biology cell membranes unit 1

• cellular transport are substances such as nutrients, oxygen, wastes, etc. need to pass through the cell membrane. Movement of substances across the cell membrane
• Glycoproteins are made up of carbohydrate chains attached to proteins on the outside bilayer for cell recognition and adhesion.
• cholesterol is found within the bilayer and regulates the fluidity of the membrane.
• the definition of hydrophilic is water loving, likely to mix with, or be dissolved in water.
• the definition of hydrophobic is water hating, likely to repel or fail to mix with water.
• phosphate heads are hydrophilic and mix the water so are located on the outside of the bilayer.
• lipid tails are hydrophobic and do not mix with water, so are located on the inside of the bilayer.
• proteins are embedded in the membrane to allow for the transport of the substances in and out of the cell.
• structure given the name fluid mosaic model because proteins embedded in the bilayer resemble a mosaic and individual molecules can move freely
• cell membranes are selectively permeable which allows gases or liquid to pass through
• Lipid Bilayer only allows certain substances to pass through since it is permeable to small substances and lipid-soluble substances, such as oxygen, some water.
• Lipid bilayer is impermeable to water-soluble substances, ions and larger molecules such as glucose and amino acids.
• passive transport doesn't use 3 energy types which are diffusion, osmosis, and facilitated diffusion.
• diffusion is the movement of molecules from an area of high concentration to an area of low concentration, until equilibrium is reached.
• Osmosis is the diffusion of water across a selectively permeable membrane, from an area of high conc. to an area of low conc. until equilibrium is reached.
• Hypotonic refers to a solutions having less osmotic pressure, or concentration, than another solution between a semi-permeable membrane.
• hypertonic solution contains a higher concentration of solutes compared to another solution.
• isotonic is a solution is said to be isotonic when it has the same concentration of solutes as another solution across a semipermeable membrane.
• osmosis occur when the membrane is impermeable to a specific solute, so water needs to move in order to balance concentration.
• When cells are placed in fresh water, water enter the cell
• Plant cells: as water enters, the vacuole enlarges and puts turgor pressure on th cell wall.
• Animal cells: as water enters, the cytoplasm swells, leading to the cell membrane rupturing
• facilitated diffusion refers to the substances that diffuse across the membrane through proteins and larger molecules and lipid-insoluble molecules cross the membrane in this way as they cannot move through the bilayer.
• the two types of transport protein involved in facilitated diffusion are protein channels and carrier proteins.
• the function of protein channels forms narrow pathways for smaller ions and water to diffuse through
• the function of carrier proteins is to bind to selected molecules on one side of the membrane, change shape and release it on the other side.
• in cellular transport, all 3 types of passive transport move substances down their concentration gradient which is from high conc. to low conc.
• In active transport, cell uses energy because molecules are being moved against their concentration gradient from low conc. to high conc.
• There are 3 faster processes in active transport: 


  3 types: protein pumps, endocytosis exocytosis
• endocytosis is the material that is engulfed in bulk, by infoldings of the membrane. Endocytosis is the process of actively transporting molecules into the cell by engulfing it with its membrane.
• Exocytosis is used to release the molecules out of the cell (e.g. protein). Exocytosis provides the opposite function and pushes molecules out of the cell. Like all systems in the human body, the need for homeostasis enables an equal flow of molecules in and out of the cell. This means the amount of molecules entering the cell by endocytosis is equal to the amount of molecules exiting the cell via exocytosis.
• Efficiency of organisms

  • If an organism is not small in size, then it will need adaptations to ensure it is efficient in transporting substances in and out.
  • Larger animals have adapted to increase their efficiency for exchange processes
  • Circulatory system to move material between the surface and the core of the organisms