31. using the picture below, answer the following questions and particles moving across a boundary. the membrane between the solutions is permeable to both the circle particles and the triangle particles.
image of side a and side b with a selectively permeable membrane, showing circle and triangle particles
describe the movement of the circles over time.
describe the movement of the triangles over time.
answer the following two questions fully and in complete sentences. these are excellent essay questions.
32. compare and contrast the structure and function of the cell wall with that of the cell membrane.
33. how do facilitated diffusion and active transport differ?

Question

Accepted Answer

### Question 31 (Movement of Circles)
# Brief Explanations:
To determine the movement of circle particles, we analyze their concentration on each side. Side A has fewer circle particles than Side B (visually, count the circles: Side A has 5, Side B has 10). Since the membrane is permeable to circles, they will move by diffusion (from high to low concentration) until equilibrium. So circles move from Side B to Side A over time to equalize concentration.
# Answer:
The circle particles will move from Side B to Side A over time. This is because Side B has a higher concentration of circle particles (more circles) compared to Side A, and the membrane is permeable to them. Through the process of diffusion (movement from an area of higher concentration to an area of lower concentration), the circles will spread out until the concentration of circle particles is equal on both sides of the membrane.

### Question 31 (Movement of Triangles)
# Brief Explanations:
For triangle particles, count their concentration: Side A has many triangles (visually, 7), Side B has 0. The membrane is permeable to triangles, so they diffuse from high (Side A) to low (Side B) concentration until equilibrium. Thus, triangles move from Side A to Side B over time.
# Answer:
The triangle particles will move from Side A to Side B over time. This is because Side A has a higher concentration of triangle particles (all the triangles are on Side A initially, with none on Side B), and the membrane is permeable to them. By the process of diffusion (movement from an area of higher concentration to an area of lower concentration), the triangles will spread out from Side A to Side B until the concentration of triangle particles is equal on both sides of the membrane.

### Question 32 (Cell Wall vs Cell Membrane)
# Brief Explanations:
- **Structure**: Cell wall (in plants, fungi, bacteria) is rigid, made of cellulose (plants), chitin (fungi), or peptidoglycan (bacteria). Cell membrane is flexible, a phospholipid bilayer with embedded proteins, found in all cells.
- **Function**: Cell wall provides structural support, protection, and prevents over-expansion in water. Cell membrane regulates substance transport (selective permeability), cell signaling, and maintains cell integrity.
- **Compare/Contrast**: Both are protective and involved in cell structure/transport, but cell wall is rigid (external), cell membrane is flexible (internal, around cytoplasm). Cell wall is not selectively permeable (more porous), cell membrane is selectively permeable. Cell wall is absent in animal cells; cell membrane is universal.
# Answer:
### Structure:
- **Cell Wall**: Rigid, external structure (in plants, fungi, bacteria) composed of cellulose (plants), chitin (fungi), or peptidoglycan (bacteria). It has a thick, non - flexible (or less flexible) composition with a porous nature.
- **Cell Membrane**: Flexible, internal structure (present in all cells) made of a phospholipid bilayer with embedded proteins (integral and peripheral). It is thin and has a fluid - mosaic arrangement.

### Function:
- **Cell Wall**: Provides structural support and protection to the cell, helps maintain cell shape, and prevents the cell from bursting in a hypotonic environment (e.g., in plant cells, it allows turgor pressure to be maintained). It is not involved in active transport of substances and has a more passive role in controlling cell expansion.
- **Cell Membrane**: Regulates the movement of substances into and out of the cell (selective permeability), participates in cell - cell communication (via receptors and signaling molecules), and helps maintain the cell’s internal environment. It is involved in active and passive transport mechanisms (e.g., facilitated diffusion, active transport) to move molecules across the membrane.

### Comparison/Contrast:
- **Similarities**: Both structures are involved in protecting the cell and have a role in defining the cell’s boundary (helping to separate the cell from its external environment).
- **Differences**: The cell wall is rigid and external, while the cell membrane is flexible and internal. The cell wall is only present in some cell types (plants, fungi, bacteria), while the cell membrane is universal. The cell wall is not selectively permeable in the same way as the cell membrane (it is more porous and allows larger molecules to pass through), and the cell membrane is actively involved in transporting specific substances via its embedded proteins, while the cell wall has a more passive structural role.

### Question 33 (Facilitated Diffusion vs Active Transport)
# Brief Explanations:
- **Energy Requirement**: Facilitated diffusion is passive (no energy, uses transport proteins to move down concentration gradient). Active transport is active (requires energy - ATP - to move against concentration gradient, also uses transport proteins).
- **Concentration Gradient Direction**: Facilitated diffusion moves from high to low concentration (with gradient). Active transport moves from low to high concentration (against gradient).
- **Protein Type**: Facilitated diffusion uses channel or carrier proteins. Active transport uses carrier proteins (often “pumps,” like sodium - potassium pump).
# Answer:
### 1. Energy Requirement
- **Facilitated Diffusion**: It is a passive transport process, meaning it does not require the input of cellular energy (such as ATP). Molecules move down their concentration gradient with the help of transport proteins.
- **Active Transport**: It is an active transport process that requires energy (usually in the form of ATP). This energy is used to move molecules against their concentration gradient.

### 2. Concentration Gradient Direction
- **Facilitated Diffusion**: Molecules move from an area of higher concentration to an area of lower concentration (down the concentration gradient). For example, glucose moving into a cell when its concentration outside the cell is higher.
- **Active Transport**: Molecules move from an area of lower concentration to an area of higher concentration (against the concentration gradient). For example, the sodium - potassium pump moves sodium ions out of the cell (where sodium concentration is low inside relative to outside) and potassium ions into the cell (where potassium concentration is high inside relative to outside).

### 3. Transport Proteins
- **Facilitated Diffusion**: It uses either channel proteins (which form pores for specific molecules, like ion channels) or carrier proteins (which bind to the molecule and change shape to transport it). These proteins do not require energy to function for this transport.
- **Active Transport**: It uses carrier proteins (often called “pumps”). These carrier proteins undergo conformational changes that require energy (ATP hydrolysis) to move molecules against the concentration gradient. An example is the sodium - potassium pump, which is a carrier protein that uses ATP to move sodium and potassium ions against their respective gradients.

In summary, facilitated diffusion is passive (no energy, down gradient) using channel/carrier proteins, while active transport is active (needs energy, against gradient) using carrier “pump” proteins.

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QUESTION IMAGE

Question

Explanation:

Question 31 (Movement of Circles)

Answer:

Question 31 (Movement of Triangles)