Komposisi Cairan Tubuh

Komposisi cairan ekstra sel dan intra sel berbeda satu sama lainnya. Komposisi utama cairan tubuh adalah air dan elektrolit. Elektrolit terdiri atas kation (ion bermuatan positif) dan anion (ion bermuatan negatif). Pada cairan tubuh jumlah anion dan kation harus sama untuk mempertahankan "elektrical neutrality". hal ini berarti bahwa jumlah partikel kation dan anion harus sama. Plasma protein misalnya, mempunyai beberapa muatan negatif, sehingga beberapa kation harus ada untuk mengimbangi tiap molekul protein.

Pertukaran Cairan Tubuh

Pemasukan
Cairan tubuh sebagian besar berasal dari minuman dan makanan yang dimakan sehari-hari dan sebagian kecil berasal dari proses oksidasi hidrogen di dalam makanan yang jumlahnya berkisar antara 150 sampai 250 ml/hari, tergantung dari kecepatan metabolisme. Jumlah cairan yang masuk, termasuk hasil sintesa di dalam tubuh, berkisar 2300 ml/hari.

Pengukuran Volume Cairan Tubuh

Cairan tubuh total
Untuk mengukur cairan tubuh total dipakai tritium radioaktif (H3) yang merupakan isotop yang tidak stabil dengan waktu paruh biologis 10 hari dan waktu paruh fisik 12 tahun. H3 akan berdifusi kedalam cairan tubuh total dalam beberapa jam sesudah disuntikkan secara intravena, dan dengan prinsip dilusi, volume cairan tubuh total dapat dihitung. Deuterium (H2) yang merupakan isotop yang stabil juga dapat dipergunakan untuk mengukur cairan tubuh total.

Ukuran dan Jumlah Cairan Tubuh

Pada seorang lelaki muda, 18% BB (Berat Badan) adalah protein, 15% lemak, 7% mineral dan sisanya 60% cairan tubuh total (TBW).
Jumlah cairan intra sel sekitar 40% BB sedang cairan ekstra sel 20% BB. Cairan ekstra sel terdiri dari cairan interstitel 15% BB sementara plasma darah 5% BB, adapun cairan transeluller karena sangat sedikit diabaikan jumlahnya. Volume darah total diperkirakan 8% BB.
Jumlah cairan tubuh total (TBW) bervariasi dan dipengaruhi oleh faktor umur, jenis kelamin dan intensitas kegemukan (obesitas). Makin tua seseorang TBW-nya makin berkurang. Sementara itu makin banyak kandungan lemak mengakibatkan TBW berkurang, sebab jaringan lemak sangat sedikit mengandung air. Pada pria TBW berkisar 55-60% BB sedang pada wanita TBW 50-55% BB, karena umumnya pada wanita kandungan lemaknya lebih banyak dari pria.

Cairan Tubuh pada Manusia

Sel-sel yang menyusun tubuh berada pada “lautan cairan” yang merupakan cairan ekstra sel. Dari cairan inilah sel-sel tubuh mengambil oksigen dan makanan serta membuang kedalam cairan tersebut sisa-sisa metabolismenya.
Cairan ekstra sel terdiri dari 3 komponen, yaitu cairan interstitel, plasma darah, dan cairan transeluller (cairan dalam rongga khusus). Plasma darah bersama komponen seluller darah (terutama sel darah merah) berada dalam pembuluh darah dan bersama-sama menentukan volume darah total. Cairan interstitel adalah bagian cairan ekstra sel yang berada di luar sistem pembuluh darah (vasculer) yang berbatasan (membasahi) dengan sel-sel tubuh. Cairan transeluler adalah cairan yang terdapat pada rongga khusus seperti dalam pleura, perikardium, cairan sendi, cairan serebropinalis dsb. Cairan ekstra sel ini bersama dengan cairan intra sel membentuk cairan tubuh total cairan ekstra sel dan 2/3 cairan intra sel.

Sistem Transport Membran

Permeabilitas membrane sel bersifat sangat selektif. Arus pergerakan molekul dan ion antara sel dan lingkungan sekitarnya diatur dengan tepat oleh berbagai system transport yang spesifik. System transport ini berperan dalam :

1.       Mengatur volume dan komposisi cairan tubuh

2.       Mengatur  masuknya bahan yang dibutuhkan seperti glukosa, asam amino dan pengeluaran bahan yang tidak dibutuhkan oleh sel misalnya bahan-bahan toksik.

