What is the exact chemical composition of human body?

What is the exact chemical composition of human body?

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I've just watched Breaking Bad Season 01 Episode 03. In that Walter gives the chemical composition of human body. The conversation is as follows

Walter White: Let's break it down. Hydrogen. What does that give us?

Gretchen Schwartz: We're looking at 63%.

Walter White: Sixty-three, that is a big bite. My next step's gotta be oxygen.

Gretchen Schwartz: Oxygen, 26%.

Walter White: Twenty-six. There you have your water.

Gretchen Schwartz: Carbon, 9%.

Walter White: Carbon, 9.

Gretchen Schwartz: For a total of 98%.

Walter White: Right.

Gretchen Schwartz: Nitrogen, 1.25%.

Walter White: One-point-two-five.

Gretchen Schwartz: That brings you to 99 and a quarter. Which only leaves you with the trace elements down where the magic happens.

Walter White: Oh, wait a minute. What about calcium? Calcium's not a trace. Got a whole skeleton to account for.

Gretchen Schwartz: You would think, right? Calcium's only 0.25%.

Walter White: What? That low? Seriously? Damn, I never would've thought that. Okay, so where does iron fit in.

Gretchen Schwartz: Iron. 0.00004%

Walter White: What? You can't have hemoglobin without iron.

Gretchen Schwartz: Apparently, it don't take take much. No doubt. Go figure.

Walter White: Sodium.

Gretchen Schwartz: Sodium, 0.04%. Phosphorus, 0.19%.

Walter White: Point-one-nine. There we go. So the whole thing adds up to… 99.888042%. We are 0.111958%. Shy.

Gretchen Schwartz: Supposedly that's everything.

Walter White: Yeah? I don't know, it just… it seems like something's missing, doesn't it? There's got to be more to a human being than that.

Gretchen Schwartz: What about the soul?

Walter White: The soul? There's nothing but chemistry here.

When I searched for it, Wikipedia has something different.

Which one is correct?

That conversation is strange. While different tables exist, the very first elements seem messed up. If the body is 60 (some sources say 70)% water, then oxygen has to be the most abundant element by weight (water - H2O - has a molecular weight of ~18 g/mol, with hydrogen contributing only 2g/mol of that weight).

The usual figures are roughly Oxygen (65%), Carbon (18%), Hydrogen (10%), Nitrogen: (3%), Calcium (1.5%), etc.

However, the writers of Breaking Bad weren't stupid. So, they weren't discussing percentages of the mass of each element, but rather the frequency of that atom in the body. The number of hydrogen atoms does indeed exceed the number of oxygen atoms.

So, by atomic percent, Oxygen is 25.6%, Carbon: 9.5%, Hydrogen: 63%, Nitrogen: 1.3%, Calcium: 0.24%, etc. So yes, the numbers are approximately correct for a normal, average, youthful (more water) 70 kg male.

So here is a table incorporating both percent by weight and percent by abundance. The writers were pretty well informed.

Does the human body contain minerals?

For the most part, the human body does not contain minerals. Scientifically speaking, a mineral is a naturally-occurring inorganic crystalline solid with a single chemical formula. Rocks are aggregates of minerals and organic materials. Except for in bones and teeth, the atoms and molecules making up a healthy body are not crystalline and are not solid. In this way, most of the molecules making up a human body fail to meet the definition of a mineral.

Confusion often arises because many health professionals, nutritionists, and biologists misuse the word "mineral". When they say "mineral" in the context of human nutrition, they really mean "dietary element". Scientifically, the phrase "trace element" should really be used instead of "trace mineral" when talking about rare atoms required by the human body. The words "element" and "mineral" do not mean the same thing. A chemical "element" is a material containing only one kind of atom. In some cases, elements can form minerals, but they don't have to. For example, hydrogen is an element, but it is not a mineral because it is neither crystalline nor a solid. In contrast, quartz is indeed a mineral, but it is not an element because it contains more than one kind of atom. A gold nugget found in the ground is both an element (because it contains only gold atoms) and a mineral (because it has a natural crystalline solid structure). The small subset of materials in the world that contain only one kind of atom and have the atoms naturally bonded into a solid crystalline lattice are called "native element minerals".

The Dictionary of Chemistry by N. Pradeep Sharma states under the entry titled mineral, "A naturally occurring substance that has a characteristic chemical composition and, in general, a crystalline structure is known as mineral." Under the entry titled element, this dictionary states, "A pure substance which cannot be broken down into anything simpler by chemical means. All elements have a unique number of protons in thier atoms." Listed below are some examples to illustrate the difference between these terms.

