Unit 4 Biology

What is the name of the gel used in gel electrophoresis?
Agarose gel
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What temperatures does a PCR machine change to?
95, 55 and 70 degrees celcius
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What happens at these temperatures?
95 - hydrogen bonds between the strands of the double stranded DNA break, 55 - The DNA primers can attach at the start of the STR, 70 - optimum temperature for the DNA polymerase to work at
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Why can't human DNA polymerase work in a PCR machine?
The temperatures are too high and would cause the DNA polymerase (which is an enzyme) to denature. Core human body temperature is only 37 degrees celcius.
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What is an autotroph?
An organism that can make organic compounds out of inorganic compounds.
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Where can you get evidence for climate change?
Pollen grains in peat bogs, tree rings, ice cores, temperature records
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What is dendrochronology?
The study of tree rings
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Why are peat bogs useful for observing climate change?
The anaerobic conditions of peat bogs slows down the decay of pollen grains, preserving it. Different layers of peat bog - different age pollen grains. Look at the plant the pollen grain came from to see the conditions at that time.
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What does Rigor Mortis mean?
Stiffness of death
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What is forensic entomology?
The study of insects maggots on a corpse - the age of the insects can give you an idea of the time the eggs were laid and the time of death, assuming the eggs were laid at the time of death.
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Where does photolysis take place?
The thylakoid space (allow in the chloroplast)
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What is photolysis?
The splitting of a water molecule using light energy.
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What are the products of photolysis?
An oxygen atom, hydrogen ions and electrons.
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What is photophosphorylation?
The synthesis of ATP from ADP and phosphate - requires energy. (The light driven addition of a phosphate)
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Where does the energy for photophosphorylation come from?
The excited electrons (gained energy from light) lose energy as they move through the electron carrier molecules in the electron transport chain. The energy lost is used in photophosphorylation.
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What is the light independent reaction of photosynthesis also called?
The Calvin Cycle
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What is the name of the enzyme that catalyses the reaction between RuBP and Carbon dioxide?
RuBISCO - Ribulose bisphosphate carboxylase
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Where does the light independent reaction take place?
The stroma
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Where does the light dependent reaction take place?
The thylakoid membrane
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What can the glucose made in the Calvin Cycle be used for?
Making a plant cell wall (cellulose), respiration, starch, lipids (for storage and waterproofing), amino acids and proteins
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What is secondary succession?
It is when succession starts and there are already living things present.
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What is a pioneer species?
The species that first colonises an area devoid of life, and can cope in harsh conditions.
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What does GPP stand for?
Gross Primary Productivity
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What does GPP measure?
The rate at which energy is incorporated into organic molecules by the plants in photosynthesis
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What does NPP stand for?
Net Primary Productivity
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What is NPP a measure of?
The rate at which energy is transferred into new plant biomass that can be eaten by herbivores and decomposers
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What is seres?
The stages of succession - when each species interacts with the environment, making it unsuitable for them but suitable for the next species.
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Give an example of a climax community.
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Why is the genetic code described as degenerate?
Some amino acids have more than one codon.
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Why is the genetic code described as non overlapping?
Each set of three bases forms one triplet and no base from one triplet is part of another triplet.
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What is an advantage of having a degenerate genetic code?
It provides some protection against mutation - more than one codon can code for a particular amino acid
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What is an advantage of the genetic code being non overlapping?
It avoids confusion about which amino acid is being coded for.
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Why are bands formed in gel electrophoresis?
The DNA is negatively charged, so it moves towards the positive electrode. The fragments separate as the smaller fragments move faster than the larger fragments.
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What does STR stand for?
Short tandem repeat.
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What is a species?
A group of organisms that can reproduce to produce fertile offspring.
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What is habitat isolation?
This is when populations occupy different habitats in the same area so do not meet to breed.
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What is temporal isolation?
This is when species exist in the same area but are active for reproduction at different times.
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What is behavioural isolation?
This is when populations do not respond to each other's reproductive displays.
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What is gametic isolation?
This is when male and female gametes from two populations are simply incompatible with each other.
