Chapter 2

Question 1

what elements make up 96% of cells

Answer 1

C, H, N, O

Question 2

Chemical properties of an element are determined by the number and arrangement of _____

Answer 2

electrons

Question 3

an atom is most stable when its _____

Answer 3

outer electron shell is completely filled

Question 4

covalent bond

Answer 4

electrons shared between two adjacent atoms

Question 5

cells are ___% water by mass

Answer 5

70

Question 6

most essential role of fatty acids

Answer 6

form lipids that assemble into sheetlike cell membranes

Question 7

weak noncovalent interactions

Answer 7

hydrogen bonds
electrostatic attractions
var der Waals
hydrophobic forces

Question 8

the atomic number of an element is determined by the number of ____

Answer 8

protons

Question 9

ionic bond

Answer 9

electrons are donated by one atom to another

Question 10

bond strength is measured by _____

Answer 10

the amount of energy that must be supplied to break the bond

Question 11

positive ions are called

Answer 11

cations

Question 12

negative ions are called

Answer 12

anions

Question 13

hydrophilic

Answer 13

polar
“water-loving”
mix well with water

Question 14

hydrophobic

Answer 14

nonpolar
doesn’t mix with water

Question 15

electrostatic attraction

Answer 15

force that draws together oppositely charged atoms

Question 16

buffers

Answer 16

mixture of weak acids and bases that maintains the pH of a solution by releasing and taking up protons

Question 17

why can scientists substitute radioisotopes for isotopes commonly found in cells when conducting experiments?

Answer 17

radioisotopes of an element differ only in the number of neutrons, so therefore they behave the same way chemically as the isotopes that occur in cells

Question 18

which subatomic particle is found in the nucleus of a hydrogen atom?

Answer 18

a proton only

Question 19

the atomic weight of an atom is its mass relative to that of what?

Answer 19

hydrogen

Question 20

four major families of small organic molecules

Answer 20

sugars
fatty acids
amino acids
nucleotide

Question 21

isomers

Answer 21

sets of molecules with the same chemical formula but different structures

Question 22

optical isomers

Answer 22

mirror-image pairs of molecules with different structures but the same chemical formula

Question 23

monosaccharides can be linked by ____ to form ____

Answer 23

covalent bonds
carbohydrates

Question 24

how are sugars linked together

Answer 24

a bond is formed between an -OH group on one sugar and an -OH group on another by a condensation reaction

Question 25

condensation reaction

Answer 25

chemical reaction in which a covalent bond is formed between two molecules as water is expelled

Question 26

hydrolysis

Answer 26

chemical reaction that involves cleavage of a covalent bond with the accompanying consumption of water (breaks bonds)

Question 27

the monosaccharide ____ has a central role as an energy source for cells

Answer 27

glucose

Question 28

sugars ___ function exclusively in the production and storage of energy

Answer 28

DO NOT

Question 29

sugars can be used to make ________ such as cellulose

Answer 29

mechanical supports

Question 30

smaller oligosaccharides can be covalently linked to proteins to form ____ or to lipids to form ____

Answer 30

glycoproteins glycolipids

Question 31

fatty acid

Answer 31

molecules that consists of a carboxylic acid attached to a long hydrocarbon chain

Question 32

what are fatty acids mainly used for

Answer 32

major source of energy during metabolism as a starting point for the synthesis of phospholipids

Question 33

amphipathic

Answer 33

possess both hydrophobic and hydrophilic regions

Question 34

when is a hydrocarbon tail saturated

Answer 34

contains the maximum possible number of hydrogens and therefore has no double bonds between its carbon atoms

Question 35

when is a hydrocarbon tail unsaturated

Answer 35

contain one or more double bonds between carbon atoms

Question 36

fatty acids are stored in the ___ of many cells in the form of fat droplets composed of _____ molecules

Answer 36

cytosol triacylglycerol

Question 37

lipids

Answer 37

organic molecule that is insoluble in water but readily dissolves in nonpolar organic solvents

Question 38

lipid bilayer

Answer 38

thin pair of closely juxtaposed sheets, composed mainly of phospholipid molecules, that forms the structural basis for all cell membranes

Question 39

amino acids

Answer 39

small organic molecules that possess a carboxylic acid group (-COOH) C-terminus and an amino group (-NH2) N-terminus, both attached to a central carbon atom

Question 40

amino acids are covalently bonded to form ____ via _____ bonds

Answer 40

proteins/polypeptides peptide

Question 41

nucleotides

Answer 41

basic building block of the nucleic acids, DNA, and RNA (nucleoside linked to a phosphate)

Question 42

pyrimidine nucleotide bases

Answer 42

six-membered pyrimidine ring cytosine (C) thymine (T) uracil (U)

Question 43

purine nucleotide bases

Answer 43

five-membered ring fused to the six-membered ring guanine (G) adenine (A)

Question 44

nucleic acids are formed by covalent _____

Answer 44

phosphodiester bonds

Question 45

on the basis of mass, which is most abundant in a living bacterial cell?

Answer 45

water

Question 46

covalent bonds are formed by the sharing of electrons. In the cell, how are covalent bonds broken?

Answer 46

by enzyme catalysis that is specific for a protein and its substrate

Question 47

macromolecule

Answer 47

polymer built from covalently linked subunits (monomers)

Question 48

Many proteins act as highly specific ____

Answer 48

enzymes

Question 49

why would polymer chains have great flexibility

Answer 49

covalent bonds

Question 50

what are macromolecules constrained by?

Answer 50

noncovalent bonds

Question 51

enzymes recognize their substrates via ____

Answer 51

noncovalent bonds

Question 52

which of the following would most likely interact by forming an ionic bond? -the enzyme hexokinase and its substrate glucose -two strands of DNA -fatty acid chain and inorganic phosphate -ATP and magnesium cations

Answer 52

ATP and magnesium cations

Question 53

How do protein, nucleic acid, and polysaccharide molecules polymerize?

Answer 53

by condensation reactions