Topic 2 - Genes and Health

• Two major adaptations for gas exchange surfaces are a large surface area and a thin layer of cells
• The respiratory organ in fish is gills
• Insects use trachea for gas exchange
• The main surface area for gas exchange in plants is the mesophyll cells
• In humans, gas exchange happens in alveoli
• Ficks Law:

  rate of diffusion =

  surface area x concentration difference/thickness of membrane
• Breathing maintains concentration difference
• When we inspire, thorax pressure decreases and air rushes in
• When we expire, thorax pressure increases and air rushes out
• Diffusion is the passive movement of particles from a high concentration to a low concentration
• Simple diffusion into cells only works for very small, uncharged particles
• What is the structure of an amino acid?

  this

  A) Carboxyl group

  B) Amine group

  C) R group

  
• There are 20 naturally occurring amino acids
• The sequence of amino acids in the polypeptide chain make up the primary structure of a protein
• Chemical reactions between R groups cause proteins to fold up
• The secondary structure of a protein can be arranged into two types of structures:

  • a helixes
  • b pleated sheets
• Some proteins may further fold into tertiary or quarternary structures
• There are two distinct groups of proteins:

  • Globular
  • Fibrous
• Fibrous proteins are repeating shapes usually used in structures like keratin
• Globular proteins are proteins folded into a compact spherical shape
• Globular proteins are soluble due to projecting hydrophilic side chains
• Enzymes are globular proteins, their shapes are important for their active sites
• An R group is polar and can form bonds with each other, these bonds include:

  • Ionic bonds
  • Disulfide bridges
  • Hydrogen bonds
• Differences in DNA mean different proteins will be produced
• A gene is a sequence of bases on a DNA molecule that codes for a sequence of amino acids
• The bond in DNA is a phosphodiester bond.
• The two strands of DNA are held together by hydrogen bonds
• DNA is made up of three main parts:

  • Deoxyribose sugar
  • Nitrogen bases
  • Phosphates
• The bases are the only interchangeable parts of the DNA
• Bases A and G have a two ring structure
• Bases C and T have a three ring structure
• Adenine and thymine form two hydrogen bonds
• Cytosine and guanine form three hydrogen bonds
• What are 3 differences between RNA and DNA?

  Sugar: RNA contains ribose sugar, while DNA contains deoxyribose sugar. Bases: RNA contains uracil as a base instead of thymine found in DNA. Structure: RNA is usually single-stranded, while DNA is double-stranded.
• Extrinsic proteins are found on the surface of a cell membrane
• Intrinsic proteins span all through cell membranes
• Ion channels allow water soluble molecules through
• Cholesterol is very hydrophobic, it stops water loss by pulling the fatty acids closer together and making the membrane stronger
• Glycolipids maintain stability and act as recognition sites
• Osmosis is the passive movement of water from an area of low water potential to high water potential across a partially permeable membrane