Chapter 2.5 - The ultrastructure of plant cells

Question 1

What is the structure and function of cell walls?

Answer 1

• Made of cellulose in plants
• Provides mechanical strength whilst remaining permeable so substances can pass in and out of the cell
• Maintains the cell shape

Question 2

What is the structure and function of vacuoles?

Answer 2

• Partially permeable membrane lined sacs which contain cell sap and helps support the plant, maintenance of turgor : rigid
• Only some small molecules can pass through the tonoplast but others cannot
• Vacuoles in animal cells are not permanent

Question 3

What is the structure and function of chloroplasts?

Answer 3

• 3 to 10 μm oval-shaped double membrane organelles
• Disc like thylakoids, network of flattened sacs, are arranged in stacks called grana(joined by lamellae membranes), light-dependent reactions of photosynthesis take place on the thylakoid membranes
• The internal fluid, stroma, is where light-independent reactions take place
• Starch produced by photosynthesis is present as starch grains
• Also contain DNA and ribosomes

Question 4

How is the internal membrane of chloroplasts beneficial?

Answer 4

It provides a large surface area needed for the enzymes, proteins, and chlorophyll molecules during the process of photosythesis