1.1 Cells

• Cell membrane - a selectively permeable membrane, controlling what enters and leaves the cell.
• Cytoplasm - site of cell reactions.
• Nucleus - control centre of the cell, contains genetic information arranged in chromosomes.
• Nuclear membrane - boundary of nucleus, controls what enters and leaves the nucleus.
• Mitochondria - site of cell respiration.
• Cell wall - (made of cellulose), a rigid structure that provides support.
• Large permanent vacuole - contains cell sap and provides support.
• Chloroplasts - contain chlorophyll, which absorbs light energy for photosynthesis.
• Animal and plant cell structures

  A) Animal cell

  B) Plant cell

  C) Mitochondria

  D) Nuclear membrane

  E) Nucleus

  F) Cell membrance

  G) Cytoplasm

  H) Large permanent vacuole

  I) Chloroplast

  J) Cellulose cell wall

  
• Bacterial cell structure

  A) Circular chromosomes

  B) Cell membrane

  C) Non-cellulose cell wall

  D) Cytoplasm

  E) Plasmid

  
• Slide - a thin piece of glass used to hold objects which are examined under a microscope.
• Plant cells

  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.
• Animal cells

  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
• Chemical stains - used to make some cell parts more obvious.
• Microscope

  A) Eyepiece

  B) Objective lens

  C) Stage

  D) Focusing knob

  E) Light source

  
• Total magnification = eyepiece magnification x objective lens magnification.
• Single-celled - where all life processes are carried out by one cell.
• Multi-celled - where cells differentiate and become specialised to carry out a particular function (e.g. red blood cells carry oxygen)
• Cells with the same structure and function are known as tissue (e.g. muscle tissue).
• Several types of tissue that carry out a particular function is an organ (e.g. the heart organ contains muscle and nerve tissue).
• Organs that work together to carry out a particular function are known as an organ system. (e.g. the circulatory system).