The Ultrastructures of Cells including Plant Cells

Question 1

Describe the structure and function of the Plasma (Cell Surface) Membrane.

Answer 1

• **Structure: **The Plasma (cell surface) membrane is the membrane found on the surface of animal cells and just inside the cell wall of palnt cells and prokaryotic cells. It’s made mainly of lipis and protein.
• **Function : **Regulates the movement of substances into and out of the cell. It also has receptor molecules on it, whihc allow it to respond to chemicals like hormones.

Question 2

Describe the structure and function of the Cell Wall in Plant Cells.

Answer 2

• **Structure: **The Cell Wall is a rigid structure that surrounds plant cells. It’s made mainly of the carbohydrate cellulose.
• **Function: **Supports plant cells.

Question 3

Describe the structure and function of the Nucleus.

Answer 3

• **Structure: **The nucleus is a large organelle surrounded by a nuclear envelope (double membrane), which contains many nuclear pores. The nucleus contains chromatin and often a structure called the nucleolus.
• **Function: **Chromatin is made from proteins and DNA (DNA controls the cell’s activites). The nuclear pores allow substances (e.g. RNA) to move between the nucleus and the cytoplasm. The nucleous makes ribosomes.

Question 4

Describe the structure **and **function of Lysosomes.

Answer 4

• **Structure: **A Lysosome is a round organelle surrounded by a membrane, with no clear internal structure.
• **Function: **Contains digestive enzymes. These are kept seperate from the cytoplasm by the surrounding membrane, and can be used to digest invading cells or to break down worn out components of the cell.

Question 5

Describe the structure and function of Ribosomes.

Answer 5

• **Structure: **A Ribosome is a very small organelle that either floats free in the cytoplams or it attatched to the rough endoplasmic reticulum (RER).
• **Function: **The site where proteins are made.