Sél (biologi)
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Sél ngarupakeun unit struktural jeung fungsional sadaya organisme hirup. Sababaraha organisme, kayaning baktéri, unisélular, ngan diwangun ku sél nunggal. Organisme séjén, kayaning manusa, kaasup multisélular, (manusa mibanda kira 100 triliun sél). Tiori sél, munggaran dikembangkeun abad ka-19, ngunikeun yén sadaya organisme diwangun ku hiji atawa leuwih sél; sadaya sél datangna ti sél nu saméméhna geus aya; sadaya fungsi vital hiji organisme lumangsung jeroeun sél sarta yén sél ngandung informasi turunan nu dipikabutuh pikeun ngatur fungsi sél sarta pikeun neruskeun informasi ka sél wedalan salajengna.
Kecap sél asalna tina basa Latin cella, rohangan leutik. Ngaran ieu dipilih ku Robert Hooke sabab anjeunna nempo kamiripan antara sél cork jeung rohangan leutik.
Daptar eusi |
[édit] Ihtisar
[édit] Pasipatan sél
Unggal sél mangrupakeun éntitas nu mulasara diri: bisa ngasupkeun gizi, ngarobah gizi jadi énergi, migawé pungsi husus, sarta baranahan sakumaha perluna. Unggal sél neundeun paréntah-paréntah sorangan pikeun migawé tiap kagiatan-kagiatanana.
Sadaya sél mibanda sababaraha kabisa:
- Réproduksi ku cell division.
- Métabolisme, kaasup ngasupkeun bahan kasar, ngawangun komponén sél, "nyiptakeun" énergi, sarta ngaluarkeun byproduct. Lumangsungna fungsi sél gumantung kana kabisana pikeun nyerep jeung migunakeun énergi kimia nu diteundeun dina molekul organik. Énergi ieu diturunkeun tina jalur métabolik.
- Biosintésis protéin, mesin sél kayaning énzim. Sawatara sél mamalia ngandung nepi ka 10.000 rupa protéin.
- Némbal kana stimuli internal atawa éxternal kayaning parobahan temperatur, pH, atawa kadar gizi.
- Patali marga vésikel.
[édit] Tipe sél
Hiji cara pikeun ngagolongkeun sél, nyaéta naha maranéhna hirup nyorangan atawa ngagorombol. Aya rupa-rupa organisme, ti mimiti sél tunggal (disebut organisme unisélular) nu hirup sacara mandiri atawa ngabentuk koloni jeung sél lianna, nepi ka bentuk multisélulér nu masing-masing sélna babagi pancén sahingga teu bisa hirup sosoranganan. Awak multisélulér manusa ngandung kira 220 tipeu sél jeung jaringan.
Sél bisa digolongkeun kana dua kategori dumasar struktur internalna:
- sél prokariot nu strukturna basajan; aya dina organisme sél tunggal. Dina sistim tilu domain klasifikasi ilmiah, sél prokariot aya dina domain Archaea jeung Eubacteria.
- sél eukariot nu mibanda organél katut mémbranna masing-masing; organisme eukariot sél tunggal téh rupa-rupa, tapi nu ngabentuk koloni jeung multisélulér gé aya (kingdom multisélulér di antarana Animalia, Plantae, jeung Fungi nu sakabéhna eukariot).
[édit] Komponén sél
Sadaya sél boh prokariot atawa eukariot mibanda mémbran, nu ngabungkus sél, misahkeun interiorna tina lingkungan sabudeureunana, sacara ketat ngontrol naon nu asup jeung kaluar sarta mulasara poténsi listrik sél. Di jero mémbran aya sitoplasma (zat nu ngeusian ampir sakabéh eusi sél) nu asin. Sadaya sél mibanda DNA, bahan wawarisan gén, jeung RNA, nu ngandung informasi nu dipikabutuh pikeun ngéxprésikeun rupa-rupa protéin kayaning énzim, mesin utama sél. Sajeroeun sél dina rupa-rupa wanci aya rupa-rupa biomolekul séjén. Artikel ieu bakal ngabahas sacara ringkes komponén-komponén utama ieu lajeng diteraskeun ku dadaran ringkes pungsina.
[édit] Mémbran sél - jakét panyalindung sél
Artikel utama: mémbran sél
Wates luar sél eukariot disebut mémbran plasma, sedengkeun di prokariot ilahar disebut mémbran sél. Mémbran ieu pikeun misahkeun sarta panyalindungan pikeun sél ti lingkungan sabudeureunana, diwangun utamana tina lapis ganda lipid (molekul sarupa lemak) jeung protéin. Nu narapel na éta mémbran nyaéta rupa-rupa molekul nu meta salaku torowongan jeung kompa, nu mindahkeun molekul-molekul ka jeung ti sél.
