are an effective way to prevent being bitten by mosquitoes
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21
Q

State the causative agent for small pox

A

Variola, Virus

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22
Q

State the causative agent of Acquired Immunodeficiency Syndrome (AIDS)

A

Human Immunodeficiency Virus (HIV), Virus

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23
Q

Define opportunistic infections and describe their relevance to AIDS

A
  • As HIV infects and destroys helper T cells, the body’s immunity is decreased making it easier for other pathogens to infect the body.
  • These pathogens cause opportunistic infections which occur due to the weakened immune system.
  • This means AIDS itself is not a disease but rather a collection of the opportunistic diseases.
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24
Q

Describe the transmission of HIV

A
  • HIV is unable to survive outside the human body and so is only spread by intimate human contact i.e. the exchange of bodily fluids.
  • HIV spreads easily through sexual intercourse, blood donation, sharing of needles, and across the placenta from mother to child.
  • Homosexuals practicing anal sex (due to lack of lubrication and thin lining of rectum)and having multiple sex partners increase the spread of HIV.
  • HIV/AIDS is largely prevalent in Africa with 70% of deaths from AIDS occuring in Africa. This leads to malnutrition, TB, and malaria becoming more prevalent.
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25
Q

Describe the treatment of AIDS

A
  • There is no cure for AIDS and no vaccine for HIV.
  • Drug therapy is used to slow the onset of AIDS, meaning HIV+ people have increased life expectancy.
  • However, drugs are expensive and have variety of side effects.
  • Those unable to keep to a strict regimen can become susceptible to strains of HIV that have developed resistance.
26
Q

Describe how transmission of AIDS can be prevented

A
  • Education about spread of infection and encouraged to change behaviour
  • Condoms, Femidoms and Dental Dams used to reduce risk of infection during intercourse
  • Contact tracing to identify sexual partners or drug needle sharers who may be at risk if a person tests HIV+
  • Giving up drug usage and to stop sharing needles
  • Widespread testing of populations
  • HIV+ women should not breastfeed
27
Q

State the causative agents of tuberculosis

A

Mycobacterium bovis, M. tuberculosis, Bacteria

28
Q

Describe how TB is transmitted

A
  • It is spread when infected people with the active form of the illness cough or sneeze.
  • Bacteria travel through the air in tiny droplets of liquid which are inhaled by others
  • It spreads rapidly in overcrowded conditions, especially when people sleep closely together.
  • Disease primarily attacks homeless, people who live in substandard conditions, those with low immunity, malnutrition, or HIV+.
  • M. bovis occurs in spreads to humans from cattle through unpasteurised milk and cows
29
Q

Describe the treatment of TB

A
  • Samples of sputum (mucus and pus) are analysed by microscopy to identify bacteria
  • Use of several antibiotics to ensure all bacteria are killed
  • Incomplete course of treatment leads to antibiotic-resistant bacteria
30
Q

How can TB be prevented?

A
  • Contact tracing and subsequent testing of contacts
  • Vaccine is available, however, effectiveness decreases with age.
  • Cattle are destroyed if have TB
  • Milk is pasteurised
31
Q

State the causative agent of Measles

A

Morbillivirus, Virus

32
Q

Describe the transmission of measles

A
  • Very contagious
  • Sneeze or cough droplets inhaled by uninfected, causing transmission.
  • Spread increases in overcrowded conditions
  • Spread occurs in those not vaccinated, such as in developing countries, or those who have chosen not to get vaccinated
33
Q

Describe the treatment of measles

A
  • Bed rest
  • Medication to lower fever
  • No specific medication for the measles itself
34
Q

Define the term antibiotic

A

A drug that kills or stops the growth of bacteria, without harming the cells of the infected organisms.