1. Materials that are elements, but not minerals

  • helium (He)
  • oxygen (O)
  • fluorine (F)
  • mercury (Hg)
  • sodium vapor (Na), such as in lamps
  • molten iron (Fe)
  • amorphous carbon (C)
  • any single atom by itself can be called an element

2. Materials that are minerals, but not elements

  • table salt (NaCl)
  • quartz (SiO2)
  • calcite (CaCO3)
  • hematite (Fe2O3)
  • ice (H20)

3. Materials that are both minerals and elements (native element minerals):

For example, table salt contains sodium atoms and chlorine atoms bound into a solid, ionic, cubic crystalline lattice. Naturally occurring salt is therefore a mineral. But as soon as you sprinkle salt on your tongue and begin to eat it, the salt dissolves in the water on your tongue. This means that the sodium and chlorine atoms break apart and float around in the water. You no longer have a mineral. You have elemental ions in solution. Your body then uses the dissolved elemental sodium ions to regulate fluid pressure levels and to send electrical signals along your nerves. In this way, you can eat minerals, but once you eat them, they aren't minerals anymore. Furthermore, you can get dietary elements from non-mineral sources. For example, you can get dietary sodium from milk, which is not a mineral. In fact, we get most of our dietary elements from non-mineral sources. The only mineral we really eat on a regular basis is table salt.

The one exception in a healthy human is bone mineral, such as in bones and teeth. Bone mineral is indeed an inorganic, crystalline, solid with a single chemical formula and therefore qualifies as a genuine mineral. The mineral in your bones is called hydroxyapatite and has the chemical formula Ca5(PO4)3(OH). Our bodies build bone mineral on the spot, so we don't have to swallow hydroxyapatite crystals. But we do have to eat food with enough of the right kinds of atoms to build bone mineral. Looking at the chemical formula, we see that our bodies can't build bone mineral unless we supply it with enough calcium, phosphorus, oxygen, and hydrogen. A typical person has almost unlimited access to hydrogen and oxygen atoms through the water he drinks and the air he breaths. In contrast, a person can only get enough calcium and phosphorus to build healthy bones if he eats and drinks foods containing these elements.

Minerals can also form in the human body as part of disease states such as in kidney stones.


An atom is the smallest unit of matter with unique chemical properties. Atoms are the chemical units of cell structure. They consist of a central nucleus with protons and neutrons and orbit(s) of electrons. A proton carries a +1 positive charge, while a neutron has no charge. Thus the nucleus has a net positive charge. Electrons carry a –1 negative charge and are consequently attracted to the positive nucleus. In general, the number of protons usually equals the number of electrons. Recall that atoms have unique (individual) chemical properties, and thus each type of atom is called a chemical element, or just element.

Atomic number refers to the number of protons in an atom, while atomic weight refers to the number of protons and neutrons in an atom, measured in daltons. It is possible for elements to exist in multiple forms, called isotopes the only difference is the number of neutrons in the nucleus, while protons and electrons always stay the same as the original element.

The human body depends upon four major elements for form and function: Hydrogen (H), Oxygen (O), Carbon (C), and Nitrogen (N).

What is the human body made of?

Ask the three main branches of science what the human body is mostly made from and their answers sound like the punchline to a geeky joke.

“Water,” says the biologist, giving a reply that has surprised generations of schoolchildren who understandably may have expected something more solid.

“Oxygen,” insists the chemist, raising the insubstantiality of our existence a step further.

“Nothing,” retorts the physicist, clearly winning what seems like a competition to make humans disappear in a puff of logic.

But each answer, more implausible than the next, is correct in its own way. Apparently.


Professor Shirley Hodgson, a fellow of the Royal Society of Biology and an expert in the genetics of cancer at St George’s University of London, explained: “The human body is made up of trillions of cells.

“Importantly, all of these cells contain a lot of water, meaning that humans are in fact around 65 per cent water. The water in cells helps with chemical reactions, transports oxygen and waste, and acts as a shock absorber.”

But humans are also not entirely, well, human.

“Some of these cells are our own, and form our organs, muscles and bones, but a surprising number of them are bacteria,” Professor Hodgson said.

“We are host to many millions of bacteria, particularly in the gut, the microbiome.

“Bacteria are very helpful in improving our immunity, and are vital for the digestion of food. Sometimes bacteria can also be harmful, but there is a remarkable mutual benefit from our coexistence.”

Within our cells are “molecular machines” that perform a vast array of different functions.

“In the nucleus is the DNA, the blueprint for all our characteristics, and the cell reads this DNA message to make tens of thousands of different proteins, all of which have important jobs, from acting as hormones to helping form your skin and hair,” Professor Hodgson said.

Various different cells make up organs that work together to make a functioning animal.

In addition to the reproductive, digestive, cardiovascular, respiratory and nervous systems are the less well known lymphatic system, which helps protect the body against pathogens, and the endocrine system, including the thyroid and adrenal glands, which is involved in regulating hormones.

The renal system, including the kidneys and bladder, helps eliminate chemical waste, while our skin, hair, sweat glands and nails protect the body and control its temperature.

But a very different picture emerges if one takes a “purely chemical” point of view.

“The human body is made up of a long list of ‘ingredients’, with the most abundant being oxygen (65% by mass), carbon (18%), hydrogen (10%), nitrogen (3%), calcium (1.4%) and phosphorous (1.1%),” Elisabeth Ratcliffe, of the Royal Society of Chemistry (RSC) wrote in an email.

