2. 5 - Ultrastructure of Plant Cells

What type of cell wall do plant cells have?

Cellulose cell wall

What is the function of the cellulose cell wall?

Provides strength, support and prevents bursting under osmotic pressure

Do plant cell walls provide a barrier to substances?

No, they are fully permeable

What organelle in plant cells is the site of photosynthesis?

Chloroplast

What pigment do chloroplasts contain?

Chlorophyll

What is the function of chlorophyll?

Absorbs light energy for photosynthesis

What is the name of the flattened membrane sacs in chloroplasts?

Thylakoids

What is a granum?

Stack of thylakoids

What is the stroma in a chloroplast?

Fluid-filled space containing enzymes for the light-independent reactions

What is the function of the starch grains found in chloroplasts?

Energy storage (product of photosynthesis stored as starch)

What organelle maintains cell turgor in plant cells?

Central vacuole

What is the membrane surrounding the central vacuole called?

Tonoplast

What does the vacuole contain?

Cell sap (water, ions, sugars, pigments, waste products)

What is the role of the vacuole in plants?

Maintains turgor pressure, stores substances, pigments contribute to colour of petals/fruits

Name two organelles present in plant cells but not in animal cells.

Chloroplasts and permanent vacuole

What is the diameter of a typical plant cell?

~10–100 μm

What is the function of plasmodesmata?

Channels through cell walls for transport and communication between plant cells

What is the difference between amyloplasts and chloroplasts?

Amyloplasts store starch; chloroplasts carry out photosynthesis

Why don’t plant cells burst in hypotonic solutions?

The cellulose cell wall prevents lysis, leading to turgid cells instead

What happens to a plant cell in a hypertonic solution?

The cell becomes plasmolysed (cytoplasm pulls away from the cell wall)