Biology 4.1 (Shortened)

Question 1

How do bacteria reproduce? and how is this different from mitosis?

Answer 1

-Binary Fission
-Binary fission is for growth and DNA replication happens at the same time as separation, no mitotic spindle.

Question 2

Why is Malaria not in the UK?

Answer 2

-Too cold climate for mosquitos and pathogens
-Pathogens wouldn’t reproduce fast in cold climates.
-Going forward however global warming could cause malaria to be prevalent in the UK

Question 3

What is the definition of direct transmission?

Answer 3

-The pathogen is directly transferred from one organism to another

Question 4

What are different types of direct transmission?

Answer 4

-Physical contact (sexual intercourse or touching contaminated surfaces)
-Droplet infection (coughing or sneezing)
-Inoculation (sharing needles, break in skin)
-Ingestion (consuming contaminated food)

Question 5

What is the definition of indirect transmission?

Answer 5

-When a disease is transmitted from one organism to another via either a vector (organism that spreads disease by carrying pathogen) or a fomite (inanimate objects that harbor pathogens)

Question 6

What are social and climate factors that affect transmission?

Answer 6

-Culture (traditional factors can increase transmission)
-Socioeconomic factors (poorly trained health workers)
-Climate (new vectors and diseases can emerge as temperatures rise)

Question 7

What are stages of inflammation?

Answer 7

1.Tissue gets injured and bacteria enters site
2.The site become filled with tissue fluid due to inflammatory factors
3.Tissue cells release cytokines which attract phagocytotic white blood cells
4.phagocyte engulfs pathogen to form a phagosome
5.Phagocyte fuses with lysosome and releases hydrolytic enzymes which digest bacterium

Question 8

What is the difference between cell mediated response and humoral?

Answer 8

-Cell mediated response target pathogens that have invaded cells or cells that have been changed (cancer) whereas humoral targets pathogens in bodily fluids using antibodies

Question 9

How does blood clot?

Answer 9

1.Blood vessel is damaged and blood is exposed to collagen fibres
2.Platelets stick to exposed to collagen fibres forming a plug, they also release clotting factors.
3.Prothrombin is converted into thrombin, this process requires calcium and vitamin k.
4.Thrombin catalyses the conversion of inactive soluble fibrinogen into insoluble active fibrinogen, this forms a fibrin mesh which traps RBCs creating a clot.
5.Blood clot is reabsorbed

Question 10

Why doesn’t blood normally clot?

Answer 10

Anticoagulants such as hepanin prevent blood clotting.

Question 11

How does the cell mediated response happen?

Answer 11

1.Macrophage destroys pathogen and displays its antigen on its surface (antigen-presenting cell)
2.APC interacts with specific t-helper cell and releases interleukin 1
3.This stimulates T-helper cell to release a cytokine, interleukin 2 which stimulates growth of t-killer cells (the process of activating a t helper cell is called clonal selection).
4.T-killer cell detects antigen and produces peforin which forms pores in its membrane allowing water and ions in and causing lysis.
5.T memory cells are formed and are ready to respond if they ever come in contact with that antigen

Question 12

What is humoral response?

Answer 12

1.Macrophage destroys pathogen becoming an APC.
2.APC interacts with t helper cell, binds with it, releasing interleukin 1
3.This stimulates the T-helper cell to release interleukin 2 which stimulates the differentiation of a b-effector cell into a plasma cell
4.Plasma cell divides by mitosis which produces loads of clones which can produce antibodies that destroy the pathogen by agglutination and neutralization.
5.B memory cells are produced and ready to respond if they come in contact with that antigen

Question 13

What is a disease that can spread between humans and animals? How can you prevent the transmission of these diseases?

Answer 13

-A zoonotic disease e.g. bird flu strain H1N1
-You can prevent transmission by reducing contact with these animals

Question 14

How can Pathogens be transmitted between plants?

Answer 14

-Direct transmission ( when a healthy plant infects an uninfected plant through contact e.g between leaves)
-Indirect transmission(1. Soil pathogens can remain in soil and infect plants when planted they get into the soil for e.g. via dead plant leaves dropping into soil 2. Vectors like wind, water, infected insects (when an infected insect attacks a plant pathogen enters).

Question 15

Where does fungus live in a plant and why?

