| Date | November 2020 | Marks available | 2 | Reference code | 20N.2.SL.TZ0.3 |
| Level | Standard level | Paper | Paper 2 | Time zone | TZ0 / no time zone |
| Command term | Outline | Question number | 3 | Adapted from | N/A |
Question
The diagram shows part of two neurons.
[Source: © International Baccalaureate Organization 2020.]
Outline how the amphipathic properties of phospholipids play a role in membrane structure.
State the name of the structure shown.
X indicates the movement of a structure in the neuron. Explain what events trigger this movement and what happens next.
Markscheme
a. part hydrophobic/not attracted to water/non-polar AND part hydrophilic/attracted to water/polar; Both needed.
b. bilayer formed (formed naturally by phospholipids in water);
c. hydrophilic heads/parts face outwards AND hydrophobic tails/parts face inwards;
Do not allow water loving/hating in mpa or mpc.
synapse/synaptic
a. depolarization of pre-synaptic membrane / action potential/nerve impulse arrives;
b. uptake of calcium / calcium ions diffuse in / calcium channels open;
c. structures containing neurotransmitter/vesicles move to/fuse with membrane;
d. neurotransmitter/acetylcholine released by exocytosis into cleft/binds to postsynaptic membrane/receptors;
Examiners report
Knowledge of amphipathic properties in part a was good. In b, most could state that the diagram shows a synapse. A variety of spelling is usually allowed, but in this case ‘synapsis’ was not allowed in English as this refers to the pairing of homologous chromosomes. There were some G2 comments that the X could be taken as the structure. However X clearly points to an arrow, not a structure. Most were able to gain some marks by describing the events, but some lost marks by not clearly indicating that it is the vesicle containing the neurotransmitter that moves.
Syllabus sections
- 22M.1.HL.TZ2.3: Which plasma membrane is the least fluid at high temperatures?
- 21N.1.SL.TZ0.2: Which features of phospholipids give them their amphipathic properties? A. Basic phosphate...
- 16N.1.SL.TZ0.3: The cell membrane model proposed by Davson–Danielli was a phospholipid bilayer sandwiched...
- 18M.1.SL.TZ2.3: Which molecule regulates the fluidity of cell membranes? A. Phospholipid B. Cholesterol C....
- 22M.1.SL.TZ1.2: More than 90 % of cellular cholesterol is located in the cell’s plasma membrane. What is the...
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19M.3.SL.TZ2.1b.ii:
Label the model B diagram to show a phospholipid.
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22M.1.HL.TZ2.5:
Which feature(s) allow(s) transport of glucose in blood plasma?
I. It is hydrophobic.
II. It is polar.
III. Its solubility is low at 37 °C.
A. I only
B. II only
C. I and II only
D. II and III only
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21N.1.SL.TZ0.1:
The image shows part of a mammalian cell.
[Source: Louisa Howard, Katherine Connollly - Dartmouth Electron Microscope Facility. Available at:
https://en.wikipedia.org/wiki/File:Microvilli.jpg.]What is the specialized function of this mammalian cell?
A. Locomotion
B. Absorption
C. Reception of stimuli
D. Gas exchange
- 19N.2.SL.TZ0.5a: Draw a section of the Singer-Nicolson model of an animal cell membrane.
- 18N.1.SL.TZ0.4: What part of the plasma membrane is fluid, allowing the movement of proteins in accordance...
- 19M.3.SL.TZ2.1d: State one technological improvement, other than enzymatic digestion, that led to the...
- 17M.1.SL.TZ2.3: What is a role of cholesterol in animal cells? A. It increases body fat. B. It controls...
- 17M.1.HL.TZ1.2: Which evidence falsifies the Davson–Danielli model? I. The presence of globular proteins...
- 17M.1.SL.TZ2.27: The bacterium Neisseria gonorrhoeae causes infections related to the human reproductive...
- 17N.1.SL.TZ0.05: In the diagram, which part of the membrane structure does the molecule below form?
