transport across membranes

• functions of membranes

  controls substances in and out

  gives structure that reactions can happen on

  separates organelles from the cytoplasm

  separates enzymes from the rest of the cell
• organelles with a single membrane

  lysosomes, endoplasmic reticulum, golgi apparatus
• organelles with double membrane

  chloroplast, nucleus, mitochondria
• why do phospholipids form bilayers?

  theyre surrounded by water on either side and the hydrophobic tails want to face inwards to avoid the water
• early model - sandwich model

  proteins in their own layer on top of the phospholipids
• differences between early model and fluid mosaic model

  newer model has cholesterol, glycoproteins/lipids and channel/carrier proteins

  new model in a mosaic but old model has separate layers
• substances through the membrane?

  small, non polar
• substances not directly through the membrane?

  large, polar
• functions of proteins in membranes?

  channel proteins are where molecules can pass through

  carrier proteins with a specific shape

  enzymes, antigens and receptors
• channel protein structure?

  hydrophyllic sides on the inside
• what are glycolipids?

  a carbohydrate with a lipid on the surface of the membrane
• what are glycoproteins?

  a carbohydrate with a protein on the surface of the membrane
• functions of glycoproteins and glycolipids?

  Cell recognition, cell signaling, immune response.
• ways molecules are transported across membranes?

  Diffusion, facilitated diffusion, active transport, endocytosis, exocytosis, osmosis
• simple diffusion

  high to low concentration through the membrane
• facilitated diffusion

  requires a channel or carrier protein

  channel is less specific
• osmosis

  diffusion of water across from high to low WP
• active transport

  all types of molecules through carrier proteins from low to high, using energy
• co transport

  sodium and potassium out by AT so now low concentration in the cell, ions move in by facilitated diffusion, brings in glucose which then diffuse from high to low concentration in the blood
• epithelial cells of the ileum adapted for absorption?

  microvilli increase SA

  carrier proteins for transport

  channel proteins for facilitated diffusion

  carrier proteins for AT

  mitochondria release energy for AT
• factors that increase the rate of gas exchange?

  Sa increases, temp increases, diffusion distance decreases, diffusion gradient gets steeper