Chapter 2: Cells

• Cytoplasm is found inside the cell and contains all the other cell structures.
• The large nucleus is surrounded by a nuclear membrane to separate it from the cytoplasm.
• The cell membrane surrounds the cell.
• The cell wall is made of cellulose and surrounds the cell membrane in plant cells.
• Chloroplasts are organelles found in the cytoplasm that are packed with the pigment chlorophyll and so are green in colour.
• Vacuoles are large vesicles that take up a large part of the interior of plant cells.
• The actual size of the cell can be found using the magnification equation.
• Magnification is calculated by dividing the image size by the actual size.
• The magnification is a unitless number.
• The actual thickness of a leaf can be calculated by dividing the drawing thickness by the magnification.
• When given a question with two different units, ensure that both units are converted to the same unit before doing the calculation.
• Millimetres and micrometres are related such that 1mm = 1000μm and 1cm = 10,000μm.
• The magnification is the same as the power of the microscope.
• If the answer to a question is the same as one of the incorrect options in a multiple choice question, it means that the answer is incorrect.
• The following diagram may help with unit conversion between mm and μm.
• The organisation of the organism is a topic in CIE IGCSE Biology.
• Some of the processes carried out by living organisms are illustrated in a diagram, and the correct magnification of the image is x 5.
• The terms 'cell', 'tissue', 'organ', and 'organ system' can be used to describe a leaf, a root, and a stem.
• A list of subcellular structures includes the nucleus, ribosomes, vacuole, and chloroplast.
• A plant cell and an animal cell can be observed under a light microscope, and the structures 1, 2, and 4 would always be visible in a plant cell.
• The size of structures can be represented in different orders, for example, chromosome → red blood cell → stomach → gene → nucleus.
• The functions of the components in a root hair cell are support, active transport, energy release, and nutrition.
• Rearranging the equation for magnification to find things other than the magnification becomes easy when you remember the triangle - whatever you are trying to find, place your finger over it and whatever is left is what you do.
• The size of specimens can be calculated using millimetres as units.
• Levels of organisation in an organism can be represented as a cell, tissue, organ system, organ, or cell.
• Image size can be calculated using the equation: Image size = Magnification x Actual Size.
• Magnification is calculated using the equation: Magnification = Image (Drawing) Size / Actual Size.
• A better way to remember the equation for magnification is using an equation triangle: Magnification equation.
• Actual size can be calculated using the equation: Actual size = Image (Drawing) Size / Magnification.
• Magnification does not have any units and is just written as 'x 10' or 'x 5000'.
• Cells are the basic functional and structural units in a living organism.
• Levels of organisation in a living organism include cells, tissues, organs, organ systems, and the organisation of the organism itself.
• Tissues are groups of cells of similar structure working together to perform the same function.
• Organs are made from different tissues working together to perform specific functions.
• Organ systems are groups of organs with related functions, working together to perform body functions.
• The organisation of the organism includes levels such as the cell, tissue, organ, organ system, and the organisation of the organism itself.
• Palisade mesophyll cells are column-shaped to maximize absorption of sunlight and fit as many in a layer under the upper epidermis of the leaf as possible.
• Xylem vessels are continuous columns of water running through them.
• Palisade mesophyll cells contain many chloroplasts for maximum photosynthesis.
• Their walls become thickened with a substance called lignin which means they are able to help support the plant.