2.5 Plant Structure

Question 1

What are the features of plant cell walls

Answer 1

Plant cells are rigid structures. Wall made of cellulose

Have a cell wall surrounding cell membrane.

Made of cellulose, a complex carbohydrate.

Freely permeable to substances.

Give cell its shape.

Contents of cell press against wall making it rigid.

Acts as a defence mechanism, protecting cell against pathogens.

Question 2

What Plant cell organelles are unique to plant cells

Answer 2

Vacuoles -
1) membrane lined sacs in cytoplasm containing cell sap.

2) many plant cells have large, permanent vacuoles which help with maintaining turgor.
3) membrane of vacuole is called TONOPLAST.
4) it’s selectively permeable so only small molecules can pass.

Chloroplasts -
1) responsible for photosynthesis

2) found in cells in the green parts like leaves and stems.
3) double membrane structure
4) fluid enclosed in chloroplast is called STROMA.
5) have internal network of membranes which form flattened sacs called thylakoids; several of these together are called a granum (plural = grana).
6) grana are joined by lamellae; grana contains chlorophyll pigments where light reactions occur.
7) starch produced by photosynthesis is present as starch grains.
8) chloroplasts have ribosomes and DNA so can make one proteins.
9) internal membranes provide large SA needed for enzymes, proteins and pigment during photosynthesis.