1.4.2 Protein fold Protein folds are often very extensive arrangements, combining elements of secondary and supersecondary structure. Some of the most common protein folds are described in Table 4: view document with examples of proteins that contain them. Notice that proteins can be conveniently divided into three classes, on the basis of the elements of secondar
1.4.1 Motifs and supersecondary structures Supersecondary structures or motifs are particular arrangements and combinations of two or three secondary structures, often with defined topology (or connectivity). Table 3: view document describes some of the most common of these. The term ‘motif’ is also used to describe a consensus sequence of amino acids, i.e. a partial sequence c
1.1 Introduction Proteins are made up of one or more polypeptide chains, polymers of amino acid residues found in all proteins. The structure that a polypeptide adopts is determined by the component amino acid units – both their chemical properties and the order in which they occur in the polymer – and by the structure of the peptide bond that links them. Protein structure is described in terms of four levels of organisation: primary, secondary, tertiary and quaternary. The linear sequence of amino
Introduction Proteins are the ‘doers’ of the cell. They are huge in number and variety and diverse in structure and function, serving as both the structural building blocks and the functional machinery of the cell. Just about every process in every cell requires specific proteins. Let us begin by listing some of the basic cellular processes and the role that proteins play. Chemical catalysis Enzymes, which are responsible for catalysing biological
1.3 Adding observations, images and locations to iSpot Observations are the main thing on the site. To make an observation, you need to provide this information: If you don't have a photograph just describe what you saw in as much detail as possible, including size, colour, behaviour etc. Y
8.7 Luminosity functions Samples of galaxies can be biased due to the flux limit of the sample that is observed. This is the so called Malmquist bias. Read Pe 8.6 Line spectra: Activity 8 Quasar redshifts Read Peterson section 1.3.5 (pages 16 and 17) by clicking the link below. 7.9 Compton scattering Electromagnetic radiation interacts strongly with electrons. If a photon encounters an electron, there is a high probability that a scattering interaction will occur. In the low-energy non-relativistic regime, i.e. where h 7.7 Radiation detection In astronomy we detect the radiation from large numbers of electrons, rather than being able to distinguish the contributions of individual electrons. The electrons will have a range of velocities and of orientations with respect to the magnetic field, so the synchrotron spectrum we observe will be the sum of lots of individual spectra with varying values of 7.5 Emission from spiralling electrons: synchrotron radiation In the very first reading (Activity 1) we encountered the term ‘non-thermal’ describing the spectrum of light emitted from AGN. In this subsection we will learn more about the most important type of non-thermal radiation: synchrotron emission. When a charged particle moves in the presence of a magnetic field it experiences a Lorentz force, which produces an acceleration whose direction is perpendicular to both the magnetic field line and the velocity of the particle, 7.3 Polarization of electromagnetic radiation So far we have described electromagnetic radiation in terms of its wavelength, frequency and speed. It has another, sometimes important, property: polarization. Figure 10 shows the electric and magnetic field in a plane-polarized electromagnetic wave. In any electromagnetic radiation, the electric an 5 The Scopes monkey trial This section was written by Gary Slapper. In 2007, Professor Michael Reiss, a Church of England priest and the head of science at London's Institute of Education, said that it is becoming more difficult to teach evolution in schools because of the spread of creationism. Similar debate has long been burning in the United States. Also in 2007, a creationist museum opened near Cincinnati, where children in animal skins play amid model dinosaurs, suggesting they once coexisted and th 1 Evolution versus creation: science and non-science Science aims to extend our understanding of natural phenomena through testing of explanatory hypotheses by reference to hard evidence. It is not concerned with ideas that cannot be tested in this way, such as subjective opinions (for example, what is good or evil, beautiful or ugly) or religious beliefs (about, say, ‘the meaning of life’ and the existence of gods or spirits), though we will return to ideas like this at the end of this unit. The remit of science was eloquently summarised b 1.6 Summary The number of chromosomes is characteristic of each species and can vary enormously between species. Sexual reproduction always includes two distinctive processes: the production of gametes, which involves meiosis, and fertilisation. The two processes are accompanied by changes in the chromosome number, from diploid to haploid and from haploid to diploid, respectively. Genetics is based on the concept of the gene as the unit of inheritance. A particular phenotypic character is det 1.3.3 A breeding experiment: stage two We now turn to the second stage of the breeding experiment, but this time we will follow the phenotypes and genotypes simultaneously. The purple (Gg) grains of the F1 generation are planted and when these have developed into mature F1 plants they produce male and female flowers. These F1 plants are crossed with each other, as shown in Figure 8. The fertilised ovules develop into grains borne on cobs, and these grains are the beginning of the second f 3.8 Glucagon Glucagon is another hormone produced by the pancreas. Question: Can you recall which cells make glucagon? 14 Unit questions and answers Note: Question 1 is included in Section 3. 8 Managing the BSE/vCJD episode up to May 1990 BSE was formally recognised as a new disease in November 1986. However, this information was kept under ‘embargo’ at first while an initial epidemiological study – involving the collection of data from 200 herds – was started. The Ministry of Agriculture, Fisheries and Food (MAFF) was officially informed about BSE by the Chief Veterinary Officer (CVO) in June 1987. By December 1987, those responsible for analysing the data from the initial epidemiological study had concluded that the 2 The biology of prions The increasing interest in kuru during the 1950s and 1960s had the effect of stimulating research into TSEs in humans and other animals. Summarise, in general terms, the possible causes of disease in animals. 6 Thermoregulation and mammalian fur A coat of profuse mammalian body hair is commonly called fur. Fur provides insulation, which is a property that one first thinks of as useful for mammals to help retain body heat. Fur is a unique and fundamental feature of mammals, though not all living species possess it.
Activity 9: Radio-quiet quasars
Activity 8: Quasar redshifts
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