بسم الله الرحمن الرحيم
(وجعلنا من الماء كل شي حي( الأنبياء 30 صدق الله العظيم
Al - Iraqia university Prof. Dr. Samia –Alshahwani
College of medicine Y1 L5 16-12- 2015
Human Biology
P1 Human organization
Ch 2 Chemistry of life
2.2 Water (H2O) & Living Things
Objectives: Describe hydrogen bonds
List water properties.
Summarize pH scale structure & buffer importance
Recognize water role in human body
“If there is a magic on this planet it is contained in water”
Anthropologist Loren Eiseley
Water is at the center of life, it forms high percent in the body, in all stages, 100% in fetus (early period), 80% at birth, 60–70% adult, & 50% elderly, its physical & chemical properties make life possible, water is major component of every cell, cells need water. Water contains electrolytes & ions, forms electrical pathways for nerve functions. In water, electrons circulates O atom more than H because O is larger, of greater ability to attract electrons than smaller H atoms. Negative charged electrons are closer to O atom, so O atom becomes slightly negative (δ−), in turn H is slightly positive (δ+) therefore, water is polar fig. 2.7a, left structural water model & right, space-filling
Hydrogen Bond: Attraction of slightly positive, covalent bonded hydrogen to slightly negative atom, it occur between hydrogen atom & either oxygen or nitrogen atom, is weak, broken easily. Fig. 2.7b, hydrogen atom, slightly positive, bonds to slightly negative oxygen atom of another molecule.
Water properties Water is important in physiology & homeostasis, its molecules are cohesive (cling together), polarity & hydrogen bond is beneficial for life, water properties are;
1-Water is liquid at room temperature: therefore we are able to drink it, cook & bath in, hydrogen bond keeps it liquid at room temperature. It boils, become gas at 100°C, without hydrogen bond, body would be gaseous
Fig. 2.7 Hydrogen bonds &water molecules
a-2 models for water structure left share electrons between oxygen & hydrogen atoms. right, water is polar because, electrons move closer to oxygen, creating a partial negative charge, whereas hydrogen has partial positive charge. b- partial charges allow hydrogen bonds (dotted lines) to form temporarily between molecules
2- Water temp. Rise &falls slowly, prevent sudden change. Hydrogen bonds cause water to absorb heat before it boils (Fig. 2.8a). Calorie of heat energy raises temperature of 1 g of water 1°C.1 water holds heat, & its temperature falls slowly, therefore, water protects from rapid temp changes & maintains relative temperature, water is a good temperature buffer.
3-Water has high vaporization heat, keep body from overheating. It takes large heat amount to vaporize (Fig. 2.8a). (Converting 1 g of hot water to steam require 540 calories of heat) This moderate earth’s temperature so that life can continue, in hot environment, mammals sweat, body cool, heat used to evaporate sweat. (Fig. 2.8b).
4-Frozen water is less dense than liquid, ice floats on water; water is denser at 4°C than at 0°C. Substances contract when they solidify, but, water expands when it freezes because in ice, water molecules form a lattice in which hydrogen bonds are farther apart than in liquid water (Fig. 2.8c). Because ice is lighter than cold water, water freeze from top to down. Ice acts as an insulator to prevent water below from freezing, so aquatic organisms are protected.
5-Water molecules are cohesive, yet flow freely. Therefore, liquids fill vessels, (blood vessels). Water molecules cling together because of hydrogen bond. Water’s cohesive property allows dissolved and suspended molecules to be distributed in a system. Therefore, water is an excellent transport medium. Blood fills arteries & veins because is about 92% water. After blood transports oxygen &nutrients these used to produce energy. Blood removes wastes, carbon dioxide.
6--Water is solvent for polar (charged) molecules, facilitates chemical reactions. When ions & molecules disperse in water, they move & collide, allowing reactions to occur e.g. NaCl
Life depends on water’s cohesive property. Thin water film coats lung surface & inner chest wall, lungs stick to chest wall, keep it open so we can breathe. Ions and molecules that interact with water are hydrophilic means (water-loving). Nonionized & nonpolar molecules that do not interact with water are called hydrophobic or (water-fearing)
Acids and Bases when water molecules dissociate release equal number of hydrogen ions (H+) & hydroxide ions (OH−): Few water molecules at a time dissociate, & actual number of H+ or OH− is 10−7 moles/liter. Mole is a unit of scientific measurement for atoms, ions, &molecules.
