Biology 1

• Light microscope 


  It uses light to form magnified images.
• Electron microscope 


  It uses electrons to produce magnification up to 2 million times
• Magnification = image size / real size
• Cell membrane 


  Controls what enters and leaves the cell
• Nucleus


  A large structure that contains genes that controls the activities of the cell
• Cytoplasm


  Jelly-like substance that fills the cell - many reactions take place here
• Mitochondria


  Tiny structure where respiration takes place, releasing energy for cell processes.
• Ribosomes


  Where protein synthesis happens
• Plant cell sub-cellular structures

  Cell wall

  Permanent vacuole

  Chloroplast
• Animal cells and plant cells are eukaryotic cells.
• Bacterial cells are prokaryotic cells.
• Prokaryotic cells 


  Cell membrane

  Cytoplasm

  Cell wall

  No Nucleus

  Plasmids

  Flagellum

  Chromosomal DNA
• Eukaryotic cells

  Cell membrane

  Nucleus

  Cytoplasm
• Differentiation(animals)

  Animal cells differentiate at an early stage.

  Cells acquire different structures so they can carry out particular functions.

  Cell division is mainly for repair and replacement.
• Ciliated cells


  Hair-like structures

  Line trachea

  Sweep mucus with dirt and bacteria.
• Sperm cells


  Have tail for movement

  Have lots of mitochondria to provide energy for movement

  Have enzymes in the acrosome to digest outer layer of egg.
• Nerve cells


  Have long axon to connect distant parts .

  Have dendrites to make connections with other cells.
• Root hair cells

  Absorb water and mineral ions.

  Have large vacuole to increase rate of absorption by osmosis

  Have many mitochondria to release energy for active transport.
• Differentiation (plants)


  Meristem are undifferentiated cells.

  Cells acquire different structures so they can carry out particular functions.

  They maintain ability to differentiate through their life.
• Xylem cells


  Lignin (dead cells) provide strength and support.

  No end walls so water and mineral ions can flow easily  .

  Pits that let water and ions move out
• Sterilisation 


  Killing microorganisms
• Binary fission 


  Bacteria reproducing through simple cell division.
• Cell cycle


  Interphase

  Mitosis

  Cell division
• Interphase


  Cell growth

  DNA replicated to form 2 copies of each chromosome.
• Mitosis


  Each set of chromosomes is pulled to each end.

  Nucleus divides.
• Cell division


  Cell membrane and cytoplasm divide.

  2 identical cells form.
• Mitosis makes two cells.
• Mitosis makes cells that are genetically identical.
• Diploid means two sets of chromosomes.
• Zygote is a single cell formed when an egg cell and sperm cell join together
• Stem cells (animals)

  Embryonic stem cells from embryo

  Adult stem cells from bone marrow
• Stem cells (plants)

  Meristem from tips of roots and shoots.
• Stem cell treatment

  Treats diabetes.

  Treats paralysis.

  Replace damaged or missing cells in pancreas or nervous system.
• Embryonic stem cells

  ❌ Embryo destroyed

  ✅ Easy to extract

  ✅ Produce any type of cell
• Adult stem cells

  ❌ Produce only few types of cells

  ✅ No rejection

  ✅ No ethical issue
• Embryonic and Adult stem cells

  ✅ Replace faulty cells.

  ❌ Cells may not stop dividing causing cancer.

  ❌ Risk of viral infection.
• The number of particles decreases as you go down a concentration gradient.
• Diffusion is from an area of higher concentration to an area of lower concentration.
• Ways to increase rate of diffusion


  - Increase difference in concentration

  - Increase temperature

  - Increase surface area

  - Decrease membrane thickness
• Osmosis is the diffusion of water from a dilute solution to a concentrated solution through a partially permeable membrane.