“There are over 60 elements in our bodies in total, mostly in minute quantities. Some people are surprised at how little of some elements is needed to support life.

“For example iron, which is so important for transporting oxygen around the body, only makes up 0.006 per cent of our chemical composition.”

The typical human body contains miniscule amounts of poisonous materials like mercury, arsenic and even selenium. At high doses, the latter would be fatal. But if about 0.000019 per cent of our body was not made of selenium, we would be dead as it is a key component of healthy thyroid function.

Radioactive uranium, absorbed from the environment around us, is present in the body at 0.00000013 per cent.

The Chemistry of Life: The Human Body

Editor's Note: This occasional series of articles looks at the vital things in our lives and the chemistry they are made of. You are what you eat. But do you recall munching some molybdenum or snacking on selenium? Some 60 chemical elements are found in the body, but what all of them are doing there is still unknown. Roughly 96 percent of the mass of the human body is made up of just four elements: oxygen, carbon, hydrogen and nitrogen, with a lot of that in the form of water. The remaining 4 percent is a sparse sampling of the periodic table of elements.

Some of the more prominent representatives are called macro nutrients, whereas those appearing only at the level of parts per million or less are referred to as micronutrients. These nutrients perform various functions, including the building of bones and cell structures, regulating the body's pH, carrying charge, and driving chemical reactions. The FDA has set a reference daily intake for 12 minerals (calcium, iron, phosphorous, iodine, magnesium, zinc, selenium, copper, manganese, chromium, molybdenum and chloride). Sodium and potassium also have recommended levels, but they are treated separately. However, this does not exhaust the list of elements that you need. Sulfur is not usually mentioned as a dietary supplement because the body gets plenty of it in proteins. And there are several other elements &mdash such as silicon, boron, nickel, vanadium and lead &mdash that may play a biological role but are not classified as essential. "This may be due to the fact that a biochemical function has not been defined by experimental evidence," said Victoria Drake from the Linus Pauling Institute at Oregon State University. Sometimes all that is known is that lab animals performed poorly when their diets lacked a particular non-essential element. However, identifying the exact benefit an element confers can be difficult as they rarely enter the body in a pure form. "We don't look at them as single elements but as elements wrapped up in a compound," said Christine Gerbstadt, national spokesperson for the American Dietetic Association. A normal diet consists of thousands of compounds (some containing trace elements) whose effects are the study of ongoing research. For now, we can only say for certain what 20 or so elements are doing. Here is a quick rundown, with the percentage of body weight in parentheses. Oxygen (65%) and hydrogen (10%) are predominantly found in water, which makes up about 60 percent of the body by weight. It's practically impossible to imagine life without water. Carbon (18%) is synonymous with life. Its central role is due to the fact that it has four bonding sites that allow for the building of long, complex chains of molecules. Moreover, carbon bonds can be formed and broken with a modest amount of energy, allowing for the dynamic organic chemistry that goes on in our cells. Nitrogen (3%) is found in many organic molecules, including the amino acids that make up proteins, and the nucleic acids that make up DNA. Calcium (1.5%) is the most common mineral in the human body &mdash nearly all of it found in bones and teeth. Ironically, calcium's most important role is in bodily functions, such as muscle contraction and protein regulation. In fact, the body will actually pull calcium from bones (causing problems like osteoporosis) if there's not enough of the element in a person's diet. Phosphorus (1%) is found predominantly in bone but also in the molecule ATP, which provides energy in cells for driving chemical reactions. Potassium (0.25%) is an important electrolyte (meaning it carries a charge in solution). It helps regulate the heartbeat and is vital for electrical signaling in nerves. Sulfur (0.25%) is found in two amino acids that are important for giving proteins their shape. Sodium (0.15%) is another electrolyte that is vital for electrical signaling in nerves. It also regulates the amount of water in the body. Chlorine (0.15%) is usually found in the body as a negative ion, called chloride. This electrolyte is important for maintaining a normal balance of fluids. Magnesium (0.05%) plays an important role in the structure of the skeleton and muscles. It also is necessary in more than 300 essential metabolic reactions. Iron (0.006%) is a key element in the metabolism of almost all living organisms. It is also found in hemoglobin, which is the oxygen carrier in red blood cells. Half of women don't get enough iron in their diet. Fluorine (0.0037%) is found in teeth and bones. Outside of preventing tooth decay, it does not appear to have any importance to bodily health. Zinc (0.0032%) is an essential trace element for all forms of life. Several proteins contain structures called "zinc fingers" help to regulate genes. Zinc deficiency has been known to lead to dwarfism in developing countries. Copper (0.0001%) is important as an electron donor in various biological reactions. Without enough copper, iron won't work properly in the body. Iodine (0.000016%) is required for making of thyroid hormones, which regulate metabolic rate and other cellular functions. Iodine deficiency, which can lead to goiter and brain damage, is an important health problem throughout much of the world. Selenium (0.000019%) is essential for certain enzymes, including several anti-oxidants. Unlike animals, plants do not appear to require selenium for survival, but they do absorb it, so there are several cases of selenium poisoning from eating plants grown in selenium-rich soils. Chromium (0.0000024%) helps regulate sugar levels by interacting with insulin, but the exact mechanism is still not completely understood. Manganese (0.000017%) is essential for certain enzymes, in particular those that protect mitochondria &mdash the place where usable energy is generated inside cells &mdash from dangerous oxidants. Molybdenum (0.000013%) is essential to virtually all life forms. In humans, it is important for transforming sulfur into a usable form. In nitrogen-fixing bacteria, it is important for transforming nitrogen into a usable form. Cobalt (0.0000021%) is contained in vitamin B12, which is important in protein formation and DNA regulation.