[édit] Sitoskeleton - rorongkong sél
Artikel utama: Sitoskeleton
Sitoskeleton nyaéta komponén sél nu penting, pajeulit, sakaligus dinamis, nu meta pikeun nyusun/ngatur sarta mertahankeun bentuk sél; nyangsangkeun organél dina tempat samistina; mantuan nalika éndositosis, ngasupkeun bahan luar ku sél; sarta mindahkeun bagian-bagian sél dina prosés tumuwuh jeung motiliti. Aya loba pisan protéin nu patali jeung sitoskeleton, nu masing-masing ngatur struktur sél ku ngarahkeun, ngagulungkeun, sarta nyambungkeun filamén.
[édit] Sitoplasma - rohangan jero sél
Artikel utama: Sitoplasma
Jeroeun sél aya rohangan badag nu dieusi cairan nu disebut sitoplasma, kadang disebut sitosol. Na prokariot, rohangan ieu rélatif teu kabagi-bagi. Na eukariot, sitosol mangrupa "sop" tempat pagalona sagala organél. It is also the home of the cytoskeleton. The cytosol contains dissolved nutrients, helps break down waste products, and moves material around the cell through a process called cytoplasmic streaming. The nucleus often flows with the cytoplasm changing its shape as it moves. The cytoplasm also contains many salts and is an excellent conductor of electricity, creating the perfect environment for the mechanics of the cell. The function of the cytoplasm, and the organelles which reside in it, are critical for a cell's survival.
[édit] Bahan genetik
Aya dua rupa bahan genetik: asam déoxiribonukléat (DNA) jeung asam ribonukléat (RNA). Organisme lolobana diwangun tina DNA, tapi aya sababaraha virus nu mibanda RNA salaku bahan genetikna. Informasi biologis nu dikandung ku organisme disandikeun dina runtuyan DNA atawa RNAna.
Bahan genetik prokariot diatur dina struktur sirkular basajan nu aya na sitoplasma. Bahan genetik eukariot leuwih pajeulit sarta dibagi kana unit diskrét nu disebut gén. Bahan genetik manusa dijieun tina dua komponén béda: génom inti jeung génom mitokondria. Génom inti kabagi kana 24 molekul DNA liniér, nu masing-masing dikandung dina kromosom nu béda. Génom mitokondria nyaéta molekul DNA sirkular nu misah ti DNA inti. Najan génom mitokondria leutik pisan, tapi nyandi sababaraha protéin nu penting pisan.
[édit] Organél
Artikel utama: Organél
Awak manusa ngandung pirang-pirang organ, kayaning jantung, burih, ginjal, nu masing-masing ngajalankeun pungsi nu béda. Sél ogé mibanda sakumpulan "organ leutik" nu disebut organél, nu diluyukeun atawa dihususkeun mibanda hiji atawa leuwih pungsi penting. Organél ngan aya na eukariot jeung salawasna dikuriling ku mémbran panyalindung.
- Inti sél - puseur sél: Inti sél is the most conspicuous organelle found in a eukaryotic cell. It houses the cell's chromosomes and is the place where almost all DNA replication and RNA synthesis occur. The nucleus is spheroid in shape and separated from the cytoplasm by a 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. During processing, DNA is transcribed, or synthesized, into a special RNA, called mRNA. This mRNA is then transported out of the nucleus, where it is translated into a specific protein molecule. In prokaryotes, DNA processing takes place in the cytoplasm.
- Ribosom - mesin produksi protéin: Ribosoms are found in both prokaryotes and eukaryotes. The ribosome is a large complex composed of many molecules, including RNAs and proteins, and is responsible for processing the genetic instructions carried by an mRNA. The process of converting an mRNA's genetic code into the exact sequence of amino acids that make up a protein is called translation. Protein synthesis is extremely important to all cells, and therefore a large number of ribosomes—sometimes hundreds or even thousands—can be found throughout a cell.
- Mitokondria jeung kloroplas - generator: Mitokondria are self-replicating organelles that occur in various numbers, shapes, and sizes in the cytoplasm of all eukaryotic cells. As mentioned earlier, mitochondria contain their own genome that is separate and distinct from the nuclear genome of a cell. Mitochondria play a critical role in generating energy in the eukaryotic cell, and this process involves a number of complex metabolic pathways. Chloroplasts are similar to mitochondria but are found only in plants.
