lec 2- The chemical basis of life

Question 1

what are covalent bonds?

Answer 1

covalent bonds are when pairs of electrons are shared between pairs of atoms

Question 2

when is an atom most stable?

Answer 2

an atom is most stable when its outermost electron shell is filled

Question 3

what does carbon share electron pairs with most commonly?

Answer 3

carbon, hydrogen, oxygen, nitrogen, sulfur

Question 4

which ones are flexible:
single bond
double bond
triple bond

Answer 4

flexible
not flexible
not flexible

Question 5

what is a nonpolar covalent bond?

Answer 5

equal sharing of electrons (eg. carbon dioxide)

Question 6

what is a polar covalent bond?

Answer 6

unequal sharing of electrons

Question 7

can a polar covalent bonded hydrogen still form another bond?

Answer 7

Yes, a hydrogen bond with an electronegative atom

Question 8

what is a hydrogen bond?

Answer 8

a weak chemical interaction, between an electronegative atom and a hydrogen and a hydrogen covalently linked to another electronegative atom

Question 9

how can weak hydrogen bonds become strong?

Answer 9

by having multiple in one place, hence why they are strong in DNA

Question 10

does water hydrogen bond with another water molecule?

Answer 10

yes

Question 11

what accounts for 75-85% of a cells weight?

Answer 11

water

Question 12

why does sweating make the body cooler?

Answer 12

sweating makes the body cooler because energy is needed to break hydrogen bonds, and when evaporation occurs, the energy is absorbed getting rid of the heat and making the body cooler

Question 13

how many hydrogen bonds can a water molecule form?

Answer 13

up to 4 hydrogen bonds simultaneously

Question 14

what happens if all water molecules have 4 hydrogen bonds?

Answer 14

becomes ice

Question 15

what are ionic bonds?

Answer 15

attraction between charged atoms

Question 16

if water is not around, are ionic bonds strong?

Answer 16

yes

Question 17

do covalent bonds require more energy to break than noncovalent bonds?

Answer 17

yes

Question 18

what is hydrophobic effect?

Answer 18

hydrophobic effect is when a nonpolar molecule interacts with water, causing water to form a cage around it called clathrate because the nonpolar molecules do not want to form bonds or interact with water

Question 19

what are the major components of cell membranes?

Answer 19

lipids, proteins, and carbohydrates