Pretest on Membrane Function
water and oxygen
1. Consider the ions and molecules in Model 1. a. Identify at least two substances that would need to move into a cell to maintain homeostasis
(a)
10. Is the inner surface of the embedded protein likely to be polar or nonpolar in the examples shown in Model 3? Explain your reasoning. (a) It is likely to be polar because the protein channel helps polar molecules pass through the membrane (b)It is nonpolar because it does not allow small molecules to enter or exit the membrane (c) both a and b
Facilitated diffusion is passive transport of small, polar molecules from a high concentration to a low concentration. Passive transport is diffusion of small, nonpolar molecules moving from high to low concentration.
11. Summarize the two types of passive transport discussed above. In your answer consider the types of molecules that are transported, the direction of transport, and any external energy or special structures that are needed in the process
Active transport is when the cell uses ATP as energy to move molecules from across a membrane from a low concentration to a higher concentration
12. Summarize active transport. In your answer consider the direction of transport and any external energy or special structures that are needed in the process.
(a) aquapoints (b) water
13. Some embedded proteins are called _______(a)_________. What molecule do you think aquaporins assist in transporting across a membrane?
Refer to diagram on page 5 of Section 2 small nonpolar, type 4, no embedded protein required
14. The molecules below are often moved into or out of cells during biological processes. Categorize each molecule into one of the four types (from Model 1). Using that classification decide whether or not they would be able to cross the cell membrane freely without the help of a membrane protein. Refer to diagram on page 5 of Section 2. N₂:
respiration
1b. Consider the ions and molecules in Model 1. Briefly explain why the cell needs each of the substances you identified in part a. -the cell needs oxygen for ______________
hydrolysis
1b. Consider the ions and molecules in Model 1. Briefly explain why the cell needs each of the substances you identified in part a. -the cell needs water for __________________
urea and carbon dioxide
2a. Consider the ions and molecules in Model 1 a. Identify at least two substances that would need to move out of a cell to maintain homeostasis
respiration (this is used as a source)
2b. Consider the ions and molecules in Model 1. Briefly explain the source of the molecules you identified in part a -the source of carbon dioxide is _______________
protein metabolism
2b. Consider the ions and molecules in Model 1. Briefly explain the source of the molecules you identified in part a -the source of urea is _______________
Answer is on answer sheet page 1 of section 2:Membrane Function
3. Complete the table by labeling the types of substances as polar or nonpolar and large or small (cover answers up with small pieces of paper and answer verbally)
Answer is on answer sheet page 2 of section 2:Membrane Function
4. The four diagrams in Model 2 illustrate movement of four types of substances (see the table in Model 1) across a phospholipid bilayer. a. Use your knowledge of membrane structure and the chemical structures in Model 1 to identify the shapes used in Model 2. See answer sheet p. 2 cover answers and answer verbally
Answer is on answer sheet page 2 of section 2:Membrane Function
4. The four diagrams in Model 2 illustrate movement of four types of substances (see the table in Model 1) across a phospholipid bilayer. b. Label each diagram in Model 2 with the ion or molecule type (i.e., Type 1 Ions or Type 2 Molecules) based on the information in Model 1. See answer sheet p. 2 cover answers and answer verbally
Answer is on answer sheet page 2 of section 2:Membrane Function
5. For each diagram in Model 2, circle on the side of the membrane where the ion or molecule would have originated it he normal function of a cell. See answer sheet p. 2 cover answers and answer verbally
ions
6. Assume the substances in Model 2 were on only one side of the membrane to start. The diagrams illustrate what would happen after some time has passed. a. Which substances in Model 2 appear to be completely blocked by the membrane
carbon dioxide
6. Assume the substances in Model 2 were on only one side of the membrane to start. The diagrams illustrate what would happen after some time has passed. b. Which substances in Model 2 appear to be able to pass freely through the membrane
glucose and urea
6. Assume the substances in Model 2 were on only one side of the membrane to start. The diagrams illustrate what would happen after some time has passed. c. Which substances in Model 2 appear to pass through the membrane with some difficulty
urea is smaller than glucose
6. Assume the substances in Model 2 were on only one side of the membrane to start. The diagrams illustrate what would happen after some time has passed. d. Urea appears to pass through more easily than glucose. What characteristic of urea might help explain this observation?
