bio exam prep

  1. I can describe the structure of phospholipids and its importance for membrane function  

  • A phospholipid has a hydrophilic(able to interact with water/polar) head consisting of phosphate and glycerol and hydrophobic( resist or unable to interact with water/non-polar)  fatty acid tails 

  • Membranes are considered semi-permeable because they only allow certain substances to enter the cell. 

  • Hydrophilic (polar) components: Phosphate heads of phospholipids, hydrophilic parts of integral membrane proteins, peripheral membrane proteins, and carbohydrate chains of glycolipids and glycoproteins (exposed to the aqueous environment).

  • Hydrophobic (nonpolar) components: Fatty acid tails of phospholipids, hydrophobic regions of integral membrane proteins, and the steroid rings of cholesterol (in the membrane core).

  • Different types of proteins : integral = go through the cell membrane, and are used to transport substances in and out of the cell. Peripheral : exist on the outside of the cell membrane where the head is and are used to act as enzymes or maintain cell shape 

  • Only small non-polar molecules can pass through the cell membrane easily 

  • alcohol impacts the membrane structure by increasing its fluidity, altering its permeability, impairing membrane protein function, and affecting lipid composition, all of which can disrupt normal cell function  

  1. I can describe the fluid mosaic model of cell membrane 

  • The membrane is fluid because the parts of it are always moving around and shifting, the fatty acid structure plays apart in this because the kinks in unsaturated fatty acids help create space in between so other things can fit or so things can move around more freely while saturated fatty acids help the phospholipids pack together more tightly 

  • Cholesterol is a packing molecule that sticks in between the phospholipids of the membrane to help regulate its fluidity. At high temperatures: Cholesterol restricts movement of phospholipids and stabilizes the membrane, preventing it from becoming too fluid. At low temperatures: Cholesterol prevents tight packing of phospholipids, ensuring the membrane doesn’t become too rigid. 

  • Components of the plasma membrane : 1. Carrier proteins help with facilitated and active transport. 2. Glycoproteins/glycolipids help with cell signaling and cholesterol helps with cell fluidity.  

  1. I can describe the mechanisms the cells use to transport molecules across the membrane

  • Active transport is when molecules are moved using special transport proteins using energy(atp) and special transport, because molecules are moved against their concentration gradient (from areas of lower concentration to areas of higher concentration).Passive transport is when no energy is required and the movement just happens naturally due to the concentration gradients when substances move from areas of higher concentration to areas of lower concentration, which is a process known as diffusion. 

  • Types of passive transport : 1. Simple diffusion is when Small or nonpolar molecules (like oxygen or carbon dioxide) move directly through the lipid bilayer without any help from proteins. 2. Facilitated diffusion is when bigger molecules that cannot freely pass through move or are transported by going through the transport proteins imbedded in the cell membrane  

  • Types of active transport : primary active directly uses ATP to pump molecules against their concentration gradient goes through a transport protein (usually a pump) and directly uses energy from ATP hydrolysis (breaking down ATP) to move ions or other molecules across the membrane. Secondary active : uses ion gradients (created by primary active transport) to drive the movement of other molecules, either in the same direction (symport) or opposite direction (antiport) to the ion 

  • Sodium potassium pump : he pump moves 3 sodium ions (Na⁺) out of the cell, and 2 potassium ions (K⁺) into the cell for each cycle. This is important because: Sodium has a higher concentration outside the cell than inside and Potassium has a higher concentration inside the cell than outside.

  • Types of facilitated diffusion proteins : carrier : undergo a conformational change (shape change) when a molecule binds to them, allowing them to transport the molecule across the membrane. Once the molecule is released on the other side, the protein returns to its original shape. Channel : These proteins form pores or channels in the membrane that allow specific molecules (like ions or water) to pass through. They are typically selective 

  1. I can describe mechanisms that organisms use to maintain solute and water balance 

  • Osmosis is a type of passive transport that specifically refers to the movement of water molecules across a semipermeable membrane (like the cell membrane). With the purpose of reaching equilibrium, so the water molecules move from places of high concentration to low concentrations 

  • Isotonic : The solute concentration outside the cell is the same as the solute concentration inside the cell.Water movement: There is no net movement of water. Water molecules move in and out of the cell at the same rate, so the cell's shape remains unchanged.

  • Hypertonic : The solute concentration outside the cell is greater than the solute concentration inside the cell.Water movement: Water will move out of the cell, because water naturally moves toward the area with more solute (to dilute it).Result: The cell will shrink or shrink and possibly become crenated (in animal cells) or plasmolyzed (in plant cells).

  • Hypotonic: The solute concentration outside the cell is lower than the solute concentration inside the cell.Water movement: Water will move into the cell, because water moves to where there is more solute (to dilute it).Result: The cell will swell and could eventually burst (lyse) if too much water enters, especially in animal cells. Plant cells, however, are protected by their cell wall and will just become turgid (firm).

Different membrane transport

Unimportant- Channel transports as single solute

Cotransport- Channel transports 2 things simultaneously in the same direction One solute's inward movement often powers the other's Also known as symporters 

Anti transport- Channel transports 2 things simultaneously in opposite directions 

These channels are also known as antiporters