Biology 4

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  • Created by: katy b
  • Created on: 30-03-15 10:31

Photosynthesis

  • ATP is the immediate sourse of energy in a cell and is synthesised from ADP and an organic phosphate by phosphorylation.
  • ATPase catalyses the break down of ATP by hydrolysis.
  • A coenzyme is a molecule that aids the function of an enzyme.
  • Chloroplasts are small organelles that have a double membrane and contain thylakoids (stack of grana), photosyntheitc pigments eg cholophyll, and two photosystems.
  • The light dependant reaction takes place in the grana and creates ATP, Reduced NADP and O2. Light is excited by electrons in chlorophyll. The photolysis of water then produces photons, electrons and O2. Energy excited from these electrons makes ATP and generates Reduced NADP.
  • The light independant reaction takes place in the stroma and creates glucose, ATP and NADP. Carbon dioxide is combined with RUBP to form 2xGP. ATP and redused NADP are used to reduce GP to TP. TP is used to make hexose sugars or to regenerate RUBP.
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Ecology

  • An ecosystem is all the organisms living in a particular area and all the abiotic factors.
  • NPP = GPP - plant respiration.
  • Interspecific competiton is competition between different species, and intraspecific is within a species.
  • Niche - the role of a species within it's habitat.
  • Biotic factors are living and abiotic factors are non living ( eg climate, PH, oxygen avalablitly.)
  • Succession:
  • Primary succession happens when a pioneer species takes hold of an uncolonised part of land. They change the abiotic conditions and when they die they enrich the soil for other plants.
  • Climax communities are extablished after primary and subsequent successions, and is when they ecosystem supports the larges and most complex comminuty of plants and animals that it can. It is steady and there is competition and interaction between species.
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Global Warming

  • Global warming is the recent rise in global temperature. It can be proven in a few ways:
  • Temperature records - it is reliable but gives short term records so cannot be used to predict far into the future.
  • Dendrochronology - the thickness of a ring (one produced each year) depends on the climate (warmer = thicker).
  • Pollen in peat bogs - pollen is preserved in peat bogs which accumulate layers as they age. The pollen grains can be analysed to identify the species that were alive at the time. An increase in pollen means and increase in temperature.
  • Global warming is caused by the build up of greenhouse gasses such as methane or CO2 in the upper layers of the atmosphere, where they abosrb IR radiation that is refelected from the earth.
  • Biofuels can be used in place of fossil fuels to reduce global warming. These are fuels made from plants, and are usually described as being carbon neutral as they take in as much carbon dioxide when alive as they do when they are burnt. However the processes of making the fuel or getting the biomass are usually not carbon neutral. The biomass can be taken from beat bogs of forests. This is also non sustainable and reduces plant numbers, whiuch reduces photosynthesis, which increases carbon dioxide.
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Evolution

  • Speciation can be due to reproductive or geographic isolation, both of which cause a restiction of gene flow, which then causes mutations which can be passed on from mother to child to become more prominant.
  • Reproductive isolation may be due to incompatable genitalia or mating rutials.
  • Geographical isolation is usually due to a geographical barrier meaning that the two species cannot get to each other to breed.
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Genetics

  • DNA is made up of nucleotides that have a sugar, phosphate and a base. It is also a polynucleotide and contains four possible bases - A, T, C and G. T is replaced by U in RNA.
  • DNA is non-overlapping which means that each triplet is read in sequence, independent of those around it.
  • DNA is also degenerate which means that there are more combinations of triplet codes than there are amino acids.
  • Start and stop codons are found at the end of a gene.
  • Transcription happens in the nucleus, and is where mRNA makes a coopy of the sequence of bases on a strand of DNA. DNA is unwond by RNA Helicase and RNA Polymerase attached to the DNA, breaking the hydrogen bonds between the two strands. Free RNA nucleotides line up along the strand and bond complimentarily with the bases. RNA Polymerase joins this all together into the mRNA strand. This then moves out of the nucleus through a nuclear pore.
  • mRNA is modified before translation. Introns are taken out and exons are left. These are then joined back together by splicing and this can happen in any order.
  • Translation occurs at the ribosomes in the cytoplasm. tRNA have an anticodon and an animo acid and they bind to each codon creating a polypeptide chain of amino acids as they go.
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DNA Profiling

