University:
Kentucky State University
Course:
CHE 315 | Biochemistry
Academic year:

2019
Views:

361

Pages:

12
Author:

imophulebf14

Water 11 Why water is important to our bodies? 1. ~60% of our body is water, 70-85% of the weight of a typical cell 2. A solvent of many substances our bodies need such as glucose, ions, etc. 3. Acts as a medium in which acids and bases release their chemical groups to maintain a constant cellular environment or homeostasis. 4. Essential buffer that maintain pH 5. Temperature regulation- high sppecific heat capacity. 6. A participant in many biochemical reactions. 12 Water distribution in body compartments Lymph 13 Water structure H-bond energy is 20 kj/mole (5 kcal) Electronegativity of O atom is 3.5 Electronegativity of H atom is 2.1 Water is electrically neutral (net charge is zero) Bent geometry → dipole Covalent bond energy is 460 kj/mole (110 kcal) Water and Hydrogen Bonds (H-bonds) -A hydrogen bond is a weak noncovalent interaction between the H of one molecule and the more electronegative atom of an acceptor molecule. -A dipolar molecule with an uneven distribution of electrons between the hydrogen and oxygen atoms forms H-bonds with other polar molecules, thus acts as a solvent. Donor Acceptor (4 kcal) 15 Hydrogen Bonds (H-bonds) H-bond is stronger if X─H A A is O, N or F X is O, N or F Average number of H-bond in liquid water at 10ᵒC is 3.4 in ice crystals is 4 Number of H-bonds decrease with higher temperatures 16 H-bonding gives water its unusual physical properties Higher melting and boiling points Heat of vaporization Higher freezing point Surface tension H-bond has: H-bond Highly cohesive (ice) A bond energy of 20 kj/mole Life time 1x 10-9 second 17 H-bond and physical properties v v Water forms H-bonds with other polar molecules - H-bonds are not unique only for water - H atoms bonded to O, N or any electronegative atom can form H-bond - H atoms bound to carbon atoms, which are not electronegative, do not form H-bonds 19 Water as a solvent H-bonds between water and polar molecules. R denotes additional atoms. Hydration shells surrounding anions and cations. 20 Hydrophobic interactions and micelle formation in a cage like structure 21 Water and Thermal Regulation Water structure resists sudden and large temperature changes because: High thermal conductivity thus, facilitates heat dissipation from high energy consumption areas into the body water pool. High heat of fusion, so a large drop in temperature is needed to convert liquid water to ice. High heat capacity and heat of vaporization; when liquid water (sweating) is converted to a gas and evaporates from the skin, we feel a cooling effect. Temperature → H-bonds Temperature → H-bonds 22

Water in Biochemistry

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