2.5 The ultrastructure of plant cells

Question 1

What components of a cell are specific to only plant cells?

Answer 1

Cellulose cell wall, vacuoles, chloroplasts

Question 2

Description and function of the cell wall

Answer 2

• the cell wall surround the cell membrane
• plant cell walls are mode of cellulose (a complex carbohydrate)
• they are freely permeable so substances can pass into and out of the cell through the cellulose wall
• the cell walls of a plant cell gives it shape and support as the cell wall it rigid
• cell wall acts as a defence mechanism, protecting the contents of the cell against invading pathogens

Question 3

Description and function of vacuoles

Answer 3

• vacuoles are membrane lined sacs in the cytoplasm containing cell sap
• the membrane of the vacuole is called the tonoplast and is selectively permeable (only some small molecules can pass through it)
  -many plant cells contain permanent vacuoles which maintain turgor pressure so contents of the cell push against the cell wall to maintain the rigid framework of the cell

Question 4

description and function of chloroplasts

Answer 4

• responsible for photosynthesis in plants (found in green parts of the cells)

-they have a double membrane structure
-the fluid enclosed in the chloroplast is called the stroma
- they have an internal network of membranes, which form flattened sacs called thylakoids
- several thylakoids stacked together are called a geranium. the grana are joined together by membranes called lamellae
- the grana contain chlorophyll pigments where light dependent reactions occur during photosynthesis
- chloroplasts contain DNA and ribosomes so can produce their proteins

• the internal membranes provide the large surface area needed for the enzymes , proteins and pigment molecules necessary in the process of photosynthesis