  • A sample of DNA is obtained. This can be very small and still work.
  • Then PCR is used to amplify the sample. The DNA sample is put into a solution with free nucleotides, primer and DNA Polymerase, then is heated to 95 degress so that the hydrogen bonds between the strands can be broken. It is then cooled to 50 degrees so that the primers can bind to the DNA. Then it is heated again to 70 degrees so that the DNA Polymerase works, causing synthesis to occur.
  • Gel electrophoresis is then used. A flourescent tag is added to the DNA, and it is placed into a well in some gell, which is then covered by a conducting fluid and an electrical current is passed through it. This causes the DNA to move up the gel in accordance to its size (DNA is naturally positivley charged.) Smaller parts move faster and further. This creates bands on the gell which can be compared to another sample. The only reason that two seperate DNA samples would be the same is if they are from identical twins, but the more related you are the more similar your DNA, therefore the more bands that you have that match in two samples, the more related the two samples are.
  • This technique can be used in DNA analysis, to see if someone has committed a crime, and also to see if there are genetic relationships between animals.
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Microorganisms

  • A pathogen is an organism that causes disease. This can include some bacteria, fungi and all viruses.
  • HIV: Human Immunodeficiency Virus, destroys immune system cells, and can eventually lead to AIDS and opportunistic infections such as TB.
  • TB: Mycobacterium Tuberculosis is a bacteria that infects phagocytes in the lungs, and become dormant in parts of the lungs called tubercules. They can then become reactivated and cause weakened immune systems. Symptoms include weakness and fever.
  • Bacteria are sinbgle celled, prokaryotic microorganisms that include a plasma membrane, cytoplasm, ribosomes, flagellum, plasmids and cell wall.
  • Viruses are nucleic acids surrounded by a protein. They are surrounded by a protisn coat called a capsid.
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The Immune Response.

  • Non-Specific Immune Response: this includes inflammation, the production of antiviral protiens called interferons and phagocytosis. Interferons prevent viruses spreading by inhibiting the production of viral proteins, activate the specific immune response and promote inflammation. Phagocyotsis is when a white blood cell recognises the antigens on a pathogen and the cytoplasm of the phagocyte engulfs the pathogen and contains it in a phagocytic vacuole where it is broken down by a lysosome which fuses with the vacuole. The white blood cell then presents the pathogens antigens to activate other immune system cells eg T-cells.
  • Specific Immune Response: Phagocytes activate T-cells, which bind to the antigens presented by phagocytes, activating the T-cell which then divides and differentiates into T-helper, T-memory or T-killer cells. B-cells are activated by T-cells and by binding to a complimentary antigen. Activated B-cells divide by mitosis into plasma cells and B-memory cells.
  • Plasma cells are clones of B-cells that secrete antibodies which bind to antigens on a pathogenb to create an antigen-antibody complex. Antibodies help to clear an infection by aggulating proteins (clumping pathogens together so that they can be neutralised all at once), neutralising toxins (prevent toxins from affecting human cells), and preventing the pathogen binding to human cells by blocking the cell surface receptors needed to bind to host cells.
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Immunity and Antibiotics.

  • Active Natural immunity - when you become immune after catching a disease.
  • Active Artificial immunity - when you become immune after you have been given a vaccine.
  • Passive Natural immunity - when you become immune from antibodies from your mother.
  • Passive Artificial immunity - when you become immune after being injected with antibodies.
  • Vaccines give you immunity without giving you the disease. This is because they contain a small number of inactive antigens that can create antibodies without harming you.
  • Antibiotics can be bacteriocidal (they kill bacteria) or bacteriostatic (they prevent bacteria from growing).
  • Some hospital aquired infections such as MRSA can be bacteria resistant.
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Determining Time of Death

  • Body temperature. Depending on the state of the body after death, temperature can be used by refering to a temperature-time graph.
  • Degree of muscle contraction. 4-6 hours after death the body gets into rigor mortis. Anaerobic respiration occurs in the muscles due to lack of oxygen, causing a build up of lactic acid, causing the PH of cells to decrease which inhibits enzymes that produce ATP, so the bonds between myosinb and actin stiffen.
  • Forensic entomology. The colony of insects on a body shows the time of death by how much they have been allowerd to develop, eg eggs mean that it is recent.
  • Extent of decomposition. Immediatley after death bacteria and enzymes begin to decompose a body. Different conditions affect the rate of this.
  • Stages of succession. This looks at the types of organism present in a body after death.
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