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Fill in the blanks. Movement of materials in and out of cells is controlled by the_________________. The sites of protein synthesis are______________________. Glycerol and fatty acids combine to form___________________. Breakdown of organic nutrients in cells to release energy and form ATP is called_________________. In a__________________reaction, smaller molecules are combined to form a larger molecule. The building units of proteins are____________________. Choose the correct answer. Which of the following are functions of nucleic acids? They pass instructions from parents to offspring. They help make proteins. They contain instructions for proteins. all of the above. Types of lipids include: polysaccharides. amino acids. nucleotides. triglycerides. According to the fluid mosaic model of membrane structure, proteins of the membrane are mostly spread in a continuous layer over the inner and outer surfaces of the membrane. confined to the hydrophobic int...
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About Water

Molecular Structure of Water and the Properties of Water

Water comprises on average approximately two-thirds of the human body by weight. Molecular
 

Structure of Water 

Water is a polar molecule that can form four hydrogen bonds with other water molecules. Properties of Water Water is present in three phases (air vapor, liquid. and ice), depending on the temperature. Cohesion is attraction between water molecules, surface tension is the inward pull of water molecules at the surface, and adhesion is the attraction of water molecules for substances other than water. Water's high specific heat and high heat of vaporization help maintain a normal body temperature.

 

Water as the Universal Solvent

Polar organic molecules, such as glucose, dissolve and remain intact within water and are nonelectrolytes. Salts. acids, and bases dissolve and dissociate in water and are electrolytes. Nonpolar substances do not form hydrogen bonds with water and are separated from water molecules by hydrophobic exclusion. The polar portion of an amphipathic molecule dissolves in water, and the nonpolar portion does not. Amphipathic molecule: form chemical barriers within the body, including membranes and micelles.

Acids and Basic Solutions, pH and Buffers

Water has a neutral pH, and its pH is changed by the addition of either in aid or a base. 

Water: A Neutral Solvent

Positively charged hydrogen ions are equal to negatively charged hydroxyl ions in pure water; thus, water is neutral. 

 Acids and Bases

Acids increase and bases decrease the hydrogen ion concentration in solution. 

pH, Neutralization, and the Action of Buffers 

pH (potential hydrogen) is a measure of hydrogen ion concentration in solution. pH values are inversely related to hydrogen ion concentration. Neutralization is the return of an acidic or basic solution to neutral. A buffer helps prevent pH changes by absorbing and releasing hydrogen ions. 

Water Mixtures

Mixtures are formed from the mixing of two or more substances. Mixtures are not chemically changed, and the components can be separated by physical means. 

Categories of Water Mixtures 

Types of water mixtures include suspensions, colloids and solutions. Emulsions are a type of suspension formed by water and a liquid nonpolar substance when it is agitated. 

Expressions of Solution Concentration 

The concentration of solutions can be expressed m several ways including mass/volume. mass/volume percent, molality. Osmoles, osmolarity, and osmolality reflect number of particles m solution and are relevant in the movement of water by osmosis.

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