A cell is the simplest unit of life and they are responsible for keeping an organism alive and functioning. This introduction to cells is the starting point for the area of biology that studies the various types of cells and how they work. There is a massive variety of different types of cells but they all have some common characteristics. Almost every different type of cell contains genetic materiala membrane and cytoplasm.
Cell membrane and membrane-bound organelles Subcellular components All cells, whether prokaryotic or eukaryotichave a membrane that envelops the cell, regulates what moves in and out selectively permeableand maintains the electric potential of the cell. Inside the membrane, the cytoplasm takes up most of the cell's volume.
All cells except red blood cells which lack a cell nucleus and most organelles to accommodate maximum space for hemoglobin possess DNAthe hereditary material of genesand RNAcontaining the information necessary to build various proteins such as enzymesthe cell's primary machinery.
There are also other kinds of biomolecules in cells. This article lists these primary cellular componentsthen briefly describes their function. Cell membrane Detailed diagram of lipid bilayer cell membrane The cell membraneor plasma membrane, is a biological membrane that surrounds the cytoplasm of a cell.
In animals, the plasma membrane is the outer boundary of the cell, while in plants and prokaryotes it is usually covered by a cell wall. This membrane serves to separate and protect a cell from its surrounding environment and is made mostly from a double layer of phospholipidswhich are amphiphilic partly hydrophobic and partly hydrophilic.
Hence, the layer is called a phospholipid bilayeror sometimes a fluid mosaic membrane. Embedded within this membrane is a variety of protein molecules that act as channels and pumps that move different molecules into and out of the cell.
Cell surface membranes also contain receptor proteins that allow cells to detect external signaling molecules such as hormones. Cytoskeleton A fluorescent image of an endothelial cell. Nuclei are stained blue, mitochondria are stained red, and microfilaments are stained green.
The cytoskeleton acts to organize and maintain the cell's shape; anchors organelles in place; helps during endocytosisthe uptake of external materials by a cell, and cytokinesisthe separation of daughter cells after cell division ; and moves parts of the cell in processes of growth and mobility.
The eukaryotic cytoskeleton is composed of microfilamentsintermediate filaments and microtubules. There are a great number of proteins associated with them, each controlling a cell's structure by directing, bundling, and aligning filaments.
The subunit of microtubules is a dimeric molecule called tubulin. Intermediate filaments are heteropolymers whose subunits vary among the cell types in different tissues.
But some of the subunit protein of intermediate filaments include vimentindesminlamin lamins A, B and Ckeratin multiple acidic and basic keratinsneurofilament proteins NF—L, NF—M. Genetic material Two different kinds of genetic material exist: Cells use DNA for their long-term information storage.
The biological information contained in an organism is encoded in its DNA sequence. Prokaryotic genetic material is organized in a simple circular bacterial chromosome in the nucleoid region of the cytoplasm. Eukaryotic genetic material is divided into different,  linear molecules called chromosomes inside a discrete nucleus, usually with additional genetic material in some organelles like mitochondria and chloroplasts see endosymbiotic theory.
A human cell has genetic material contained in the cell nucleus the nuclear genome and in the mitochondria the mitochondrial genome. In humans the nuclear genome is divided into 46 linear DNA molecules called chromosomesincluding 22 homologous chromosome pairs and a pair of sex chromosomes.
Although the mitochondrial DNA is very small compared to nuclear chromosomes,  it codes for 13 proteins involved in mitochondrial energy production and specific tRNAs.
Foreign genetic material most commonly DNA can also be artificially introduced into the cell by a process called transfection. This can be transient, if the DNA is not inserted into the cell's genomeor stable, if it is.
Certain viruses also insert their genetic material into the genome. There are several types of organelles in a cell. Some such as the nucleus and golgi apparatus are typically solitary, while others such as mitochondriachloroplastsperoxisomes and lysosomes can be numerous hundreds to thousands.
The cytosol is the gelatinous fluid that fills the cell and surrounds the organelles. The central and rightmost cell are in interphaseso their DNA is diffuse and the entire nuclei are labelled.
The cell on the left is going through mitosis and its chromosomes have condensed. A cell's information center, the cell nucleus is the most conspicuous organelle found in a eukaryotic cell. It houses the cell's chromosomesand is the place where almost all DNA replication and RNA synthesis transcription occur.
The nucleus is spherical and separated from the cytoplasm by a double membrane called the nuclear envelope. The nuclear envelope isolates and protects a cell's DNA from various molecules that could accidentally damage its structure or interfere with its processing.
This mRNA is then transported out of the nucleus, where it is translated into a specific protein molecule. The nucleolus is a specialized region within the nucleus where ribosome subunits are assembled. In prokaryotes, DNA processing takes place in the cytoplasm. Mitochondria are self-replicating organelles that occur in various numbers, shapes, and sizes in the cytoplasm of all eukaryotic cells.
Mitochondria multiply by binary fissionlike prokaryotes. Chloroplasts can only be found in plants and algae, and they capture the sun's energy to make carbohydrates through photosynthesis.structures inside an eukaryotic animal cell All cells, whether prokaryotic or eukaryotic, have a membrane that envelops the cell, separates its interior from its environment, regulates what moves in and out (selectively permeable), and maintains the electric potential of the cell.
Inside the membrane. Abstract: The bacterial flagellum is a complex molecular system with multiple components required for functional motility. Such systems are sometimes proposed as puzzles for evolutionary theory on the assumption that selection would have no function to act on until all components are in place.
This introduction to cells will take you through the basic structure of cells, the difference between prokaryotic and eukaryotic cells and you will learn about organelles. STRUCTURE OF A CELL Every cell is different but there is a basic structure that is common to all cells. Bacterial cells are prokaryotic.
Choose two structures of bacterial cells and explain how these structures allow bacteria to function as unicellular organisms.
We will write a custom essay sample on. Prokaryotic and Eukaryotic specifically for you. The animal cell is eukaryotic. Prokaryotic cells are usually smaller and simpler than eukaryotic cells.
They do not have a nucleus or other membrane-bound organelles. In prokaryotic cells, the DNA or genetic material which is located in the main part of the cell forms a single large circle that coils up on itself.
Prokaryotic cells. Eukaryotic cells. Similarities. Single celled organism. Can be solo celled or multi-celled: Contains cytoplasm, a gel-like substance consisting of cytosol and the cell's organelles. Contains cytoplasm: Contains (smaller) ribosomes to synthesise proteins Contains (larger) ribosomes to synthesise proteins.