Is human body made of cells or atoms or molecules?

To answer this question, I'm going to start by talking about bigger things and moving us down into smaller things.

Let's start with the human body. The body is a whole bunch of stuff covered in skin. So let's focus on skin for a moment.

What is skin made of? The simple answer is skin cells (I'm ignoring the structures and levels of skin because it's quite complex and we don't need to consider it here). And other structures are like this - muscle is composed of muscle cells, bone of bone cells, nerves of nerve cells, etc.

So we know that the body is made of cells.

Cells are made of proteins, which are a type of molecule, and water, which is another molecule, and other things which are all made of molecules. Within the centre of the cell is DNA and RNA, both extremely complicated molecules.

So we know that the cells of the body are made up of molecules.

What are molecules made of?

Molecules are collections of atoms. Water is made up of oxygen and hydrogen atoms. Proteins are made of carbon, hydrogen, oxygen, and other elements.

So we know that the molecules that make up the cells of the body are made of atoms.

In the end, it is correct to say the body is made of cells. And it's correct to say it's made of molecules. And to say it's made of atoms.

Clay as a Scriptural Allegory

God desires to finish the work of His hands ( Philippians 1:6 ). Charles Spurgeon summarizes the potter’s wheel as a wheel of circumstances continually revolving. Men—vessels of clay—are placed upon it, but they are not all formed alike. There are some men who yield to God’s conforming of them to His Son ( Romans 8:29 ), and there are sadly many others who reject the Master Potter. There are outlines in the clay just like lines on a painted vase.

[The first outline is]—faith in Christ. . . . [N]ext . . . is love for Christ. It is only the bare outline . . . for the glory which excels is not there yet. The vase is only in its embryo, but yet sufficiently developed to give a[n insight] of its finished form but as for the [designs and images] that shall be inlaid, as for all the various colours that shall be used upon it, you cannot guess as yet, nor could you, unless you could climb up to the potter’s seat and see the plan upon which he looks as the clay revolves upon the wheel.11

An 18th century Bible scholar, Matthew Henry, has a similar view:

Do we know when the Master Potter’s work is done? Remember, Adam and Eve weren’t originally designed to die they could have lived forever in perfect fellowship with God. When sin entered the world, death came ( Romans 6:23 ). However, because of God’s love for us, He developed a way to restore us to Him. By the death and resurrection of Jesus Christ, the way to heaven was opened for us. The apostle Paul tells us about how our bodies will be reborn once they die, and how our bodies are only a seed in the ground that will be transformed ( 1 Corinthians 15:35–54 ). Through this resurrection, the work of His creation in us will be finished.

It is extremely difficult to discuss only the technical and elemental aspects that are incorporated into our bodies without discussing the spiritual breath that was used in our creation . In conclusion two poems are provided as a humble attempt of representing God ’s spiritual component in us. First, in the Book of Psalms, the sacred book of poetry, songs, and hymns, we find King David’s insightful comforting words:

And since David’s time in the 11th century BC. the same questions and insights of ourselves as God ’s continual creation still apply. The words and ideas of the following 20th century poem were combined by two Christian friends united in Christ’s Holy Spirit. One artist and teacher (Diane Peacock) expressed her thoughts to her friend, gifted author (Mary Lauzon), who then crafted the poem:


When God delivers us
into this world,
we are not yet fully formed.
like a blob of clay
we are wet and gooey,
too soft to stand,
too unformed to make a statement.

He delivers us
into human hands,
those who take our exterior
and gently smooth and form us,
and sometimes those
who press too hard,
who compress our being,
who reach in too far and distort us.

The look we desire for ourselves
is sometimes pinched away
by those who carelessly carve and chisel
and at puberty we’re baked
into a hardened form,
lopsided. Steep sides, narrow neck,
we cry out, as we emerge from the kiln,
“Is this what you intended?”

As adults, stiff and sore
from all the previous molding,
we crack, chip
and are sometimes given another stint
on the potter’s wheel
We whirl and churn
Not knowing who we’re becoming
or why. We know we’re no
Raku original.

At times the glaze
Of human hands on our lives

Gives us another appearance.
We moan, complain.

It’s rarely a look we want.

We forget the original artist.
We forget the one who formed us from dirt,
who had his hand on us first,

who placed his original print
on the underside of our soul.
We are more than decorative.
And if we took time each day
to tip ourselves over
we’d see the engraved print of his finger
standing in relief, marking us as his,
marking us as godly original.

