What are the structures and functions of different parts of a cell?
For being so small, cells are surprisingly complex. It can be hard to keep track of their different parts, especially when considering the various types of cells. In this study guide, we will identify different parts of a cell, describe their structures and explain their functions.
What three components do all cells have in common?
The cell is the building block of an organism, its smallest living unit. By definition, all cells have the following:
A cell membrane: As a barrier between the cell and its environment, the membrane provides structure, protection and control over the movement of materials in and out of the cell.
Cytoplasm: This refers to the contents of the cell membrane excepting the nucleus. One of its main components is cytosol, a jelly-like substance which acts as protection and support for the remaining contents.
DNA: Each cell contains genetic material. However, the way it is stored is one of the distinguishing factors between a eukaryote (a plant or animal cell for example) and a prokaryote (like a bacterium). These represent the two main types of cells. The former has a nucleus — for its DNA — as well as other organelles while the latter does not. Organelles are parts of a cell that have a specialised function and their own membranes.
What are the different parts of the nucleus and their functions?
The nucleus, as the location of a cell’s genetic material, functions as its control centre. The nuclear membrane (or envelope) is a double membrane that regulates the movement of materials to and from the cytoplasm. The nucleolus is a large, oval structure that produces ribosomes, which are small particles made up of protein and RNA that synthesize (or make) proteins. They can either be free or attached to the endoplasmic reticulum.
What is the endoplasmic reticulum (ER)?
Present in most eukaryotic cells, this organelle is a network of flattened sacs or tubules that is connected to the nuclear membrane. It transports various materials, such as proteins, and is also involved in their synthesis. The rough ER is studded with ribosomes while the smooth ER is not. The ER cooperates closely with the Golgi apparatus and lysosomes and together they form what is known as the GERL system.
What are the Golgi apparatus (or body or complex) and lysosomes?
Present in most eukaryotic cells, the Golgi apparatus is an organelle composed of stacks of flattened sacks. It modifies, packages and transports proteins. Lysosomes are small, round organelles that contain enzymes to help break down and process unwanted materials. Simply put, they are like garbage collectors and are commonly found in animal cells but not plant ones.
What are some parts present in plant cells but not animal ones?
There are several differences between animal and plant cells besides the question of lysosomes. For instance, plant cells have a cell wall but animal cells do not. This outer layer (typically made of cellulose for plant cells) helps support and protect the cell and acts as a filtering mechanism.
Chloroplasts too are found in plant cells but not animal ones. These rounded organelles get their green colour from the chlorophyll they contain, which enables photosynthesis—when the energy of sunlight is used to make glucose for nourishment, a process which releases oxygen.
What are some organelles present in both plant and animal cells?
Both plant and animal cells can have mitochondria. These are sphere- or rod-shaped organelles with a double membrane. They are the powerhouse of the cell in that they break down nutrients, such as glucose, to provide energy. This process is called cellular respiration. Vacuoles are also found in both plant and animal cells. These organelles are basically fluid-filled storage compartments. They might hold nutrients or waste products for example. Plant cells have only a single, large vacuole—its largest organelle. In contrast, animal cells can have multiple ones and they are relatively smaller.
This guide covered basic cell parts, but there are many more to be found, in particular if one starts looking at cells with specialised functions.