- 19N.2.HL.TZ0.4a.i: State the property of amphipathic phospholipids that enables them to form a bilayer.
- 17M.1.SL.TZ1.21: Cladograms can be created by comparing DNA or protein sequences. The cladogram on the left is...
- 21M.1.SL.TZ2.3: What special property of phospholipid molecules explains their ability to spontaneously...
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22M.2.SL.TZ2.4b:
The Davson-Danielli model of membrane structure was proposed in the 1930s. When electron micrographs of membranes were first produced, they were used as evidence for this model. The micrograph shows two adjacent membranes (indicated with arrows).
[Source: DENNIS KUNKEL MICROSCOPY/SCIENCE PHOTO LIBRARY.]
Explain how the appearance of membranes in electron micrographs was used as evidence to support the Davson-Danielli model.
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22M.2.HL.TZ2.8a:
Outline four different processes, with examples, that allow substances to pass through the plasma membrane.
- 20N.2.HL.TZ0.2a.ii: State the role of cholesterol in animal cell membranes.
- 19M.3.SL.TZ1.1b: Explain how electron micrographs such as this helped to falsify the Davson–Danielli model of...
- 21M.1.SL.TZ1.6: Which statement applies to cholesterol? A. It is hydrophobic and found on the outside of the...
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20N.2.HL.TZ0.2a.i:
Outline how the amphipathic properties of phospholipids play a role in membrane structure.
- 17N.1.SL.TZ0.04: In the diagram, which structure is an intrinsic or integral protein?
-
19M.3.SL.TZ1.1a:
Using the scale bar, calculate the magnification of the image.
- 17M.2.HL.TZ1.1f.ii: Suggest a reason for the greater expression of the gene for the urea transporter after an...
- 17M.2.HL.TZ1.5b: Outline four different functions of membrane proteins.
-
18M.2.HL.TZ1.6a:
Draw a labelled diagram to show the fluid mosaic model of the plasma membrane.
- 17M.2.SL.TZ1.1c: Estimate how much smaller drilled oysters raised in seawater at a high CO2 concentration were...
- 18M.2.HL.TZ2.5a: Discuss alternative models of membrane structure including evidence for or against each model.
- 19M.3.SL.TZ2.1a: State the scientists who proposed model A.
- 19M.3.SL.TZ1.1c: Explain how the amphipathic nature of phospholipids allows them to form bilayers.
- 19M.1.HL.TZ1.3: Which is an essential feature of the Davson–Danielli model of membrane structure? A. A...
- 19M.2.SL.TZ1.7b: Describe the functions of proteins in cell membranes.
- 19M.2.HL.TZ1.5c: Explain how hydrophobic and hydrophilic properties contribute to the arrangement of molecules...
- 19M.3.SL.TZ2.1c.i: Deduce one conclusion about the structure of the plasma membrane reached by the scientists...
- 19M.3.SL.TZ2.1c.ii: Suggest one reason for maintaining a pH of 7.5 throughout the experiment.
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18M.2.SL.TZ1.5a:
Draw a labelled diagram to show the fluid mosaic model of the plasma membrane.
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18M.2.SL.TZ2.5a:
Draw an annotated diagram of the fluid mosaic model of membrane structure.
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21M.1.SL.TZ1.3:
The Davson–Danielli model of membrane structure proposed that membranes were composed of a phospholipid bilayer that lies between two layers of globular proteins, as shown in this diagram.
[Source: Cornell, B. 2016. https://ib.bioninja.com.au/standard-level/topic-1-cell-biology/13-membrane-structure/membrane-models.html]
What evidence supported this model?
A. An electron micrograph that showed two dark lines with a lighter band in between
B. Freeze-fracture electron microscopy
C. Evidence that all membranes are identical
D. The hydrophobic regions of protein would be in contact with water
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19M.3.SL.TZ2.1b.i:
Label the model A diagram to show a region of protein.
