Biology Key Concepts - Topic 1

• Catalyst

  Substance that increases the speed of a chemical reaction without being used up or changed in the process.
• Enzymes

  Specific type of catalyst that is made by a living organism called biological catalyst. Made of proteins which is made in ribosomes, specific to only one type of substrate and reusable as it remains unchanged in an reaction.
• Why do organisms need enzymes?

  Because most chemical reactions are slow.
• How do enzymes work?

  Enzyme has active site which is complementary to the substrate (reactant).

  If substrate doesn't fit into active site then reaction won't be catalyzed.
• Denaturing

  Caused by extreme heat/pH

  Active site changes shape. This will lead to:

  • Substrate no longer fitting into active site
  • Enzyme can't break down substrate.
• Microscopes

  Allow us to see small cell organelles e.g. nuclei, mitochondria, chloroplasts.
• Light microscope

  Light needs to pass through a specimen.

  Relatively cheap

  However not good enough to study sub-cellular structures
• Electron Microscope

  Electrons are scattered over a specimen producing an image.

  Electron Microscopes have:

  • greater magnification (see smaller objects)
  • greater resolution (see clearly)

  E.g. Ribosomes are very small cannot see with light microscopes need an electron microscope.
• Magnification

  How many times larger the image is than the object.
• Resolution

  Smallest distance between two objects that can be seen as separate.
• Microscope core practical

  1. Get a thin specimen onto slide
  2. Add stain e.g. Iodine (see objects more clearly)
  3. Then add protective slip (so specimen doesn't get contaminated)
  4. Place on stage
  5. Place on lowest magnification
  6. Focus
  7. Increase magnification
  8. Refocus
• Total Magnification

  = eyepiece lens x objective lens

  e.g. 10x 4x = 40x

  10x 10x = 100x

  10x 20x = 200x

  
• I = A M and Conversion

  Image size = actual size x magnification

  *Must make sure measured in mm

  *Convert units to same

  *Then calculate

  e.g. 3.4mm = 3400um

  300nm = 0.3um

  
• Animal Cell

  Nucleus - controls cell

  Ribosomes - where protein synthesis happens

  Mitochondria - Where respiration takes place and where energy is released.

  Cell membrane - controls what enters and leaves the cell

  Cytoplasm - Where chemical reactions happen

  
• Plant Cell

  *Has all the cells from an animal cell but has a bit more.

  Nucleus

  Ribosomes

  Mitochondria

  Cell membrane

  Cytoplasm

  Chloroplast - traps light energy for photosynthesis

  Vacuole - contains cell sap (helps keep cell shape)

  Cell wall - made of cellulose also keeps shape of cell

  
• Bacterial cell 


  Cell wall

  Cell membrane

  Cytoplasm

  Slime coat - protection

  Chromosomal DNA - Most of the DNA in a cell

  Plasmid DNA - loops of DNA

  Flagellum - movement*

  * = not all bacterial cells have this.

  
• Ciliated Cell

  Cilia move back + forth to move substrate along. Found in egg tubes (Fallopian)

  
• Sperm Cell

  Mid-section: contains mitochondria make energy - move.

  Flagellum - for movement

  Haploid nucleus - 1/2 chromosomes

  Acrosome - contains enzymes to digest through jelly coat.
• Egg Cell

  Haploid nucleus - 1/2 chromosomes

  Jelly coat - for protection, hardens after sperm cell enters to stop more from entering.

  Cytoplasm - contains nutrients to enable growth of zygote to embryo.

  
• Example of enzymes 


  Substrate: Enzyme: Product: Where:

  starch amylase glucose mouth

  protein protease amino acids stomach

  fat (lipid) lipase fatty acids + glycerol small intestine
• Enzymes + pH

  -Each enzyme will have it's own optimum pH and range of pH it can work at.

  -Outside of there optimum they begin to denature.

  -Further away from there optimum the more they denature.