Chemical Composition of Cells

Question 1

covalent bond

Answer 1

bond in which electrons are shared between atoms. in biology, considered a strong bond.

Question 2

macromolecule

Answer 2

large, complex organic macromolecules

Question 3

monomer

Answer 3

small molecule used as a building block to make polymers

Question 4

polymer

Answer 4

long molecules consisting of many identical or similar monomer “building blocks” linked by covalent bonds

Question 5

dehydration reaction

Answer 5

H and OH removed from monomers so that they can be linked. requires enzymes and energy. produces water.

Question 6

hydrolysis reaction

Answer 6

degradation of polymers. covalent bond within a polymer is broken, water is split into H and OH, which attach where the covalent bond used to be. Releases energy. requires enzymes.

Question 7

amphipathic

Answer 7

having both hydrophilic and hydrophobic segments

Question 8

major classes of biological macromolecules

Answer 8

• carbohydrates
• lipids
• nucleic acids
• proteins

Question 9

carbohydrates (function)

Answer 9

energy storage:
Plants-sugars (mono and disaccharides) and starch (polysaccharide)
Animals-glycogen in liver and muscles (polysaccharide)

structure:
plants-cellulose in cell walls (polysaccharide)
animals-chitin in exoskeletons

Question 10

carbohydrate monomer

Answer 10

monosaccharide:
5- or 6-carbon linear or cyclic molecule
one carbon has a carboxyl group (if linear) or hemiacetal/hemiketal (if ring shaped) and the remaining carbons have hydroxyl groups
-contain only C, H, O

Question 11

glycosidic linkage

Answer 11

covalent bond that links monosaccharides
-water is removed by taking a H from one molecule and an OH from the other, leaving the CO of one molecule to join the C of the other (-C-O-C-)

Question 12

lipids (function)

Answer 12

long term energy storage-fats and lipids (triacylglycerol)
structure-phospholipids in cellular membranes
modulate membrane fluidity-cholesterol
signaling-sterols

Question 13

triacylglycerol

Answer 13

subset of lipids
glycerol (3Cs and 3 OHs) and fatty acids (carbohydrate chains with a carboxyl group on one end)
not polymers
-fatty acids attached to glycerol by ester linkage
-store energy long term
contain C, H, O

Question 14

phospholipid

Answer 14

subset of lipids
-(charged or polar headgroup bonded to) phosphate group bonded to glycerol with two fatty acid tails
-structural function, make up cell membranes
contain C, H, O, P, and many headgroups contain N

Question 15

sterols

Answer 15

subset of lipids

• exist only as monomeric compounds
• structure of 4 fused carbon rings with varying functional group attachments

Question 16

cholesterol

Answer 16

sterol, a subset of lipids

• precursor to all other sterols
• component of animal cell membranes (modulates fluidity)
• synthesized in liver, consumed in animal fats

Question 17

nucleic acids (function)

Answer 17

• DNA stores genetic material

- RNA uses and decodes genetic material

Question 18

nucleotide

Answer 18

monomer of nucleic acids

• composed of pentose sugar, phosphate group and nitrogenous base
• composed of C, H, O, N, P

Question 19

pentose sugar

Answer 19

-substituent of nucleotides (nucleic acid monomers)
5-membered carbon ring
in ribose (RNA), C2 has OH group
in deoxyribose (DNA), C2 has H only

Question 20

Nitrogenous bases

Answer 20

pyrimidines:
6-membered C and N rings
include cytosine, thymine (DNA) and uracil (RNA)
purines: 
fused 5- and 6-membered C and N rings
include adenine and guanine

Question 21

nucleic acids

Answer 21

chain of nucleotides with sugar-phosphate backbone bound by phosphodiester linkage (-C-Pgroup-C-)
-link 3’-OH of one nucleotide to 5’-Pgroup of the next

Question 22

proteins (function)

Answer 22

• accelerate chemical reactions (enzymes)
• transportation of materials across the cell membrane
• movement (contractile and motor proteins)
• structure

Question 23

amino acid

Answer 23

protein monomer
-amino group and carboxyl group bonded to central alpha carbon
-side chain R-group also bonded to the central carbon
Contain C, H, O, N, and sometimes S (from the side chain, always check structure if given)

Question 24

1 protein structure

Answer 24

amino acids linked by peptide bonds in a unique order determined by DNA
(stabilized by peptide bonds)

Question 25

2 protein structure

Answer 25

stabilized by backbone interactions

• hydrogen bonding between amino groups and carboxyl groups in the polypeptide backbone
• alpha helix, the coiling of a single amino acid around itself
• beta pleated sheets, where amino acid chain segments fold side by side (can be a single amino acid or multiple)

Question 26

3 protein structure

Answer 26

the overall shape of a single polypeptide
-stabilized by side chain interactions
(H-bonding, ionic bonding, disulfide covalent bonding, hydrophobic effect and VWD forces (all between side chains))

Question 27

4 protein structure

Answer 27

structure of multiple polypeptides folded together
-stabilized by same side chain interactions as 3 structure (H-bonding, ionic bonding, disulfide covalent bonding, hydrophobic effect and VWD forces (all between side chains))

Question 28

prions

Answer 28

a prion is an /infectious protein particle/

• cannot be degraded/denatured by heat or acid
• derived from a protein in our brains, PrP
• cause normal proteins, PrP^C to refold into abnormally into prion particles, PrP^Sc