Junior Cycle Science The Cell & Microscope Biology

What are Cells? Cells are the tiny building blocks of all living things. You have 10,000 trillion trillion cells in your body. Some living things have only one cell! All cells have the following: Cell Membrane – holds the cell together and controls what goes in and what goes out. Cytoplasm – A watery substance. Nucleus – The control centre of the cell. Vacuoles – Storage areas

Plant Cells Plants cells have the following extra bits: Chloroplasts – Little structures with green chlorophyll which allow plants make their food. Cell Wall – A tough outer layer which gives the plant strength. Large Vacuoles – Storage of water and nutrients.

Animal Cells Plant Cells No Cell Wall Have a Cell Wall Have NO Chloroplasts Have Chloroplasts Have small vacuoles Have Very BIG Vacuoles

Cell Organisation You have many different types of cells, depending on the job it has. Blood cells are different from nerve cells which are different from muscle cells. Cells are organised into tissues. A tissue is a group of similar cells which carry out a function (e.g. muscle or bone) Tissues are organised into organs. An organ is a group of tissues which have a particular function (e.g. lung, heart, ear etc) Organs are organised into SYSTEMS. A system is a group of organs working together.

Cell Organisation

Cell Division & Growth We all started life as one cell, a fertilised egg. This cell divided into two cells, which divided again and again and again. Growth occurs when cells divide. As cells grow they change into different types of cells.

The Microscope The average cell is less than one – tenth of a millimetre long. To see them we need to look at them using a microscope. A microscope has four main parts: The Eyepiece The Objective Lens The Stage The Focus Wheels Total magnification is the eyepiece lens powers multiplied by the objective lens power.