  • Mixtures are substances composed of two or more components (physically mixed together). Most matter in nature exists in the form of mixtures. There are three main types of mixtures: solutions, colloids, and suspensions.
  • Solutions– are homogeneous mixtures of components (either gases, liquids, or solids). Homogeneous means the mixture has the same composition throughout. For instance, if samples are taken from the mixture, they will have the same makeup and composition. Air and seawater are examples of homogeneous mixtures. The substance present in the greatest amount is called a solvent and is usually a liquid. Substances present in smaller amounts are called solutes. Solutes are usually dissolved by the solvent. Water is the human body’s main solvent. Most solutions in the body are true solutions (solutions containing gases, liquids, or solids dissolved in water). Saline solution is an example of a true solution.
  • Concentration of solutions– True solutions are described in terms of their concentration which can be indicated in several ways. Solutions in most colleges and hospitals are described by percentage (parts per 100). When using this method, the percentage is always based on the solute and the solvent is usually water. For instance, if the solution is 100 ml and the solute is 8 ml, the solution percentage would be 8.

Distinguishing mixtures from compounds

Mixtures differ from compounds in several important ways:

  1. No chemical bonding occurs between the components of a mixture (chemical bonding does occur between compounds).
  2. Some mixtures can be separated by physical means (straining, filtering). Compounds can only be separated by chemical means (breaking bonds).
  3. All compounds are homogeneous. In contrast, some mixtures are homogeneous, while others are heterogeneous.

What is the exact chemical composition of human body? - Biology

Cell Structure & Function

Physiology - science that describes how organisms FUNCTION and survive in continually changing environments

Levels of Organization:

CHEMICAL LEVEL - includes all chemical substances necessary for life (see, for example, a small portion - a heme group - of a hemoglobin molecule) together form the next higher level


CELLULAR LEVEL - cells are the basic structural and functional units of the human body & there are many different types of cells (e.g., muscle, nerve, blood, and so on)

TISSUE LEVEL - a tissue is a group of cells that perform a specific function and the basic types of tissues in the human body include epithelial, muscle, nervous, and connective tissues

ORGAN LEVEL - an organ consists of 2 or more tissues that perform a particular function (e.g., heart, liver, stomach, and so on)

SYSTEM LEVEL - an association of organs that have a common function the major systems in the human body include digestive, nervous, endocrine, circulatory, respiratory, urinary, and reproductive.

There are two types of cells that make up all living things on earth: prokaryotic and eukaryotic. Prokaryotic cells, like bacteria, have no 'nucleus', while eukaryotic cells, like those of the human body, do. So, a human cell is enclosed by a cell, or plasma, membrane. Enclosed by that membrane is the cytoplasm (with associated organelles) plus a nucleus.

Cell, or Plasma, membrane - encloses every human cell

    • Structure - 2 primary building blocks include protein (about 60% of the membrane) and lipid, or fat (about 40% of the membrane). The primary lipid is called phospholipid, and molecules of phospholipid form a 'phospholipid bilayer' (two layers of phospholipid molecules). This bilayer forms because the two 'ends' of phospholipid molecules have very different characteristics: one end is polar (or hydrophilic) and one (the hydrocarbon tails below) is non-polar (or hydrophobic):
      • Functions include:
        • supporting and retaining the cytoplasm
        • being a selective barrier
          • The cell is separated from its environment and needs to get nutrients in and waste products out. Some molecules can cross the membrane without assistance, most cannot. Water, non-polar molecules and some small polar molecules can cross. Non-polar molecules penetrate by actually dissolving into the lipid bilayer. Most polar compounds such as amino acids, organic acids and inorganic salts are not allowed entry, but instead must be specifically transported across the membrane by proteins.
          • Many of the proteins in the membrane function to help carry out selective transport. These proteins typically span the whole membrane, making contact with the outside environment and the cytoplasm. They often require the expenditure of energy to help compounds move across the membrane
              • recognition
              • Cytoplasm consists of a gelatinous solution and contains microtubules (which serve as a cell's cytoskeleton) and organelles (literally 'little organs')
              • Cells also contain a nucleus within which is found DNA (deoxyribonucleic acid) in the form of chromosomes plus nucleoli (within which ribosomes are formed)
              • Organelles include:
                • Endoplasmic reticulum -
                  • comes in 2 forms: smooth and rough the surface of rough ER is coated with ribosomes the surface of smooth ER is not
                  • functions include: mechanical support, synthesis (especially proteins by rough ER), and transport
                  • consists of a series of flattened sacs (or cisternae)
                  • functions include: synthesis (of substances likes phospholipids), packaging of materials for transport (in vesicles), and production of lysosomes
                  • membrane-enclosed spheres that contain powerful digestive enzymes
                  • functions include destruction of damaged cells (which is why they are sometimes called 'suicide bags') & digestion of phagocytosed materials (such as bacteria)
                    • Mitochondria -
                      • have a double-membrane: outer membrane & highly convoluted inner membrane
                          • inner membrane has folds or shelf-like structures called cristae that contain elementary particles these particles contain enzymes important in ATP production
                          • primary function is production of adenosine triphosphate (ATP)
                          • composed of rRNA (ribosomal RNA) & protein
                          • may be dispersed randomly throughout the cytoplasm or attached to surface of rough endoplasmic reticulum
                          • often linked together in chains called polyribosomes or polysomes
                          • primary function is to produce proteins
                          • paired cylindrical structures located near the nucleas
                          • play an important role in cell division
                          • cilia are relatively short & numerous (e.g., those lining trachea)
                          • a flagellum is relatively long and there's typically just one (e.g., sperm)
                            • Villi - projections of cell membrane that serve to increase surface area of a cell (which is important, for example, for cells that line the intestine)

