Biology - Topic 3

• Organelles are subcellular structures that make up a cell. For example, mitochondria, nucleus and ribosomes. Each individual organelle has a specific role to play and multiple organelles form one single cell.
• Cells come into all sorts of shapes and sizes, we call different cells specialised cells. For instance, epithelial, muscle and glandular.
• Tissues are a group of similar cells that work together to carry out a particular functions. Epithelial cells from epithelial tissue covers the body's surface. Muscle cells form muscle tissue which contracts and relaxes to move different parts of our body. Glandular cells work together to form glandular tissue which makes and secretes chemicals
• Organs are a group of different tissues working together to perform a particular function. So epithelial tissue, muscle tissue and glandular tissue may work together to form an organ like the stomach, which has a function of breaking down proteins. Different combinations of tissues may form organs like the pancreas or the liver.
• The organ system is a group of organs that work together to perform a particular function. For instance, the stomach, the pancreas and liver and other organs work to form the digestive system.
• The digestive system - Many organs working together to digest and absorb food. Digestion - breaking down food molecules and absorbing them into blood so

  they are transported to where they are needed