Biology- Cells

• How to make plant cell slides

  1- Peel a thin, transparent layer of epidermal cells from the inside of an onion. 2 - Place cells on a microscope slide. 3 - Add a drop of water or iodine (a chemical stain). 4 - Lower a coverslip onto the onion cells using forceps or a mounted needle. This needs to be done gently to prevent trapping air bubbles.
• Chemical stains are used to make some cell parts more obvious.
• How to make plant cells slides

  1 - Remove cells from the inside of your cheek using a cotton bud 2 - Smear the cotton bud onto a microscope slide 3 -Add a drop of methylene blue (a chemical stain) 4 - Lower a coverslip onto the cheek cells using forceps or a mounted needle. This needs to be done gently to prevent trapping air bubbles.
• Total magnification = magnification of objective lens X magnification of eyepiece lens
• Magnification of objective lens = Total magnification / magnification of eyepiece lens
• Magnification of eyepiece lens = total magnification / magnification of objective lens
• Nucleus

  Control centre of the cell. It contains the cell’s genetic information arranged in chromosomes.
• Chromosomes

  Threadlike structure found in the nucleus. Made of DNA which contains the genetic information of the cell.
• Cytoplasm

  Chemical reactions take place here.
• Mitochondria

  Site of cell respiration. Very abundant in cells that need a lot of energy (e.g. muscle cells).
• Cell membrane

  A selectively permeable boundary surrounding the cell which allows some substances to enter and leave the cell while preventing others.
• cellulose cell wall

  A rigid structure outside the cell membrane that provides support.
• Large permanent vacuole

  Contains cell sap and when full pushes the cell membrane against the cell wall, providing support.
• Chloroplasts

  Contain chlorophyll, a green pigment that traps light for photosynthesis.
• 5 features of bacterial

  1 - do not contain a nucleus - DNA is a circular chromosome that floats in the cytoplasm. 2 - Have a cell membrane. 3 - Have cytoplasm . 4 - Have a non-cellulose cell wall. 5 - Have plasmids - rings of DNA floating in cytoplasm also.

   
• Single cell organism

  where all life processes are carried out by one cell.
• Multi cell organism

  where cells differentiate and become specialised to carry out a particular function 
• Levels of organisation

  cell - tissue - organ - organ system - organism
• Where does plant growth occur

  mainly at the shoot and root tips on special growth zones like buds
• How does plant cell growth occur?

  Size increase often caused by increasing the size of cells by absorbing water into the vacuole
• Plant cell specialisation

  Most plant cells can differentiate into different cell types
• Where does animal cell growth occur?

  New cells can be made by most tissues
• How does animal cell growth occur?

  Size increase is brought out by increasing the number of cells
• As organisms increase in size, it reduces their surface area to volume ratio
• what are the main organs and functions of the digestive system?

  gut, liver, pancreas – to convert large insoluble molecules into small, soluble molecules, which can be transported in the blood
• What are the main organs and functions of the respiratory system?

  Trachea, lungs – taken oxygen and get rid of carbon dioxide
• What are the main organs and functions of the circulatory system?

  Heart, blood vessels – transport materials to and from the cells of the body
• What are the main organs and functions of the sensory system

  Ears, eyes, nose, tongue, skin – to allow the body to detect stimuli
• What are the main organs and functions of the nervous system?

  Brain, spinal cord – to conduct messages from one part of the body to another
• What are the main organs and functions of the musculoskeletal system?

  Muscles, skeleton – shape, form, and movement
• What are the main organs and functions of the reproductive system?

  Testes, ovaries – to produce offspring