What is a tonoplast

Options

A. Outer membrane of mitochondria
B. Inner membrane of chloroplast
C. Membrane boundary of the vacuole of plant cells
D. Cell membrane of a plant cell

Explanation

### Step-by-Step Solution:

1. **Definition of Tonoplast**: The tonoplast is a membrane that surrounds the vacuole in plant cells. It is a single membrane that acts as a boundary for the vacuole.

2. **Function of Tonoplast**: The primary function of the tonoplast is to facilitate the transport of ions and other materials into the vacuole. This transport can occur against the concentration gradient.

3. **Concentration Gradient**: The tonoplast helps maintain a higher concentration of certain substances within the vacuole compared to the cytoplasm of the cell. This is important for various cellular processes and storage functions.

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