Cell Structure

Life's fundamental building blocks are cells. Every organ of every animal, plant, fungus, and bacterial species is made up of cells. The building blocks of a house are analogous to the cells in a body. Prokaryotes and eukaryotes are the two main categories of cells.

Prokaryotic and eukaryotic cell structures

Prokaryote is defined as a type of cell that lacks a nucleus. Bacteria, for instance, are typically unicellular prokaryotes, meaning they only contain one cell. However, there are instances in which an organism is unicellular but has a nucleus, making it a eukaryote. Yeast is one example of this.

Eukaryote, on the other hand, is a type of cell that has a nucleus. Eukaryotes, with the exception of yeast, are multicellular due to their ability to contain millions of cells. Eukaryotes include, but are not limited to, humans, plants, and animals. Eukaryotes and prokaryotes have similar characteristics in terms of cell structure, but they also differ in other areas. The accompanying figure provides a general overview of the cell architectures we will be talking about in this post as well as highlights their similarities and distinctions.

Cell organelles

There are numerous cell organelles, and whether or not a cell is present will depend on the type of cell, its purpose, and whether the organism is prokaryotic or eukaryotic.

Cell membrane

Cell membranes are present in both bacterial and eukaryotic cells. This separates the contents of the cell from the medium around it. A few things can enter or leave a cell through the single membrane that makes up a cell.

In animals, the plasma membrane serves as the cell's outer boundary, whereas in plants and prokaryotes, it is normally covered by a cell wall. This membrane serves to separate and shield a cell from its surroundings and is composed primarily of a double layer of amphiphilic phospholipids (partly hydrophobic and partly hydrophilic). As a result, the layer is known as a phospholipid bilayer or, less commonly, a fluid mosaic membrane. A macromolecular structure termed the porosome, the universal secretory portal in cells, is embedded inside this membrane, as are a number of protein molecules that operate as channels and pumps, moving different substances into and out of the cell.
The membrane is semi-permeable and selectively permeable, meaning it can allow a material (molecule or ion) to flow freely, to a limited extent, or not at all. Cell surface membranes also have receptor proteins, which allow cells to detect external signalling chemicals like hormones.

Cytoplasm

Cytoplasm is the gelatinous liquid that fills the inside of a cell. It is composed of water, salts, and various organic molecules.

The cytosol is a component of the cytoplasm. The cytoplasm includes the cytosol, all the organelles, and the liquid contents inside the organelles. The cytoplasm does not include the nucleus. The main component of cytosol is water.

Some intracellular organelles, such the nucleus and mitochondria, are enclosed by membranes that separate them from the cytoplasm.

The majority of chemical reactions occur in the cytoplasm, a jelly-like liquid found inside each cell. It has enzymes that regulate these chemical processes.

Ribosomes

A ribosome is an intercellular structure made of both RNA and protein, and it is the site of protein synthesis in the cell. The ribosome reads the messenger RNA (mRNA) sequence and translates that genetic code into a specified string of amino acids, which grow into long chains that fold to form proteins. Proteins are generated in cells at the site of protein synthesis, which is the ribosome.

Eukaryotic cell structure

Prokaryotic cells are significantly simpler than eukaryotic cells. Prokaryotes don't have specialized structures since they are single-celled. For instance, eukaryotic cells create tissues, organs, and organ systems in the human body (e.g. cardiovascular system).

The following structures are specific to eukaryotic cells:

Nucleus

The nucleus houses the majority of the genetic material in a cell and has its own double membrane known as the nuclear membrane. Ribosomes cover the nuclear membrane, which has nuclear pores throughout. The majority of the genetic material in a eukaryotic cell is kept in the nucleus as chromatin (this is not the case in prokaryotic cells). Chromatin is a structure in which histone proteins wrap lengthy DNA strands to fit into the nucleus. The nucleolus is another structure within the nucleus that synthesises rRNA and assembles ribosomal subunits, both of which are required for protein synthesis.

Mitochondria

Mitochondria are known for producing cellular energy by making ATP. All organ systems require ATP to function. For example, all of our muscle activities necessitate the use of ATP.

They also have their own genetic material, mitochondrial DNA, making them one of the few cell organelles that posses it. Plant chloroplasts are another example of an organelle that has its own DNA.

