Lecture 26- Diffusion and Osmosis
Explain how a plant cell depends on osmosis for maintaining structure and what happens to a plant cell when placed in hypertonic, hypotonic, and isotonic solutions?
A plant cell is affected by Tonicity. When a plant cell is placed in a hypertonic solution then the size of the cell doesn't change, but the plasma membrane on the inside shrivels up. If laced in a hypotonic solution, the cell swells inside the cell wall. This is good for a plant. Plants prefer to have this happen. This is called Turgor. If placed in a isotonic solution then nothing happens.
What does it mean for a molecule to move up or down its concentration gradient?
Concentration gradient flows from high concentration to low concentration. When the concentration moves down or with it. It releases energy. When the concentration moves up or against it. It requires energy.
What do the terms hypertonic, hypotonic, and isotonic mean?
Hypertonic means that there is a high concentration of something (like water) inside a cell, hypotonic means a low concentration and isotonic basically means that it is at a balance.
What is similarity and how is it determined
Osmolarity is the concentration of a solution in parts of solute divided by volume of water. Osmolarity is an estimation of the osmolar concentration of plasma and is proportional to the number of particles per litre of solution; it is expressed as mmol/L Calculated osmolarity= 2 (Na+) + 2 (K+) + Glucose + Urea (all in mmol/L)
What is Osmosis?
Osmosis and diffusion are both passive processes, meaning that no energy is required. That's because they are going with the gradient. He did mention in the video that these processes can release energy.
Biological membranes are often described as being semi-impermeable or selectively permeable, what do those terms mean?
Semi-impermeable and selectively permeabke are terms that refer to how easy a molecule can cross the membrane of a cell. Impermeable means that a molecule cant cross the membrane while selectively permeable means they can, but not every single molecule will make it through.
If cell placed in a solution swells and bursts which of the following could be said?
The cell will shrink because it loses water. If placed in a hypotonic solution, it will swell up. If the solution is hypotonic, water flows into the cells. If the solution is hypertonic, water flows out of the cells.
What is a concentration gradient? How is it different from an electrochemical gradient?
The concentration gradient is when a solute travels across the membrane from its higher concentration to its lower. When the solutes travel from high to low with the concentration gradient, this releases energy. When a solute travels from the lower concentration to the higher (against the concentration), energy is consumed. The electrochemical gradient pushes the molecules or ions in a direction dependent on the charge rather than the concentration.
What is the difference between simple and facilitated diffusion?
The manner in which substance will diffuse across the membrane. In simple diffusion, things will pass through on their own without any help of proteins. Certain things are limited to passing through; things such as non-polar or lipid-soluble molecules can easily pass through. Facilitated diffusion is when materials need help forms proteins or glycoproteins and channel proteins. They function just as their name implies, carrier proteins will carry substance through, but only specific substances, whereas channel proteins allow substances to pass straight through. Channel proteins can either be open at all times or they can be gated.
What is osmotic pressure?
The pressure which needs to be applied to a solution to prevent the inward flow of water across a semipermeable membrane. It also defined as the minimum pressure needed to nullify osmosis.
What types of molecules are permeable through the membrane and what types of molecules are impermeable through the membrane?
This means that some substances are permeable, or they can move through the membrane either freely or limited, while other substance are impermeable, meaning they can't move through the cell at all. Large and charged molecules are impermeable, while smaller non polar molecules are freely permeable. Smaller polar molecules have limited permeability.
What is turgor?
Turgor, pressure exerted by fluid in a cell that presses the cell membrane against the cell wall. Turgor is what makes living plant tissue rigid. Loss of Turgor, resulting from the loss of water from plant cells, causes flowers and leaves to wilt.
Why and how does water flow across a cell membrane?
Water flows across a cell membrane because the concentration of water is higher or lower. Water will always flow from the high concentration to the lower concentration of water. This is what allows water to pass through the cell membrane. If the concentrations on both sides of the membrane then water won't flow across it.
