What are Prokaryotic Cells?
Unicellular organisms that don’t possess membrane-bound organelles, such as nucleus and mitochondria are known as prokaryotic cells. They are classified into two groups based on the constituents of the cell wall Bacteria as well as Archaea. In prokaryotes the cell membrane is a container for DNA, water-soluble proteins, and metabolites that reside in the cell’s cytoplasm. They do not have distinct compartments. Instead, microcompartments function as primitive organelles made by proteins shells.
Most prokaryotes range from 0.2 to 2 millimeters in size. There are four types of shapes that can be recognized in bacteria such as spherical (cocci) rod-shaped (bacilli) as well as spiral-shaped (spirochaete) and the comma-shaped (vibrio). Cyanobacteria also create large colonies, and myxobacteria with multicellular stage in their life cycles. Bacteria comprise an cytoskeleton that is primitive and a cell’s wall made by peptidoglycan which is the polymer that is linked to with carbohydrates as well as small proteins. Cell wall protects cells, helps maintain the shape and stops the cell from becoming dehydrated. Certain bacteria have an outer layer , called capsule, that is sticky and helps cells to adhere to the surface. Flagella, which is a wipe-like structure, aids in moving through the use of the motor that rotates. However fimbriae is a hair-like structure can also assist in attachment.
Certain bacteria are comprised of glycocalyx that protects the cell’s membrane. The cytoplasm of Bacterial is a gel-like substance that dissolves various organic molecules and cells’ components. Small 70S ribosomes are found for protein synthesis. Genomic DNA can be found in the nucleoid region within the cells. Bacteria are composed of one circular chromosome. Certain DNA fragments are located in the cytoplasm, as circular plasmids.
Both archaea and bacteria exhibit sexual reproduction through binary fission. Bacterial gene transfers occur in three ways such as transduction that is mediated by the bacteriophages, conjugation through plasmids, and natural transform. This is referred to as the horizontal transfer of genes. Pili are rod-shaped structures that enable the transfer of genes. The transfer of genes in archaeal cells occurs via cytoplasmic bridges.
Because prokaryotes have a wide variety, they get energy from inorganic compounds such as hydrogen sulfide as well as the photosynthesis process and organic compounds. They are also able to live in harsh environments, like Antarctica snow-covered surfaces hot springs, hot springs, and underground hydrothermal vents. Archaea are extremophilesthat live in extreme pH levels temperature, radiation and pH. Eukaryotes may be evolved from prokaryotes.
Prokaryotic cell features
Here’s a summary of what you could see in a prokaryotic bacteria cell.
- Nucleoid: A region in the middle of the cell which contains its DNA.
- Ribosomes: Ribosomes are accountable for the production of protein.
- Cell wall: Cell wall offers structure and protects against the external environmental. The majority of bacteria have a strong cell wall that is made of carbohydrates and proteins known as peptidoglycans.
- Cell membrane: Every prokaryote is equipped with a cell membrane, which is also called the plasma membrane. It is what separates the cell from its external environment.
- Capsule: Some bacteria possess an amorphous layer of carbohydrates which surround the cell wall , referred to as the capsule. The capsule assists the bacterium connect to the surfaces.
- Fimbriae: Fimbriae can be described as hair-like, thin structures which aid in cellular attachment.
- Pili: The Pili are rod-shaped structures that play multiple roles such as attachment and DNA transfer.
- Flagellas: Flagellas are small tail-like structures that aid in moving.
Examples of prokaryotes
Bacteria and archaea are the two types of prokaryotes.
What are Eukaryotic Cells?
Eukaryotes are multicellular organisms that contain organelles that are enclosed by membranes, specifically mitochondria, nucleus, the golgi apparatus as well as chloroplasts within plants. Multicellular eukaryotes have specific tissues created by different kinds of cells. Eukaryotes are classified under the four kingdoms of Kingdom Protista, Kingdom Plantae, Kingdom Fungi, and Kingdom Animalia.
A eukaryotic cell is bigger by size (10 bis 100 um) in comparison to prokaryotes. In eukaryotes there are a variety of cell types like animal cells, fungal cells, and plant cells are identified. Eukaryotic cytoskeleton is made up of microfilaments and microtubules as well as intermediate filaments. It plays an essential role in cell organization and shape. The fungi and plants both have cells with a wall composed of hemicellulose, cellulose, pectin and chitin.
