B1.1 Cells 1. Observing cells 2. Plant and animal cells All living organisms are made of cells. Cells are the building blocks of life – they are the smallest units in an organism. Scientists use microscopes to observe small objects in detail. To make an observation, the object you wish to observe needs to be thin so light can travel through it. Adding a coloured dye will make the object easier to see. 2. Plant and animal cells Animal cells have an irregular shape. The diagram below shows the structures that an animal cell contains: The cell wall strengthens the cell and provides support. The vacuole contains a watery liquid called cell sap. It keeps the cell firm. Chloroplasts contain a green substance called chlorophyll, which traps energy transferred from the sun. Photosynthesis takes place inside the chloroplasts. 3. Specialised cells Specialised cells have changed their shape and structure so that they are suited to carry out a particular job. A nerve cell carries electrical impulses around the body. A red blood cell transports oxygen around the body. Sperm cells carry make genetic material The cytoplasm is where the chemical reactions take place in a cell. The cell membrane is a barrier that controls what moves in and out of the cell The nucleus controls the cell, and contains genetic material needed to make new cells Respiration occurs in the mitochondria – this chemical reaction transfers energy. The eyepiece lens and the objective lens are used together to magnify the object or specimen. The equation below can be used to help calculate the magnification. The plant cell has a more regular structure and contains the same components as an animal cell plus 3 extra components

4. Movement of substances Leaf cells are found at the top of the leaf and carry out photosynthesis Root hair cells absorb water and nutrients from the soil. Amoeba Euglena Key word Definition amoeba A unicellular organism. cell wall The plant cell component that surrounds the cell, providing support. cells The smallest functional units in an organism – the building blocks of life. chloroplasts The plant cell component where photosynthesis takes place. concentration A measure of the number of particles of a substance in a given volume. diffusion The movement of liquid or gas particles from a place of high concentration to a place of low concentration. euglena Unicellular organism that performs photosynthesis. flagellum A tail-like structure that allows euglenas to move. leaf cell The plant cells that contain chloroplasts, where photosynthesis takes place. Key word Definition microscope An optical instrument used to magnify objects, so small details can be seen clearly. nerve cell An animal cell that transmits electrical impulses around the body. nucleus The cell component that controls the cell and contains genetic material. observation Carefully looking at an object or process. organisms Living things. red blood cell An animal cell that transports oxygen around the body. root hair cell A plant cell that takes in water and minerals from the soil. specialised cell A cell whose shape and structure enable it to perform a particular function. sperm cell A cell containing male genetic material. unicellular Consisting of just one cell. vacuole The plant cell component that contains cell sap and helps to keep the cell firm. 4. Movement of substances Diffusion is the movement of gas or liquid particles from an area of high concentration to an area of low concentration. The diffusion of water is known as osmosis 5. Unicellular organisms A unicellular organism contains only one cell an example of this is an amoeba. An amoeba contains a cell membrane filled with cytoplasm, and a nucleus to control growth and reproduction. Euglena is a microscopic unicellular organism. Euglenas appear green as they contain chloroplasts for photosynthesis. Their eye spot locates light, and they use their flagellum to swim towards it. In low light levels they can engulf food.