3.       Menimbulkan gradient konsentrasi untuk ion-ion tertentu yang berperan dalam eksitabilitas sel saraf dan otot.

Proses transport melalui membrane terjadi melalui 2 mekanisme,yaitu transport aktif dan transport pasif. Transport pasif terjadi tanpa memerlukan energy sedangkan transport aktif memerlukan energy. Yang termasuk transport pasif adalah :

a.       Difusi sederhana

b.      Transport dengan fasilitas

c.       Transport lewat ion channel

Pada difusi sederhana molekul akan bergerak dari daerah yang konsentrasinya tinggi ke konsentrasi rendah. Misalnya oksigen yang banyak di luar sel akan berdifusi masuk ke dalam sel. Difusi sederhana sangat ditentukan oleh kelarutan suatu bahan dalam lemak. Apabila suatu bahan larut dalam lemak, maka bahan tersebut akan lebih mudah berdifusi disbanding bahan yang larut dalam air. Kecepatan difusi suatu zat dipengaruhi oleh beberapa factor :

1.       Permeabilitas membrane sel (ditentukan oleh ketebalan membrane, kelarutan suatu bahan dalam lemak, jumlah channel, temperature, dan diameter molekul)

2.       Perbedaan konsentrasi molekul/ion

3.       Perbedaan tekanan pada kedua sisi membran

4.       Perbedaan potensial listrik pada kedua sisi membrane

Luas permukaan membrane.
Transport dengan cara difusi fasilitas mempunyai mempunyai perbedaan dengan difusi sederhana yaitu difusi fasilitas terjadi melalui carrier spesifik dan difusi ini mempunyai kecepatan transport maksimum (Vmax). Suatu bahan yang akan ditransport lewat cara ini akan terikat lebih dahulu dengan carrier protein yang spesifik dan ikatan ini akan membuka channel tertentu untuk membawa ikatan ini kedalam sel. Jika konsentrasi bahan ini terus ditingkatkan, maka jumlah carrier akan habis berikatan dengan bahan tersebut sehingga pada saat itu kecepatan difusi menjadi maksimal (Vmax). Pada difusi sederhana hal ini tidak terjadi,makin banyak bahan kecepatan transport bahan makin meningkat tanpa batas.
Transport ion channel khusus bagi ion-ion yang sulit di transport secara difusi akibat muatan listriknya. Ion channel ini mempunyai sifat yang sangat selektif dan terbukanya channel tesebut akibat potensial listrik sepanjang membrane sel dan melalui ikatan channel dengan hormone atau neurotransmitter
Beberapa ion harus di pertahankan jumlahnya lebih besar di luar sel (misalnya Natrium) atau Kalium harus dipertahankan lebih banyak dalam sel. Hal ini tentunya tidak tercapai dengan transport pasif, sebab transport pasif hanya akan menyeimbangkan konsentrasi ion-ion di dalam dan di luar sel. Untuk itu perlu transport aktif yang memakai energy untuk melawan perbedaan konsentrasi, misalnya transport Na dari dalam sel ke luar sel lewat Na pump. Transport aktif terbagi atas transport aktif primer dan sekunder. Transport aktif sekunder juga terdiri atas co-transport dan counter transport (exchange).
Transport aktif primer memakai energi langsung dari ATP, misalnya pada Na-K pump dan Ca pump. Pada Na-K pump, 3 Na akan dipompa keluar sel sedang 2 K akan dipompa kedalam sel. Pada Ca pump, Ca akan di pompa keluar sel agar konsentrasi Ca dalam sel rendah.

MEMBRAN SEL

Sel dan organel yang terdapat dalam sel, dilapisi oleh membrane yang terutama tersusun oleh lemak dan protein. Lemak yang terdapat dalam membran memungkinkan membran  berfungsi sebagai barrier yang membatasi pergerakan molekul yang dapat larut dalam air melewati membrane . Molekul protein yang dapat menembus membran sel, berfungsi sebagai tempat lewatnya bahan-bahan tertentu. Selain itu protein yang terdapat pada permukaan membrane seperti reseptor, enzim dan pump (pompa) masing-masing berfungsi sebagai katalisator dan pompa yang melakukan transport aktif ion-ion tertentu kedalam maupun keluar sel.

Selain berfungsi sebagai barrier yang permeabilitasnya selektif, membrane sel juga berfungsi mengatur arus informasi antara sel dengan lingkungan sekitarnya. Hal ini dimungkinkan oleh adanya reseptor yang spesifik pada permukaanmembran sel.

