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International Baccalaureate: Biology
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- Marked by Teachers essays 11
- Peer Reviewed essays 1
* There are 3 types: 1)Ionic bond: metal + non- metal (ex: NaCl, BeF2) and 2)Covalent bond: non-metal + non-metal (ex: O2, H2, N2) and 3)and 3)Polar Covalent bond: between 2 non-metals/metals, electrons are not shared equally.(ex: HCl) 1)London Forces ?Weakest, between atoms and molecules, Formed temporary by uneven number of electrons 2)Dipole-Dipole Forces ?between polar molecules ? positive end of one molecule attracts negative end of another molecule --Stronger than London forces 3)Hydrogen Bonds ?Strongest force ? between N, O or F of one molecule AND H of another.
- Word count: 622
Plagues are clusters of protein fragments called beta-amyloid that are built up between the nerve cells. Tangles are made up of twisted strands of protein called tau. http://thebrain.mcgill.ca/flash/d/d_08/d_08_m/d_08_m_alz/d_08_m_alz_1a.jpg Beta-amyloid is a fragment of a protein found in the neuron?s cell membrane called amyloid precursor protein (APP). APP is a transmembrane protein, which means the APP molecule passes through the cell membrane of neuron. In order for beta-amyloid to be released from the APP molecule, two enzymes must be involved which are beta-secretase and gamma-secretase. http://thebrain.mcgill.ca/flash/d/d_08/d_08_m/d_08_m_alz/d_08_m_alz_1b.jpg First, beta-secretase cut the peptide chain of APP outside the cell membrane at a certain length.
- Word count: 715