Cells

Cells

• All organisms are made of cells. Some are unicellular and larger organisms have millions of cells
• Magnification = size in drawing / size of real object

Specialised cells

• Many cells are made to do certain activities better than others

- ciliated cells move mucus upward in the trachea and bronchi

- root hair cells absorb water and mineral salts

- palisade mesophyll cells take part in photosynthesis

- red blood cells transport oxygen

- sperm and egg cells fuse together to produce a zygote

• Hand lens (x 10): Cells often seen as dots
• Light microscope (up to x 1500): Light beams over the specimen observed. Glass lenses are used to magnify and focus the image
• Electron microscope (up to x 10 million): It uses a beam of electrons and even some structures not visible by a light microscope can be seen

• Micrograph: A picture made using a microscope
• Photomicrograph: A picture made using a light microscope
• Electron micrograph: A picture made using an electron microscope

_{Structures seen under light microscope are:}

• _{Cell membrane: A partially-permeable thin layer of fat and protein that surrounds the cell. It holds the cell together and controls substances entering and leaving it}
• _{Cell wall: A fully permeable wall, made of criss-cross fibres of cellulose, that surrounds the plant cell with the membrane. It gives the cell extra support and defines its shape}
• _{Cytoplasm: A clear, watery jelly inside the cell. It supports cell structures, many chemical reactions take place in it, and it has water and many solutes.}
• _{Vacuoles: A large space in a plant cell, surrounded by a membrane inside the cytoplasm. It has a cell sap (a solution of sugars and other substances), it helps support the shape of the cell and it stores certain materials. Animal cells have vesicles, which are small, and have water and nutrients}
  
• _{Chloroplasts: Most of the cells in the green part of the plant have them.They have chlorophyll and they often have starch grains made by photosynthesis. Photosynthesis takes place here and chlorophyll absorb sunlight for photosynthesis. Some animal cells have glycogen, granules similar to starch, in the cytoplasm}
• _{Nucleus: It is an organelle which has genetic information in chromosomes (that determines the characteristics of the cell) and it manages cell division}
  

• A plant cell has a cell wall, often have chloroplasts with starch grains while an animal cell doesn't have either
• Both have a cell membrane, cytoplasm and a nucleus
• Plant cells often have large vacuoles while animal cells have small vacuoles (vesicles)
• Plant cells are often regular in shape while animal cells are often irregular in shape