                            DNA (Deoxyribonucleic acid) - controls cell function via transcription and translation (in other words, by controlling protein synthesis in a cell)

                            Transcription - DNA is used to produce mRNA

                              • sequence of amino acids in a protein is determined by sequence of codons (mRNA). Codons are 'read' by anticodons of tRNAs & tRNAs then 'deliver' their amino acid.
                              • Amino acids are linked together by peptide bonds (see diagram to the right)
                              • As mRNA slides through ribosome, codons are exposed in sequence & appropriate amino acids are delivered by tRNAs. The protein (or polypeptide) thus grows in length as more amino acids are delivered.
                              • The polypeptide chain then 'folds' in various ways to form a complex three-dimensional protein molecule that will serve either as a structural protein or an enzyme.

                              COMPONENTS OF THE CELLULAR ENVIRONMENT

                              • comprises 60 - 90% of most living organisms (and cells)
                              • important because it serves as an excellent solvent & enters into many metabolic reactions
                              • found in both intra- & extracellular fluid
                              • examples of important ions include sodium, potassium, calcium, and chloride
                              • about 3% of the dry mass of a typical cell
                              • composed of carbon, hydrogen, & oxygen atoms (e.g., glucose is C 6 H 12 O 6 )
                              • an important source of energy for cells
                              • types include:
                                • monosaccharides (e.g., glucose) - most contain 5 or 6 carbon atoms
                                • disaccharides
                                  • 2 monosaccharides linked together
                                  • Examples include sucrose (a common plant disaccharide is composed of the monosaccharides glucose and fructose) & lactose (or milk sugar a disaccharide composed of glucose and the monosaccharide galactose)
                                  • several monosaccharides linked together
                                  • Examples include starch (a common plant polysaccharide made up of many glucose molecules) and glycogen (commonly stored in the liver)
                                  • about 40% of the dry mass of a typical cell
                                  • composed largely of carbon & hydrogen
                                  • generally insoluble in water
                                  • involved mainly with long-term energy storage other functions are as structural components (as in the case of phospholipids that are the major building block in cell membranes) and as "messengers" (hormones) that play roles in communications within and between cells
                                  • Subclasses include:
                                    • triglycerides - consist of one glycerol molecule + 3 fatty acids (e.g., stearic acid in the diagram below). Fatty acids typically consist of chains of 16 or 18 carbons (plus lots of hydrogens).
                                      • phospholipids - a phosphate group (-PO 4 ) substitutes for one fatty acid & these lipids are an important component of cell membranes
                                      • steroids - include testosterone, estrogen, & cholesterol
                                      • about 50 - 60% of the dry mass of a typical cell
                                      • subunit is the amino acid & amino acids are linked by peptide bonds
                                      • 2 functional categories = structural (proteins part of the structure of a cell like those in the cell membrane) & enzymes
                                        • Enzymes are catalysts. Enzymes bind temporarily to one or more of the reactants of the reaction they catalyze. In doing so, they lower the amount of activation energy needed and thus speed up the reaction.
                                        • Simple diffusion = net movement of a substance from an area of high concentration to an area of low concentration. The rate of diffusion is influenced by:
                                          • concentration gradient
                                          • cross-sectional area through which diffusion occurs
                                          • temperature
                                          • molecular weight of a substance
                                          • distance through which diffusion occurs
                                          • Facilitated diffusion= movement of a substance across a cell membrane from an area of high concentration to an area of low concentration. This process requires the use of 'carriers' (membrane proteins). In the example below, a ligand molecule (e.g., acetylcholine) binds to the membrane protein. This causes a conformational change or, in other words, an 'opening' in the protein through which a substance (e.g., sodium ions) can pass.
                                            • Active transport = movement of a substance across a cell membrane from an area of low concentration to an area of high concentration using a carrier molecule
                                              • Endo- & exocytosis - moving material into (endo-) or out of (exo-) cell in bulk form

                                              Shown here is one way that active transport can occur. Initially, the membrane transport protein (also called a carrier) is in its closed configuration which does not allow substrates or other molecules to enter or leave the cell. Next, the substance being transported (small red spots) binds to the carrier at the active site (or binding site). Then, on the inside of the cell, ATP (Adenosine TriPhosphate) binds to another site on the carrier and phosphorylates (adds one of its phospate groups, or -PO 4, to) one of the amino acids that is part of the carrier molecule. This attachment of a phosphate group to the carrier molecule causes a conformational change in (or a change in the shape of ) the protein so that a channel opens between the inside and outside of the cell membrane. Then, the substrate can enter the cell. As one molecule of substrate enters, the phosphate group comes off the carrier and the carrier again 'closes' so that no other molecules can pass through the channel. Now the transport protein, or carrier, is ready to start the cycle again. Note that as materials are transported into the cell, ATP is used up and ADP and -PO 4 accumulate. More ATP must be made by glycolysis and the Kreb's cycle.

