The Human Cell

Cells are of two types: Prokaryotes are single-celled organisms , while eukaryotes can be either single-celled or multicellular. Prokaryotes include bacteria and archaea , two of the three domains of life.

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Prokaryotic cells were the first form of life on Earth, characterised by having vital biological processes including cell signaling. They are simpler and smaller than eukaryotic cells, and lack membrane-bound organelles such as a nucleus. The DNA of a prokaryotic cell consists of a single chromosome that is in direct contact with the cytoplasm.

The nuclear region in the cytoplasm is called the nucleoid. Most prokaryotes are the smallest of all organisms ranging from 0. Plants , animals , fungi , slime moulds , protozoa , and algae are all eukaryotic. These cells are about fifteen times wider than a typical prokaryote and can be as much as a thousand times greater in volume. The main distinguishing feature of eukaryotes as compared to prokaryotes is compartmentalization: Most important among these is a cell nucleus , [3] an organelle that houses the cell's DNA.

This nucleus gives the eukaryote its name, which means "true kernel nucleus ". All cells, whether prokaryotic or eukaryotic , have a membrane that envelops the cell, regulates what moves in and out selectively permeable , and 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 DNA , the hereditary material of genes , and RNA , containing the information necessary to build various proteins such as enzymes , the cell's primary machinery. There are also other kinds of biomolecules in cells.

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This article lists these primary cellular components , then briefly describes their function. The cell membrane , or 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 phospholipids , which are amphiphilic partly hydrophobic and partly hydrophilic.

Hence, the layer is called a phospholipid bilayer , or 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. The cytoskeleton acts to organize and maintain the cell's shape; anchors organelles in place; helps during endocytosis , the uptake of external materials by a cell, and cytokinesis , the 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 microfilaments , intermediate 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.

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But some of the subunit protein of intermediate filaments include vimentin , desmin , lamin lamins A, B and C , keratin multiple acidic and basic keratins , neurofilament proteins NF—L, NF—M. 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, [3] 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.

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4. International Human Cell Atlas Initiative | Wellcome Sanger Institute.

In humans the nuclear genome is divided into 46 linear DNA molecules called chromosomes , including 22 homologous chromosome pairs and a pair of sex chromosomes. Although the mitochondrial DNA is very small compared to nuclear chromosomes, [3] 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 genome , or stable, if it is.

Certain viruses also insert their genetic material into the genome.

Human Physiology/Cell physiology

There are several types of organelles in a cell. Some such as the nucleus and golgi apparatus are typically solitary, while others such as mitochondria , chloroplasts , peroxisomes and lysosomes can be numerous hundreds to thousands. The cytosol is the gelatinous fluid that fills the cell and surrounds the organelles. Many cells also have structures which exist wholly or partially outside the cell membrane. These structures are notable because they are not protected from the external environment by the semipermeable cell membrane. In order to assemble these structures, their components must be carried across the cell membrane by export processes.

Many types of prokaryotic and eukaryotic cells have a cell wall. The cell wall acts to protect the cell mechanically and chemically from its environment, and is an additional layer of protection to the cell membrane. Different types of cell have cell walls made up of different materials; plant cell walls are primarily made up of cellulose , fungi cell walls are made up of chitin and bacteria cell walls are made up of peptidoglycan.

A gelatinous capsule is present in some bacteria outside the cell membrane and cell wall.

Anatomy & Physiology Cell Structure and Function Overview for Students

The capsule may be polysaccharide as in pneumococci , meningococci or polypeptide as Bacillus anthracis or hyaluronic acid as in streptococci. Capsules are not marked by normal staining protocols and can be detected by India ink or methyl blue ; which allows for higher contrast between the cells for observation.

The DNA code contains instructions needed to make the proteins and molecules essential for our growth, development and health. Can you spare minutes to tell us what you think of this website? Facts In the Cell. Cells are the basic structures of all living organisms. Cells provide structure for the body, take in nutrients from food and carry out important functions. Cells group together to form tissues , which in turn group together to form organs , such as the heart and brain. Our cells contain a number of functional structures called organelles.

These organelles carry out tasks such as making proteins , processing chemicals and generating energy for the cell. The Chan Zuckerberg Science Initiative is thrilled to be part of this international collaborative effort.

What is a cell?

As with the Human Genome project, this initiative is likely to stimulate further innovations in Single Cell Genomics and related technologies, enabling us to delve even deeper into how cells function. In sickness and in health, cells are the fundamental units of life, and only by knowing our cells will we be able to fully comprehend the mechanisms of human disease. More details about the meeting and Human Cell Atlas initiative can be found at http: The first phase of the Human Cell Atlas is likely to involve pilot projects at institutions around the world, and the development of a white paper detailing the steps to create a full Human Cell Atlas.



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4. International Human Cell Atlas Initiative.

The phase 1 pilot projects already underway and being discussed this week have been organized through close coordination with research partners around the world. These are designed to generate insights into efficient and effective sampling and analysis strategies — which will inform the full-scale effort. These projects include surveys of:. Broad Institute of MIT and Harvard was launched in to empower this generation of creative scientists to transform medicine. The Broad Institute seeks to describe all the molecular components of life and their connections; discover the molecular basis of major human diseases; develop effective new approaches to diagnostics and therapeutics; and disseminate discoveries, tools, methods, and data openly to the entire scientific community.

Broad, the Broad Institute includes faculty, professional staff, and students from throughout the MIT and Harvard biomedical research communities and beyond, with collaborations spanning over a hundred private and public institutions in more than 40 countries worldwide. The Wellcome Trust Sanger Institute is one of the world's leading genome centres.

Through its ability to conduct research at scale, it is able to engage in bold and long-term exploratory projects that are designed to influence and empower medical science globally. Institute research findings, generated through its own research programmes and through its leading role in international consortia, are being used to develop new diagnostics and treatments for human disease.