Assignment:
Q1. Diffusion is:
- Directional
- Non-random
- Passive
- None of the above
Q2. An artificial membrane separates two sides of a beaker. The left side contains 50 glucose molecules and the right side contains 100 fructose molecules. If you add channels to the membrane for glucose molecules but do not add any for fructose molecules and then wait for a while. which will more likely be true?
- The 50 glucose molecules 'all have moved from the left side to the right side of the beaker because the channels allowed them to cross the membrane
- The 50 glucose molecules will not have moved to the right side of the beaker because there are already 100 fructose molecules on the right side of the beaker
- About 25 glucose molecules sill be on the right side of the beaker and 25 will be on the left side of the beaker
- Both sides of the beaker contain approximately equal numbers of glucose and fructose molecules
Q3. You have a round pie plate filled with water. You carefully release a drop of red food coloring in the center of the plate. What happens to the red dye molecules right after the drop is placed?
- Dye molecules move in all directions and since most directions take them away from the drop they spread out
- There are more total molecules concentrated within the drop compared to outside the drop so they bounce off each other more in the drop and spread out
- Dye molecules are repelled by the other dye molecules in the drop and the repulsion causes them to spread out
Q4. If you wait for a long time, what will happen to the color of the water in the pie plate?
- The water throughout the pie plate hill be the same color as the initial drop
- The water will remain completely clear except for a small area in the center of the pie plate
- The center of the pie plate will be very red and the edges will be faintly red
- The entire pie plate will be faintly red
Q5. After waiting for a long time, the dye molecules in the pie plate will:
- Continue moving in the same manner as when the drop was first placed in the water
- Slow down because they have moved to a lower concentration area
- Stop moving because they have reached equilibrium
- Speed up, because they are farther from other dye molecules and have more space to move
Q6. Plants use sunlight to produce sugar molecules in their leaves. Some of this sugar is needed by cells in the roots. Would you expect plants to rely on diffusion to transport the sugar molecules from leaves to roots. and why?
- Yes because diffusion will happen naturally so the plant does not have to spend energy on it
- Yes because all materials in living tissues move by diffusion
- No because it would take too long for the sugar molecules to diffuse that far
- No because diffusion only operates over small distances not over long distances
Q7. To move to the roots of a plant, a sugar molecule must exit the cell where it was produced and enter the stream of plant fluid that carries sugar to other parts of the plant (known as phloem). A newly created sugar molecule is transported to the phloem through diffusion. This means that sugar molecules:
- Move randomly viithin the cell until by chance they exit the cell and enter the phloem
- Travel away from the cell organelle where they are produced (chloroplast) until they enter the phloem
- Travel away from areas of high sugar concentration such as the chloroplast until they enter the phloem
- Move randomly until they encounter the phloem and then stop moving as they are carried along by the phloem
Q8. The tips of neuronal axons communicate with other nerve cells by releasing small molecules called neurotransmitters. These neurotransmitters need to cross a very tiny pocket of fluid to reach the next neuron: the distance is about 0.001 times the length of the smallest axon in this lab. Could this happen through diffusion?
- Yes because the neurotransmitters sillvant to reach their target neuron on the other side of the fluid pocket
- Yes because the neurotransmitters are at high concentration near the diffusing axon and at low concentration next to the receiving neuron
- No because diffusing any distance takes a very long time and neural communication has to happen rapidly
- No because diffusion does not work within very small spaces. only in large areas where there is room for the molecules to move
Q9. If the tip of the axon is on the left and the receiving neuron is on the right. which direction Is a neurotransmitter molecule that was just released most likely to move?
- Left
- Right
- Either up or dam
- Either left or right
- All directions equally likely
10. If you were to watch an individual neurotransmitter molecule just after it was released, what would happen to it?
- The molecule would rapidly collide with a large number other molecules at first and the collision rate would remain just as high over time
- The molecule would rapidly collide with a small number of other molecules at first and then the collision rate would increase as the molecule Effuses into the middle of the fluid pocket
- The molecule would rapidly collide with lots of other molecules at first and then the collision rate would decrease over time as the molecule offuses away from the axon.