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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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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
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1.3.3 Reverse turns and loops

In compact globular proteins, a polypeptide often makes a sharp turn called a reverse turn. For instance, these turns often link adjacent strands in antiparallel β pleated sheet (as represented in Figure 12a). Also known as β bends, reverse turns involve four amino acid residues with a hydrogen bond between the C=O group of the f
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1.2. Getting started

Registering is free and only requires a user name, email address and password. Sign up to iSpot.(Right-click on the link to open it in a new window or tab). Watch the video on how to register.


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Acknowledgements

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Grateful acknowledgement is made to the following sources for permission to reproduce material in this unit:

The content acknowl
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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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7.3 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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5 Distances in extragalactic astronomy

Recall Hubble's law:

This relationship between redshift, z, of a distant galaxy which is given by

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6 Inheritance of more than one pair of contrasting characters

We have considered the inheritance of one pair of contrasting characters that involves the segregation of the two copies of one gene in maize. A single chromosome carries many genes, of the order of 2 000 to 4 000 in each human chromosome, each carrying its own information, and each with its specific location, its own locus, on the chromosome. In a pair of homologous chromosomes, there will be many pairs of genes strung along their length.

These observations raise some intriguing questi
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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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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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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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1.6.1 Describing uniformly accelerated motion

An important special case of non-uniform motion along a line is that which arises when an object is subjected to constant acceleration. This kind of motion is called uniformly accelerated motion. An object falling under gravity near to the surface of the Earth, such as the apple of Figure 24, provides
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1.5.6 Velocity and acceleration as derivatives

Recalling that the instantaneous velocity of a particle at time t is given by the gradient of its position–time graph at that time, we can now use the terminology of functions and derivatives to say that the velocity of the particle is given by the derivative of its position function. In terms of symbols:

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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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1.3.3 Position–time graphs

Tables do not give a very striking impression of how one thing varies with respect to another. A visual form of presentation, such as a graph, is usually much more effective. This is evident from Figure 7, which shows the graph obtained by plotting the data in Table 2 and then drawing a smooth curve through the resulting points.

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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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6.2.1 Injecting the radioactive substance

The injection may be given immediately before the imaging process, or there may, for certain procedures, be a delay of several hours.

The patient's details and the dose being administered are carefully checked by two people before the injection is given. A lead-screened syringe is used to protect the staff from unnecessary radiation dose (see
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T
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