Mitochondria, like the nucleus, have a double membrane, but no pores or ribosomes are attached.

Endoplasmic reticulum (ER)

Endoplasmic reticulum is classified into two types: rough endoplasmic reticulum (RER) and smooth endoplasmic reticulum (SER).

The RER is a system of channels that connects directly to the nucleus. It is in charge of all protein synthesis as well as the packaging of these proteins into vesicles, which are then transferred to the Golgi apparatus for further processing. Ribosomes are required for protein synthesis. These are affixed directly to the RER, giving it a rough appearance.

The SER lacks ribosomes and therefore has a smoother appearance. The SER produces lipids and stores calcium.

Centrioles

Centrioles are paired barrel-shaped organelles located in the cytoplasm of animal cells near the nuclear envelope. Centrioles play a role in organizing microtubules that serve as the cell's skeletal system. They help determine the locations of the nucleus and other organelles within the cell.

Golgi body

A Golgi body, also known as a Golgi apparatus, is a cell organelle that aids in the processing and packaging of proteins and lipid molecules, particularly proteins destined for cell export. The Golgi body is a sequence of stacked membranes named after its discoverer, Camillo Golgi.

Lysosome

A lysosome is a membrane-bound cell organelle that contains digestive enzymes. Lysosomes are engaged in a variety of cellular functions. They breakdown extraneous or worn-out cell components. They can be used to kill viruses and bacteria that try to get in.

Plant cell structure

Plant cells have a similar structure to animal cells, but don't have centrioles, lysosomes or cilia.

Plant cells have distinct characteristics such as chloroplasts, cell walls, and intracellular vacuoles. Photosynthesis occurs in chloroplasts; cell walls allow plants to be robust and upright; and vacuoles help govern how cells handle water and other substances.

Cell wall

The cell wall of plant cells covers the plasma membrane and offers tensile strength as well as resistance to mechanical and osmotic stress. It also enables cells to create the pressure of cell contents against the cell wall know as turgor pressure. This pressure also gives plant cells their distinctive shape and appearance. In plants the cell wall is made from cellulose. The prokaryotic cell wall is made of murein and fungi have cell walls made of chitin.

Chloroplast

Photosynthesis, which produces nourishment for the plant, takes place in chloroplasts. They contain chlorophyll, a green chemical that absorbs the light required for photosynthesis.

Vacuole

Vacuoles are cell organelles that are membrane-bound. Vacuoles are normally tiny in animal cells and help to sequester waste materials. Vacuoles in plant cells help to maintain water balance. A single vacuole can sometimes take up the majority of the internal space of a plant cell.

Prokaryotic cell structure

Prokaryotes, which include bacteria are much simpler than eukaryotes.

A bacterial cell has cytoplasm, a cell membrane, and a cell wall around it. Instead of a "real" nucleus, the cell possesses a single circular strand of DNA that is free to move around in the cytoplasm. Plasmids are tiny DNA rings that can be found inside bacterial cells in one or more instances.

Plasmids

Plasmids are DNA rings that are found in most bacterial organisms. These DNA rings are distinct from the rest of the chromosomal DNA in bacteria. They can be passed on to other bacteria in order to communicate genetic information. Plasmids are frequently the source of bacteria's genetic benefits, such as antibiotic resistance.

Capsule

Bacteria typically have capsules. Its sticky outer coating keeps the cell from drying out and aids bacteria in adhering to one other and surfaces. It is composed of polysaccharides (sugars).

Eukaryotes and Prokaryotes

What is cell structure?

Cell structure includes all the structures that make up a cell. Different cell types have different structures: Prokaryotes vary from eukaryotes. Plant cells have different structures than animal cells. And specified cells may have more or fewer organelles depending on the function of the cell.  

Which structure provides the most energy?

Though energy itself cannot be produced, energy-rich molecules can. This is mainly produced in the mitochondria in the process called aerobic respiration.  

What cell structures are found only in the eukaryotic cell?

Mitochondria, nucleus, chloroplasts (only plant cells), vacuoles.

What is the structure and function of the cell membrane?

This separates the cellular contents from the surrounding medium. The cell membrane is a single membrane and it allows certain substances to enter or leave the cell.

What structures are found in both plant and animal cells?

Mitochondria, cell membrane, nucleus, ribosomes, cytoplasm.