2.2 Properties of Water

Transcription

1 2.2 Properties of Water I. Water s unique properties allow life to exist on Earth. A. Life depends on hydrogen bonds in water. B. Water is a polar molecule. 1. Polar molecules have slightly charged regions due to unequal sharing of electrons. _ Ex) water molecule *oxygen hogs electrons and is partially negative O *hydrogen becomes partially H H positive 2. Oppositely charged ends of neighboring water molecules are attracted to each other (like a magnet). a. This allows water to bead up on smooth surfaces. + +

2 2.2 Properties of Water C. Hydrogen bonds are responsible for three important properties of water. 1. high specific heat water absorbs large amounts of energy without raising its temperature very much 2. cohesion molecules stick to themselves Ex) water rising above the level of a glass without spilling 3. adhesion molecules stick to other charged molecules that are near them Ex) water not spilling out of container that is flipped upside down with a paper lid

3 2.2 Properties of Water D. Many compounds dissolve in water to form a solution. 1. solution formed when one substance dissolves in another a. A solution is a homogeneous mixture (mixed together so well that you cannot distinguish the different parts) b. Like Dissolves Like polar water is able to dissolve any polar substance or any ionic compound due to the charges Ex) salt (NaCl ionic compound) dissolves in water c. solvent substance that dissolves other substances d. solute substance that is dissolved solution

4 2.2 Properties of Water E. Some compounds form acids or bases. 1. Some compounds break into ions (dissolve) in water. a. acids releases a hydrogen ion (H + ) it dissolves in water 1. creates acidity 2. have high H + concentration b. bases - removes hydrogen ions from solution 1. creates alkalinity 2. have high OH - concentration 2. We measure H + concentration with the ph scale. a. ph scale runs from 0-14 Stronger H+ conc. ß Acids Neutral Bases à Weaker H+ conc.

5 2.2 Properties of Water 3. Most organisms need to keep their internal ph close to 7 (neutral) a. accomplished with the help of chemicals called buffers Ex) buffers in your blood maintain a normal ph and keep your body at homeostasis

6 II. Carbon-based molecules are the foundation of life. A. Carbon can form covalent bonds with up to four other atoms, including other carbon atoms 1. structure - 3 general types of structures a. straight chain b. branched chain c. ring

7 B. Many carbon-based molecules are made of many small subunits bonded together. a. monomers individual subunits b. polymers combinations of monomers

8 C. Carbohydrates are made of carbon, hydrogen, and oxygen. 1. monosaccharides simple sugars Ex) glucose 2. polysaccharides starches, cellulose, and glycogen

9 3. Carbohydrates can be broken down to provide energy for cells. 4. Some carbohydrates are part of cell structure. Polymer (starch) Starch is a polymer of glucose monomers that often has a branched structure. Polymer (cellulose) monomer Cellulose is a polymer of glucose monomers that has a straight, rigid structure

10 III. Lipids are nonpolar molecules that include fats, oils, and cholesterol. A. Many contain carbon chains called fatty acids. B. Fats and oils contain fatty acids bonded to glycerol. Triglyceride C. Lipids have several different functions. 1. broken down as a source of energy (fats) 2. used to make hormones

11 3. make up cell membranes a. polar phosphate head b. nonpolar fatty acid tails Phospholipid

12 D. Fats and oils have different types of fatty acids. 1. saturated fatty acids 2. unsaturated fatty acids

13 IV. Proteins are polymers of amino acid monomers. A. Twenty different amino acids are used to build proteins in organisms. B. Amino acids differ in side groups, or R groups. C. Amino acids are linked by peptide bonds.

14 D. Proteins differ in the number and order of amino acids. 1. Amino acids interact to give a protein its shape. 2. Incorrect amino acids change a protein s structure and function. Hemoglobin hydrogen bond

15 V. Nucleic acids are polymers of monomers called nucleotides. A. Nucleotides are made of a sugar, phosphate group, and a nitrogen base. A phosphate group nitrogen-containing molecule, called a base deoxyribose (sugar) B. There are 2 kinds: DNA and RNA. 1. DNA stores genetic information. 2. RNA builds proteins. DNA RNA

16 2.5 Enzymes VI. Enzymes are catalysts for chemical reactions in living things. A. Catalysts substances that speed up chemical reactions by decreasing activation energy needed B. Enzymes are catalysts in living things 1. Enzymes are needed for almost all processes. 2. Most enzymes are proteins. 3. Disruptions in homeostasis can prevent enzymes from functioning.

17 2.5 Enzymes 4. Enzymes function best in a small range of conditions. 5. Changes in temperature and ph can break hydrogen bonds. 6. An enzyme s function depends on its structure. a. An enzyme s structure allows only certain reactants to bind to the enzyme. 1. substrates bind to enzyme s active sites substrates (reactants) enzyme Substrates bind to an enzyme at certain places called active sites.

18 2.5 Enzymes b. Lock-and-Key Model only particular substrates will bond to certain enzymes (like keys in a lock only certain keys work) 1. substrates brought together 2. bonds in substrates weakened Substrates bind to an enzyme at certain places called active sites. The enzyme brings substrates together and weakens their bonds. The catalyzed reaction forms a product that is released from the enzyme.