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Transport Across the Cell Membrane

The worksheet focuses on understanding transport mechanisms across the cell membrane, including diffusion, osmosis, and active transport. Below is a detailed explanation and solution for each part of the worksheet.

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#### 1. Flow Chart: Transport Across the Cell Membrane

The flow chart categorizes different types of transport based on whether they occur with or against the concentration gradient and whether they require energy (ATP).

##### Left Side: Passive Transport
- Occurs down the concentration gradient (high → low)
- REQUIRES: No energy
- For the transport of water: Osmosis
- For the transport of glucose: Facilitated diffusion
- For the transport of CO₂ and O₂: Simple diffusion
- Water moves until it reaches: Equilibrium

##### Right Side: Active Transport
- Occurs against the concentration gradient (low → high)
- REQUIRES: ATP
- For small ions: Na⁺/K⁺ pump
- For bulk transport into the cell: Endocytosis
- For bulk transport out of the cell: Exocytosis

##### Matching Terms
- ATP energy: Active transport
- Simple diffusion: For the transport of CO₂ and O₂
- Active transport: Occurs against the concentration gradient
- Osmosis: For the transport of water
- Phospholipid bilayer: The structure of the cell membrane
- Exocytosis: Bulk transport out of the cell
- Facilitated diffusion: For the transport of glucose
- Passive transport: Occurs down the concentration gradient
- Solute: Molecules being transported
- Amoeba eating: Example of endocytosis
- Down: Occurs down the concentration gradient
- Protein channel: Facilitated diffusion
- Hormone export: Example of exocytosis
- No energy: Passive transport
- Equilibrium: Water moves until it reaches equilibrium
- Against: Occurs against the concentration gradient
- Na⁺/K⁺ pump: For small ions
- Protein pump: Active transport mechanism
- Endocytosis: Bulk transport into the cell

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#### 2. Osmosis Questions

##### Question 1: Why wouldn't bacteria be able to survive on salted fish? Explain using the concept of osmosis.
- Explanation: Salted fish contains a high concentration of solutes (salt). When bacteria are placed in this environment, the concentration of solutes outside the bacterial cells is much higher than inside. According to the principle of osmosis, water moves from an area of lower solute concentration (inside the bacterial cells) to an area of higher solute concentration (outside the bacterial cells). This causes the bacterial cells to lose water, leading to dehydration and ultimately death. Therefore, bacteria cannot survive on salted fish due to the loss of water through osmosis.

##### Question 2: Indicate the tonicity of each solution (isotonic, hypertonic, hypotonic) and the direction of water movement.
- Beaker A:
- Tonicity: Hypertonic (concentration of solutes outside the cell is higher)
- Direction of water movement: Out of the cell
- Beaker B:
- Tonicity: Isotonic (concentration of solutes is equal inside and outside the cell)
- Direction of water movement: No net water movement
- Beaker C:
- Tonicity: Hypotonic (concentration of solutes outside the cell is lower)
- Direction of water movement: Into the cell

##### Question 3: Roots of a plant absorbing water from the soil
- a. Why water moves from the soil into the root hair cell?
- Explanation: The root hair cells have a higher concentration of minerals (solutes) compared to the soil. According to osmosis, water moves from an area of lower solute concentration (soil) to an area of higher solute concentration (root hair cells). This movement of water helps the plant absorb nutrients from the soil.
- b. Complete each sentence below:
- 1. The soil is hypotonic compared to the root cells.
- 2. The root cells are hypertonic compared to the soil.

##### Question 4: Soft drinks as thirst quenchers
- Explanation: Soft drinks with a low solute concentration are considered "thirst quenchers" because they help replenish the body's water supply. When consumed, these drinks move water into the cells (hypotonic effect), helping to rehydrate the body. On the other hand, soft drinks with a high solute concentration can dehydrate cells because they cause water to move out of the cells (hypertonic effect). Therefore, soft drinks with low solute concentrations should be marketed as "thirst quenchers."

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Final Answers

#### Flow Chart
- Left Side (Passive Transport):
- Requires: No energy
- For water: Osmosis
- For glucose: Facilitated diffusion
- For CO₂ and O₂: Simple diffusion
- Water moves until: Equilibrium
- Right Side (Active Transport):
- Requires: ATP
- For small ions: Na⁺/K⁺ pump
- For bulk transport into the cell: Endocytosis
- For bulk transport out of the cell: Exocytosis

#### Osmosis Questions
1. Bacteria on salted fish: Bacteria cannot survive due to water loss through osmosis.
2. Tonicity and water movement:
- Beaker A: Hypertonic, out of the cell
- Beaker B: Isotonic, no net water movement
- Beaker C: Hypotonic, into the cell
3. Plant roots absorbing water:
- a. Water moves from soil to root hair cells due to osmosis.
- b. Soil is hypotonic; root cells are hypertonic.
4. Soft drinks as thirst quenchers: Drinks with low solute concentrations should be marketed as "thirst quenchers."

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Final Answer Box

\[
\boxed{
\text{
1. Bacteria cannot survive due to water loss through osmosis. \\
2. A: Hypertonic, out; B: Isotonic, none; C: Hypotonic, in. \\
3. a. Water moves due to osmosis; b. Soil is hypotonic, root cells are hypertonic. \\
4. Drinks with low solute concentrations should be marketed as "thirst quenchers."
}
}
\]