1. Cell structure and Function
1.5. Cell Organelles
Plant organelles
Dr V Malathi and Mrs Sushumna Rao
Organelles are structures found within the cytoplasm of eukaryotic cell. Each organelle is enclosed within a membrane and performs a specific function.
Organelles in animal cells include the nucleus, mitochondria, endoplasmic reticulum, Golgi apparatus, vesicles, vacuoles etc .,
Ribosomes are not enclosed within a membrane but are still commonly referred to as organelles in eukaryotic cells.
Organelles/ cell structures specific for plant cell
“plant cell” by OpenStax is licensed under CC BY 4.0
The Cell Wall
The cell wall is a rigid covering that protects the cell,
It provides structural support, and gives shape to the cell.
Fungal and protistan cells also have cell walls.
The plant cell wall is mainly composed of an organic constituent called , a polysaccharide comprised of glucose units.
While the chief component of prokaryotic cell walls is peptidoglycan,
Chloroplasts
Chloroplasts are plant cell organelles that carry out
They have their own DNA.
Photosynthesis is the process by which plants through a series of reactions use carbon dioxide, water, and light energy to make glucose and oxygen.
Plants are as they are able to make their own food, like sugars, while animals are as they must ingest their food.
This is a major difference between plants and animals;
Chloroplasts have outer and inner membranes
Within the space enclosed by a chloroplast’s inner membrane there is a set of interconnected and stacked fluid-filled membrane sacs called
Each stack of thylakoids is called a (plural = grana).
The fluid enclosed by the inner membrane that surrounds the grana is called the
The space inside the thylakoid membranes is called the thylakoid space.
The chloroplasts contain a green pigment called chlorophyll, which captures the light energy for carrying out the process of photosynthesis.
The light harvesting reactions take place in the thylakoid membranes.
The synthesis of sugar takes place in the stroma.
Like plant cells, photosynthetic protists also have chloroplasts. Some bacteria perform photosynthesis, but their chlorophyll is not relegated to an organelle.
“Chloroplast structure” by OpenStaxis licensed under CC BY 4.0
The Central Vacuole
The central vacuole is an unique and essential component of plant cell and occupies most of the space of the cell.
The central vacuole plays a key role in regulating the concentration of water in the cell against the changing environmental conditions.
The the liquid inside the central vacuole provides turgor pressure, which is the outward pressure caused by the fluid inside the cell.
The wilting of a plant when we forget to water it for few days is because of shrinking of the central vacuole caused due to the movement of water out of the central vacuole ,as the water concentration in the soil becomes lower than the water concentration in the plant.
This loss of support to the cell walls of plant cells results in