35
Q

Describe the action of penicillin and explain why it has no effect on human cells or viruses

A
  • Penicillin prevents the synthesis of the cross links that form between peptidogylcan polymers in bacterial cell walls.
  • Does this by inhibiting the enzymes that build these cross links.
  • Means penicillin is only active when bacteria is growing
  • As the bacteria secretes autolysins to create holes in the cell wall for the wall to stretch, as the peptidoglycan chains do not link up, the cell wall becomes weaker.
  • Water that moves into the bacteria cause the cell to burst as cell wall cannot withstand the pressure.
  • Does not affect human cells as they do not have cell walls.
  • Viruses are also not affected as they do not even have cells
36
Q

Explain how bacteria can become resistant to antibiotics

A
  • An existing gene within the bacterial genome may change spontaneously i.e. a mutation occurs
  • Bacteria that are susceptible to antibiotics are selected against and die
  • Bacteria that are resistant to antibiotics are selected for and pass the mutated gene onto other bacteria
  • Misuse or incomplete treatment of antibiotics may gain resistance as some susceptible bacteria may survive and mutate
37
Q

Describe the ways in which antibiotic resistance can be passed between different bacteria

A

Vertical Transmission:
- Bacteria only have one loop of double-stranded DNA meaning when they perform binary fission, each daughter cell receives a copy of the plasmid and are resistant.

Horizontal Transmission:

  • Plasmids are transferred from from one bacterium to another
  • Happens when conjugation, forming of a tube, occurs between bacteria to move DNA.
38
Q

What are the dangers of an antibiotic resistant infection?

A
  • Increase risk of death from otherwise curable diseases
  • Cause longer stays at hospitals
  • Serious complications can arise
39
Q

How can antibiotic resistance be reduced?

A
  • Only use when appropriate and necessary
  • Reduce selling without doctor’s prescription
  • Use specific antibiotics, not wide-spectrum
  • Complete course of medication
  • Change type of antibiotics used for certain diseases, not always same one used
  • Use to cure rather than prevent infections
40
Q

Define the terms antigens, and antibodies

A

Antigens: A substance that is foreign to the body and so stimulates an immune response

Antibodies: A glycoprotein known as an immunoglobulin that is secreted in response to an antigen. The antibody has a region that is complementary to a specific antigen

41
Q

Distinguish between self and non-self

A

Non-self: A substance or cell recognised by the immune system as foreign, stimulating an immune response.

Self: Substances produced by the body that are not recognised as foreign. Immune response is not stimulated.

42
Q

Distinguish between the external defence system and the internal defence system

A

External defence system: Physical, chemical or cellular defences that prevent pathogens from entering the body.

Internal defence system: White blood cells that recognise and destroy pathogens or non-self substances that successfully enter the body.

43
Q

Describe the development and distribution of neutrophils

A
  • Produced in the bone marrow
  • Travel throughout the body, leaving the blood through the capillaries to ‘patrol’ tissues.
  • Released from stores in large numbers during infection
  • Short lived cells
44
Q

Describe the development, distribution and action of macrophages

A
  • Larger than neutrophils
  • Found in organs and lymph nodes rather than remaining in blood
  • Made in bone marrow and travel in blood as monocytes
  • Develop into macrophages once settled in organs
  • Long-lived cells
  • Cut up pathogens to expose antigens, more important in initiating immune response
45
Q

Describe the process of phagocytosis

A
  1. Attraction (chemotaxis): Chemicals released from cells like histamine, as well as chemicals released from the pathogens, attract passing neutrophils.
  2. Pathogens covered in antibodies and that are clustered together stimulates the recognition and attachment of the neutrophil to the pathogen.
  3. Endocytosis occurs, capturing pathogen in a phagocytic vacuole
  4. Digestive enzymes are secreted into phagocytic vacuole using lysosomes. The pathogen is destroyed.
  5. Neutrophil may die forming a collection of dead neutrophils. Forms pus.
46
Q

Describe the development of B and T cells

A
  • Only mature lymphocytes can carry out immune responses
  • Each type of B and T lymphocytes is specialised to respond to one antigen
  • Each type of lymphocyte will replicate to form a group of identical cells known as clones which all produce the same antibodies.

B-lymphocytes: Remain in bone marrow until they mature and then spread throughout body, concentrating in lymph nodes and spleen.

