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  1. 1. ISSUE 13 jANUARY 2011Big THE CELLPicturebRiNgiNg CUTTiNg-EDgE SCiENCE iNTo THE CLASSRooM Insider knowledge Revealing the secrets of your cells What are cells for? How do cells divide, develop and communicate? What are stem cells and why are they important? What happens when cells die? fo r t e a c h ce e © David S Goodsell, 2000 ur rs A res o a n d le a r n e E FRE rs
  2. 2. BigPicture CoNTENTS Big Picture Introducing the cell A close-up look at the structure of animal cells. 3 Big Picture is a free resource for teachers, Beginnings and basics How do cells divide, develop and grow into complex organisms? 4–5 school and college students, and learners of any age. Published twice a year, each Cells and their surroundings How do cells interact with their environment? 6–7 issue comes as a printed magazine with accompanying online articles and other A matter of life and death How long do cells live? What happens when they die? 8–9 content. Here’s how to get the most from your issue. Stem cells and development What are stem cells and how are they used in medical research? 10–11 Stem cells and the future What might developments in stem cell science mean for us? 12–13 Real voices Three people’s stories about the roles of cells in their lives. 14–15 How to use Big Picture magazine How to use the Big Picture website Each issue of Big Picture focuses on a topic that is current, As well as twice-yearly magazines, there’s loads of other relevant to the biology curriculum, rooted in science, and that has useful material available on the Big Picture website debate-provoking aspects. The issues are divided into double- ( The exclusive online page spreads, each dealing with a different aspect of the topic. content is created for each issue, and includes articles, videos, games, image galleries, animations, lesson plans, activities and The spreads are a jigsaw of articles, images, diagrams and ‘Fast more. our selected links help you and your students to get the Facts’, allowing you to dip into each issue, and each spread, as most out of the web for each topic. you need. Every issue contains a series of ‘real voices’ – interviews with people whose lives are affected and shaped by the topic in Also on this site, you can download PDFs of the current and all question. Whether you want to stimulate debate, to provide up-to- 13 past issues of Big Picture. There are also curriculum-matching date, scientifically accurate examples around particular issues, or details, and info on how to order copies of the magazines. to get across complex ideas to your students, Big Picture helps you to bring cutting-edge science into your classroom. – including Annie Cavanagh for studying specific diseases muscular dystrophy Big Using stem cells Huntington’s, Parkinson’s, and type 1 diabetes – have been made by Picture You seem different… Stem cells hold great potential for reprogramming adult cells from patients into a stem cells would for their roles? treating disease. pluripotent state. Pluripotent How are cells specialised give researchers the chance to test drugs cells and range of hormones and digestive If we can learn how to control the but only if they can on different types of cell, 1 Stem ment Each cell type is specialised enzymes. Small regions of the cells we might be able how and when c differentiation of stem develop ways of controlling for the role it plays; specifi pancreas known as the Islets of of cell damage in the cells. from to remedy many kinds these stem cells differentiate. Scanning electron micrograph of embryonic kidney characteristics range Langerhans contain four different body. Embryonic stem cells are pluripotent, Adult stem cells (those found in develop general making key proteins to cell types, which each make and so the most versatile, but their use organs) are . This approach Red blood (for more, see differentiated tissues and involved in cell differentiation properties like shape. different hormones. The most in drugs for, in this small is not without controversy potentially useful too. Researchers single adult can also be used to screen cells, for example, are common cells there – beta cells are using tissues. shape pages 12–13). companies use Cambridge, for example, instance, repairing damaged biconcave discs. This – make insulin and amylin. Some pharmaceutical the biological signals area, skin stem cells to explore – not gives a large surface cells specialise? test new drugs. Stem cells Stem cells are very special stem cells to How do 2 oxygen helping the cells to ship Getting some culture a signal s but A stem cell will receive only can they renew themselve ted from the lungs to the tissues, from its surroundings that differentia and a little of the carbon dioxide grown they can also become an embryo Many types of cell are pattern triggers a change in the in the other way. on and cells. Stem cells found The shape also gives of genes that are turned off, directing the cell towards a in the lab for research. cells found can become any of the hold great 1 flexibility, helping the cells be kept alive outside more specialised state. Having Many kinds of cell can dish. If they grow and in the body and, as such, smallest squeeze through the a detailed understandin g of the body in a laboratory g replacement red blood cell culture. Many cell capillaries. Developing