Cell biology

• The nucleus is the control centre of the cell, containing DNA which controls all activities within the cell.
• A cell membrane controls what goes in and out of the cell
• Cytoplasm is where chemical reactions take place.
• Ribosomes make proteins
• Chloroplasts contain chlorophyll to absorb light energy during photosynthesis
• Mitochondria provides energy for the cell
• Cell wall gives plant cells support and protection
• Vacuole stores water, waste products and pigments
• Where are eukaryotic cells found?

  Plants, animals, fungi and protists
• Prokaryotic cells don't have a nucleus or mitochondria.
• magnification=image size/actual size
• Animal cells have a cell membrane, cytoplasm, nucleus, mitochondria and ribosomes
• Plant cells have the same as animal cells but they also have chloroplast, cell wall, and vacuole
• A chromosome is a DNA molecule made up of sections called genes
• The cell cycle is the series of events that occur in a cell to divide and produce two new cells
• All multicellular organisms require a continuous supply of new cells to replace those that are damaged or destroyed.
• In stage one the cell cycle, the cell grows and duplicates its DNA. The genetic material also duplicates so that both daughter cells will have exactly the same DNA as each other
• In stage two of the cell cycle, mitosis happens. The membrane of the nucleus, holding the genetic material breaks down and the chromosomes and pulled away from each other. Both halves are completely identical to each other
• In stage 3 of the cell cycle, the cytoplasm and cell membrane splits and these are called daughter cells. They are identical
• Stem cells are cells with the potential to develop into many different types of cells in the body
• Stem cells divide by mitosis to form more cells
• Stem cells are able to differentiate into any type of cell in the body (specialised cells)
• Many multicellular organisms are specialised. They have specific roles in the organism
• Sperm cells - in human and animal

  The role of a sperm cell is to deliver genetic material to an egg in order to fertilise it. They have a very long tail called a flagellum which allows the sperm cell to swim through the uterus to reach the egg. They have a lot of mitochondria which provides energy required for swimming. At the very front of the sperm, they have a lot of digestive enzymes which are used to break a hole into the egg when the sperm reaches it
• Nerve cells 


  They send electrical impulses around the body
• Muscle cells


  These cells are able to contract (get shorter). They have a lot of mitochondria to provide energy for muscle contraction
• Root hair cells

  The hairs increase the surface area of the root, so that it can absorb water and dissolved minerals more effectively. They do not contain chloroplast as they are underground
• Xylem cells

  Xylem are found in the plant stem. They form long tubes.These tubes carry water and dissolved minerals from the roots to the leaves
• Phloem cells

  Phloem tubes carry dissolved sugars up and down the plant
• Diffusion is when particles move from an area of high concentration to an area of low concentration. They spread out
• Cells need oxygen for respiration which is carried out by mitochondria. Cells are surrounded by a high concentration of oxygen
• Osmosis is the movement of water molecules from a region of high water concentration to a region of low water concentration
• Active transport is the movement of molecules from an area of low concentration to an area of high concentration against a concentration gradient