- Rétikulum éndoplasma jeung awak Golgi - ménéjer makromolekul:: The endoplasmic reticulum (ER) is the transport network for molecules targeted for certain modifications and specific destinations, as compared to molecules that will float freely in the cytoplasm. The ER has two forms: the rough ER and the smooth ER. The rough ER is labeled as such because it has ribosomes adhering to its outer surface, whereas the smooth ER does not. Translation of the mRNA for those proteins that will either stay in the ER or be exported (moved out of the cell) occurs at the ribosomes attached to the rough ER. The smooth ER serves as the recipient for those proteins synthesized in the rough ER. Proteins to be exported are passed to the Golgi apparatus, sometimes called a Golgi body or Golgi complex, for further processing, packaging, and transport to a variety of other cellular locations.
- Lisosom jeung peroxisom - the cellular digestive system: Lysosomes and peroxisomes are often referred to as the garbage disposal system of a cell. Both organelles are somewhat spherical, bound by a single membrane, and rich in digestive enzymes, naturally occurring proteins that speed up biochemical processes. For example, lysosomes can contain more than three dozen enzymes for degrading proteins, nucleic acids, and certain sugars called polysaccharides. Here we can see the importance behind compartmentalization of the eukaryotic cell. The cell could not house such destructive enzymes if they were not contained in a membrane-bound system.
[édit] Anatomi sél
[édit] Sél prokariot
Prokariot dibédakeun ti eukariot dumasar susunan intina, hususna ku teu ayana mémbran inti. Prokariot ogé teu boga organél-organél nu has sél eukariot. Fungsi organélna lolobana, kayaning mitokondria, kloroplas, jeung awak Golgi, diwengku ku mémbran plasma prokariot. Svl prokariot mibanda tilu wewengkon arsitéktural: appendages called flagella and pili—proteins attached to the cell surface; a cell envelope consisting of a capsule, a cell wall, and a plasma membrane; and a cytoplasmic region that contains the cell genome (DNA) and ribosomes and various sorts of inclusions. Other differences include:
- The cytoplasm of prokaryotes (the liquid which makes up most of the cell volume) is diffuse and granular due to ribosomes (protein factories) floating in the cell.
- The plasma membrane (a phospholipid bilayer) separates the interior of the cell from its environment and serves as a filter and communications beacon.
- Most prokaryotes have a cell wall (some exceptions are Mycoplasma (a bacterium) and Thermoplasma (an archaeon)). It consists of peptidoglycan in bacteria, and acts as an additional barrier against exterior forces. It also prevents the cell from "exploding" from osmotic pressure against a hypotonic environment.
- A prokaryotic chromosome is usually a circular molecule (an exception is that of the bacterium Borrelia burgdorferi, which causes Lyme disease). Even without a real nucleus, the DNA is somehow condensed in a nucleoid. Prokaryotes can carry extrachromosomal DNA elements called plasmids, which are usually circular. Plasmids can carry additional functions, such as antibiotic resistance.
- Some prokaryotes have flagella which enable them to move actively instead of passively drifting.
[édit] Sél eukariot
Sél eukariot ukuranana kurang leuwih sapuluh kalieun sél prokariot sarta eusina bisa nepi ka 1000 kalieunana. Bébéda utama antara prokariot jeung eukariot nyaéta sél eukariot mah ngandung kompartemén nu napel na mémbran tempat lumangsungna kagiatan métabolik husus. Utamana inti, a membrane-delineated compartment that houses the eukaryotic cell’s DNA. It is this nucleus that gives the eukaryote—literally, true nucleus—its name. Eukaryotic organisms also have other specialized structures, performing dedicated functions, the aforementioned organelles.. Other differences include:
- The cytoplasm of eukaryotes does not appear as granular as that of prokaryotes, since an important part of the ribosomes are bound to the endoplasmic reticulum.
- The plasma membrane resembles that of prokaryotes in function, with minor differences in the setup. Cell walls may or may not be present.
- The eukaryotic DNA is organized in one or more linear molecules, called chromosomes, which are highly condensed (e.g. folded around histones). All chromosomal DNA is stored in the cell nucleus, separated from the cytoplasm by a membrane. Some eukaryotic organelles can contain some DNA.