Acidic Solutions (High H+ Concentrations) Lemon, vinegar, tomatoes, &coffee are acidic. Acids dissociate in water, releasing hydrogen ions (H+). The acidity depends on how fully it dissociates. e.g. inorganic acid hydrochloric acid (HCl), dissociates: HCl → H+ + Cl-
If hydrochloric acid is added to water, number of hydrogen ions (H+) increases. Therefore, HCl is called strong acid. Hydrochloric acid is produced by stomach and aids in digestion.
Basic Solutions (Low H+ Concentrations);Milk of magnesia & ammonia are base. A base takes up hydrogen ions (H+) or release hydroxide ions (OH−).e.g. base sodium hydroxide (NaOH), NaOH → Na+ + OH if sodium hydroxide is added to water, number of hydroxide ions increases. Sodium hydroxide is strong base.
pH Scale used to indicate acidity & basicity (alkalinity) of a solution. Pure water with equal number of hydrogen ions (H+) & hydroxide ions (OH−) has pH of 7. pH scale simplify discussion of hydrogen ion concentration [H+] &hydroxide ion concentration [OH−]. It eliminates use of cumbersome numbers. To understand relation between hydrogen ion concentration & pH, consider following;
To determine pH, each number is expressed in scientific notation. Negative value of the exponent (superscript number) equals pH. So for a solution of 0.000001 moles per liter of hydrogen ions, scientific notation is 1 × 10−6, and the pH is −[−6] or pH 6. Of the two values above and below pH 7, which one indicates a higher hydrogen ion concentration than pH 7, therefore, refers to acidic solution A number with smaller negative exponent indicates greater quantity of (H+) than one with a larger negative exponent. Therefore, pH 6 solution is acidic.
Basic solutions have fewer (H+) than hydroxide ions. Of the three values, pH 8 solution is basic because it indicates lower [H+] conc. (greater hydroxide ion concentration) than pH 7 solution. PH scale (Fig. 2.9) ranges 0 - 14. As we move toward higher pH, each unit has 10 times basicity of previous unit; & as we move toward lower pH, each unit has 10 times acidity of the previous unit. .
Buffers : Body fluids pH is maintained within a narrow range or health suffers. pH stability is possible because the body & the environment have buffers to prevent pH changes. Problem arises when precipitation , rain or snow become acidic, environment run out of natural buffer, rain pH 5.7 Rain becomes acidic because burning of fossil fuels emits sulfur dioxides (SO2) & nitrogen oxides (NO2 ) in air it combine with water to produce sulfuric acid (H2SO4) &nitric acid (HNO3)
Buffers keep pH in normal limits because they either take up excess (H+) or (OH−), pH of blood in health is 7.4 slightly basic (alkaline). Blood contains combination of carbonic acid & bicarbonate ions. When (H+) are added to blood, reaction occurs:H+ + HCO3-→ H2CO3When (OH−) added, reaction occurs: OH- + H2CO3 → HCO3-+ H2O These prevent change in blood pH.
Water role in human body (fig.2.10): Water is the miracle elixir that sustains us. Hydration is a primary needs for the body, to digest & eliminate, flush kidneys, liver, for colon to move bowels, as waste remains long, toxins reabsorbed in blood & circulates to organ. Adult should drink 1.5 liters of water daily, to balance water losses and body hydrated, brain consists of about 90% of water, cannot function well if it is not supplied by enough water, you will get headache, migraine, fatigue. Muscle consists of 75% water, bone consist 22% water, and blood consist of about 83%. Look to water filters to drink water, if tap water is used in the morning (to drink or cook in) let water flow from the tap for about 3 minutes, because water inside the pipes was in contact with leaded pipe over night & some lead dissolved in water, making it with high percent of lead, which is carcinogenic. (New types of pipes are made now but still the old type used in some places). Drink water after waking up on empty stomach. Consider water for health, water sharpens mental function & improves life. We cannot live more than 3 -5 days without water. Sodas, coffee, energy drinks cause dehydration.