Eukaryotic cells consist of various organelles that are membrane bound. The nucleus is surrounded by two membranes known as the nuclear envelope. The nuclear membrane is the endoplasmic retina (ER) which plays a role in maturation of proteins as well as transportation. Ribosomes are huge, up to at 80S in size, and are bound to ER. Ribosome-bound ER is also known as rough ER. Vesicles are involved in the transformation of different cells’ molecules like golgi bodies peroxizomes and lysosomes. Mitochondria is also protected by two bilayers of phospholipids. They transform sugar into ATPs for use for energy. Plant cells contain chloroplasts to aid in the photosynthesis.
Usually, eukaryotes comprise of multiple chromosomes within the nucleus. The chromosomes are linear and, most of the time, they have multiple copies, which is known as homologous. Eukaryotes reproduce sexually via meiosis or mitosis, sexually and union of gametes.
Eukaryotic cell features
Within a cell of the eukaryotic family, each membrane-bound component performs specific functions within the cell. Here’s a brief overview of the main elements of cells that are eukaryotic.
- Nucleus: The nucleus holds genetic information stored in chromatin form.
- Nucleolus: Located inside the nucleus, it is the part of the eukaryotic cell where ribosomal DNA is created.
- Plasma membrane: The plasma membrane an phospholipid bilayer which covers the entire cell as well as organelles inside.
- Cell wall or cytoskeleton: The cytoskeleton , also known as the cell wall gives structure, permits cell movement, and also plays part in the division of cells.
- Ribosomes: The Ribosomes are responsible for the synthesis of proteins.
- Mitochondria: Mitochondria, also called the cells’ powerhouses are the cells the cells that produce energy.
- Cytoplasm: It is the cell’s region in between the nuclear envelope as well as the plasma membrane.
- Cytosol: Cytosol is a gel-like substance inside the cell which houses the organelles.
- Endoplasmic Reticulum: Endoplasmic Reticulum is an organelle that is dedicated to maturation of proteins as well as transportation.
- Vesicles and vacuoles: These are membrane bound sacs that are involved in storage and transportation.
Other organelles that are common to numerous but not all eukaryotes comprise those of the Golgi organelle, the chloroplasts, and Lysosomes.
Examples of eukaryotes
Animals, plants, fungi, algae and protozoans are all eukaryotes.
Difference Between Prokaryotic And Eukaryotic Cells – Prokaryotic cells vs Eukaryotic Cells
| Characteristics | Eukaryotic Cell | Prokaryotic Cell |
| Nucleus | Present | Absent |
|---|---|---|
| Number of chromosomes | More than one | One–but not true chromosome: Plasmids |
| Cell Type | Usually multicellular | Usually unicellular (some cyanobacteria may be multicellular) |
| True Membrane bound Nucleus | Present | Absent |
| Example | Animals and Plants | Bacteria and Archaea |
| Genetic Recombination | Meiosis and fusion of gametes | Partial, undirectional transfers DNA |
| Lysosomes and peroxisomes | Present | Absent |
| Microtubules | Present | Absent or rare |
| Endoplasmic reticulum | Present | Absent |
| Mitochondria | Present | Absent |
| Cytoskeleton | Present | May be absent |
| DNA wrapping on proteins. | Eukaryotes wrap their DNA around proteins called histones. | Multiple proteins act together to fold and condense prokaryotic DNA. Folded DNA is then organized into a variety of conformations that are supercoiled and wound around tetramers of the HU protein. |
| Membrane-bound Organelles | Membrane-bound organelles such as mitochondria, chloroplast, ER and vesicles are present. | Prokaryotic cells do not have membrane-bound organelles. |
| Ribosomes | larger | smaller |
| Vesicles | Present | Present |
| Glycocalyx | Some eukaryotic cells that don’t have cell walls possess a glycocalyx. | Glycocalyx acts as a capsule. |
| Sexual Reproduction | Sexual reproduction happens through meiosis. | No sexual reproduction, horizontal gene transfer and recombination can be observed. |
| Cell Division | Cell division takes place through mitosis. | Cell division occurs through binary fission. |
| Golgi apparatus | Present | Absent |
| Chloroplasts | Present (in plants) | Absent; chlorophyll scattered in the cytoplasm |
| Flagella | Microscopic in size; membrane bound; usually arranged as nine doublets surrounding two singlets | Submicroscopic in size, composed of only one fiber |
| Cytoplasm | Eukaryotic cells have complex cytoskeleton with cytoplasmic streaming. | Prokaryotic cells are primitive cytoskeleton with no cytoplasmic streaming. |
| Permeability of Nuclear Membrane | Selective | not present |
| Plasma membrane with steroid | Yes | Usually no |
| Cell wall | Only in plant cells and fungi (chemically simpler) | Usually chemically complex |
| Vacuoles | Present | Present |
| Cell size | 10-100um | 1-10um |
| Examples | Protista, fungi, plants and animals are examples. | Bacteria and archaea are examples |
