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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
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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
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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:

  • A photo and/or description of your observation
  • where you saw it (the location)
  • when you saw it (date)
  • what you saw (the identification, if you are able to suggest one - this is optional)

If you don't have a photograph just describe what you saw in as much detail as possible, including size, colour, behaviour etc. Y
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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.

Activity 9: Radio-quiet quasars

0 hours 20 minutes

Read Pe
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8.6 Line spectra: Activity 8 Quasar redshifts

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 Author(s): The Open University

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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
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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,
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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
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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
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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
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3.8 Glucagon

Glucagon is another hormone produced by the pancreas.

Question: Can you recall which cells make glucagon?

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14 Unit questions and answers

Note: Question 1 is included in Section 3.

Question 2


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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
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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.

Question 12

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5.3 Heat production

3 Reproduction in marsupials

The study of mammals requires you to deal with measurements, which we call numerical ‘data’, and you will get practice with compiling and analysing data if you work through all the units in this series. We assume only that you can add, subtract, multiply and divide. In this section, we ask you to use units
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Introduction

Mammals come in a bewildering variety of shapes and sizes and yet all of the 4700 or so species have some characteristics in common. Indeed, it's the existence of these common features that justifies the inclusion of all such diverse types within the single taxonomic group (or class) called the Mammalia.

This is the first in a series of units about studying mammals. To get the most from these units, you will need access to a copy of The Life of Mammals (2002) by David Attenboroug
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1.7.2 End-of-unit questions

Question 25

Table 8 shows the atmospheric pressure P in pascals (Pa) at various heights h above the Earth's surface. Plot a graph to give a visual representation of the data in the table. Be careful to label your axes co
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1.4.6 The signed area under a constant velocity–time graph

There is a simple feature of uniform velocity–time graphs that will be particularly useful to know about when we come to consider non-uniform motion in the next section. It concerns the relationship between the velocity–time graph and the change in position over a given time interval. Consider the following problem. A vehicle travels at a velocity vx = 12 m s−1 for 4 s. By how much does its position change over that interval?

The answer, fro
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