Water functions & benefits:
1-Cell life; Transport, mineral, glucose, vitamins & oxygen.
2- Chemical and metabolic reactions.
3- Transport of nutrients.
4- Body temperature regulation.
5- Elimination of waste.
6- Moisturize air in lungs.
7- Protect vital organs shock absorber for eyes, brain, spinal cord and fetus
8- Help absorb nutrients.
9- Detoxifies.
10- Joints, and muscles lubrication, less cramps and strains.
11-Lose weight, flush fat by- product, and avoid obesity
12- Remedy for headache & back pain due to dehydration
13-Young looking. healthy skin, moisturize skin and increase elasticity
14 -Increase productivity at work, brain think better, be alert, concentrated.
15-Better exercise. Water regulates temperature. You feel energetic, water to fuel muscle
16- Digestive system, water form saliva, raise metabolism, with fibers for bowl movement. Water decrease risk of bladder &colon cancer, it dilute cancer causing agents in urine shorten time of contact to bladder lining.
17- Health: Water decrease incidence of flue, kidney stone & heart attack, water with lemon used for respiratory disease, intestinal problem, rheumatism, arthritis & improve immune system.
1 8-Relieves fatigue: When there is lack in water intake, heart work hard to pump oxygenated blood to vital organ, it will be exhausted.
19-Good mood: When your body is well you will feel happy.
20-Thyroid Gland, every blood drop passes through thyroid gland every 15 minutes. Toxins are building up if the water you drink is not of the purest quality.
21- Liver and kidneys must have adequate pure water to flush out the toxins accumulated there.
22-Stress: relieving stress and tension in the brain. It has also been proven to help reduce anxiety, if you are prone to anxiety attacks, a great solution is to drink a few glasses of clean pure water. Water also sharpens mental functions. This means that it's important to drink plenty of water before big tests, or any other event that will require you to be at the top.
Reasons why water is important:Water needed to separate (by hydrolysis process) a phosphate group from adenosine triphosphate (ATP) or guanosine triphosphate (GTP) to get energy as illustrated: ATP +H2O = Energy + ADP + Inorganic P
GTP +H2O = Energy + GDP + Inorganic Phosphate
Energy from food is used to generate ATP or GTP before its energy can be used by the body, which makes water crucial to energy usage.
*Water is medium for electrolytes &ions it form electrical pathways for nerve functions.
Dehydration:It degrades the ability to exercise & burn calories & reduces protein synthesis needed to build muscles. Being 2% dehydrated degrade physical & mental functions. Being 15% dehydrated is lethal. Unlike vitamin deficiencies which can take weeks to make someone ill, water deficiency kill in days or hours. To avoid dehydration drink 8 glasses of water daily.
Water is important for removing toxins. Ways of removing toxin from the body 1-Bowels 2-Urination 3-Perspiration 4-Processing of toxins by liver. First three methods directly excrete water, when dehydrated, body save water by minimizing use of first three functions &will force liver to assume as much of work load as possible, this place burden on liver which has other functions in addition to detoxification. Liver by itself will not be able to do work & toxins will buildup.
Water is important for fitness; it fills without calories. Recommended daily water intake varies with size, gender, activity level & climate conditions. Who exercises should consider replacing electrolytes with water, to avoid hyponatremia (depleted sodium) or other forms of severe electrolyte, depletion.
Effects of dehydration 1-Tiredness.
2-Migrain.
3-Constipation.
4-Muscle cramps.
5-Irregular blood pressure.
6- Kidney problems.
7-Dry skin
8- Fatal.
Dehydration Symptoms
1-Dark urine.
2- Dry skin: skin is the largest organ, require water
3- Thirst; Is most obvious dehydrationsign. Drink water when you are not thirsty don’t wait till thirst
4-Hunger mistaken for indication to eat you may be dehydrated, before meal drink a glass of water.
5-Fatigue.
Studies indicated that pure water intake result in lower incidence of many diseases.
Drink water, Stay healthy & active. The more we know the better chance we can survive.There are 3 barriers between inner environment (inside the body) and outer environment; they are Skin, GIT and lung. Lung is the most sensitive .
Care for both environments & practice daily gratitude for their creator …… Thanks Samia 2015