Topics covered in this snack-sized chapter:
A cell structural and functional unit of life and the fundamental building block of any organism.
All cells share similar characteristics and can be defined by the cell theory:
- All living things are composed of cells
- All cells arise from pre-existing cells through cell division
- Cells contain hereditary material, which they pass to daughter cells during cell division
- The chemical composition of all cells is quite similar
- The metabolic processes associated with life occur within cells
Eukaryotic cells that are similar to animal cells
As a plant matures, its cells become specialized.
There are a number of important specialized types of plant cells. Some examples of specialized plant cells include:
Usually depicted as the typical plant cell because they are not very specialized
These cells synthesize and store organic products in the plant.
Most of the plant's metabolism takes place in these cells.
Have a support function in plants, particularly in young plants
Help to support plants while not restraining growth due to their lack of secondary walls and the absence of a hardening agent in their primary walls
Also have a support function in plants but unlike collenchyma cells, they have a hardening agent and are much more rigid
Also have a support function in plants but unlike collenchyma cells, they have a hardening agent and are much more rigid
Conduct organic nutrients such as sugar throughout the plant
When you compare a plant cell with an animal cell, you find them to be closely similar except that the animal cell lacks chloroplast and cell wall.
A plant cell generally ranges from 10 to 100 micrometers in size.
Each cell contains the following organelles:
Supposed to be the most important organelle
Carries the genetic information present in this organelle which inherits the physical traits from one generation to another
Has a dark stained nucleolus mainly responsible for protein formation
Apart from this, the nucleus coordinates all the cell functions and regulates the metabolism of plants.
The passage of food and water and the influx of nutrients in and out of the cells are some of the characteristic functions of a plant cell.
As the name indicates, this membranous sheath surrounding the nucleus protects it from physical damage.
The ground substance or the matrix which is jelly-like material in which all the cell organelles are embedded and suspended
The main cytoplasm function in a cell is to keep all the cell constituents intact.
Similar to a nuclear membrane, the main cell membrane function is to give the cell an appropriate shape and size.
This thin membrane is made up of cellulosic fibers and proteins and its main function is transport of materials through cells.
Distinguishing part which is not present in animals and mainly responsible for imparting rigidity to the cells
Made up of cellulose and provides support and protection to the plant
The cell wall material differs with plant species and gives a definite shape (elongated, oval, round, rectangular, squarish).
Another peculiar organelle present in plant cells
As mentioned before, plants prepare their own food with a unique process called photosynthesis with the aid of these plastids.
The plastids consist of pigments which absorb light and make food.
The most common plastid is chloroplast containing the green pigment chlorophyll.
Among the largest cell organelles also known as the engine house or the energy house of the cells
Provide the energy required for all the cellular activities by breaking down complex carbohydrates prepared during photosynthesis (glucose to energy)
The main site for protein synthesis since these are rich in ribonucleic acids
Could be bound to the endoplasmic reticulum or free-floating in the cytoplasm
Structure that modifies proteins produced in the ribosomes
Not all of the proteins made by ribosomes need changing, but those that do, get altered here.
On the basis of presence or absence of ribosome on the surface, two classes of ER can be recognized:
- Rough endoplasmic reticulum: covered with ribosome, helps to transport materials through the cell and produce proteins
- Smooth endoplasmic reticulum: responsible for the production of hormones and secretory products
The proteins formed and bound by the ER need to be processed so as to perform normal functions.
Golgi membranous sacs or dictyosomes chiefly associated with ER release protein chains after processing them.
Plant cells are characterized by larger and lesser number of vacuoles and mainly responsible for maintaining the fullness of a cell.
An alternative function of these is to store ions, sugars and secondary metabolites.