4.3 Photosynthesis, respiration and decay Green plants absorb solar radiation and use its energy to fuel photosynthesis — a chem
4.2 The terrestrial carbon cycle Figure 1.10 shows the rates of natural carbon exchange between the terrestrial system and the atmosphere. 3.2 Tides Tides are caused by the gravitational pull of the Moon and to a lesser extent the Sun. Although tides affect all fluid bodies on Earth in some measure, including some parts of the solid Earth itself, their main effect is on the seas and oceans. Ultimately the kinetic energy of tides is conve 2.2 Present-day energy use Global annual consumption of all forms of primary energy increased more than tenfold during the 20th century (Author(s): 2.1 What contributes to the spectra of galaxies? This section reviews what you may already know about the spectra of galaxies. The topic will later be developed further to help you appreciate the spectra of active galaxies. The four main constituents of a galaxy are dark matter, stars, gas and dust. Even though dark matter is the main constituent of a galaxy, it does not contribute to the spectrum of the galaxy so we need not consider it any further. The spectrum of a galaxy contains contributions from stars, gas and (som Learning outcomes By the end of this unit you should be able to: explain how and why the optical spectrum of an active or starburst galaxy differs from that of a normal galaxy; explain how and why the broadband spectrum of an active or starburst galaxy differs from that of a normal galaxy; describe briefly the observed features of starburst galaxies and the four main classes of active galaxies (quasars, radio galaxies, Seyfert galaxies and blazars); Introduction Active galaxies provide a prime example of high-energy processes operating in the Universe. This unit introduces the evidence for activity from the spectra of some galaxies, and the concept of a compact active galactic nucleus as a unifying model for the observed features of several types of active galaxy. It also develops the key skill of applying arithmetic and simple algebra to solving scientific problems. This course is an adapted extract fromt he course Author(s): 1 How did the notion of public dialogue arise? There is a good case to be made that the emphasis on ‘dialogue’ in relation to science and the public in the UK coincided with the publication in 2000 of the House of Lords report on Science and Society. But the impact of that report has to be seen in the context of what was happening under the ‘public understanding of science’ (PUS) banner in the years between the publication of the Bodmer report (1985) and the House of Lords report 15 years later. In the UK, this period 4.5 Summary of Section 4 Proteins that serve similar functions often have similar amino acid sequences. The sequence of a protein can point to a particular function and can also be used to predict protein conformation. Homologous proteins contain statistically significant (i.e. above random) similarities in their amino acid sequences. The SH2 domain is an example of a domain that is highly conserved across different eukaryotes and is common to many diff 4.1 Introduction The availability of genomic sequence data from every major taxonomic group of organisms on Earth has allowed extensive comparisons to be made between their protein-coding regions, with over 800 000 protein sequences from these organisms being available for comparison in 2003. From these comparisons, it has become apparent that there is extensive homology between the amino acid sequences of many proteins, even between apparently distantly related organisms. In some proteins, this homology exte 1.4.4 Covalent cross-linkages stabilise protein structure Proteins that are secreted by the cell, or are attached to the extracellular surface of the plasma membrane, can be subject to more extreme conditions than those experienced by intracellular proteins. Often, covalent cross-linkages stabilise these proteins by connecting specific amino acids within a polypeptide or between polypeptide chains in multisubunit proteins (see below). Typically such a linkage will be a covalent sulfur–sulfur bond which forms between the –SH groups of two cystein 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 1.3.1 Helices A variety of helical structures can be identified in proteins using X-ray diffraction. A helix can be described by the number of units (amino acid residues) per turn (n) and by its pitch (p), which is the distance that the helix rises along its axis per turn. These parameters are indicated in Figure 8 for a number of helices 1.3 Protein secondary structure From our consideration of the steric constraints that apply to peptide bonds and amino acid residues in a polypeptide, we have already begun to discuss some of the factors that determine how the backbone of the polypeptide folds. The conformation adopted by the polypeptide backbone of a protein is referred to as secondary structure. Whilst it is true to say that all proteins have a unique three-dimensional structure or conformation, specified by the nature and sequence of their amino a 1.2 The peptide bond and primary structure of proteins The primary structure of a protein is defined as the sequence of amino acids of which it is composed. This sequence ultimately determines the shape that the protein adopts, according to the spatial limitations on the arrangement of the atoms in the protein, the chemical properties of the component amino acid residues, and the protein's environment. The peptide bonds that link amino acid residues in a polypeptide are formed in a condensation reaction between the acidic carboxyl gr 1.1 So what's it all about? iSpot is a website aimed at helping anyone identify anything in nature. Once you've registered, you can add an observation to the website and suggest an identification yourself or see if anyone else can identify it for you. You can also help others by adding an identification to an existing observation, which you may like to do as your knowledge grows. Your reputation on the site will grow as people agree with you identifications. You may also like to visit our forums which offer lively debat 1 Unit introduction Living organisms use the components of the world around themselves and convert these into their own living material. An acorn grows into an oak tree using only water, oxygen, carbon dioxide, some inorganic materials from the soil, and light energy. Similarly a human baby grows into an adult by digesting and metabolising food and drink. The parents in each case pass to their progeny, or offspring, the information and specification for building cells from materials around them. This information Introduction This unit looks at how units if inheritance are transmitted from one generation to the next. First you will look at what happens to the chromosomes of animals and plants during the process of sexual reproduction. Then you will examine how genes are transmitted in particular patterns from generation to generation. These two approaches combine to illustrate how the patterns of inheritance can be explained by the behaviour of chromosomes during sexual reproduction. This unit is from our ar 6.3 Risk Risk is a difficult concept. Most of what we do in life involves making choices and taking risks. Sometimes the risks are small, and sometimes they are large. It can be difficult sometimes to know what the risk of doing something is. Past experience can also influence the way we think about risk. If one was knocked over by a car crossing the road, then even though the risk of it happening again is small we may remain worried and concerned about crossing the road. How you explain risk is 5.3 Type 2 diabetes Type 2 diabetes was previously called non insulin-dependent diabetes. People with Type 2 diabetes produce insulin but it may be in insufficient amounts and/or their cells are resistant to the action of insulin (Figure 7). Hyperglycaemic symptoms, such as thirst and passing large amounts of urine, may be absent. Ketoacidosis does
