Topic Cell Theory1. What is Cell Theory Cells are the basic building blocks of all living things. An average cell is between 0.01 and 0.1 millimetres across. You need to use a microscope to see cells. All cells come from pre-existing cells. All organisms are composed of one or more cells (Schleiden+Schwann) The cell is the basic unit of life in all living things (Schleiden+Schwann) All cells are produced by the division of pre-existing cells (Virchow)

2. Contribution to the cell theory by Hooke, Janssen, Leeuwenhoek, Schleiden and Schwann and Virchow

ScientistContributions

Robert HookeDiscovered cells while looking at a thin slice of corkDescribed cells as tiny boxes/ honeycombThought cells only existed in plants and fungi

Hans and JanssenProduced first compound microscope by combining 2 convex lenses within a tube

LeeuwenhoekUsed handmade microscope to observe pond scum and discovered single celled organisms (animalcules)Observed blood cells from fish, birds, frogs, dogs, humans

SchleidenConcluded that all plant parts are made up of cells

SchwaanStated that all animal tissues are made of cells

VirchowConcluded cells must arise from pre-existing cells (omnis cellula e cellula)

3. Label a microscope and describe the function of the various parts

PartFunction

Iris leverControls lighting

ArmHolds microscope/acts as handle when carrying

StageWhere you place the slide

EyepieceWhen you look through, magnifies image x10

Coarse focusMoves body tube up/down for focusing

Fine focusMoves body tube up/ down for more detail

BaseSupports and stabilises microscope

LightProvides the light required to view the image

Iris diaphragmControls amount of light passing through object

StagePlatform where slide is positioned

Objective lensUsed to see detail of the specimen. Can be low/ high power

Nose pieceCan be rotated to choose different objective lens

4. Differences between a monocular and binocular light microscopeMonocular Microscope: One eyepiece lens Choice of 2 or 3 objective lenses of different magnification Used for examining thin specimens on glass slides Can be magnified up to 200-400 times their normal size As light passes through, image is formed on the retinaBinocular microscope: Two eyepiece lenses Gives a more three-dimensional effect Used to examine larger specimens Less magnification Light reflects off these specimens before it enters the lens system of the microscope

5. Rules for using a Microscope Always carry a microscope with 2 hands- one hand holding the arm, the other supporting the base Place the microscope securely on the bench, away from direct sunlight Look at the microscope side on to wind the body to its lowest point, then focus by winding the body tube upwards. This will prevent the glass slide from breaking Always begin with the lowest magnification, then work your way up6. Field of ViewWhen looking into a microscope, the field of view changes, depending on the magnification youre using. As the magnification increases, the field of view decreases. This means that you see less of the specimen you are viewing, but in for more detail. The higher the magnification of the objective lens, the more detailed the image.Benefits of Low Magnification:A) You get to see a larger field of view. B) It's the better way to see moving objects. * How to work out the total magnification of a microscope: You multiply the magnification of the eyepiece by the multiplication of the lens youre using. So for example, if the eyepiece is 10x and the lens is 40x, that will create a magnification of 400x.7. Different cellsOrganelle which carries out respiration in cells: The mitochondria

Similarities:-Cytoplasm-Mitochondria-Nucleus-Vacuole-RibosomesOrganelle which carries out photosynthesis in cells: ChloroplastDifference between plant and animal cell1.Plant cells are larger than animal cells.2.Plant cells have chloroplasts 3.Plant cells have a cell wall 4. Plant cells have a larger vacuole5. Plant cells have plastids8. Unicellular and Multi-cellular OrganismsA unicellular organism is made up of only one kind of cell capable of performing all the required functions, whereas a multi-cellular organism is made up of many cells, like in our case, there are about 100 trillion cells in our body9. Osmosis and Diffusion Diffusion is the movement of particles from an area of high concentration to an area of low concentration without using energyOsmosis is the movement of water molecules from an area of high concentration to low concentration10. Cells Tissues and OrgansCells: The cell is the smallest unit of life. All living things are made of cells. One kind of cell creates one kind of tissue.Tissues: Tissues are large groups of cells all doing the same job.Organs: Organs are groups of tissues that work together to do a job.Organism: An individual life form11. Why multi-cellular organisms require specialised organs and systemsAll the life processes in a unicellular organism take place in that one cell. Multicellular organisms need organ systems to carry out functions such as:Communication between cells, eg the nervous system and circulatory systemSupplying the cells with nutrients, eg the digestive systemControlling exchanges with the environment, eg the respiratory system and excretory system12. Distinguish between the microbesBacteria: A simple, tiny cell that can have either a good or bad effect. It is made up of a cell wall, cell membrane and cytoplasm. No nucleus. The three basic shapes are cocci (spherical), bacillus (rod-shaped) and spirilla (spiral). Divide by fission.Viruses: Much smaller than other microbes. Structure contains a protein coat surrounding a chemical that contains the instructions of building a new virus.Fungi: Moulds made up of thread like structures. They feed on dead and decaying material, helping to return nutrients to the natural cycles of the environment.Protists: Single-celled organisms that live in water and areas of high moisture. Make their own food using energy in sunlight. 13. Difference between fungi and bacterial colonies on an agar plateFungal colonies are usually fuzzy-looking, irregular in outline, and grey or black. They can also be quite large. Any colony over a half inch in diameter is most likely a fungus. Bacterial colonies are typically small with clearly defined edges. They may be a variety of colors, including white. They may appear smooth or rough but not fuzzy.Bacterial colonies are generally roundish and small. They can grow to touch each other if the specimen is left too long. They can be colourful, especially in differential media. Mold is fuzzy and can overgrow the whole plate. It can be other colours too.

Define binary fissionBinary fission is the form of asexual reproduction and cell division used by all prokaryotic and eukaryotic organisms. It is the division of the cell into two parts and each have the potential to grow to the size of the original cell.Process which bacteria divides:

14. Reproduction of VirusesVirus comes into contact with a host cell. It hijacks the cell, forcing it to become a virus factory. When it is full of new viruses, it bursts open releasing the viruses. They then go on to infect more cells. (Refer to image)15. Labelled fungus

16. Beneficial effects of microbes-Play an important role in food production-Can be used to treat and prevent diseases-The microbes that live on us protect us from harmful microbes-Can produce important vitamins for our body-Can purify water-Can reduce atmosphere nitrogen

17. Harmful effects of microbes and how they can be minimised-Microbes can harmfully affect the human body, areas in the home, clothing and food-Lung infections and allergic reactions can develop if fungi grow in common areas-Bacteria and fungi can create odours affecting clothing and footwear-Common diseases created by microbes result in the most deaths worldwide18. Role of micro-organisms in soil fertilityOrganic matter together with microbes and nutrients can be applied from an external source. In the latter case, the microbes metabolize the organic matter turning it into humus. This process replenishes and maintains long term soil fertility by providing optimal conditions for soil biological activity. ""As the microbes metabolize organic matter, they help maintain good soil structure by developing compounds that cement small soil particles together into aggregates, allowing for both increased drainage and moisture retention. Microbes also change the organic matter into inorganic nutrients that can be used by growing plants. " "19. Reproduction methods of Microbes:Bacteria: Cell division and binary fission. Parent cell divides into 2 identical daughter cells. Fungi:

Procedure to Making a Wet Mount1.Place specimen on microscope slide. 2.Place three drops of liquid (e.g. iodine) on the specimen.3.Place coverslip onto slide, on its side, beside the specimen and liquid. 4.Cover the coverslip slowly to avoid air bubbles5.Blot away excess liquid from beside the coverslip with absorbent paper.