biology topic 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 hydrophilic on the outside
• Explain globular proteins.


  Round, compact, hydophobic/philic arrange themselves

  soluble
• Explain fibrous proteins

  long strands

  insoluble

  rope shape

  lots of bonds - strong

  found in supportive tissue
• what is haemoglobin used for

  carries oxygen around the body
• what is collagen used for

  forms connective tissue in animals
• what is the sturucture of a cell membrane


  head - philic - attracts water

  tail (2) - phobic - repel water
• 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
• facilitated diffusion with channel protein (passive)


  the channel forms pores for particles to move down concentration gradient
• Endocytosis (needs energy)


  Capturing a particle from the outside of a cell and engulfing it with the cell membrane
• Exocytosis (needs energy)


  Vesicles with the membrane fuse and release contents on the outside of the cell
• active transport


  the movement of molecules against concentration gradient from high to low
• water potential

  less negative to more negative molecules (osmosis)