9.2 Study Guide Flashcards
What is simple diffusion?
Diffusion of molecules directly over the phospholipid bilayer from high to low concentration. Molecules can pass directly through the lipid bilayer if they are small and nonpolar. The rate of diffusion is greater in simple diffusion than in facilitated.
What is facilitated diffusion?
The diffusion of molecules across the membrane with the help of channel proteins. Substances move from high to low concentration, down the concentration gradient. No energy is used by the cell to make facilitated diffusion, the particles already have energy. Each protein is specific to a particular substance.
What is osmosis and what do hypertonic, hypotonic, and isotonic mean?
The diffusion of water across a semi-permeable membrane to dilute higher solute concentrations. Hypertonic: High % of solute, lower % of water. Hypotonic: lower % of solute, higher % of water. Isotonic: Equal % of solute and water.
What is active transport?
The transportation of molecules against concentration gradient (low to high). Conformational shape change transports solute from one side of membrane to another. Protein “pumps”. “Costs” energy= ATP.
What are endocytosis and exocytosis?
Endocytosis: Proteins go to the cell membrane, and vesicles from the Golgi apparatus collect the proteins and carry them inside the cell.
Exocytosis: Vesicle comes from Golgi body and carry proteins out of the cell.
What is structure and what are the properties of phospholipids?
Phospholipids have a hydrophilic head with a phosphorus molecule. They have hydrophilic tails. Phospholipids bond with each other to form a phospholipid bilayer. This layer is flexible. The hydrophobic tails connect in the middle and the hydrophilic heads face outward towards the inside and outside of the cell.
What are the different parts of the cell membrane? What do they do?
The cell membrane is made of the phospholipid bilayer, cholesterol, proteins, glycolipids, and glycoproteins. The phospholipid bilayer is flexible and provides a protective barrier for the cell. Cholesterol is in animal membranes and helps stabilize the membrane and stiffens the cell membrane. Proteins help transport molecules across the membrane, assist with enzyme activity, act as surface receptors, identity markers, help with membrane adhesion, and attachment to the cytoskeleton.
What is the importance of the surface area to volume ratio?
A large surface area to volume ratio is beneficial to cells. Having a large surface area allows cells to diffuse more nutrients and molecules into and out of the cell. Having a low volume allows cells to diffuse these molecules quickly and efficiently.
Compare and contrast different types of transport in term of what type of particles they move, whether they go down or against the concentration gradient, whether they require transport proteins, whether they require energy.
In simple diffusion, small, nonpolar molecules like oxygen and carbon dioxide are transported. In facilitated diffusion and active transport, small and nonpolar/charged molecules are transported across the cell membrane. Ex: Water, glucose, amino acids, ions, sodium, potassium. In simple and facilitated diffusion, molecules move down the concentration gradient, from high to low density. In active transport, molecules go up the concentration gradient, from low to high. Facilitated diffusion and active transport require transport proteins. Active transport requires energy in the form of ATP.
Predict which way solutes will diffuse across a membrane.
Solutes, along with other molecules, will diffuse across the membrane to the side with a lower density of that molecule/solute.
Predict which way water will diffuse across a membrane via osmosis.
Water will diffuse across the membrane towards the side that has more solutes and less water molecules. Water will diffuse to the side that is hypertonic.
What does it mean for the cell membrane to be semi-permeable?
Semi-permeable means that only certain things are let through the cell membrane.