these changes and how they reproduce, you have a promise for generatin cells begin with a nucleus and us to culture ‘lines’ (or types) are used in research. a number are triggered may allow tissues and cells to treat , including 4 before substitute for whole organelles, but lose them control them. To some extent, they can for animal testing of of diseases and disorders in effect they start work, which organisms, particularly disease and full However, cultures diabetes, Parkinson’s reduces the cells to bags of haemoglobin, the protein EM Unit, UCL Medical toxicity or drug effects. (a layer one cell usually consist of a monolayer the mix of cells multiple sclerosis. that carries oxygen and carbon School, Royal Free Campus thick) of a single type of cell, not distorted, also lack the three- dioxide. If the shape is found in real tissues. They 2 disease can result. For example, of tissues and organs, dimensional structure sickle- and support their in the inherited disease which have defined shapes Stem cells cell anaemia, some red blood cells in carefully ordered arrangements. stem cells? is as much art What do we mean by cells become sickle-shaped Successful tissue culture owing to abnormal haemoglobin carefully controlled all its descendants will be as science. Cells need If a differentiated cell divides, the right do more, molecules clumping together. conditions to grow, including other. A stem cell can growth factors in identical to it and each Organs often contain temperature, gas mix and differentiated cells. They’re producing stem cells and on sub-populations of cells. The blood cells. the medium they grow in. The longest-lived means that they can go makes a Sickled and normal red cancer cells, which also self-renewing, which pancreas, for instance, cultures often derive from normal controls and on dividing. potency – how much they can have found ways to override 4 Stem cells vary in their lines have to be egg and the products of on cell division. Such cell differentiate. A newly fertilised totipotent cells. These cancerous cells may made of checked continually. The its first few divisions are do in a tumour that’s cell type in the body, including go on changing, as they cells can give rise to any easy for cultures to University of Edinburgh produce a whole organism. still in the body. It is also the placenta, and so can by other cells. If this a few steps beyond the egg in become contaminated 3 Embryonic stem cells, may not be – they can become any goes unnoticed, experiments development, are pluripotent think. but not a whole organism. testing what the investigators type of specialised cell, of can make just a few types Multipotent cells, which red marrow that can generate cell, include those in bone found adult stem cells (those or white blood cells. Most www.nucleusinc. Art, all rights reserved. in differentiated tissues and organs) are multipotent. just one Medical illustration copyright © 2010 Nucleus Medical FAST FACT those in the skin, make are Unipotent cells, such as Stem cell therapies fully differentiated cell type, usually where lots of new micrograph of epithelial (skin) cells. More, and bigger already in use in the Transmission electron form of bone marrow cells are needed regularly. focuses on the transitions between Organs can grow by transplants – the first of A lot of research getting more cells, these states. A basic question is whether pluripotent by default, or need some This way up and function. or larger ones. which was performed in cells’ development in 1956. Source: cells carry on as they are continuing signal to remind them to stop differentiating. cells Direction is important An organ can grow in two ways. that embryonic stems absorption. The cell keeps track Adding more cells makes it Research strongly suggests cells, as – including keep making more stem A cell’s development of which end is which, so that bigger. But so can increasing Munich are self-sustaining, and protein signals from a particular its direction – is constantly molecules go the right way. the size of individual cells (called long as they receive no influenced by the cells A more complex example is ‘hypertrophy’). We use both Medical Art Service, 3 that triggers cell differentiation. surrounding it. An epithelial found in the ear, where a type methods. The embryonic heart sheet, for example, is of epithelial cell in the inner ear increases in size by adding extra – the asymmetric. One face turns vibrational signals into cells, but after birth, our hearts too thick to Heart muscle becomes apical surface – is exposed electrical messages so we can grow by hypertrophy. Normal heart (cut section). (hypertrophy). the gut, the watery contents of hear. These hair cells, which By exercising, we stimulate The In this or to the air in the lungs. have a bundle of fine cilia, have this process, and the hearts of which stimulates hypertrophy. surface again. In heart failure, case, despite the increase in opposite face – the basal a top and bottom, but have to athletes can grow much larger things of can result from many actually – sits on supporting layers be arranged in the right direction still. This so-called physiological diet and size, heart performance Cross-section of bone. tissue. well. If they such as infection, poor collagen and connective along another axis as hypertrophy is normal; when is an worsens. into high blood pressure, there Cells that secrete molecules lose this orientation, or planar you stop training, your heart heart that membrane increased load on the the gut need different polarity, the sense of hearing will adapt and slowly reduce bottom, proteins at the top and may be impaired. JANUARY 2011 • 11 for and so do those specialised THE CELL 10 • Big Picture 13: 1 Title – Each spread deals with a particular aspect of the title topic. 