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What is hybrid sterility?
This is when healthy individuals produced from the mating of two different species cannot themselves reproduce e.g. mules.
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What is hybrid inviability?
This is when individuals produced from the mating of two different species are not healthy and do not survive.
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What is lysozyme and how does it work?
Lysozyme is an enzyme found in tears, sweat and the nose. It destroys bacteria by breaking down the bacterial cell walls.
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What is interferon and what does it do?
Interferon is a chemical released from virus infected cells to stop protein synthesis in viruses.
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What does a bactericidal antibiotic do?
It kills the bactera
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What does a bacteriostatic antibiotic do?
It prevents the multiplication of bacteria. The host's own immune system can then destroy the pathogens.
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How can antibiotics disrupt bacterial cell growth and division?
Inhibition of bacterial cell wall synthesis; disruption of the cell membrane; inhibition of nucleic acid synthesis, replication and transcription; inhibition of protein synthesis; inhibition of a specific enzyme found in the bacterial cell only.
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What is the name of the bacteria that causes Tuberculosis?
Myobacterium Tuberculosis
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What is the role of fever?
The hypothalamus increases the core body temperature. This may enhance immune functions and phagocytosis. It may also make viruses and bacteria reproduce more slowly - enzymes.
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What is a biofuel?
A biofuel is any source of energy produced, directly in plants or indirectly in animals, by recent photosynthesis. Provides a renewable energy source and is carbon neutral.
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What is the name of the chemical released during inflammation?
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What cells release histamine?
Damaged white blood cells and mast cells, found in the connective tissue below the skin and around the blood vessels, release histamine.
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What does histamine do?
It causes the arterioles to dilate, increasing blood flow in the capillaries at the infected site. It also increases the permeability of the capillaries; cells in the capillary wall separate slightly so the vessel leaks. This causes oedema.
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What is oedema?
Oedema is swelling caused as a result of plasma fluid, white blood cells and antibodies leaking from the blood into the cell.
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What is phagocytosis?
The engulfing of bacteria and other foreign matter in the blood and tissue.
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Where are B and T cells produced and where do they mature?
They are both produced in the bone marrow; B cells mature in the bone marrow and T cells mature in the Thymus.
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What are antibodies?
Antibodies are a special protein molecule of a class known as immunoglobulins. They act as labels, binding to antigens on the cell surface membrane, allowing phagocytes to recognise and destroy the cell.
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What are cytokines?
They are chemicals released by T helper cells that stimulate division and differentiation of the B cells.
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What do B effector cells do?
They differentiate to produce plasma cells, which release antibodies into the blood and lymph. These cells are relatively short lived, lasting only a few days.
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What is the role of memory cells?
They allow an individual to respond more quickly to the same antigen in the future.
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How do we avoid attacking our own immune system?
Some of the membrane proteins on the surface of our cells acts as bar codes. They mark the body cell as self and allow us to distinguish between our cells and foreign invaders. There are many alleles for these proteins so they're unique for everyone.
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What do lymph nodes contain?
A large concentration of white blood cells, to allow them to kill any bacteria that has been carried away by the lymph.
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Where can you find high concentrations of macrophages?
Lymph nodes, spleen and liver.
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What happens to the ingested material during Phagocytosis?
It is enclosed in a vacuole and lysosmes fuse with it. They release digestive enzymes that destroy the foreign material.
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How does the TB bacteria evade the immune system?
It can survive inside macrophages, so resists the killing mechanism used by these cells (phagocytosis). It has a very thick, waxy cell wall, making it difficult to destroy. They can also suppress T cells, reducing antibody production/killer T cells.
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What is glandular TB?
TB moving to infect other parts of the patient. Common sites include bones, lymph nodes and CNS. The main symptom of glandular TB is enlarged lymph glands, usually in the armpits or neck.
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What cells do HIV invade?
T helper cells and macrophages.
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How does HIV invade?
The glycoprotein gp120 binds to the CD4 receptors on the surface of T helper cells. They then combine with a second receptor. This allows the envelope surrounding the virus to fuse with the T helper cell membrane and the viral RNA can enter the cell.
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What happens during splicing?
mRNA is edited, with some sections being removed and other sections spliced together. Introns are removed.
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What are the coding sections of DNA called?
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What are non coding sections of DNA called?
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How big are viruses and bacteria?