Ions cannot pass through the membrane because they are charged and the membrane is hydrophobic
7a. The majority of the membrane is made of non polar hydrocarbon chains. Use the diagrams in Model 2 and the table in Model 1 to explain the permeability of the membrane for each of the four types of substances in Model 1. Hint: Life dissolves like. Type 1 ions:
Large, polar molecules can pass through the membrane if they have some nonpolar groups
7b.The majority of the membrane is made of non polar hydrocarbon chains. Use the diagrams in Model 2 and the table in Model 1 to explain the permeability of the membrane for each of the four types of substances in Model 1. Hint: Life dissolves like. Type 2 Molecules (Large, polar biomolecules):
Small, polar molecules like urea can pass through the membrane because they are small, but polarity can make it harder to pass through
7c.The majority of the membrane is made of non polar hydrocarbon chains. Use the diagrams in Model 2 and the table in Model 1 to explain the permeability of the membrane for each of the four types of substances in Model 1. Hint: Life dissolves like. Type 3 Molecules (small, polar molecules)
Small, nonpolar molecules will blend well with the nonpolar part of the bilayer
7d.The majority of the membrane is made of non polar hydrocarbon chains. Use the diagrams in Model 2 and the table in Model 1 to explain the permeability of the membrane for each of the four types of substances in Model 1. Hint: Life dissolves like. Type 4 Molecules: (small, non polar molecules):
See answers on p4, section 2 of POGIL sheet
8. Label the embedded proteins in the membrane diagrams of Model 3. See answers on p4, section 2 of POGIL sheet. Cover & answer verbally.
The protein channel helps molecules pass through the membrane.
9. What appears to be the effect of inserting a protein channel into the membrane on the movement of molecules across the membrane
organelles
Additionally, eukaryotic cells are made more complex by the presence of internal membranes that form _________________, so the cells may become more specialized.
active transport
Embedded proteins may also be involved in _____________________ where the cell uses energy from ATP to move molecules across a membrane against the concentration gradient
(a) cell membrane (b) regulating movement of material in and out of the cell
The _______(a)________ separates the cell from the external environment and plays a critical role in _______________
passive transport
The driving force for this diffusion process is simply the natural movement of the molecules in random directions. Whether the molecules are allowed to cross or not is only due to the polarity of the molecules themselves and their size. No energy is needed which is why diffusion is considered a type of _____________. This process is illustrated in Model 2 for several types of molecules.
homeostasis
The membrane is critical to the maintenance of ______________ in living organisms.
large polar, type 3, needs embedded protein
The molecules below are often moved into or out of cells during biological processes. Categorize each molecule into one of the four types (from Model 1). Using that classification decide whether or not they would be able to cross the cell membrane freely without the help of a membrane protein. Refer to diagram on page 5 of Section 2. Alanine
small polar, type 1, needs embedded protein (dup answer)
The molecules below are often moved into or out of cells during biological processes. Categorize each molecule into one of the four types (from Model 1). Using that classification decide whether or not they would be able to cross the cell membrane freely without the help of a membrane protein. Refer to diagram on page 5 of Section 2. HCO₃⁻
small polar, type 1, needs embedded protein
The molecules below are often moved into or out of cells during biological processes. Categorize each molecule into one of the four types (from Model 1). Using that classification decide whether or not they would be able to cross the cell membrane freely without the help of a membrane protein. Refer to diagram on page 5 of Section 2. H₃O⁺
large polar, type 3, needs embedded protein (dup answer)
The molecules below are often moved into or out of cells during biological processes. Categorize each molecule into one of the four types (from Model 1). Using that classification decide whether or not they would be able to cross the cell membrane freely without the help of a membrane protein. Refer to diagram on page 5 of Section 2. Sucrose
compartments
These organelle membranes create ______________ within the cell that can do specific functions.
facilitated diffusion
When an embedded protein assists in the passive transport of molecules across a barrier in the direction of the concentration gradient (from high concentration to low concentration) it is called _______________________
diffusion
_______________ is the process of molecules traveling through a membrane barrier from a location of high concentration to a location of low concentration.
