BIOCHEMISTRY

1. BIOCHEMISTRY

2. Water • Polarity—due to uneven distribution of electrons between the oxygen and hydrogen atoms, one end of the water molecule is slightly negative and one is slightly positive • The polarity of water allows hydrogen bonds to form between its molecules and is responsible for many of its special properties

3. Special Properties of Water • Cohesion--attraction between molecules of the same substance; because of the hydrogen bonds, water is extremely cohesive • Adhesion--attraction between molecules of different substances

4. Acids and Bases • Water can react to form ions • Water forms hydrogen ions (H+) and hydroxide ions (OH-) • An acid is a compound that forms H+ ions in a solution • A base is a compound that forms OH- ions

5. pH Scale • pH is a measure of the concentration of H+ ions in a solution • The scale goes from 1 to 14 • 7 is neutral meaning the solution is not an acid nor a base • Acids have a pH below 7 • Bases have a pH above 7

6. Four Substances That Make Up Living Things • Carbohydrates • Lipids • Proteins • Nucleic Acids

7. Carbohydrates • Includes sugars, starches, and cellulose • Function to store energy and to provide shape to organisms • Composed of carbon, hydrogen, and oxygen

8. Carbohydrates (cont.) • Can be divided into 3 groups based on their size: • Monosaccharides: simple sugars like glucose, galactose and fructose • Disaccharides: double sugars like sucrose, lactose and maltose • Polysaccharides: chains of sugars like starch, glycogen, cellulose and chitin

9. Monosaccharides • Glucose - "Blood sugar" is the immediate source of energy for cellular respiration. It is a moderately sweet sugar found in vegetables and fruit. • Galactose - Galactose is not normally found in nature, but is mostly hydrolyzed from the disaccharide lactose, which is found in milk. • Fructose - Fructose is also called the fruit sugar. Fructose is found in fruits, honey, and the sole sugar in bull and human semen.

10. Disaccharides • Lactose is the second most common double sugar and is found in milk. It is a combination of glucose and another small sugar called galactose. • Maltose is the third most double common sugar. It is not found in the foods that we eat. Instead, the body makes it when a person eats foods that contain starches such as potatoes and bread. • Sucrose is the most common double sugar that people eat in common foods. It is found in fruits, potatoes, pasta, breads, cereals and other common foods.

11. Polysaccharides • Starch: a storage polysaccharide in plants • Glycogen: a highly branched storage polysaccharide in animals. • Cellulose: a structural polysaccharide in plants. Cellulose is a major component of plant cell walls. • Chitin: a structural polysaccharide in fungi and animals. Chitin stiffens the cell walls of fungi and some algae and is an important component of the exoskeletons of insects and crustaceans.

12. Lipids • Include fats, phospholipids and steroids • Insoluble in water • Functions include: • Provide long-term energy storage • Act as insulators • Important in cell membranes • Act as hormones

13. Lipids (cont.) • Structure: • Fats: a glycerol and 3 fatty acids • Phospholipids: a glycerol, a phosphate group and 2 fatty acids • Steroids: four fused rings with various side groups

14. Nucleic Acids • Large, complex molecules that include deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) • Function in carrying genetic information • Composed of nucleotides

15. Proteins • Make up ½ of the dry body weight • Have several functions including: • Movement (muscles) • Structure (collagen) • Regulation (enzymes) • Transport (hemoglobin) • Nutrition • Defense (antibodies)

16. Proteins (cont.) • Structure is a complex molecule composed of 20 different, smaller molecules called amino acids • The amino acids are bound to each other by a peptide bond.

17. Enzymes • A group of proteins that act as catalysts • A catalyst is a substance that speeds up the rate of a chemical reaction • Enzymes are not used up during the reaction, so once they catalyze the reaction, they can be used again and again Unchanged Enzyme

18. Enzymes (cont.) • The substance that binds to the enzyme is called the substrate • The enzyme/substrate complex must have the correct shape in order to bind • The location on the enzyme where the substrate binds is called the active site. The enzyme-substrate complex is like a lock and key mechanism. Substrate Enzyme

19. Enzymes (cont.) • Enzymes can catalyze reactions that break down the substrate (catabolic) or join two substrates together (anabolic)

20. Activation Energy • Enzymes catalyze reactions by decreasing the activation energy, the amount of energy needed to start a reaction. • The energy released is the same whether the reaction is catalyzed by an enzyme or not.

21. Enzyme Inhibitors • Substances that bind to the active sites of enzymes but are not the substrate are known as competitive inhibitors because they compete with the substrate for the active site

22. Enzyme Inhibitors • Substances that bind to enzymes at a site other than the active site are called non-competitive inhibitors • When non-competitive inhibitors bind to the enzyme, the enzyme changes shape so the substrate can no longer bind to the active site