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5.3.1 Allosteric regulation

In many proteins, the binding of a particular ligand at one site affects the conformation of a second remote binding site for another ligand on the same protein. This effect is called allosteric regulation and it is an important mechanism by which a protein's binding capacity and/or its activity are regulated. Thus the switch between two different protein conformations can be controlled by binding of a regulatory ligand.

Author(s): The Open University

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5.2 All proteins bind other molecules

All proteins bind to other molecules (generically termed ligands). Ligands that can bind to proteins include:

  • ions, e.g. Ca2+;

  • small molecules, e.g. H2O, O2 and CO2, glucose, ATP, GTP, NAD;

  • macromolecules, i.e. proteins, lipids, polysaccharides, nucleic acids.

These interactions are specific and key to the protein's function and, of course, are critically d
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4.3 Conserved protein domains

By comparing the extensive protein databases, it is possible to identify many thousands of conserved domains. For example, within eukaryotes, over 600 domains have been identified with functions related to nuclear, extracellular and signalling proteins. The majority of conserved domains are evolutionarily ancient, with less than 10% being unique to vertebrates.

Author(s): The Open University

4.2 Amino acid sequence homologies and why they occur

Consider two genes encoding proteins that have 50% of their amino acid sequence in common.

  • How can this sequence homology be explained in terms of evolution?

  • The most parsimonious explanation is that the similarities result from the fact that the two organisms share a common evolutionary past and that the genes encoding
    Author(s): The Open University

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1.6 Fibrous proteins

Most of the proteins described so far have been globular proteins. There are, however, some distinctive features that characterise fibrous proteins and we present here a general overview of these. Elongated fibrous proteins frequently play a structural role in the cell. They do not readily crystallise but tend to aggregate along their long axis to form fibres. X-ray diffraction studies of these fibres, in contrast to analysis of protein crystals, provides only very limited information on the
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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
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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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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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7.5 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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7.4 Faraday depolarization

Radiation of wavelength λ which starts off linearly polarized in a particular direction and travels through a plasma has its direction of polarization rotated by an angle

where ne is the electron density, B| | is the component of the m
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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
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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
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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.

Question

Summarise, in general terms, the possible causes of disease in animals.


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Learning outcomes

After studying this unit you will know more about:

  • the way that prion molecules cause diseases such as BSE and vCJD, and how the key discoveries about prions were made;

  • the patterns of BSE and vCJD in populations, and how this information is used to predict the number of cases there may be in future (and to assess the accuracy and precision of such predictions);

  • how science can make important contributions to managing episodes such as BSE/vCJD, and
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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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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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1.5.2 Instantaneous acceleration

The procedure of Question 15 for determining the instantaneous velocity of the car can be carried out for a whole set of different times and the resulting values of vx can be plotted against t to form a graph. This has been done in Figure 28, which shows how the velocity varies with time. At time t = 0 s, the car has zero velocity because it starts from rest. At later times, the velocity is positive because the car moves in the direction of in
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1.4.5 Velocity–time and speed–time graphs

Just as we may plot the position–time graph or the displacement–time graph of a particular motion, so we may plot a velocity–time graph for that motion. By convention, velocity is plotted on the vertical axis (since velocity is the dependent variable) and time (the independent variable) is plotted on the horizontal axis. In the special case of uniform motion, the velocity–time graph takes a particularly simple form – it is just a horizontal line, i.e. the gradient is zero. Ex
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1.1 The description of motion

The concepts that have been developed to allow the description of motion – concepts such as speed, velocity and acceleration – are now so much a part of everyday language that we rarely think about them. Just consider the number of times each day you have to describe some aspect of motion or understand an instruction about motion; obey a speed limit or work out a journey time. We may take the description of motion for granted, but the concepts involved are so fundamen
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Acknowledgements

Video Materials

This extract is taken from S809 © 2005 The Open University.

All written material contained within this unit originated at the Open University.


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