                                              Characteristics of Facilitated Diffusion & Active Transport - both require the use of carriers that are specific to particular substances (that is, each type of carrier can 'carry' one type of substance) and both can exhibit saturation (movement across a membrane is limited by number of carriers & the speed with which they move materials see graph below).

                                              CELLULAR METABOLISM:

                                              Cells require energy for active transport, synthesis, impulse conduction (nerve cells), contraction (muscle cells), and so on. Cells must be able to 'capture' and store energy & release that energy in appropriate amounts when needed. An important source of energy for cells is glucose (C 6 H 12 O 6 ):

                                              C 6 H 12 O 6 + O 2 ----------> CO 2 + H 2 O + ENERGY

                                              However, this reaction releases huge amounts of energy (for a cell). So, cells gradually break down glucose in a whole series of reactions & use the smaller amounts of energy released in these reactions to produce ATP (Adenosine Triphosphate) from ADP (Adenosine Diphosphate). Then, cells can break down ATP (as in this reaction):

                                              (*Those of you who know about food Calories may be surprised by this number. After all, an entire candy bar may contain only 200 food Calories. The explanation lies in the capital C. One food Calorie, spelled with a capital C, is 1000 times larger than one physiologist's calorie, spelled with a small c.)

                                              The energy released in this reaction is used by cells for active transport, synthesis, contraction, and so on. Cells need large amounts of ATP &, of course, must constantly make more. But, making ATP requires energy. The breakdown of glucose does release energy. But, how, specifically, is the energy released in the breakdown of glucose used to make ATP.

                                              A primary source of ENERGY is OXIDATION. Specifically, cells use a type of oxidation called HYDROGEN TRANSFER to generate energy:

                                              These hydrogen transfer reactions are so-named because pairs of hydrogens are 'transferred' from one substance (XH 2 in the above reaction) to another (YH 2 in the above reaction). Because the reactants (XH 2 + Y) represent more energy than the products (X + YH 2 ), this reaction releases energy.

                                              In a cell, hydrogen transfer reactions occur in MITOCHONDRIA. Pairs of hydrogens are successively passed from one substance to another, and these substances are called HYDROGEN CARRIERS.

                                              XH 2 + NAD ----> NADH 2 + FAD ----> FADH 2 + Q ----> QH 2 + C-1 ----> C-2 ---->

                                              These hydrogen transfer reactions release energy that is used to make ATP from ADP (in other words, to add a third phosphate to adenosine diphosphate in a reaction called phosphorylation). So, what occurs in mitochondria involves hydrogen transfer (a type of oxidation) + phosphorylation, or, in other words, OXIDATIVE PHOSPHORYLATION. Oxidative phosphorylation produces lots of energy but requires hydrogen. Where do the hydrogens come from?

                                              Sources of hydrogen include GLYCOLYSIS and the KREB'S CYCLE.

                                              Glycolysis involves the breakdown of glucose. Cells obtain glucose from the blood. Blood glucose levels are maintained by the interaction of two processes: glycogenesis and glycogenolysis. Glycogenesis is the production of glycogen from glucose and occurs (primarily in the liver and skeletal muscles) when blood glucose levels are too high (for example, after a meal).

                                              Glycogenolysis is the reverse process - the breakdown of glycogen to release individual molecules of glucose. This occurs when blood glucose levels begin to decline (for example, several hours after a meal). The interaction of these two processes tends to keep blood glucose levels relatively constant.

                                              Glucose taken up by cells from the blood is used to generate energy in a process called glycolysis.

                                              In the first few steps of glycolysis, glucose is converted into fructose-1,6-diphosphate. These reactions, like all chemical reactions, involve making and breaking bonds between atoms, and this sometimes requires energy. Even though glycolysis, overall, releases energy, some energy must be added initially to break the necessary bonds and get the energy-producing reactions started. This energy is called activation energy. In the above diagram, energy (i.e., a molecule of ATP) is needed at steps 1 & 3. So, before the energy-producing reactions of glycolysis begin, a cell must actually use two molecules of ATP.

                                              Overall, glycolysis can be summarized as:

                                              Glucose ----> 2 Pyruvic Acid (or pyruvate) + 2 net ATP + 4 hydrogens (2 NADH 2 )

                                              So, glycolysis produces 2 direct ATP (ATP produced directly from the reactions that occur during glycolysis) and 6 indirect ATP (the 4 hydrogens produced in glycolysis will subsequently go through oxidative phosphorylation and produce 3 ATP per pair, i.e., 4 hydrogens equals 2 pair and 2 pair times 3 ATP equals 6 ATP). Thus, glycolysis produces a total of 8 ATP.