Ikatan suatu substrat dengan reseptornya yang spesifik pada permukaan membrane sel akan menyebabkan terjadinya transduksi  sinyal yang selanjutnya akan mengaktifkan berbagai mata rantai reaksi biokimia dalam sel, sehingga dapat disimpulkan bahwa membrane sel berfungsi dalam proses komunikasi antara sel.

Membrane sel komposisinya terutama terdiri dari protein 55%, lemak 42% dan karbohidrat 3%, tetapi persentase ini bervariasi pada berbagai sel. Terdapak 3 jenis lemak yang terdapat pada membrane sel yaitu  fosfolipid, kolsterol, dan glikolipid. Pada membrane sel fosfolipid membentuk 2 lapisan (lipid bilayer) dimana lapisan hidrofilik terletak pada bagian luar (berhadapan dengan cairan ekstrasel) dan bagian dalam sel (berhadapan dengan sitoplasma), sementara bagian hidrofobik terletak antara kedua lapisan hidrofilik ini.

Protein pada membrane sel terbagi atas protein integral dan protein perifer. Sebagian besar protein integral membentuk channel pada membrane dan membentuk pompa sebagai tempat lewatnya ion-ion. Sementara protein perifer biasanya hanya terikat dengan protein integral atau dengan bagian hidrofilik membrane, dan umumnya protein perifer ini membentuk enzim.

Protein pada membrane umumnya dalam bentuk glikolipid dan glikoprotein. Karbohidrat ini berfungsi meningkatkan hidrofilisitas lemak dan protein, mempertahankan stabilitas membrane oleh adanya struktur yang disebut glikokaliks. Glikokaliks akan berinteraksi dengan glikokaliks sel lain sehingga berfungsi melekatkan satu sel dengan sel lainnya. Glikolipid yang terdapat pada membrane sel juga berperan dalam reaksi imunologis, dengan membentuk antigen dalam darah.

Cytoplasm and Organelles

Tues is not simply a small bag containing liquids, enzymes and chemicals, but also contain physical structures are so perfectly composed, called organelles and is essential for cell function. For example, without the mitochondria, it is more than 95% of energy supplied by the cell would soon disappear.
Cytoplasm filled with particles and organelles either small or large, with sizes from several nanometers to a few micrometer. Part of the cytoplasm of clear liquid in which particles called didispersikan cytosol containing mainly proteins, electrolytes, glucose and less fat soluble mixture. Part of the cytoplasm immediately below the cell membrane Barada often contain microfilaments, microfilaments are mainly composed of actin fibrialle. This is a booster material resembling the cell membrane half-solid gel (semisolid). Cytoplasmic region called the cortex or ektoplasma. Cytoplasm which is located between the cortex and nuclear membrane and the liquid is called reticulum.
In the cytoplasm is spread various materials, namely neutral fat globules, glycogen granules, ribosomes, secretory granules and five kinds of the most important organelles endoplasmic reticulum, Golgi apparatus, mitochondria, lysosomes and peroxisomes.

1. Nucleus of the cell (nucleus)
Cell nucleus is a central regulator of cell activity. Nucleus contains large amounts of DNA called genes. Genes found on chromosome function to regulate RNA synthesis characteristics of the protein needed for a variety of enzymatic activities, and regulate cell reproduction. Cell nucleus consisting of nucleolus, nucleus nukleoplasma and cell membranes.
Membrane in the cell nucleus consisting of 2 layers, where the outer layer associated with a diameter large enough to pass by the protein molecules synthesized in the cell nucleus.
In the cytoplasm there that do not contain nucleoli membrane. Nucleolus contains many RNA and protein and increases in size when the current synthesize proteins. Genes regulate protein synthesis and RNA and save it in the nucleolus. RNA and protein will be in transport out into the cytoplasm through the porus is at the core of the cell membrane.
DNA found on the chromosome is double stranded structure (double helix) which consists of:
1. Phosphate
2. Group pentose (sugar) that is deoxyribose
3. Purine bases nitrogen namely: adenine and guanine; pirimidine: sitosine and thymine
And pentose phosphate groups to form the physical structure of DNA, whereas the 4 different bases was carried genetic information. In DNA, adenine always binds with thymine and guanine always bound to sitosine.
Because DNA is located in the cell nucleus was almost all cell activity occurs in the cytoplasm, the RNA formed which can diffuse into the cytoplasm to regulate specific protein synthesis. RNA formation process is governed by the DNA transcription process.
Differences RNA and DNA structures is that in RNA is ribose pentosenya, and the group bonded with the base adenine is uracil (no thymine). RNA formation process occurs under the influence of the enzyme RNA polymerase. After the RNA formed will be released nukleoplasma. There are 3 types of RNA are formed by the DNA, where each type of RNA has a different function, namely:
1. Messenger RNA (mRNA), working with the genetic code to the cytoplasm to regulate protein synthesis.
2. Transfer RNA (tRNA) to transport amino acids to the ribosome for protein molecules are used up.
3. Ribosomal RNA (rRNA) to form the ribosome along with 75 other proteins.
If RNA molecules into contact with ribosomes, the protein molecules will be formed along the ribosome. Ribosome formation process is called translation. So in the chemical process occurs ribosome preparation of amino acids to form proteins.

