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A-LEVEL BIOLOGY > Water > Flashcards

Water Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

how is water bonded?

A

2 covalent bonds between hydrogens and oxygen

share electrons to get a stable octete

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2
Q

why is water a dipolar molecule?

A

oxygen atoms are slightly -ve -> attract electrons more than slightly +ve hydrogen atoms
unequal charge distribution

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3
Q

why is water important?

A

its a metabolite in: hydrolysis + condensation reactions

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4
Q

whats a metabolite?

A

a substance formed in or necessary for metabolism

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5
Q

whats metabolism?

A

the sum of chemical reactions in the body or a cell

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6
Q

describe the structure of water

A

2 hydrogen atoms covalently bonded to 1 oxygen atom

each hydrogen atom shares a pair of electrons witht he oxygen

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7
Q

why is water a polar molecule? affinity etc.

A

oxygen -> greater affinity for electrons than hydrogens (wants a stable octete) so it pulls electrons closer
makes oxygen slightly -ve and hydrogens slightly +ve
creates 2 charged regions (dipolar)

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8
Q

why does oxygen pull electrons more strongly than hydrogen?

A

it has more protons + a greater affinity

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9
Q

how do hydrogen bonds form?

A

slightly -ve charge of oxygen atom makes it attract the slightly +ve hydrogen atom of another water molecule

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10
Q

where do a lot of water’s properties come from?

A

its ability to form hydrogen bonds

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11
Q

why does water have a very stable structure?

A

it has numerous hydrogen bonds

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12
Q

functions of water as a solvent?

A

it acts as a solvent for other polar molecules:
salts
simple alcohols
sugars

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13
Q

why is water important as a solvent?

A

most metabolic reactions occur in water as it allow molecules to move freely

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14
Q

why is water attracted to other polar molecules?

A

its a polar molecule itself

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15
Q

define hydrophobic

A

substances that cant become part of water’s hydrogen bonded structure
don’t dissolve in water

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16
Q

examples of substances that don’t dissolve in water?

A

triglycerides

large polymers

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17
Q

what are triglycerides?

A

a type of fat

common type of fat in the body

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18
Q

define shc

A

amount of energy needed to increase the temp of 1g of a substance by 10°C

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19
Q

why is water’s shc high?

A

it has hydrogen bonds

high amount of energy required

20
Q

describe water as a cooling agent

A

high freezing + boiling points for its size due to H-bonds

a lot of energy needed to change states

21
Q

why is water a good coolant?

A

has a high latent heat of vapourisation

lots of energy needed to change state from liq. to gas

22
Q

describe water’s insulation

A

max density -> 4C
so coolest water is at the top -> water freezes from the top
this is important in aquatic habitats

23
Q

describe water as a reagent

A

used in hydrolysis

used as a source of hydrogen e.g. in photosynthesis

24
Q

how can polymers disassemble?

A

by hydrolysis

it adds a water molecule which breaks a bond

25
Q

why is water a good transport mode?

A

it’s cohesive/sticky

26
Q

what happens during hydrolysis?

A

adds water molecule

breaks bond

27
Q

describe cohesion between water molecules at air-water surface

A

cohesion causes surface tension

can make solid-like surfaces

28
Q

column of water and cohesion explaination

A

cohesion explains why molecules are pulled up a narrow tube (straw) when you drink
like xylem in transpiration

29
Q

other water functions

A 
solvent
latent heat of fusion
buffer
penetration by light
raw material for photosyn.
hydrolysis react.
30
Q

why is water cohesive?

A

due to H-bonds molecules stick together

31
Q

describe adhesion and water molecules

A

due to the nature of water, it’s molecules bind to other molecules

32
Q

describe light and different temps. of water

A

hot water -> light penetrates (less dense)

cold water -> light refracts (more dense)

33
Q

describe maintenance of constant temp. of water

A

water -> high SHC

so no sudden changes in temp (needs a lot of energy) -> doesn’t affect reactions or habitats

34
Q

explain water and latent heat of vaporisation

A

it’s high for water due to strong H-bonds

35
Q

define latent heat of vaporisation

A

amount of heat energy needed to turn a given quantity of liquid into gas

36
Q

explain water and density

A

H-bonds pull molecules close together -> high density

ice has a lower density

37
Q

explain water and surface tension + cohesion

A

H-bonds between molecules pull the molecules on top of a body of liquid downwards towards the others

38
Q

why is water an important solvent in living organisms?

A

most biochemical react. occur in aqueous solution

39
Q

what are vesicles?

A

pack and transport material in cells

40
Q

define hydrophobic

A

charged molecules can’t pass thought cell membrane without help/repel water molecules
not soluble in water

41
Q

define hydrophylic

A

molecules can form ionic or a hydrogen bond with water molecule
soluble in water

42
Q

how are different water molecules bonded?

A

hydrogen bond forms between non-bonding pair of electrons on the oxygen atom of 1 water molecule and the hydrogen atom (‘positive end’) of another water molecule

43
Q

describe sucrose

A

contains glucose
non-reducing
has glycosidic bonds
transported in phloem

44
Q

describe maltose

A

contains glucose
reducing
has glycosidic bonds
in malt foods in which starch is broken down

45
Q

which bond joins 2 monosaccharides?

A

1-4 glycosidic bond

46
Q

why does ice have a low density?

A

orientation of h-bonds causes the water molecules to push further apart

A-LEVEL BIOLOGY (8 decks)

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