Plant cell structure is best explained with a labeled plant cell diagram. The plant cell parts can be grouped into 3 parts: plant cell wall, cell surface membrane and cytoplasm (inside which the plant cell organelles are suspended), based on how they are seen with a light microscope and electron microscope. The functions of each plant cell parts will be listed.
Labeled Plant Cell Diagram showing the organelles
The plant cell diagrams shown consist of the structure when viewed with a light microscope and when viewed with an electron microscope. The plant cell structure viewed with a light microscope only shows few plant cell parts as some organelles cannot be seen; there are more organelles seen using an electron microscope, hence the this is called the Ultrastructure of plant cell.
Plant cell structure: A list of Plant cell parts with their functions as seen with Light and Electron Microscope
- Cell wall
- Plasma membrane (or the cell surface membrane)
- Cytosol (or Cytoplasm)
- Large vacuole with tonoplast (the membrane of the vacuole)
- Endoplasmic reticulum (ER) consisting of smooth and rough endoplasmic reticulum
- Golgi apparatus or Golgi complex
Plant cell organelles and their functions
Each listed plant cell parts will be described and their functions given. Located in the cytoplasm of cells are structures called organelles. The organelles are membrane bound structures in the cytoplasm of a cell that are separate entities with each having its individual function.
Plant cell wall and plasmodesmata
Plant cell wall is a rigid structure that surrounds the cell membrane. It is mainly made up of cellulose a polysaccharide that makes the cell wall rigid. the function of the cell wall is to give rigidity and shape to the plants and it also protects other plant cell parts or organelles. Plant cell wall also allows free movement of molecules and ions through to the cell surface membrane.
The plasmodesmata are fine strands of cytoplasm that functions mainly in linking neighbouring cells such that there is a communication between two adjacent cells. The plasmodesmata (singular: plasmodesma) form pore-like structures in plant cell walls and allow movement of molecules across adjacent plant cells. The plasmodesma is not an organelle.
Plant Plasma membrane or cell surface membrane
The cell surface membrane is extremely thin measuring about 7 nm which when magnified can be seen to have three layers (trilaminar appearance). The cell membrane is partially permeable and functions mainly to protect organelles and control exchange between the cell and its environment.
Plant cell Cytoplasm
The cytoplasm of plant cells is the fluid material found between the nucleus and the cell surface membrane. The consistency of the cytoplasm varies from aqueous (watery) to jelly-like. The function of the cytoplasm is to support the organelles of plant cell.
The mitchondria (singular: Mitochondrion) are commonly referred to as the power houses of the plant cell because they are the centers for aerobic respiration where the energy needed for the metabolism of plants takes place. The mitochondria are capsule-like or sausage-shaped double membrane structures (they are made up of two membranes) that are found scattered in the cytoplasm. The mitochondria also help in the synthesis of lipids.
Plant cell Nucleus
The cell nucleus is the largest organelle of plants and is made up of a double layer of membrane (called the nuclear membrane or nuclear envelope); this nuclear envelope contains small pores that allow and control the exchange of molecules and substances such as messenger RNA (mRNA), ribosomes, ATP, nucleotides and some proteins. The nucleus functions as the control center of the cell as all regulatory process are carried out in the nucleus.
The nucleus contains chromosomes which code the DNA of the cell (the genetic material of the cell). During metaphase stage of mitosis or meiosis in the cell cycle, the nucleus first divides before cytokinesis (division of the cytoplasm). Also within the nucleus is the nucleolus which helps in making ribosomes.
Plant cell vacuole
The plant vacuole is a large organelle found in the central part of the cytoplasm surrounded by its own membrane called the tonoplast. The tonoplast helps to control the exchange of molecules between the plant vacuole and its cytoplasm. The function of the vacuole is to store pigments ( such as the color of flower petals or red pigment of beetroots), sugars, enzymes for metabolism, waste products, oxygen, mineral salts, carbon dioxide and other organic compounds. The plant cell vacuole also helps to regulate the osmotic pressure a cell by controlling the inward and outward flow of water.
Endoplasmic reticulum (ER)
The endoplasmic reticulum is an extended system of flattened compartments forming sacs that spread throughout the cell. The membrane of the ER is continuous with the outer membrane of the nuclear envelope. There are two types of ER: rough endoplasmic reticulum (with ribosomes on it) and smooth endoplasmic reticulum (without ribosomes on it). The ER breaks off and joined together to form stacks of the golgi bodies.
The functions of the endoplasmic reticulum depends on the type. The rough ER form part of the secretory pathway because the proteins can be exported from the cell via the Golgi vesicles. The Smooth ER helps to make lipids and steroids and some hormones.
Ribosomes are tiny organelles that measure about 25 nm in size often seen as tiny dots located mostly on endoplasmic reticulum (making the Endplasmic reticulum rough hence the name rough endoplasmic reticulum). The function of ribosomes is the synthesis of proteins synthesis as they are made of RNA (ribonucleic acid) and protein. The proteins made by the ribosomes on the rough ER enter the sacs and are modified and transported to where they are needed.
The Golgi body consist of a stack of flattened sacs that are formed at one end from vesicles which bud off from the Endoplasmic Reticulum. One end of the golgi body forms stack while the other end forms golgi vesicles which serve the function of the golgi body. The stack of sacs of the golgi body together with the vesicles being formed are called Golgi apparatus or Golgi complex.
The function of the Golgi body is to collect, processe and sort molecules such as the proteins from the rough endoplasmic reticulum which are then transported in the Golgi vesicles to where they are needed. The enzymes in the Golgi body of plant cell also help to convert sugars into cell wall components.
The Chloroplasts are found in the leaves and other green parts of the plant. The function of the chloroplasts is to absorb sunlight during the process of photosynthesis (energy synthesis using sunlight). The chloroplasts are relatively large organelles compared to other organelles and can easily be seen scattered inside the cytoplasm with a light microscope.
Most of the plant cell parts described are also found in animal cells. The differences between plant and animal cells are the existence of chloroplast, cell wall and large vacuole in plant cells which are not present in animal cells.