2. Endoplasmic reticulum (ER)
RE is an organelle that has a membrane surface is very broad. RE consists of vesicles and tabulus that serves as the synthesis of proteins and fats. RE membrane surface that contains no granules called ribosomes and granuler RE / Rough RE and some do not contain granules called agranuler RE / RE smooth. ribosomes contained in RE granuler served as protein synthesis, was working for agranuler RE synthesis and metabolism of fatty acids and phospholipids.

3. Golgi apparatus (AG)
Golgi apparatus is also called the Golgi complex has a close relationship with granuler RE. A few minutes after the protein synthesized by the RE, will be transported to the Golgi vesicles are located near the cell nucleus. AG had to modify the function of the glycoprotein carbohydrate units and the police who directed protein sorting and in accordance with the appropriate place.

4. Lysosomes

Lysosomes are organelles vesikuer formed in Golgi apparatus that will spread throughout the cytoplasm. Lysosomes function as intracellular digestive system that will digest and dispose of materials that are not needed or foreign objects such as parts of dead cells or bacteria. Lysosomes have a lower pH than the cytoplasm.
Digestive function of lysosomes is carried out through acid hydrolase enzymes that can digest various organic materials into simpler materials such as proteins into amino acids and glycogen into glucose.

5. Peroxisome
Are small organelles found in the cytoplasm with a diameter of 0.5 m drafts have membrane. Containing oxidase which will react with hydrogen to form hydrogen peroxide (H202), also contains the enzyme catalase which would convert H202 into water and oxygen. Mechanism oxidase-catalase-H202 is essential for the synthesis of fatty acids into acetyl-coenzym A further entry in the Krebs cycle for energy formation. Organelles peroxisomes was also found in liver and kidney contribute to the process of gluconeogenesis (formation of glucose from fat / protein).

6. Mitochondria
Is a source of energy (power house) from the cells extract energy function of the food. Mitochondria are major organelles within the cell and occupies about 25% volume of cytoplasm.
Mitochondria have 2 layers of membrane, outer membrane and the membrane inside. Outer membrane has pores that allow large molecules to pass through. Membrane consists of the 80% protein and 20% fat and protruding into the.
In this bulge (Krista) there are many enzymes oksidatuf fosforilase. These enzymes play a role in the process of glucose and fat oxidation and synthesis of ATP from ADP. On the inside of the mitochondria (matrix) there are also many enzymes needed for the extraction of energy from the released groceries.Energy used for ATP synthesis.
Mitikondria also present on the DNA, the same as those found in the cell nucleus. This DNA that regulate the ability of mitochondria to conduct self-replication when the activity of mitochondria to produce energy increases.