Viruses are only 200-400 nm whereas bacteria are between 0.5-5 micrometres.
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What is active natural immunity?
Exposed to antigen by getting the disease. The body produces memory cells which make it immune to disease in the future.
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What is passive natural immunity?
A mother's antibodies cross the placenta and are also found in breast milk. These antibodies can protect against any invading pathogen that the mother has encountered.
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What is active artificial immunity?
The injection of dead or weakened disease organisms, toxins or antigen fragments means that the body is exposed to the antigen and produces memory cells.
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What is passive artificial immunity?
Injected with antibodies that can provide immediate protection against the invading pathogens they are specific for.
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How do we prevent entry of pathogens?
The skin, mucous membranes, digestive system (stomach acid ad gut flora) prevent pathogens from entering.
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What is the acute phase of AIDS?
HIV antibodies appear in the blood after 3-12 weeks. Rapid replication of the virus and loss of T helper cells . After a few weeks, infected T helper cells are recognised by T killer cells, which start to destroy them - less virus replication.
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What is the chronic phase of AIDS?
The virus continues to replicate but is kept in check by the body's immune system. There may be no symptoms, but increasing tendency to suffer colds or other infections. Dormant diseases like TB and shingles can reactivate. Can last for many years.
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What is the disease phase of AIDS?
Increased number of viruses in circulation (viral load) and a declining number of T helper cells indicated the onset of the disease phase. The immune system is vulnerable to other diseases - oppurtunistic infections.
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How can you contract HIV?
Can only be passed on in body fluids, such as blood, vaginal secretions and semen, but not urine or saliva.
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What is the role of T killer cells?
APC binds to a complementary receptor on the T killer cell, and it divides to form memory cells and an active clone (stimulated by cytokines). The T killer cell releases enzymes that created pores in the infected cell which leads to lysis.
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How does the human body cool?
It cools following a sigmoid curve.
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What are detritivores?
Primary consumers that feed on dead organic material called detritus.
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What are decomposers?
Species of bacteria and fungi that feed on the dead remains of organisms and on animal faeces.
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What is the law of limiting factors?
The law of limiting factors states that when a process is affected by more than one factor, its rate is limited by the factor furthest from its optimum value.
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How many molecules of GALP make a hexose sugar and what happens to the rest?
2/12 GALPs make a hexose sugar, 10/12 are involved in the recreation of RuBP. The 10 GALPs rearrange to form 6 5 carbon molecules, then phosphorylation using ATP forms RuBP.
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What catalyses the breakdown of ATP to ADP?
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What is deflected succession?
A community that remains stable only because human activity prevents succession from running its course.
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What are abiotic factors?
Non living or physical factors. E.g. solar energy input, climate, topography, oxygen availability, edaphic (soil) factors (pH etc), pollution, catastrophes (floods, earthquakes etc.)
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What are biotic factors?
Living factors. E.g. competition, grazing, predation, parasitism, mutualism
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What are anthropogenic factors?
Factors arising from human activity, can be abiotic or biotic.
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What is NADP?
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Why isn't all the energy available to the different trophic levels in a food chain?
Not all the food gets eaten, some energy is lost in faeces and urine and much of the energy absorbed by the consumer is used in respiration.
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Which greenhouse gas (not carbon dioxide) is increasing and why?
Methane. More cows, which produce methane in their farts and when they belch. Also can be formed from the incomplete combustion of fuels, and by the anaerobic decay of organic matter in waterlogged conditions.
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How can the age of the layers of peat be determined?
Carbon-14 dating
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What is extrapolation?
Extending a line
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What assumptions are made when you extrapolate?
We have enough data to establish the trend accurately and present trends will continue.
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What is phenology?
The study of seasonal events in the lives of animals and plants, such as the times of flowering or fruiting.
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What happens during rigor mortis?
After death, muscles become starved of oxygen - oxygen dependent reactions stop; anaerobic respiration, producing lactic acid. pH of the cell falls, inhibiting enzymes > inhibiting anaerobic respiration. ATP isn't produced, muscles become fixed.
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What is autolysis?
When the body's own enzymes, from the digestive tract and from lysosmes, break down cells.
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What temperatures does a PCR machine change to?


95, 55 and 70 degrees celcius

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What happens at these temperatures?


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Why can't human DNA polymerase work in a PCR machine?


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What is an autotroph?


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