Unit 1: Chemistry of Life

Question 1

the makeup of H2O

Answer 1

• polar molecule that can form hydrogen bonds
• covalent bonds between oxygen and hydrogen atoms; oxygen has a higher electronegativity so the electrons gravitate towards the oxygen = POLAR covalent bond

Question 2

properties of water

Answer 2

1) cohesive/adhesive behavior: water is STICKY
2) high specific heat: more energy required to separate water molecules during phase changes
3) moderating climate: high heat capacity –> ability to absorb and release high amounts of energy
4) expansion upon freezing: ice floats on water, ice insulates water beneath it
5) solvent of life: partially positive and negative ends allow it to dissolve ionic compounds

Question 3

pH

Answer 3

• pH: power of Hydrogen = concentration of H+ ions in solution
• pH = -log[H+]
• acidic: less than 7 (more H+)
• basic: more than 7 (more OH-)
• neutral: 7 (water)
• buffers: maintain constant pH levels by forming acids or bases

Question 4

biological macromolecules

Answer 4

• primarily made of CHONPS: carbon, hydrogen, oxygen, nitrogen, phosphorus, and sulfur
• structure and function of a macromolecule is determined by the monomers it’s made from

Question 5

carbon

Answer 5

“backbone” of macromolecules; found in all macromolecules; very versatile in how it bonds to other atoms; four valence electrons & single, double, or triple bonds

Question 6

hydrogen

Answer 6

one valence electron & one bond; found in all macromolecules; sometimes not drawn in (but always there)

Question 7

oxygen

Answer 7

six valence electrons & two bonds, found in all types of macromolecules

Question 8

nitrogen

Answer 8

five valence electrons & three bonds; found in nucleic acids and proteins

Question 9

phosphorus

Answer 9

five valence electrons & three bonds; found in nucleic acids and lipids

Question 10

sulfur

Answer 10

six valence electrons & two bonds; typically found in proteins

Question 11

dehydration synthesis

Answer 11

links monomers to form larger molecules by taking an H & HO to form a separate H2O molecule

Question 12

hydrolysis

Answer 12

separates monomers by distributing the H & HO from an H2O molecule

Question 13

carbohydrates

Answer 13

• made of monosaccharides
• store energy or have structural functions; linkages determine function

Question 14

lipids

Answer 14

• nonpolar
• energy storage, cell membranes, insulation
• made of fatty acids
• include phospholipids and steroids

Question 15

phospholipids

Answer 15

• glycerol molecule + two fatty acids + phosphate group
• have both hydrophobic and hydrophilic regions

Question 16

nucleic acids

Answer 16

• made of nucleotides
• carry genetic info
• consist of 5-carbon sugar, nitrogenous base, and phosphate group
• directionality: phosphate group attached to 5’ carbon side and 3’ carbon has hydroxyl group for new nucleotides to be added to

Question 17

proteins

Answer 17

• made of amino acids
• primary, secondary, tertiary, and quaternary structure
• enzyme catalysis, maintaining cell structure, cell signaling, cell recognition

Question 18

amino acids

Answer 18

• amino group + carboxylic acid group + hydrogen atom + R-group

Question 19

R-group

Answer 19

unique for each amino acid; determines amino acid’s identity

Question 20

primary structure

Answer 20

• amino acids joined by peptide bonds
• directionality: amino (NH2) terminus and carboxyl (COOH) terminus
• order of amino acids determines primary structure

Question 21

secondary structure

Answer 21

hydrogen bonds form between adjacent amino acids, forming secondary structure; includes alpha helixes and beta-plated sheets

Question 22

tertiary structure

Answer 22

• 3D folded protein, determined by hydrophobic/hydrophilic interactions between R-groups
• most stable: hydrophilic R-group son the surface and hydrophobic R-groups on the inside

Question 23

quaternary structure

Answer 23

• multiple polypeptide chains joined together to complete protein

Question 24

DNA

Answer 24

• sugar: deoxyribose
• nitrogenous bases: adenine, thymine, cytosine, guanine
• structure: double-stranded helix
• function: holds genetic info
• location: usually found in nucleus

Question 25

RNA

Answer 25

• sugar: ribose
• nitrogenous bases: adenine, uracil, cytosine, guanine
• structure: usually single-stranded, but can form 3D structure when folded
• function: transcribes and regulations the expression of genetic info
• location: nucleus and cytoplasm

Question 26

pyrimidines

Answer 26

• class of macromolecules that includes thymine, uracil, and cytosine

Question 27

purines

Answer 27

• class of macromolecules that includes adenine and guanine

Question 28

pyrimidine + purine bonds

Answer 28

• when DNA strands form, a purine complements a pyrimidine and forms hydrogen bonds
• thymine + adenine = 2 H-bonds
• guanine + cytosine = 3 H-bonds