1. Chapter 3: Part II Biochemistry

2. Water makes up between 60 and 70% of organisms’ bodies

3. Polarity Molecules with partial charges on opposite ends are polar Oxygen atoms are larger than hydrogen, so electrons spend more time near oxygen, giving it a slight negative charge, and hydrogen a slight positive charge.

4. Why is polarity important? “Like dissolves like” – polar substances are good at dissolving other polar substances and substances that are ionic – hydrophilic Ex: sugar and salt Polar substances DO NOT dissolve substances that are nonpolar (without charged ends) – hydrophobic Ex: oil, grease, wax Polarity helps chemical reactions to take place.

5. Negative ends of water are attracted to Na + Positive ends of water are attracted to Cl -

6. Hydrogen bonds form when a covalently-bonded H + is attracted to a negatively-charged atom in a neighboring molecule (such as oxygen in neighboring water molecule, or chlorine in NaCl). Hydrogen bonds are relatively weak bonds.

8. Properties of water Ice floats Water absorbs and retains heat Water molecules stick to each other Water molecules stick to other polar substances

9. Ice floats: When water freezes, hydrogen bonds lock water molecules into a structure that has empty spaces, making it less dense than liquid water Liquid waterIce

10. Water absorbs and retains heat Because of hydrogen bonds, water can absorb large amounts of energy Absorbs lot of heat before it boils Helps keep cells at an even temperature despite changes in the environment – homeostasis again!! Allows large bodies of water to maintain a relatively constant temperature.

11. Water molecules stick to each other Cohesion – the attraction of water molecules to each other Cohesive forces are strong enough to cause water to act as though it has a thin “skin” on its surface – surface tension. Jesus lizards walking on surface tension

12. Water molecules stick to other polar substances Adhesion - the attraction between particles of different substances. Ex: Water sticks to the surface of your car after it rains, sticks to your skin after a shower

13. Capillarity - adhesion and cohesion enable water molecules to move upward through narrow tubes Ex: water moving through a stem of a plant, helps blood flow in blood vessels

14. Organic Molecules Examples: carbohydrates, lipids, proteins, nucleic acids Always contain carbon Why carbon? Carbon has 4 electrons in outer shell – can form covalent bonds with up to 4 other atoms.

15. Carbon can share electrons with other carbon atoms to form a chain Hydrocarbon chain can turn back on itself to form a ring

16. Carbohydrates Importance: Quick energy and short-term energy storage Make up cell wall in plants Make up shells of crabs, lobsters and insects Help cells to recognize one another

17. Monosaccharides (single sugar): glucose – blood sugar fructose – found in fruit galactose – found in milk Glucose, fructose, and galactose all have the same molecular formula, C 6 H 12 O 6, but different structural formulas

18. Fructose Galactose Glucose

19. Below are 3 ways to represent glucose:

20. Disaccharide - made from linking two monosaccharides together. Examples of disaccharides: Maltose = glucose + glucose Sucrose = glucose + fructose Lactose = glucose + galactose

21. Sucrose

22. Polysaccharides – contain many glucose units Ex: starch, glycogen, & cellulose Starch - can be up to 4000 glucose units

23. Ex: Glycogen – after eating starchy foods, the body converts glucose in the blood into glycogen – stored in liver and released as needed

24. Ex: Cellulose – found in plant cell walls. Glucose units joined in such a way that we can’t digest it – passes through as roughage – may help prevent colon cancer

25. Foods they can be found in: Simple sugars –Fruit, milk, sweets, sodas, juices Starches – Breads, pasta, rice, corn, wheat, cereal, leafy vegetables, carrots

26. Lipids Examples: Fats - solid at room temp. – animal origin Oils - liquid at room temp. – plant origin Waxes – protective covering on plants & animals Phospholipids and steroids Lipids do not dissolve in water - nonpolar

27. Importance: Long-term energy reserves Form membranes in cells Hormones such as testosterone and estrogen Insulation, nerve impulses Repel water – duck feathers

28. Structure – 1 glycerol plus 3 fatty acid molecules

29. Saturated vs. unsaturated fatty acids: Saturated – no double covalent bonds between carbon atoms – makes butter and lard solids Monounsaturated – has 1 double bond between carbon atoms Polyunsaturated – 2 or more double bonds – makes cooking oil liquid Unsaturated and polyunsaturated are better for you than saturated fats

31. Foods they can be found in: Butter, foods fried in oil, bacon, red meat, cheese

32. Proteins Importance: Build living tissue – hair, nails, tendons, ligaments, muscle, bone, etc. Act as enzymes to speed reactions Act as antibodies to fight disease

33. Proteins are made of amino acids Central carbon atom Hydrogen atom Amino group (-NH 2 ) Carboxyl group (-COOH) “R” group – which differs between amino acids

35. Amino acids are joined by peptide bonds to form polypeptides.

36. Foods they can be found in: Meat, eggs, cheese, beans, nuts, soy

37. Levels of organization:

40. Shape of protein is related to its function. When exposed to extremes in heat or pH, proteins change their shape – undergo denaturation – normal bonding between R groups is disturbed. Change cannot be reversed – protein no longer works.

41. Nucleic Acids Examples: DNA (deoxyribonucleic acid) and RNA (ribonucleic acid) Importance: molecules of inheritance – needed for cell reproduction and making proteins Structure – made of nucleotides.

43. DNA is double-stranded, with complementary base pairing – A and T, C and G always pair.