Cell Structure

All living things are made up of cells. An organelle is a specialised structure inside a cell that performs a particular function. The different parts of a cell are called subcellular structure. Animal Cells- Nucleus- contains genetic material that controls the activities of the cell Cytoplasm- gel-like substance where most of the chemical reactions happen and it contains enzymes that control these reactions Cell Membrane- holds the cell together and controls the entry and exit of substances in the cell                                                                                                                     - semi- permeable Mitochondria- here sugar and oxygen react together to release energy that the cells need to work by the process of aerobic respiration. Ribosomes- these are where proteins are made in the cell Plant Cells- Plant cells usually have all the organelles that animal cells have, plus a few extra ones: Rigid Cell Wall- made of cellulose and supports and strengthens the cell Permanent Vacuole- contains cell sap, a weak solution of sugar and salts Chloroplasts- these contain a green substance called chlorophyll, which absorbs light needed for photosynthesis needed to make food for the plant Cells can be either prokaryote or eukaryote. Eukaryotes (plants and animals) have a nucleus around them with a membrane around it to hold the genetic information inside. Bacterial Cells- Prokaryotes such as bacteria and algae are single-celled organisms. Bacteria don't have chloroplasts or mitochondria They don't have a true 'nucleus'- instead they have a single circular strand of DNA that float freely in the cytoplasm They also may contain one or more small rings of DNA called plasmids. Prokaryotic cells are smaller than eukaryotic cells    

Cell Differentiation: Differentiation is the process which a cell changes o become specialised for its job As cells change, they develop different subcellular structures and turn into different types of cell. This allows them to carry out specific functions. Most differentiation occurs as an organism develops. In most animal cells, the ability to differentiate is lost at an early age, after they become specialised. However, a lot of plants never lose this ability. The cells that differentiate are mainly used for repairing and replacing cells, such as skin or blood cells.

Specialised Cells: A cell that has been adapted to have special features to perform a particular function. Animal/Plant                                                                  Function                                                                         Adaptation  Sperm- Animal                                                         to fertilise an egg cell                                                       long tail and streamlined head to swim easily                                                                                                                                                                                         towards the egg, lots of mitochondria for energy,                                                                                                                                                                                    carries enzymes in its head to digest through the                                                                                                                                                                                      egg cell membrane   Nerve Animal                                                           carry electrical impulses from                                          these cells are long (to cover more distance)                                                                                               one part of the body to another                                      branched connections at their ends to connect to                                                                                                                                                                                    other cells and form a network throughout the                                                                                                                                                                                          body    Muscle- Animal                                                      contact quickly to allow movement                            these cells are long (space to contract), lots of                                                                                                                                                                                          mitochondria to release energy needed for contraction   Red blood- Animal                                               transport oxygen around the body                            no nucleus so more haemoglobin, bi-concave shape-                                                                                                                                                                          larger surface area so more oxygen can be transported      White blood- Animal                                          protect body from pathogens                                       nucleus changes shape to engulf bacteria, lots of                                                                                                                                                                                    ribosomes to make enzymes and antibodies to destroy                                                                                                                                                                           pathogen          Palisade Leaf -Plant                                            carry out photosynthesis                                       absorb more light:  1) lots of chloroplasts                                                                                                                                                                                                                                        2) tightly packed together                                                                                                                                                                                                                             3) near the upper surface of the cell                                                                                                                                                                                                                                                                                                                                 stomata-  for efficient diffusion of oxygen and carbon dioxide     Root hair- Plant                                               absorbing water and minerals                              long hairs that stick into the soil giving the plant a large                                                                                                                                                                        surface for absorbing water and mineral ions more effeciently   Xylem                                                    transport water and mineral ions from the roots             cells are essentially dead to allow free passage of water                                                                                                                                                                            no walls in between to form continuous hollow tubes so                                                                                                                                                                      the substances can flow through