Question

which statement is true about a cell wall but not a cell membrane?
it forms the outer layer of a cell.
it gives an animal cell its shape.
it is selectively permeable.
it is made mostly of cellulose.

Explanation:

1. Analyze Option 1: Both the cell wall (in plant cells, bacteria, etc.) and the cell membrane (in all cells) can be the outer layer (e.g., in animal cells, cell membrane is outer; in plant cells, cell wall is outer, but cell membrane is also present under it). So this is not unique to cell wall.
2. Analyze Option 2: Animal cells do not have a cell wall, so this statement is incorrect as cell wall is not present in animal cells to give them shape.
3. Analyze Option 3: Both cell wall (in a more general, less strict selective way in some cases, but still has permeability control) and cell membrane are selectively permeable. So this is not unique to cell wall.
4. Analyze Option 4: Cell walls (especially in plant cells) are made mostly of cellulose. Cell membranes are made of a phospholipid bilayer with proteins, cholesterol, etc., and do not contain cellulose. So this is true for cell wall but not cell membrane.

Answer:

It is made mostly of cellulose.