- Eukaryotes can become mobile using cilia or flagella. The flagella are more complex than those of prokaryotes.
| Prokariot | Eukariot | |
|---|---|---|
| typical organisms | bacteria | protists, fungi, plants, animals |
| typical size | ~ 1-10 µm | ~ 10-100 µm (sperm cells, apart from the tail, are smaller) |
| type of nucleus | nucleoid region; no real nucleus | real nucleus with double membrane |
| DNA | circular (usually) | linear molecules (chromosomes) with histone proteins |
| RNA-/protein-synthesis | coupled in cytoplasm | RNA-synthesis inside the nucleus protein synthesis in cytoplasm |
| ribosomes | 50S+30S | 60S+40S |
| cytoplasmatic structure | very few structures | highly structured by intercellular membranes and a cytoskeleton |
| cell movement | flagella made of flagellin | flagella and cilia made of tubulin |
| mitochondria | none | one to several dozen (though some lack mitochondria) |
| chloroplasts | none | in algae and plants |
| organization | usually single cells | single cells, colonies, higher organisms with specialized cells |
| cell division | Binary fission (simple division) | Mitosis (core division) Cytokinesis (cytoplasmatic division) |
| Typical animal cell | Typical plant cell | |
|---|---|---|
| Organelles |
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| Additional structures |
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[édit] Fungsi sél
[édit] Pertumbuhan jeung métabolisme sél
Artikel utama: Pertumbuhan sél, Métabolisme sél
Between successive cell divisions cells grow through the functioning of cellular metabolism. Cell metabolism is the process by which individual cells process nutrient molecules. Metabolism has two distinct divisions; catabolism, in which the cell breaks down complex molecules to produce energy and reducing power, and anabolism, where the cell uses energy and reducing power to construct complex molecules and perform other biological functions. Complex sugars consumed by the organism can be broken down into a less chemically complex sugar molecule called glucose. Once inside the cell, glucose is broken down to make adenosine triphosphate (ATP), a form of energy, via two different pathways.
The first pathway, glycolysis, requires no oxygen and is referred to as anaerobic metabolism. Each reaction is designed to produce some hydrogen ions that can then be used to make energy packets (ATP). In prokaryotes, glycolysis is the only method used for converting energy. The second pathway, called the Kreb's cycle, or citric acid cycle, occurs inside the mitochondria and is capable of generating enough ATP to run all the cell functions.
[édit] Nyieun sél anyar
Main article: Cell division
Within the nucleus of the cell (light blue), genes (DNA, dark blue) are transcribed into RNA. This RNA is then subject to post-transcriptional modification and control, resulting in a mature mRNA (red) that is then transported out of the nucleus and into the cytoplasm (peach), where it undergoes translation into a protein. mRNA is translated by ribosomes (purple) that match the three-base codons of the mRNA to the three-base anti-codons of the appropriate tRNA. Newly synthesized proteins (black) are often further modified, such as by binding to an effector molecule (orange), to become fully active.
Cell division involves a single cell (called a mother cell) dividing into two daughter cells. This leads to growth in multicellular organisms (the growth of tissue) and to procreation (vegetative reproduction) in unicellular organisms. Prokaryotic cells divide by binary fission. Eukaryotic cells usually undergo a process of nuclear division, called mitosis, followed by division of the cell, called cytokinesis. A diploid cell may also undergo meiosis to produce haploid cells, usually four. Haploid cells serve as gametes in multicellular organisms, fusing to form new diploid cells. DNA replication, or the process of duplicating a cell's genome, is required every time a cell divides. Replication, like all cellular activities, requires specialized proteins for carrying out the job.
[édit] Sintésis protéin
Artikel utama: Biosintésis protéin
Sintésis protéin nyaéta prosés nalika sél ngawangun protéin. Transkripsi DNA nujul ka sintésis molekul RNA utusan (Ing. messenger RNA, mRNA) tina citakan DNA. Prosés ieu mirip pisan jeung réplikasi DNA. Sanggeus mRNA dijieun, molekul protéin anyar mitembeyan disintésis ngaliwatan prosés translasi.
Mesin sélular nu boga tanggung jawab dina sintésis protéin nyaéta ribosom, nu diwangun ku RNA struktural jeung kira 80 rupa protéin. Nalika ribosom tepung jeung mRNA, mangka prosés translasi mRNA jadi protéin dimimitian. Ribosom nampa a new transfer RNA, or tRNA—the adaptor molecule that acts as a translator between mRNA and protein—bearing an amino acid, the building block of the protein. Another site binds the tRNA that becomes attached to the growing chain of amino acids, forming the a polypeptide chain that will eventually be processed to become a protein.
[édit] Sasakala sél
Sasakala sél nu patali pisan jeung sasakala hirup, kungsi jadi salasahiji hambalan pangpentingna dina évolusi hirup. Lahirna sél nandaan jalan ti kimia prébiotik ka kahirupan biologis.