                                              Next comes an intermediate step (called oxidative decarboxylation):

                                              Used with permission of Gary Kaiser

                                              the 2 Pyruvic Acid are converted into 2 Acetyl CoA & this reaction produces 4 hydrogens (2 NADH2). Those hydrogens (i.e., 2 pair of hydrogens) go through oxidative phosphorylation and produce 6 more ATP (2 pair @ 3 ATP per pair).

                                              Finally, comes the Kreb's Cycle:

                                              2 Acetyl CoA go through this cycle of reactions and produce 2 ATP (= GTP in the above diagram) + 16 hydrogens (6 NADH2 + 2 FADH2) plus the waste products carbon dioxide + water. The 16 hydrogens go through oxidative phosphorylation and produce 22 ATP [22 because 12 of these hydrogens (6 NADH2) go completely through the reactions of oxidative phosphorylation and produce 18 ATP (6 pair @ 3 ATP per pair), while 4 of these hydrogens (2 FADH2) go through only some of the reactions and produce 4 ATP (2 pair @ 2 ATP per pair).

                                              Overall, therefore, the Kreb's cycle produces 24 ATP (2 direct & 22 indirect).

                                              OVERALL ATP PRODUCTION from glucose = 8 (from glycolysis) + 6 (from the hydrogens produced when the 2 pyruvic acid are converted into 2 acetyl CoA) + 24 (from the Kreb's cycle) for a GRAND TOTAL OF 38:

                                              Direct Indirect (O.P.) TOTAL
                                              Glucose ----> 2 Pyruvic Acid 2 6 8
                                              2 Pyruvic Acid ----> 2 Acetyl CoA 0 6 6
                                              2 Acetyl CoA ----> CO 2 + H 2 O 2 22 24

                                              Overall Total = 38 ATP

                                              Glucose (carbohydrates) are not the only source of energy for cells. Fats (or lipids), like triglycerides, are also metabolized to produce energy.

                                              • Glycerol ----> Glyceraldehyde ----> Pyruvic Acid ----> Acetyl CoA ----> Kreb's Cycle
                                              • Fatty Acids are converted into molecules of Acetyl CoA in a process called BETA OXIDATION.

                                              This reaction not only produces lots of Acetyl CoA (or acetate) but lots of hydrogens. The Acetyl CoA goes through the Kreb's Cycle, while the hydrogens go through Oxidative Phosphorylation.

                                              Proteins are also used as a source of energy.

                                              Proteins are first broken down into amino acids. The nitrogen component of amino acids is then removed (in a reaction called DEAMINATION), and these deaminated amino acids are then converted into Acetyl CoA which passes through the Kreb's Cycle to make more ATP.

                                              Used with permission of Gary Kaiser

                                              What is the body made of?

                                              The human body contains around 20 different elements, mostly made inside ancient stars. If you deconstructed an 80kg human into atoms, you would get about the following amounts of the different elements:

                                              Oxygen – 52kg

                                              This element makes up more than half the mass of your body but only a quarter of its atoms.

                                              Carbon – 14.4kg


                                              The most important structural element, and the reason we are known as carbon-based life forms. About 12 per cent of your body’s atoms are carbon.

                                              Hydrogen – 8kg

                                              The hydrogen atoms in your body were formed in the Big Bang. All the others were made inside a star long ago and were flung into space by a supernova explosion. So though you may have heard that we are all stardust, that isn’t strictly true.

                                              Nitrogen – 2.4kg

                                              The four most abundant elements in the human body – hydrogen, oxygen, carbon and nitrogen – account for more than 99 per cent of the atoms inside you. They are found throughout your body, mostly as water but also as components of biomolecules such as proteins, fats, DNA and carbohydrates.

                                              Calcium – 1.12kg

                                              Phosphorus – 880g

                                              Sulphur – 200g

                                              Potassium – 200g

                                              Sodium – 120g

                                              Chlorine – 120g

                                              Magnesium – 40g

                                              Magnesium is a key component of superoxide dismutase, one of the most important detoxification enzymes.

                                              Found in haem, the oxygen-carrying part of the haemoglobin molecule inside red blood cells

                                              Fluorine – 3.0g

                                              Hardens the teeth, though fluorine is not considered essential to life.

                                              Strontium – 0.37g

                                              Strontium is found almost exclusively in bones, where it may have a benefcial effect on growth and density.

                                              Iodine 0.0128 g

                                              Iodine is an essential component of the thyroid hormone thyroxine. Iodine is the heaviest element required by the human body.

                                              Copper – 0.08g

                                              Copper is a component of many enzymes. Copper deficiency causes neurological and blood disorders.

                                              Watch the video: 10 πράγματα που θα ευχόσουν να μην ήξερες: ΑΝΘΡΏΠΙΝΟ ΣΏΜΑ (August 2022).