Plant and animal cells

• Organisms are made up of cells.
• Most organisms are multicellular and have cells that are specialised to do a particular job.
• Microscopes are needed to study cells in detail.
• There are many different types of cells in animals, each type is specialised for a particular role and ensures that the organism functions as a whole.
• The head of the sperm contains the genetic material for fertilisation.
• The acrosome in the head of the sperm contains enzymes so that the sperm can penetrate an egg.
• The middle piece of the sperm is packed with mitochondria to release energy needed to swim and fertilise the egg.
• The tail of the sperm enables it to swim.
• The nerve cell is extended, so that nerves can run to and from different parts of the body to the central nervous system.
• The nerve cell has extensions and branches, so that it can communicate with other nerve cells, muscles and glands.
• The nerve cell is covered with a fatty sheath, which insulates the nerve cell and speeds up the nerve impulse.
• Muscle cells contain filaments of protein that slide over each other to cause muscle contraction.
• The arrangement of these filaments causes the banded appearance of heart muscle and skeletal muscle.
• Muscle cells contain many well-developed mitochondria to provide the energy for muscle contraction.
• In skeletal muscle, the cells merge so that the muscle fibres contract in unison.
• There are many different types of cells in plants, each type is specialised to do a particular role and ensures that the organism functions as a whole.
• The root hair cell has a large surface area to provide contact with soil water.
• The root hair cell has thin walls so as not to restrict the movement of water.
• There are no top and bottom walls between xylem vessels, so there is a continuous column of water running through them.
• Xylem cells support the plant by becoming thickened and woody.
• Dissolved sugars and amino acids can be transported both up and down the stem.
• Companion cells, adjacent to the sieve tubes provide energy required to transport substances in the phloem.