• Plant cells contain most of the organelles found in animal cells, along with a few extra organelles that are only found in plant cells

Cell wall

• Cell walls are formed outside of the cell membrane and offer?structural support?to the cell
  • This structural support is provided by the polysaccharide?cellulose

Middle lamella

• This forms the?outermost layer?of the plant cell and acts like glue to stick adjacent plant cells together
• It provides?stability?to the plant

A diagram to show the cell wall and middle lamella of one plant cell

Plasmodesmata

• Narrow threads of cytoplasm (surrounded by a cell membrane) called?plasmodesmata?connect the cytoplasm of neighbouring plant cells
• This allows substances to be?transported?between plant cells and facilitates?cell to cell communication

Pits

• These are?very thin?regions of the cell wall
• The pits in adjacent plant cells are lined up in?pairs
• This facilitates?transport?of substances between cells

Detailed structure of plant cell wall

Chloroplasts

• Larger than mitochondria, also surrounded by a?double-membrane
• Membrane-bound compartments called?thylakoids?containing?chlorophyll?stack to form structures called?grana?(singular = granum)
• Grana are joined together by?lamellae?(thin and flat thylakoid membranes)
• Chloroplasts are the site of?photosynthesis:
• Certain parts of photosynthesis occur in?thylakoid membranes, while other parts happen in the?stroma
• Chloroplasts also contain small circular pieces of?DNA?and ribosomes used to synthesise proteins needed in chloroplast replication and photosynthesis

Chloroplasts are found in the green parts of plants - the green colour is due to the presence of the pigment chlorophyll

Amyloplasts

• Small, membrane bound organelle containing?starch granules
• They are responsible for?storing starch?in plants and converting it back to glucose when the plant needs it

Structure of an amyloplast

Vacuole and tonoplast

• The vacuole is a sac in plant cells surrounded by the?tonoplast?(selectively permeable membrane)
• Contains cell sap, which is a mixture of different substances such as water, minerals, waste and enzymes
• Vacuoles have several functions in plant cell:
  • They keep cells?turgid, which stops the plant from wilting
  • They can?break down?and?isolate?unwanted chemicals in plant cells
  • The tonoplast?controls?what can enter and leave

The structure of the vacuole

• It is important to be able to recognise the plant organelles mentioned earlier from electron microscope images

TEM electron micrograph of a plant cell showing key features