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Week 7.1.docx

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BIOL 111
Chin Sun

7.1 Human Diseases, Cell Structures and Disease-causing Agents Learning Outcomes: 1. Categorize diseases by their causes 2. Identify basic cell structure and understand their relevance to diseases and pathogens. 3. Distinguish among bacteria, viruses and eukaryotic cells and different pathogens. Readings: 18:467-476, 2: 41-46, 3: 66-69 Disease – abnormal condition(s) of an organism that impair its normal bodily functions. Diseases can be caused by external or internal factors. Internal 1. Poor nutrition e.g., rickets, scurvy, spinal bifida; 2. Genetic or internal dysfunction e.g., Huntington’s, Muscular dystrophy, autoimmune diseases, and some forms of cancer. External Toxins (e.g., 2 nd hand smoke (cancer), heavy metals (lead poisoning) Infectious agents 1. Microbes (pathogens) = disease causing organisms a) Bacteria (e.g., bird flu, cholera, plague, tuberculosis) b) Protists (e.g., malaria, Lyme disease, dysentery) 2. Viruses (e.g., flu, SARs, West Nile, AIDS, smallpox, polio) 3. Prions (infectious proteins) e.g., mad cow disease Although a number of pathogens have likely been with us through our evolutionary history, a great change occurred in the makeup of human disease 8 to 10 000 years ago as humans made the switch from being hunter-gatherers to farmers. 1. We domesticated animals as livestock and pets. This led to disease transmission from animals to humans. (e.g., Rabies, influenza) 2. We began domesticating and cultivating plants for food crops. Both actions changed our diet and had profoundly affected the type and diversity of human diseases (e.g., ergot in grain  Saint Antho,Food storage ailments e.g., Salmonella spp.), 3. Increases in human population size led to diseases whose success depends on direct person to person transmission. 4. The build up of human and animal wastes led to contaminated water/environment. This brought humans (and sometimes our animals) in contact with a new array of pathogens including both bacteria and eukaryotic parasites (e.g., Cholera, typhoid fever, dysentery, tapeworms). 5. We made profound changes to the natural environment and this favoured some pathogens. For example, slash and burn agriculture (deforestation) increased the number of breeding spots for malaria carrying mosquitoes. QUESTION: From your study of biology so far what would say is the “prime motive” of all living organisms? (What do all living organisms do? What are the purposes of their actions and behaviour?)  Find a suitable habitat to live and acquire energy and resources to grow, and to reproduce  Not all living organisms want to grow to an old age because you do not have to be that old to reproduce, and once you have reproduced you have already successfully passed on your genes and thus you will not need to live longer As living organisms, most pathogens also follow this prime motive. Habitats for pathogens  the host they infect. During reproduction or energy acquisition, many pathogens make their host ill. (The time when they cause disease. As they reproduce they happen to produce toxins or they kill other cells which cause people to have symptoms.) – Viruses infect cells and take them over to produce more viruses, kills cells to spread to a new host - Some produce toxins  cause the host to expel the newly made pathogens (e.g., vomiting or diarrhea). In this unit, we will focus on the Biology of infectious diseases. Some major causes of infectious diseases through the development… 2. What are some of the necessary conditions, in terms of the capability of the pathogens and their environment, for successful spread of new disease-causing organisms such as HIV, SARS or swine flu?  Being able to invade hosts (suitable habitats);  Overcome or evade the defense systems of the hosts and grow within the hosts;  Being able to spread to new hosts (reproduction); 3. How do diseases become more virulent, more resistant, or more infectious? 4. How do pathogens evade immediate destruction by the host’s immune system? enter human bodies along with food or water; hide from immune system by residing inside host cells (viruses); some may actually target the very cells which would normally kill the pathogen (e.g., HIV). 5.Where or how do new human diseases often originate?  By close contact with animals  By close contact with domesticated plants  Due to changing environment (climate change and degradation of natural environments) Cell Structure Anton van Leeuwenhoek and Robert Hooke first observed microscopic organisms. They proposed the cell theory: all livings things are composed of cells. "In the morning I used to rub my teeth with salt and rinse my mouth with water and after eating to clean my molars with a toothpick.... I then most always saw, with great wonder, that in the said matter there were many very little living animalcules, very prettily a-moving. The biggest sort had a very strong and swift motion, and shot through the water like a pike does through the water; mostly these were of small numbers." -Anton van Leeuwenhoek Every cell consists of a plasma membrane surrounding internal fluids or cytoplasm and a form of DNA. All cells also have a mechanism for making proteins involving tiny ribosomes. Prokaryotic and eukaryotic cells share these characteristics in common but have many more differences. Cell structure Prokaryotic cells Eukaryotic cells Smaller cells: Domains Bacteria and Domain Eukarya transportation across Archaea cells is easier Bigger cells: more specialized features (can be accounted for by having many small cells with varying functioning). If you have only large cells, you will be more impacted if they got destroyed. Big cells have constraint (transportation of material within the cell becomes more complicated). It can hold more specialized organelle to facilitate/compensate for the large size of the cell size 1- 10 µm 10 – 100 µm Location and in cytoplasm contained inside nucleus arrangement of arranged in a circular DNA strands are coiled around histone proteins genetic information chromosome and small circular and highly condensed into chromosomes during plasmids replication Internal structures ribosomes √ √ Microtubules some √ for cytoskeleton Endoplasmic reticulum None √ for processing proteins and transportation Golgi apparatus None √ for sorting, packaging proteins Mitochondria None, but may have same Most have except for a few anaerobic protists enzymes in cytoplasm Perform chemical reactions in cytoplasm involving oxygen None, if photosynthetic, perform Chloroplasts in cytoplasm Plantae and some protists External structures 1. Flagella some some 2. Plasma membrane All cells have a plasma membrane made of phospholipids. In membranes, lipids are arranged in a double layer and only allow some small uncharged molecules to pass through (e.g., C2 ; Fig 3.11a of your textbook). All living things have the ability to maintain homeostasis (constant internal environment); therefore, they must have boundaries from the outside world to mediate what comes in and out (cell membrane). Protein carriers/channels in membranes Water enters cells through “aquaporins” (small pores in the plasma membrane made of proteins). Other small molecules (e.g., glucose) can also be transported by protein carriers through membranes. Charged molecules (e.g., Na , sodium ions) must pass through ion channels which are also composed of proteins sitting in the membrane and have specificity to only allow specific ions through. Facilitated diffusion (Fig 3.11b) - no energy is required to move some molecul
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