Physiology of Cells in The Human Body

Basics of Chemistry and Molecules in Cells
Cell is the basic unit on the human body where each organ is the aggregation / fusion of different kinds of cells that are united to one another by endorsement interseluller.Any structures specialized cell types to perform a function of red blood cells. like the number 25 trillion function to raise the oxygen from the Lungs to the red blood cells. there are approximately another 75 trillion cells that make up the human body, so the number of cells in the human body amounted to 100 trillion cells.
Although many different cells to each other, but generally all the cells have properties, which resemble each other, for example: oxygen will be bound to the carbohydrate, fat or protein in each cell to release energy; general mechanism to change food into energy; each cells release final results on the reaction to the surrounding fluid; almost all cells have the ability to make reproductive and if a particular cell is damaged then the other kind of cells will regenerate.
In general, cells that make up the human body has a basic structure consisting of the cell membrane, protoplasm and nucleus of the cell (nucleus). All three have a chemical composition consisting of water, electrolytes, protein, fat and carbohydrates.
Energy
Tues need energy to do all its activities, such as glucose synthesis, muscle contraction and DNA replication. In biological systems, energy is obtained from chemical bonds and chemical reactions in the cell (food). Glucose is the main source of energy. Tues to degradation of glucose continuously and in the process of energy will remove the chemical bonds of glucose is split so that this energy can be used for all cell activity. Energy produced can be converted into various kinds of energy such as heat energy, chemical energy, mechanical energy and electrical energy. For example in the muscles and nerves, chemical energy is converted into mechanical energy in muscle contraction and electrical energy in nerve cell activity.
Energy is extracted from food materials, bound in a chemical bond known as Adenosin triphosphate (ATP), ATP which is the source of energy, where energy will be released when ATP is hydrolyzed to ADP so that 1 high-energy phosphate (12 kcal) is used for the needs cells, ADP was still able to re-produce hydrolyse 1 phosphate (12kkal) and AMP molecules. Generally, energy is extracted from food materials, will be used prior to the formation of ATP, before the energy was used for all cell activity.
Chemical Bonding
There are 2 types of chemical bonds contained in the biological system is of covalent bonds (strong bonds) and non-covalent bonds (weak bonds). Covalent bonds binding the atoms that form molecules in the organic chemical bonds, are bonds nonkovalen determine 3-dimensional structure of most biological molecules.
Energy generated at the time of the solution and the formation of covalent bonds is very large. Atoms are bound with covalent bonds are very stable, so the energy needed to break the bond is very large. Energy changes that occur to solve this covalent bond, obtained from the formation of other covalent bonds. Because of this strong covalent bonds, the molecule that is composed of a covalent bond can survive for a long time.
Nonkovalen bond present in most of the ties that held the structure of large molecules such as proteins and nucleic acids. 3-dimensional structure of these large molecules or bonds between one molecule and another molecule is very weak. At normal temperature bonding nonkovalen only temporary, but many covalent bonds together form a bond that has a high stability. Which includes bond is nonkovalen hydrogen bonds, ionic bonds, van der Waals bonds, and hydrophobic bonds.
Structure of cells and Functions
Tues composed of 2 types of chemical substances that small molecules and polimer, which both are distinguished on the size and organizational structure. Small molecules are generally composed of less than 50 atoms, and each small molecule has a structure composed of many khas.Polimer small molecule that is composed of covalent bonds in which subunits of each polymer called tau monomer residua. In addition to monomers, the structure jugadisusun by fat cells, such as cell membranes that play an important role in cell function.
Tues Organization
Cell has two major parts of the nucleus and cytoplasm. Nucleus is separated from the cytoplasm by a nuclear membrane, and cytoplasm is separated from the fluid surrounding the cell membrane. Bahgan various cells that make up a collective called the protoplasm. Protoplasm consists mainly of the 5 basic ingredients: water, electrolytes, proteins, fats, and carbohydrates.
a. Water
The main fluid medium of the cell is water, which is found in concentrations of 70-85%. Many of the chemicals dissolved in water cells, while others are in the form of suspension or membranous.
b. Electrolyte
The most important electrolyte in the cells is potassium, magnesium, phosphate, bicarbonate, sodium, chloride, and calcium. Provide inorganic electrolyte materials for cellular reactions and control mechanisms involved and the cell.
c. Protein
Plays an important role in almost all physiological processes and can be summarized as follows:
1. Enzymatic processes
2. The process of transport and storage
3. The process of movement
4. Mechanical function
5. Immunological process
6. Founder and conductor of impulses in nerve cells
7. Regulate the process of growth and regeneration.
d. Fat
Fatty acids which are components of cell membranes is a long-chain hydrocarbons, fatty acids are stored in the cell is triasilgliserol, is a very hydrophobic molecule. Because of this triasilgliserol molecules not dissolve in water / salt it will form the lipid droplets in fat cells (adipose cells) which is a source of energy. Fat molecules that make up the cell membrane has a hydroxyl group (phospholipids and cholesterol) that can bind with water, whereas the other hydrophobic groups (not bound by the water) so-called amfifatik.

e. Carbohydrates
A Carbohydrate composed of atoms C, H and O. carbohydrates that have called pentose 5 C atoms, C 6 atoms are called hexosa carbs are essential for cell function.
Carbohydrates are composed of many units called polysaccharides. Polysaccharides serve as a backup energy source and as the components that make up the outer surface of the cell membrane. Carbohydrates that bind to proteins and the bind with fat (glycolipids) is an important structure of the cell membrane. In addition to glycolipids and glycoproteins that structuring blood group antigens that can cause immunological reactions.