Lab Report 1: Cell Transport Mechanisms and Permeability Using Physioex 8.0

1.Discuss the structure of the plasma membrane and explain the process of active and passive transport through the membrane.

Which solute did not appear in the filtrate using any of the membranes? Powdered Charcoal

Explain the effect that increasing the Na+ Cl- concentration has on osmotic pressure and why it has this effect. How well did the results compare with your prediction?

The rate increased because the glucose was easier to transport with more carriers. Saturation levels decrease when carriers are added and glucose concentrations are constant. The results were the same as my prediction that assumed the glucose transport rate would increase.

Dialysis tubing is a membrane made of regenerated cellulose fibers formed into a flat tube. If two solutions containing dissolved substances of different molecular weights are separated by this membrane, some substances may readily pass through the pores of the membrane, but others may be excluded.

The dialysis tubing will be clamped at one end in order to fill it and then clamped at the other end to seal the filled bag. If the bag is not soft and floppy, the experiment will not work. Blot a bag with a paper towel to absorb the moisture and weigh it, if this blotting process is not done it could interfere with the weight readings creating inaccurate information. After the bags of the solutions are prepared, they will be placed into five different beakers with different solutions. Beakers 1-4 will be filled with tap water and the fifth beaker is filled with 40% sucrose and water. Fill each beaker with just enough water or solution so that the bag is covered and place the bags in the beakers simultaneously and record each time. Every 10 min the bags are to be taken out, blotted, and weighed again before returning them back into their respective beaker for another 10 min. The process is repeated until you have reached 90 min. The weights should be recorded in grams (g).

Using the graduated cylinder, measure 20mLs of the stock sucrose solution and 180mL of water to create a 3% sucrose solution and place it into the 250mL beaker (beaker #2). Place bags #1‐3 (red, blue, yellow) into beaker 2 and bag #4 (green) into beaker 1. Allow the bags to sit for one hour. After allowing the bags to sit for one hour, remove them from the beakers carefully open the bags, noting that often times the tops may need to be cut as they tend to dry out. Measure the solution volumes of each dialysis bag using the empty 250 ml beaker.

1. In passive transport, what determines the direction of movement of small particles? The direction of movement of particles in passive transport is determined by the concentration gradient (diffusion) between the cytoplasm and the extracellular fluid. 2. Why do the molecules in facilitated diffusion need help moving across the plasma membrane? Likely, the molecules are too large to pass unaided through the plasma membrane with the concentration gradient; they need to pass through special transport proteins.

The difference is that along with large molecules, living cells prevent molecules with positive charges and solubility. This is not representing in dialysis tubing, and is only found in living cells because the tubing is only based on molecular size (98). When referring the rate of diffusion, the concentration gradient influences the diffusion rate, based on the factors of temperature. The ability for molecules diffuse from high to low concentrations primarily depends on the concentration gradient between the two areas.(96-99). My hypothesis for the study is that in the hypotonic, hypertonic, and isotonic solutions, the direction and rate of osmosis will determine based on the concentration inside the dialysis tubing. My prediction is that if the solution is hypotonic the results will decrease, if the solution is hypertonic the results will increase and if the solution is isotonic the solution will vary and or remain constant.

What happens to the urea concentration in the left beaker (the patient)? It mixes with the water to balance out the structure.

In this lab, neutral red was used as a pH indicator. The color changes from yellow to red in a basic solution to an acidic solution. The neutral red dye was applied to Saccharomyces Cerevisiae. When the S. Cerevisiae cells come in contact with the neutral red dye, the dye gets to the cell by crossing the cell membrane. The cell membrane is the outer surface of the cell that functions as a barrier. The outside of the cell membrane is made of lipid and membrane proteins (Hardin, 2012). It is selectively permeable, which means only select ions and molecules can pass through it by transport. Membrane transport can be actively or passively moving a substance from side of the membrane to another (Hardin, 2012). Passive transport does not require energy to move molecules across the cell membrane. Diffusion is a form of passive transport that moves molecules across the membrane from an area of higher concentration to an area of lower concentration. Osmosis, diffusion, and facilitated diffusion are all examples of passive transport. Active transport requires energy to move molecules across the membrane from areas of lower concentration to higher concentration. It requires energy because it pushes sodium ions (Na+) and potassium ions (K+) (Hardin, 2012). When the dye entered the cell, it also showed its location. Sodium azide (Na+N3-) is a metabolic inhibitor that blocks the flow of electrons along

In which two of the dialysis bag contain tap water. The three other Bags were 20% sucrose 40% sucrose and 60% sucrose. To perform this lab we prepare each of 5 bags with their designated sucrose solution. In this experiment the dialysis tubing acted as selectively permeable membrane. The dialysis bag allows the passage of water molecule only because the sucrose molecule are too large to pass through the membranes. After filling those bags ,we then placed the bags into five separate beakers. Four of this beakers contained only tap waters, and the fifth beakers contains solution of 60% sucrose. We filled the first dialysis bag with 10 ml of tap water, next we filled the second bag with 10ml of 20% sucrose, the third bag was filled with 10 ml of 40% sucrose solution while the fourth bag was filled with 10ml of Tap water (H2O). We made sure that when filling this bags that we removed as much air as possible before clamping of the end of each bag. We also made sure that all of the bags rest soft and floppy instead of firm to ensure that experiment will work properly. Next we placed dialysis bag ,one through four in their own separate beakers which was filled with tap water (H2O), and our fifth bag was full of tap water was placed in beaker filled with just enough of the 60% sucrose solution to cover the bag. All of these bags remained in their designated solutions for 45 minutes. However, all of this bags were quickly removed every

Cell membrane is a selective boundary composed of a unique phospholipid bi-layer structure consisting of lipids, proteins and carbohydrates. This structure regulates the import and export to maintain homeostasis condition inside the cell. (Knox et al., 2014) The plasma membrane is referred as a fluid mosaic which also has selective permeability. The permeability of the membrane can be varied depending on the external conditions. (Mitchel, 2015)

The cell is the basic unit of living things, and is made up of multiple organelles. Organelles are membrane bound subdivisions, each specialised for a specific function. This experiment looks at the Plasma Membrane, which is a semipermeable layer surrounding the cell. It’s primary job is to control what goes in and out of the cell. Molecules can move across this membrane in either an active movement or a passive movement. Active being that which requires energy and only occurs when molecules are required to move against the concentration gradient. The concentration gradient refers to the difference in the amount of solutes in the solutions of two adjacent

The movement of molecules have two forms of transport through the plasma membrane: active transport and passive transport. Active processes require energy, such as ATP, in order for the molecules to be transported. In active transport, the cell administers ATP.i Within passive processes no energy is required and changes n pressure and concentration are the driving forces. Processes such as simple diffusion, facilitated diffusion, osmosis, and filtration are characterized as passive transport, while solute pumps are a form of active transport. Each of these form of transports occur in the cells of all living organisms and are essential to life.