[édit] Sasakala sél munggaran
Mun hirup disawang tina jihat réplikator, nyaéta molekul DNA dina organisme, sél nyumponan dua kaayaan fundaméntal: pangjaga ti lingkungan luar sarta ngawadahan aktivitas biologis. The former condition is needed to maintain the fragile DNA chains stable in a varying and sometimes aggressive environment, and may have been the main reason for which cells evolved. The latter is fundamental for the evolution of biological complexity. If freely-floating DNA molecules that code for enzymes that are not enclosed into cells, the enzymes that advantage a given DNA molecule (for example, by producing nucleotides) will automatically advantage the neighbouring DNA molecules. This might be viewed as "parasitism by default". Therefore the selection pressure on DNA molecules will be much lower, since there is not a definitive advantage for the "lucky" DNA molecule that produces the better enzyme over the others: all molecules in a given neighbourhood are almost equally advantaged.
If all the DNA molecule is enclosed in a cell, then the enzymes coded from the molecule will be kept close to the DNA molecule itself. The DNA molecule will directly enjoy the benefits of the enzymes it codes, and not of others. This means other DNA molecules won't benefit from a positive mutation in a neighbouring molecule: this means that positive mutations give immediate and selective advantage to the replicator bearing it, and not on others. This is thought to have been the one of the main driving force of evolution of life as we know it. (Note. This is more a metaphor given for simplicity than complete accuracy, since the earliest molecules of life, probably up to the stage of cellular life, were most likely RNA molecules, acting both as replicators and enzymes: see RNA world hypothesis . But the core of the reasoning is the same.)
Biochemically, cell-like spheroids formed by proteinoids are observed by heating amino acids with phosphoric acid as a catalyst. They bear much of the basic features provided by cell membranes. Proteinoid-based protocells enclosing RNA molecules could (but not necessarily should) have been the first cellular life forms on Earth.
[édit] Sasakala sél eukariot
Évolusi sél eukariot sigana ngaliwatan prosés simbiosis sél-sél prokariot. It is almost certain that DNA-bearing organelles like the mitochondria and the chloroplasts are what remains of ancient symbiotic oxygen-breathing bacteria and cyanobacteria, respectively, where the rest of the cell seems to be derived from an ancestral archaean prokaryote cell. There is still considerable debate on if organelles like the hydrogenosome predated the origin of mitochondria, or viceversa : see the hydrogen hypothesis for the origin of eukaryotic cells.
[édit] Sajarah
- 1632-1723: Antony van Leeuwenhoek kalawan otodidak nyieun lénsa jeung mikroskop, sarta ngagambar protozoa, kayaning Vorticella tina cihujan jeung baktéri tina bahamna sorangan.
- 1665 : Robert Hooke manggih sél dina cork, lajeng dina jaringan tutuwuhan migunakeun mikroskop.
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- ...I could exceedingly plainly perceive it to be all perforated and porous, much like a Honeycomb...these pores or cells, were not very deep, but consisted of a great many little boxes... – Hooke describing his observations on a thin slice of cork.
- 1839 : Theodor Schwann jeung Matthias Jakob Schleiden nu ngabuktikeun prinsip yén tutuwuhan jeung sato diwangun ku sél-sél, jinek yén sél mangrupakeun unit struktur jeung tumuwuh nu ilahar, salajengna ngedalkeun Tiori sél.
- Kapercayaan yén bentuk kahirupan bisa lumangsung sacara ngadadak kitu baé (spontan, generatio spontanea) dibantah ku Louis Pasteur (1822-1895).
- Rudolph Virchow nyebutkeun yén sél salawasna borojol tina pameulahan sél (omnis cellula ex cellula).
- 1931: Ernst Ruska nyieun mikroskop transmisi éléktron di Universitas Berlin. Taun 1935 anjeunna geus nyieun mikroskop éléktron nu résolusina dua kalieun mikroskop cahaya, revealing previously unresolvable organelles.
- 1953: Watson jeung Crick munggaran ngawawarkeun struktur hélix ganda DNA (Pébruari 28).
- 1981: Lynn Margulis medalkeun Symbiosis in Cell Evolution nu ngadadarkeun tiori éndosimbiosis.
[édit] Jejer nu patali
- Biologi
- Biologi sél
- Cell division
- Mitosis
- Sitokinesis
- Fisi binér
- Cariology, nyaéta ulikan ngeunaan inti sél.
- Sitotoxisiti
- Sél tutuwuhan
- Sél sato
- Sél supa
- Sél prokariot
- Sél eukariot
- Sél manusa
- How to prepare an onion cell slide
- Tipe sél
- Syncytium
- Kultur sél
[édit] Rujukan
[édit] Sumber
- Artikel ieu ngandung bahan-bahan ti Science Primer nu medal ti NCBI, nu, salaku publikasi pamaréntah AS, aya dina domain publik (1).