Answer 15

-The vascular tissue(the same for other pathogens)
-It grows here to acquire nutrients and its hyphae release enzymes which digest surrounding tissue causing the leave to mottle and die as it can’t photosynthesize.

Question 16

How does fungus reduce crop yield and reproduce when the conditions are harsh?

Answer 16

-It causes mottling and discolouration which reduces photosynthesis, less carbohydrate is produced, so plants are smaller in size and yield is reduced
-In harsh conditions they produce spores which can spread large distances rapidly.

Question 17

How do pathogens as a whole reduce plant growth and yield?

Answer 17

1.Reduce the rate of photosynthesis by blocking light/destroying chloroplasts
2.Increase the rate of respiration as the plant fights the infection
3.Feed on the plants’ sugars
4.Make plant lose water through wounds
5.Can block xylem and phloem

Question 18

What are passive plant defences?

Answer 18

-Cellulose cell wall- not only a physical barrier but contains chemicals that can be activated
-Lignin thickening of cell walls- waterproof and completely indigestible
-Waxy cuticle- prevents water from collecting on surface of plant and therefore any pathogens living in water from infecting the plant
-Bark-contains chemical defences]
-Stomata- when pathogenic organisms are detected the gurd cells close the stomata at that part of the plant.

Question 19

What is callose

Answer 19

-Callose is a large polysaccharide that is deposited in the end of growing end in the sieve tubes which can prevent a pathogen in the phloem spreading to the rest of the plant

Question 20

What is tylose

Answer 20

Tylose is a balloon like swelling that fills the xylem vessel this prevents the spread of pathogens, they also contain a high number of chemicals e.g terpenes

Question 21

What are chemical defences of a plant

Answer 21

-Terpenoids
-Phenols
-Alkaloids
-Defensive proteins
-Hydrolytic enzymes

Question 22

How does a plant recognise an attack?

Answer 22

1.Receptors respond to molecules on the pathogen or chemicals released by pathogen
2.They release signalling molecules which switch on genes
3.These trigger cellular responses

Question 23

How does a plant actively defend against a pathogen once recognised?

Answer 23

-Cell walls thicken and become strengthened with lignin and cellulose
-Callose is deposited between plant cell wall and cell membrane near pathogen
-Oxidative burrs produce highly reactive oxygen molecules which can damage cells of invading organisms
-increase in production of chemicals

Question 24

What is necrosis?

Answer 24

-Deliberate cell suicide, a few cells are sacrificed to save the plant (intercellular enzymes are released)

Question 25

What is canker

Answer 25

A sunken necrotic lesion in the woody tissue of the plant caused by pathogens. Cambium bark tissue dies as a result.

Question 26

When are necrosis and canker used?

Answer 26

As a last result the plant will use they just to survive from infection.

Question 27

How does the skin defend against pathogens

Answer 27

-Surface of the skin contains a layer of dry dead cells which prevent pathogens from entering the body
-When sweat evaporates it leaves salt making skin slightly acidic
-The skin harbours healthy microorganisms which outcompete pathogens for resources.
-This is a primary non specific defense

Question 28

What is sebum?

Answer 28

-Primary non-specific defenses
-Oily waxy substance produced by sebaceous glands, coats and protects skin with antimicrobial properties

Question 29

How does the gut protect against pathogens?

Answer 29

-Hydrochloric acid is secreted by parietal cells in stomach, this kills pathogens which are ingested with food, mucus is also along the length of the gut to protect against the acid
-This is a non-specific primary response

Question 30

How do mucous membranes help protect against pathogens?

Answer 30

-Line the gut, respiratory system and reproductive system
-Secreted by goblet cells
-mucous is made up of glycoproteins and traps dust and pathogens cilia then wafts it to be removed
-Also contains lysozymes which destroy cell walls of bacteria and fungi and it also contains phagocytes

Question 31

How are wounds repaired once clotted?

Answer 31

-Platelets secrete growth factors that stimulate stem cells and the production of collagen fibres which are deposited under the scab. Granulation tissue fills the wound as stem cells which divided by mitosis to become skin cells go to the edge of the wound and differentiate. New blood vessels form to suppy oxygen to the tissue The skin contracts to draw edges together and once epidermis is a normal thickness the scab falls off.

Question 32

What is the role of opsonins?

Answer 32

Chemicals that bind to pathogens making them more recognisable to pathogens they also act as binding sites so its easier to bind for phagocytosis.

Question 33

Why do fevers happen?

