biology 2

• Diffussion


  passive movement of molecules
• what is diffusion dependent one?

  concentration, thickness of diffusion pathway, surface area
• how are lungs adapted for efficient gas exchange

  Lots of alveoli - large surface area

  capillary endothelial - one cell thick, short diffusion pathway

  Breathing in and out maintains a concentration gradient
• Fick's Law of Diffusion

  surface area x concentration gradient / diffusion pathway
• what are proteins made from?

  long chains of amino acids
• What is a polypeptide?


  long chain of amino acids
• How does a polypeptide form?

  peptide bond and a condensation reaction
• What determines the shape of a protein?

  sequence of amino acids and the size of the r group
• Four structural levels of proteins


  primary, secondary, tertiary, quaternary
• what is a primary structure?

  sequence of amino acids in a polypeptide chain
• what is a secondary structure?

  the polypeptide chain folds and there is hydrogen bonds between amino acids in chains
• what are the two secondary structures

  alpha helix and beta pleated sheet
• Alpha helix


  the r group is small, the chain coils, hydrogen bonds
• beta pleated sheet


  r group is bulky, chain folds on itself, hydrogen bonds between the amino acids
• What is tertiary structure?

  secondary structure folds into a unique shape
• what are the different bonds that can occur in tertiary structure?

  hydrogen, ionic, disulfide
• What is quaternary structure?


  several different polypeptide chains held together by bonds
• what are examples of quaternary structures

  Globular - haemoglobin (functional)

  Fibrous - collagen (structural)
• what is the arrangement of groups in a 3d+ structure

  Hydrophobic place themselves on the inside and hydophilic on the outside
• How does the primary structure of a protein determine the tertiary structure

  The primary structure determines secondary structure (alpha-helixes and beta-pleated sheets etc.) which determines the tertiary structure by different charges attracting and repelling each other which make up the three-dimentional structure.

  
  

  Hydrogen bonds are formed to make alpha-helices and beta-pleated sheets. Hydrogen bonds, Ionic bonds or Disulphide bonds determine the final three-dimensional shape of the protein.
• Globular Proteins Structure


  compact and roughly spherical

  Form spherical shape when folding into their tertiary structure as:-Non-polar hydrophobic R groups are orientated towards thecentreof the protein away from the aqueous surroundings

  -Theirpolar hydrophilic R groupsorientate themselves on theoutsideof the protein

  The folding of the protein due to the interactions between the R groups results in globular proteins havingspecific shapes
• Globular Proteins function


  The orientation of their R groups enables globular proteins to be (generally)solublein water as the water molecules can surround thepolar hydrophilic R groups

  Thesolubilityof globular proteins in water means they play importantphysiologicalroles as they can be easilytransportedaround organisms and be involved inmetabolic reactions

  For example,enzymescan catalyse specific reactions andimmunoglobulinscan respond to specific antigens
• Prosthetic Group


  the non-protein component that is part of the structure of the structure of some proteins (i.e Conjugated proteins)
• conjugated protein


  a protein that is associated with non-protein structures
• fibrous proteins structure


  Fibrous proteins are long strands of polypeptide chains that have cross-linkages due to hydrogen bonds

  
  

  These proteins have little or no tertiary structure

  
  

  Fibrous proteins have a limited number of amino acids with the sequence usually being highly repetitive

  
  

  The highly repetitive sequence creates very organised structures
• Fibrous proteins Function


  Due to a large number of hydrophobic R groups, fibrous proteins are insoluble in water

  
  

  Fibrous proteins are strong and this, along with their insolubility property, makes fibrous proteins very suitable for structural roles

  
  

  Examples of fibrous proteins:

  - Keratin makes up hair, nails, horns and feathers (it is a very tough fibrous protein)

  
  

  - Elastin is found in connective tissue, tendons, skin and bone (it can stretch and then return to its original shape)

  
  

  - Collagen is a connective tissue found in skin, tendons and ligaments
• what is haemoglobin used for

  carries oxygen around the body
• what is the structure of a cell membrane

  head - philic - attracts water

  tail (2) - phobic - repel water
• what is collagen used for

  forms connective tissue in animals
• what are the different structures on the cell membrane

  cholesterol, carrier proteins, channel proteins, glycolipid, glycoprotein, intrinsic protein, extrinsic protein
• What does cholesterol do?

  regulates the fluidity of the membrane
• what do channel proteins do?

  open and close for diffusion
• what are glycolipids used in

  attachment and cell signalling
• what are glycolipids


  chains of carbs
• what are glycoproteins used in

  cell signalling and anchoring
• what types of tails are on the membrane

  saturated and unsaturated
• fluid mosaic model


  model that describes the arrangement and movement of the molecules that make up a cell membrane
• Osmosis


  diffusion of water molecules from a high to low concentration through a partially permeable membrane.
• facilitated diffusion (passive)


  use of carrier or channel proteins to move larger molecules from high to low DOWN concentration gradient
• facilitated diffusion with carrier proteins (passive)


  Larger molecule attaches to it, the carrier protein changes shape, it is then released onto the other side