T-lymphocytes: Leave bone marrow and collect in thymus, where they mature. Mature T-lymphocytes have specific T cell receptors that structurally similar to antibodies and are specific to one antigen

47
Q

Describe the action of B-lymphocytes during immune response

A
  1. Clonal selection and clonal expansion occurs. (The clone with the receptors complementary to the antigen are selected and divide by mitosis)
  2. Some of these activated B cells develop into plasma cells while others into memory cells.
  3. Plasma cells secrete antibodies that combine with the antigen that enters the body.
  4. If the antigen enters for a second time, the memory cells respond and divide to form to form plasma cells which secrete antibodies. This secondary response is much faster. This is known as immunological memory.
48
Q

Describe the action of T cells

A
  • Undergo same stages of clonal selection and expansion.

Helper T cells:

  • when activated they release hormone-like cytokines
  • some cytokines stimulate appropriate B cells to divide, develop into plasma cells, and secrete antibodies.
  • some stimulate macrophages to carry out phagocytosis more vigorously
  • some stimulate killer T cells to differentiate by producing vacuoles full of toxins.

Killer T cells:

  • Search for infected cells that are displaying foreign antigens from the pathogens
  • They attach themselves to the surface of these infected cells and secrete toxic substances
  • Both the cell and the pathogen dies.

Memory T cells are also produced for quick secondary response.

49
Q

What is the effect on white blood cells during an infection?

A
  • Number of neutrophils in the blood increase during bacterial infections, and when tissue becomes inflamed and dies.
  • Lymphocytes in the blood increase during viral infections and in TB.
  • People who are HIV+ will have a lower number of T cells.
50
Q

Describe the development of leukaemia and the effect it has on the body

A
  • Cancer of the stem cells that produce white blood cells. The myeloid cells give rise to neutrophils and monocytes, while the lymphoid cells give rise to lymphocytes.
  • The stem cells divide uncontrollably, giving many cells that do not differentiate properly and disrupt the production of normal blood cells.
  • Immature white blood cells disrupt the normal balance of components in the blood. Hence, not enough red blood cells or platelets.
  • Lack of these blood cells leads to anaemia and increased risk of excessive bleeding.
  • Number of mature white blood cells decrease, making sufferers more susceptible to infection i.e. they are immunosuppressed
51
Q

Define an autoimmune disease and explain why they occur

A
  • It is when the body fails to distinguish between self and non-self leading it to attack itself.
  • In the maturation of T cells, many cells are destroyed due to T cell receptors that are complementary to self-antigens.
  • Some of these T cells evade destruction leading to the stimulation of an immune response in which these T cells attack certain proteins.
52
Q

Explain what happens in myasthenia gravis (MG)

A
  • Targets the neuromuscular junctions between motor neurones and muscle fibres.
  • helper T cells stimulate a clone of B cells to differentiate into plasma cells to release antibodies that bind to the receptors for acetylcholine.
  • Acetylcholine is a signalling molecule that allows the transmission of impulses from neurones to muscle fibres.
  • Muscle fibres absorb receptor-antibody complexes, destroying them, and preventing the stimulation of muscle cells. This leads to the breakdown of muscle tissue.
  • MG causes muscle weakness that gets worse with activity.
53
Q

Describe the structure of antibodies

A
  • globular glycoproteins with a quartenary structure
  • plasma proteins which form the immunoglobulins
  • consists of four polypeptide chains: Two heavy or long, and two short or light chains.
  • Disulfide bonds hold chains together
  • 3D shape forms a variable region which allows it to bind to a specific antigen
  • all antibodies have at least two antigen binding sites
  • hinge region gives antibody flexibility to bind around the antigen
54
Q

Describe the different ways in which antibodies can act

A
  • combine with viruses and bacterial toxins to prevent them entering or damaging cells
  • Attach to flagella of bacteria making them less active
  • Agglutination of bacteria (clumping together) to reduce chance of spread throughout the body
  • Make holes in cell walls of bacteria, causing them to burst when they absorb water through osmosis
  • Coat bacteria making it easier for phagocytes to ingest them. (phagocytes have receptor proteins for the heavy polypeptide chain)
  • combine with toxins to neutralise them, these antibodies are called antitoxins.
55
Q