1 Left-hand menu – browse Big Picture online by title, 2 Intro – This sets the scene for the spread within the issue, article, activity or resource. and the wider world. 2 Current issue heading – Explore the online content for 3 Article – Each article can be used alongside others from the the latest issue. same spread or the rest of the issue, or as a standalone 3 Recent issues heading – Explore the online content component for a lesson. for past issues. 4 Image/diagram – illustrations and diagrams help you express 4 Sign-up link – Sign up to receive issues of Big Picture complex ideas in a visual way, as well as helping to place the and other Wellcome Trust publications. issues in question into a real-life context. 2 • Big Picture 13: THE CELL
  3. 3. introducing the cell are poised to break down the material into smaller molecules. Cell theory was put forward in the 1830s, soon after the cell nucleus was first join us as we explore the building block of life. identified in eukaryotes. It recognised that living things are made of cells, that cells are the basic units of life, and that new The cell is the smallest unit of life. Some eukaryotic organisms are multicellular. cells are created by old ones dividing into simple organisms consist of just one cell, The intricately organised insides of two. Viruses – simple entities of genes and whereas more complex beasts, like us, have eukaryotic cells allow them to have different protein – need to get into a cell and hijack its vast numbers of them. Humans are among things happening in different compartments. cytoplasmic machinery to copy themselves. the organisms built up from eukaryotic Keeping a cell going depends on getting We describe these as acellular, and they are cells, which have their DNA parcelled the right molecules to the right place at the not considered to be living. up in a nucleus, and lots of subcellular right time. Having distinct spaces does half In this issue, we’ll be focusing on animal compartments, called organelles. Prokaryotic the job, but it also requires sophisticated cells – how they reproduce, grow, move, organisms (such as bacteria) are simpler: machinery to ensure the right things get communicate and die. So join us to explore cells still with DNA, but having no nucleus into each section. Only material the cell has what we know – as well as what we still don’t or membrane-bound structures. The vast finished with, for example, can be allowed understand – about the cells that are the majority of these are unicellular, while most into a lysosome, where powerful enzymes basis of all of us. microtubules – small, tubular assemblies of lysosomes – membrane-bound protein, made from repeating tubulin subunits, organelles that are the cell’s rubbish which help maintain the cell’s internal structure disposal and recycling units; contain and move organelles and cytoplasm using hydrolytic enzymes extracellular matrix – the molecular motors. Part of the cytoskeleton material in between cells that vacuoles – internal bags, holds tissues together, usually surrounded by a membrane, made of scaffolding proteins which cells use for storage such as collagen of food or waste nucleus – the information centre microfilaments – smaller of the eukaryotic cell, where the than microtubules, these are DNA is stored, replicated and made from repeating actin copied into RNA (transcribed) subunits. Responsible for cell movement and changes in shape, and make muscle nuclear envelope – contraction possible. Part of double membrane that the cytoskeleton separates the contents of the nucleus from the cytoplasmcentrioles – a pair oforganelles that organisesmicrotubules into spindleson which chromosomes nuclear pores – gapsare separated when in the nuclear envelopecells divide that allow substances to move in and out of the nucleusGolgi apparatus –one of the wondrouslycomplex membranesystems in the cytoplasm, nucleolus – part of thewhich modifies, packages nucleus that producesand directs newly made ribosomesproteins to where theyare needed endoplasmic reticulum (ER) – an extensive network cytoplasm – everything in of membranes. Rough ER is the cell outside the nucleus; studded with ribosomes and a viscous fluid containing is a site where proteins are proteins, other organic made, modified and processed and inorganic molecules, for shipping. The roles of membranes and organelles smooth ER include lipid and steroid synthesis and drug detoxification mitochondria (singular: ribosomes – molecular machines, mitochondrion) – rod-shaped plasma membrane – a phospholipid built from RNA and protein, that bodies in the cytoplasm that bilayer that contains cholesterol make new proteins. They are found supply chemical energy to the and proteins. it surrounds the cell and in the cytoplasm and bound to the rest of the cell enables it to communicate with its rough endoplasmic reticulum neighbours and detect and respond to changes in the environment JANUARY 2011 • 3