Answer 33

-When a pathogen invades cytokines stimulate the hypothalamus to set the body temperature to a higher temp, this helps the immune system work at a faster rate and slows down the reproduction of pathogens as they reproduce best at 37 degrees Celsius.

Question 34

What is the role of mast cells?

Answer 34

-They respond to damage by releasing histamines(cause vasodilation and capillaries to become leaky so white blood cells can enter tissue) and cytokines (attract phagocytes)

Question 35

What causes swelling of lymph nodes?

Answer 35

-Excess tissue fluid drains into lymph vessels, so pathogens in tissue fluid enters lymph vessels and are transported along the lymph system to lymph nodes.

Question 36

What is the structure of an antibody?

Answer 36

-Y shaped glycoproteins
-Made up of two identical polypeptide chains called heavy chains joined to two pairs of shorter chains called light chain held together by disulfide bonds
-Disulfide bonds are also found in the polypeptide chain
-They are specific to only one type of antigen

Question 37

What parts of the antigen bind to what?

Answer 37

-Antigen binding site binds to pathogen
-The constant region binds to the pathogen

Question 38

What are the two mechanisms by which antibodies destroy pathogens?

Answer 38

-NEUTRALISATION antibodies surround the pathogen by binding onto them, this prevents the pathogen from binding onto a host cell and therefore hindering its damage
-AGGLUTINATION antibodies bind to many pathogens in one place creating a clump for a phagocyte to engulf

Question 39

Describe a primary and secondary immune response?

Answer 39

-Primary immune response- antibodies break down and b and t cells form memory cells, plasma cells also dont live for long
-Secondary immune response- longer and faster response, with a higher concentration of antibodies, clonal selection is faster, t lyphocytes form t killer cells and memory b lymphocytes differentiate into plasma cells, no symptoms are therefore shown

Question 40

Why do vaccinations not cause illness and what are the two types of immunity?

Answer 40

-Attenuated of versions of the pathogen are injected or some versions only contain antigens so can’t cause disease.
-active immunity(immune system responds to foreign antigens creating antibodies) and passive immunity (immune system doesn’t respond and antibodies come from another source.

Question 41

What is the difference between immunisation and vaccination?

Answer 41

-Vaccination is when you are given a vaccine whereas immunisation is what happens to you after you have a vaccine

Question 42

How does a vaccine work?

Answer 42

1.Vaccines contain antigens
2.immune system recognizes as non self, attacks it and produces memory cells
3. if infected again person produces plasma cells which release antibodies to neutralize pathogens

Question 43

What are the problems with antigenic variations?

Answer 43

-Memory cells from first infection won’t recognise pathogens so a primary immune response will have to be carried out again.
-Makes it difficult to develop vaccines for some diseases.

Question 44

What is an antigenic variation

Answer 44

-When a pathogen mutates to have different antigens on their surface and turn into a new strain

Question 45

What is an autoimmune and an example?

Answer 45

-immune response where antibodies attack self antigens
-Rheumatoid arthritis (caused by immune system attacking cells in joints and causes pain and inflammation)

Question 46

What are different ways medicine can be discovered?

Answer 46

1.Accidental discovery
2.Traditional remedies
3.Observation of wildlife
4.Plant research

Question 47

Why is maintaining biodiversity important for future drug discoveries?

Answer 47

-New plant discoveries could lead to discoveries of new medicines.

Question 48

When and who discovered Penicillin?

Answer 48

-Alexander Flemming
-1928

Question 49

How do antibiotics kill bacteria?

Answer 49

-They interfere with the metabolism of bacteria without affecting the metabolism of human cells therefore inhibiting/killing bacteria
-This is called selective toxicity

Question 50

How does personalised medicine work?

Answer 50

-Doctors can look at your genetic information to predict how you would respond to certain drugs and prescribe one which is the most effective
-They can also use computers to build up 3d models of drugs which are targeted to specific antigens on a pathogen

Question 51

How does antibiotic resistance develop?

Answer 51

1. Genetic mutation occurs making bacteria more resistant to antibiotics
2. Bacteria without gene for resistance die
3. Those with the advantageous allele survive and reproduce so the allele becomes common

Question 52

How do we avoid antibiotic resistance?

Answer 52

-High standards of hygeine for e.g in hospitals and care homes.
-Minimising the use of antibiotics and making sure every course is completed fully.