Cells & Systems Gr 8 Science PDF

2.0 CELLS PLAY A VITAL ROLE IN LIVING THINGS MARCELLO MALPIGHI In 1660, Marcello Malpighi looked at an intricate network of thin, hair-like vessels connecting arteries and veins in the lung tissues of frogs. These blood vessels were later called capillaries, from the Latin word for “hair.” By the ea...

2.0 CELLS PLAY A VITAL ROLE IN LIVING THINGS MARCELLO MALPIGHI In 1660, Marcello Malpighi looked at an intricate network of thin, hair-like vessels connecting arteries and veins in the lung tissues of frogs. These blood vessels were later called capillaries, from the Latin word for “hair.” By the early 1600s, a technological device had been invented that would change our understanding of life and living things. This device was the microscope. Types of Microscope There are generally two types of microscopes used in Science. 1. 2. Compound Light Microscope (up to 2000 X magnification) Electron Microscope (up to 2, 000, 000 X magnification) Compound Light Microscope A compound microscope is a high power (high magnification) microscope that uses a compound lens system. A compound microscope has multiple lenses: the objective lens (typically 4x, 10x, 40x or 100x) is compounded (multiplied) by the eyepiece lens (typically 10x) to obtain a high magnification of 40x, 100x, 400x and 1000x. The Vital Role Cell Structures Play Within each cell there are a number of specialized structures called organelles that carry out specific functions. One way to think about cells’ organization is to think of them as living factories, making all the things necessary for them to live. Animal Cells Plant Cells Unicellular Organisms They are made up of only a single cell. Most microscopic organisms, or micro-organisms, such as mycoplasma, are examples of unicellular (single-celled) organisms. Yeast **A single-celled organism can do most things that we need trillions of cells to do: eat, move, react to stimuli, get rid of waste products, and reproduce.** Virus Amoebas are common unicellular organisms that live in water. They move around using foot-like projections called pseudopods. They extend a pseudopod and the cytoplasm streams into it. Amoebas also use these pseudopods to capture food. Amoeba engulf food between two pseudopods. Paramecia (plural form of paramecium) move swiftly through the freshwater where they live. They are covered in hair-like structures called cilia, which move back and forth like oars to move them through the water. Cilia also help them gather food. On one side of the cell is a channel called an oral groove. It’s lined with cilia, which sweep food to the bottom of the groove. There, the food enters a food vacuole, which moves into the cytoplasm, and the food inside is digested. Multicellular Organisms This means that they are made up of two or more cells. Plants and animals are examples of multicellular (many-celled) organisms. Diffusion Diffusion is the movement of particles from an area where there are more of them to an area where there are fewer of them in all cells. In other words, diffusion moves particles from a more concentrated area to a less concentrated area. It’s a “balancing out” or “evening out” process that continues until the concentration of particles is the same everywhere. The cell membrane acts like a filter with extremely tiny openings that allow some particles to pass through but not large enough to let the organelles out of the cell. The membrane allows only specific substances in and specific substances out. This membrane is called a selectively permeable membrane. Osmosis Water is a substance that has particles small enough to diffuse through the cell membrane. Osmosis is a special case of diffusion. The amount of water inside a cell must stay fairly constant. If the water concentration inside the cell gets too low, water from outside the cell diffuses in. If the concentration gets too high in the cell, water diffuses out of the cell. Isotonic: In A the concentration of water in and out of the cell is the same. These cells are well balanced. Hypertonic: In B the blood cell was in salt water so the concentration of water inside the cell was higher than outside. This caused water to move out of the cell and shrink. These cells can die. Hypotonic: In photo C, the cell was placed in almost pure water. The inside of the cell contains far less water than the outside of the cell, so the water moves into the cell by osmosis, causing the cell to swell. These cells can explode.