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Mind map of Biology ch.2 The cell as the basic unit of life
Transcript of Mind map of Biology ch.2 The cell as the basic unit of life
Amazing Cells Biology:
The Cell is the
basic unit of life Development of microscopes Organisms are made up of cells that cannot be seen with the naked eye. People didn't know the existence of cells before the invention of the microscope. 1590,Hans Janssen and his son make the first two-lens microscope that could magnify objects 3 to 9 times 1665, An Englishman, Robert Hooke,looked at a thin slice of cork ,he observed some tiny structures and called them cells 1831, An English botanist, Robert Brown discovered the nucleus in cells. Inventions in one field of science often contribute to advancements in other fields. The development of microscopes and its contribute to the understanding of cells is an example. 1839, Jakob Schledien(botanist,left)&Theodor Schwann(Zoologist,right) discovered plat parts and animal parts are made up of cells, they proposed the cell theory based on their foundings. Modern Microscopes used today Light Microscope The light microscope is most commonly used in school laboratories today similar to the one created in late 1800s. It can produce image magnified by up to 1000times Electron microscopes -Transmission electron microscope The transmission electron microscope make use of electron beams that pass through the specimen to form an image. It reveals the internal structures of a specimen. It produces 2D, black and white images magnified by up to 800,000times. -Scanning electron microscope The scanning electron microscope makes use of an electron beam to scan over the surface of a specimen. It provides 3D images magnified by up to 30,000times. 2.2
Discovery of Cells 2.3 The basic structure of a cell The cell is the basic unit of life. Cells build up an organism, they work together to keep an organism alive,there are many types of cells. Our body alone is made up of more than 200 types of cells, the shape and size of cells vary, butsome features are common to all. Animal cell Plant Cell Animal Cell Cell membrane
It is thin and flexible membrane surrounding the cell
It is differentially permeable( only allows some substances to pass through), it controls the movement of substances into or out of the cell. Plant Cell Cell wall
It has a thick,rigid layer covering the cell membrane.
It is mainly made up of cellulose.
It is fully permeable(Allows all types of substances to move across.)
It protects,supports and gives shape to plant cells. Large central vacuole
It contains cell sap,which is a solution of dissolved substances such as food,pigments and waste.
It is usually large and located at the center of the cell.
When the large central vacuole is full of water, it becomes turgid and provides support to the plant. Chloroplast
It is bounded by a double membrane.
It contains a green pigment called chlorophyll.
Chlorophyll absorbs lights energy for photosynthesis. Both Cytoplasm
It is a jelly-like substance consisting of water,proteins and other chemical substances.
It holds all organelles(nucleus,endoplasmic reticulum,mitochondria etc.)
Many chemical reactions take place here. Endoplasmic reticulum(ER)
It is a network of interconnected membrane-bounded sacs.
It forms a link between the cytoplasm and the nuclear membrane.
There are two types of ER
Rough ER: With ribosomes.
Smooth ER: Without ribosomes
The ribosomes on rough ER are the sites of protein synthesis. Smooth ER is involved in the synthesis and transport of lipids. Mitochondria
It is rod-shaped and bounded by double membrane. The inner membrane is folded into finger-like projections.
It is main site where the energy-releasing stage of respiration take place. Vacuole
It is a space containing water and dissolved substances such as food and enzymes.
It is bounded by a differentially permeable membrane.
Most animal have only a few small vacuoles or even no vacuoles. 2.4
Levels of body organization. Cells are specialized in different ways and work together in terms to serve the different functions of an organism. This kind of division of labour among the different kinds of cells is commonly found in multicellular organisms. Cells work together at three levels of organization:tissue level, the organ level and the system level. Cell Similar cells group together to form a tissue. They work together to perform one or more particular functions Tissue Different tissues group together to form an organ. They cooperate to perform one or more particular functions. System Several organs work together to perform a particular task. These organs forms a system. Organ Different systems work together to support the life of an organism Organism 2.5
Using a light microscope We use a light microscope to observe cells. It is a kind of compound microscope consisting of two lenses eyepiece and an objective. The total magnification of the microscope is the product of the magnification of the eyepiece and that of the objective. The image observed under the microscope is upside down and laterally inverted. For example, if you observe the letter"p" under the microscope, the image becomes"d". We can mount the cells or tissues of animals and plants on the side for microscopic examination. Cell structures are colourless, specimens are often stained with methylene blue solution(animal cells) or iodine solution(plant cells) 2.6
Prokaryotic and eukaryotic cells Both plant and animal cells have a true nucleus surrounded by the muclear membrane. The genetic material is enclosed within the nucleus. These cells containing a true nucleus called eukaryotic cells. Organisms made up of eukaryotic cells are known as eukaryotes. Most of them have a cell wall but their cell wall does not contain cellulose as plant cell wall does.
They do not have endoplasmic reticulum. Ribosomes are lying free in the cytoplasm.
They do not have organelles bounded by a double membrane(e.g. mitochondria and chloroplasts)