Define monoclonal antibodies (Mabs) and explain how they are made in large quantites

A
  • Antibodies secreted when a large number of a particular B cell clone is secreting identical antibodies when manufacturing antibodies in large quantities.
  • As B cells that divide by mitosis do not produce antibodies, and plasma cells do not divide, it is difficult to produce a large quantity of antibodies.
  • Plasma cells can then be fused with cancer cells which divide indefinitely.
  • This fusion of cells which secretes antibodies and divides by mitosis is called a hybridoma
56
Q

How are monoclonal antibodies used in the diagnosis and treatment of diseases

A

Diagnosis:

  • Used to locate blood clots in deep vein thrombosis. (antibody against fibrin is produced and marked with radioactive chemical. Move to clot in the blood and radioactivity can be detected.)
  • Used to locate cancer cells, which have differing proteins in their cell membranes to other normal body cells.
  • Used to find exact strain of virus or bacterium causing infection
  • Used in blood and tissue typing before transfusions or transplants.

Treatment:

  • Mabs must be administered more than once.
  • As Mabs are produced in animals, they are non-self and act as antigens.
  • To overcome this:
    1. Genes are altered to code for human sequences of amino acids rather than animals sequences.
    2. Change type and position of sugar groups on heavy chains to human arrangements.
  • Used in some cancer therapies such as breast cancer
  • Used in autoimmune diseases such as rheumatoid arthritis
57
Q

Describe the different ways in which immunity is gained

A

Natural active immunity: Immunity that has developed after contacting pathogens inside the body and has occurred naturally, an immune response occurs. Memory cells are produced and protection is permanent. e.g. from an infection.

Natural passive immunity: Immunity is provided from outside the body naturally, without an immune response. Memory cells are not produced and protection is temporary. e.g. antibodies from mother in breast milk or across the placenta.

Artificial active immunity: Same as natural active immunity except is gained artificially e.g. Injection of live or attenuated pathogen.

Artificial passive immunity: Same as natural passive immunity except is gained artificially e.g. Injection of antibodies or antitoxins.

58
Q

Define a vaccine and describe what affects their effectiveness

A

Vaccine: A preparation containing antigens which is used to stimulate an immune response artificially. They are either injected into a vein or muscle, or are taken orally.

  • When a vaccine contains live microorganisms, the microorganisms reproduce meaning it mimics an actual infection. This means one injection may give lifetime protection.
  • It is less effective when dead microorganisms are used which do not replicate inside the body meaning they do not mimic an infection and so booster injections may be required.
59
Q

Explain why an effective vaccination for malaria is so difficult to create

A
  • Malaria is caused by protocists which are eukaryotes and so have many more genes than bacteria or viruses.
  • This leads to cell surfaces with many antigens
  • The protoctist also has three stages, each with its own specific antigens
  • A vaccine would then have to contains antigens for all three stages, or be specific to the infective stage, which would only work if the immune system could develop a response in a short period of time.
  • Plasmodium also conceals itself in liver and red blood cells, evading attack from antibodies in the plasma.
60
Q

Explain why an effective vaccination for cholera is so difficult to create

A

Vibrio cholerae remains in the intestines where it is beyond the reach of antibodies. (Antigenetic concealment)

61
Q

Explain why the eradication programme of small pox was so successful

A
  • Variola virus is stable. Did not mutate or change its surface antigens (no antigenetic variation or shift)
  • Vaccine was made of an attenuated virus, making it effective
  • Vaccine was resistant to temperatures making it easy to administer and transport everywhere
  • Infected people were easy to identify
  • Variola did not linger in the body after infection to become active later
62
Q

Explain why an effective vaccination for measles is so difficult to create

A
  • While the measles vaccine is largely one-dose for most people, some people have a poor response and so need boosters.
  • In large, developing cities, this can be hard as people are constantly moving and so migrants and refugees form reservoirs of infection.
  • The poor response means that a very high proportion of a population has to be vaccinated in order to provide herd immunity.

Biology AS (3 decks)

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