Diffusion
What is diffusion?
The net movement of particles from a region of higher concentration to a region of lower concentration, down a concentration gradient.
What is osmosis?
The net movement of water molecules from a region of higher water potential to a region of lower water potential through a partially permeable membrane.
What is active transport?
The movement of substances from a region of lower concentration to a region of higher concentration, against the concentration gradient, using energy from respiration.
Which two processes are passive processes, meaning they do not require energy from respiration?
Diffusion and osmosis.
In which direction do particles move during diffusion?
A. Low concentration → high concentration
B. High concentration → low concentration
C. Equal concentration → high concentration
D. Low concentration → equal concentration only
B. High concentration → low concentration
Which substance moves during osmosis?
A. Glucose
B. Protein
C. Water
D. Starch
C. Water
Which statement correctly describes active transport? A. It moves particles from high to low concentration and does not require energy. B. It moves water through a partially permeable membrane. C. It moves substances from low to high concentration and requires energy. D. It only occurs in animal cells.
C. It moves substances from low to high concentration and requires energy.
Which statement correctly compares diffusion and active transport?
A. Both move substances from low to high concentration.
B. Both require energy from respiration.
C. Diffusion moves substances down the concentration gradient, while active transport moves substances against it.
D. Diffusion only transports water, while active transport transports only mineral ions.
C.Diffusion moves substances down the concentration gradient, while active transport moves substances against it.
A student sprays perfume in one corner of a classroom. After a few minutes, students across the room can smell it. Explain how diffusion causes this to happen.
Perfume particles move randomly from the area of high concentration near the spray toward areas of lower concentration throughout the classroom. Eventually, the particles become more evenly distributed.
A potato strip is placed in a concentrated sugar solution. After 30 minutes, the potato strip becomes softer and loses mass. Explain why.
Water moves out of the potato cells into the sugar solution by osmosis because the sugar solution has a lower water potential than the cell contents. The cells lose water, causing the potato to lose mass and become softer.
Plant root hair cells can absorb mineral ions from the soil even when the concentration of mineral ions is higher inside the root cells than in the soil. What process allows this to happen?
Mineral ions are moved from a lower concentration in the soil to a higher concentration inside the root hair cells using energy from respiration.
A cell needs to move glucose from an area of low glucose concentration outside the cell to an area of higher glucose concentration inside the cell. Which transport process is most likely required, and why?
Active transport, because the glucose is being moved from a lower concentration to a higher concentration, against the concentration gradient, and therefore requires energy.
A student investigates how temperature affects the rate of diffusion. They place the same amount of potassium permanganate into two beakers: one containing cold water and one containing hot water. The purple colour spreads faster in the hot water. Explain why.
Particles have more kinetic energy at a higher temperature, so they move faster. This increases the rate of diffusion.
A plant cell is placed in a solution with a lower water potential than the cell sap. Predict what will happen to the cell and explain why.
Water moves out of the cell by osmosis. The vacuole and cytoplasm decrease in volume, and the cell membrane pulls away from the cell wall. The cell becomes plasmolysed.
A plant is placed in a solution containing mineral ions. When the plant's cells cannot carry out respiration, the uptake of mineral ions decreases significantly. Explain why.
Active transport requires energy from respiration. When respiration decreases, less energy is available for the transport proteins that move mineral ions against their concentration gradient.
Diffusion, osmosis, and active transport all involve the movement of substances across or within cells. Give one similarity and one differences between these processes.
Similarity: All involve the movement of substances and can contribute to maintaining suitable conditions inside cells.
Differences:
Two cells have the same size and are placed in the same environment. Cell A has a much steeper concentration gradient across its cell membrane than Cell B. Predict which cell will initially have a faster rate of diffusion and explain your reasoning.
A steeper concentration gradient creates a greater difference in particle concentration between the two sides of the membrane, resulting in a faster net movement of particles.
A student places identical potato cylinders into three different sugar solutions. After one hour, one potato gains mass, one shows no change in mass, and one loses mass. Explain what these results tell you about the water potential of each sugar solution compared with the potato cells.
Two identical plant roots are placed in different conditions. Root A is supplied with oxygen, while Root B is placed in a condition with very little oxygen. Both roots are surrounded by a solution containing a low concentration of mineral ions.
Root A will absorb more mineral ions. Active transport requires energy released during respiration. With more oxygen available, Root A can carry out more aerobic respiration and provide more energy for transporting mineral ions against their concentration gradient.
A student observes three situations:
Situation A: Oxygen moves from the air spaces in the lungs into the blood.
Situation B: Water moves from the soil into a plant root hair cell.
Situation C: Mineral ions move from a dilute soil solution into a root hair cell where their concentration is already higher.
Identify the transport process in each situation and explain how the concentration gradient determines the process.