Transport Across Membranes Flashcards
(46 cards)
Define diffusion?
The movement of a substance from a high concentration to a lower concentration
Give two differences between active transport and facilitated diffusion.
Active transport requires energy/ATP whereas facilitated diffusion is passive.
Active transport moves substances against the concentration gradient whereas facilitated diffusion moves substances down the concentration gradient.
Give a similarity between active transport and facilitated diffusion.
Both use carrier proteins.
Which type of molecule can diffuse across the phospholipid bilayer?
Non- polar or lipid soluble molecules.
Through what structure do water soluble molecules cross the membrane?
Through channel proteins/aquaporins
Which part of the phospholipid is hydrophobic?
Fatty acid tail.
Protein molecules found on the surface of the membrane are called …
Extrinsic proteins
Give 2 differences between a triglyceride and a phospholipid.
Phospholipids contain a phosphate group whereas triglycerides do not.
Phospholipids have 2 fatty acids whereas triglycerides have 3 fatty acids.
What is the function of the carbohydrates found on the outer surface of the membrane?
Antigens
Each carrier protein can transport …. type of molecule.
One
Name the two carbohydrate containing chemicals found in cell membranes.
Glycoproteins and glycolipid.
What is the function of the microvilli?
Increase surface area for absorption of digested food by the small intestine.
What effect does cholesterol have on the fluidity of the membrane?
Reduces the fluidity/movement of phospholipids in the membrane.
How can the structure of the membrane be changed to make the diffusion of water soluble molecules more rapid?
Increase number of channel proteins
Increase surface area.
Give three ways in which the rate of gas exchange can be increased.
Increase the surface area.
Increase the concentration gradient.
Decrease the diffusion pathway/distance
Increase the temperature
Why is the term fluid mosaic used to describe the model for membrane structure?
Fluid - phospholipid move within the membrane.
Mosaic - proteins form blocks on the surface of the membrane.
The water potential of the cell cytoplasm is -5. The cell is place in a solution with water potential of-10. Which way will the water move?
Osmosis will cause water to leave the cell ( water moves from high water potential to lower water potential).
A cell with a water potential of -5 is placed in a solution with a water potential of -5. Which way will the water move?
No net movement of water.
Water will still cross the membrane.
Same number of water molecules enter and leave the cell.
A cylinder of potato is placed into pure water.
Explain why the mass mass of the potato changes.
The cylinder will increase in mass.
Osmosis - water will enter the cylinder.
Water moves from high water potential to lower water potential through selectively permeable membrane.
Why should percentage change in mass be calculated when carrying out osmosis experiments.
Does not matter if the initial masses of the cylinders are not identical.
Allows comparison of results.
Calculating change in mass per gram of potato.
A proportion is calculated.
Give the equation for calculating the percentage change in mass.
% change in mass
= change in mass/initial mass X 100
Why is it important to dry the potato cylinders before placing them in solutions of different water potential?
Removes the cytoplasm that has leaked out of the cut cells.
Only measuring the mass of the water inside the cells.
Why is it important to dry the potato cylinders when they have been removed from the different concentrations of salt solution?
Removes the salt solution on the outside of the cells/cylinder.
Only measure the mass of water that has entered the cylinder.
Ensure the experiment is valid.
Define osmosis
Net movement of water from a high water potential to a lower water potential through a selectively/partially permeable membrane.
