AS AQA Bio (Unit 2) Need to know: Plant cell structure

Plant Cell Structure.

Plant cells are eukaryotic cells. This means they have a distinct or true nucleus, linear DNA (as opposed to circular DNA) and membrane bound organelles such as mitochondria and chloroplasts)  

A Leaf Palisade Cell

A leaf palisade cell has features adapted for its function which is to carry out photosythesis. These features are:

They are long and thin and form a continuous layer which is close to surface inorder to absorb as much sun light as possible. (Think, if they where short and thick and located deep within the leaf, they would absorb much less light.) They are also tightly packed and their rectangular shape comes into use here as it allows them to be arranged in a way where there are few gaps so as much sunlight can be captured as possible.

They contain a large number of chloroplasts which produce a green pigment called chlorophyll that absorbs sun light, these organelles are the site of photosynthesis. More chloroplasts=more light capture and more photosynthesis.

They have a large vacuole which pushes the chloroplasts to the edge of the cell inorder to capture more sunlight.

Chloroplasts

The chloroplasts envelope- refers to that inner and outer membrane that surrounds a chloroplasts. This double membrane means it is highly selective about what enters and leaves the organelle.

Thykaloids: These are disc shaped objects that contain the pigment chlorophyll which absorb sunlight for photosynthesis.

Grana- singular is granum. These are stacks of thykaloids (up to 100), and their function is to increase surface area for light absorption and attachment of enzymes that carry out first stages of photosynthesis. 

Stroma: This is the matrix around the grana. It contains enzymes needed to carry out photosynthesis and also DNA and ribosomes so the chloroplast can quickly and easily make protiens needed for photosynthesis. 

WHY ARE PLANTS …