IB Biology

Question 1

Define a hydrogen bond

Answer 1

force when a slightly positive hydrogen atom in one polar molecule is attracted to slightly negative atom of another polar molecule

Question 2

Buoyancy as a physical property of water (2)

Answer 2

buoyancy = force exerted upward by fluid which counteracts gravity

density of object < density of liquid = buoyancy force > gravity = object will float

Question 3

Why does ice float on water (2)

Answer 3

ice is less dense as water

pattern of hydrogen bonding of ice is less dense

Question 4

Viscosity as a physical property of water

Answer 4

pure water has high viscosity - hydrogen bonds cause internal friction

Question 5

Define viscosity (3)

Answer 5

how easily a fluid is able to flow

more viscosity > more friction + resistance to flow

due to internal friction when on part of a fluid moves faster relative to another part

Question 6

Define cohesion

Answer 6

ability of water molecules to stick together

Question 7

Cohesion of water for water transport in plants (5)

Answer 7

water is sucked upwards in continuous columns

column of water under tension from both ends

tension from roots due to attraction between soil + water

tension from leaves as water lost by evaporation + attraction between water and leaf cell walls

water moves upwards because force in leaves > force in roots

Question 8

Explain surface tension of water (2)

Answer 8

cohesion between water molecules > attraction between water and floating object

object must break hydrogen bonds to break the surface of water

Question 9

Define adhesion for water (2)

Answer 9

hydrogen bonds forming between water + surface of solid composed of polar molecules

allows water to stick to other objects

Question 10

Define capillary action

Answer 10

the ability of a liquid to flow through a narrow tube without external forces

Question 11

Why water is a good solvent (5)

Answer 11

polar nature of water molecule forms shells around both charged + polar molecules

prevents molecules from clumping together so they remain in solution

water’s partially negative oxygen pole attracted to positive ions

water’s partially positive hydrogen pole attracted to negative ions

both dissolve

Question 12

Define hydrophilic

Answer 12

substances chemically attracted to water

Question 13

Examples of hydrophilic substances (2)

Answer 13

glucose

positive or negative ions (e.g sodium + chloride ions)

Question 14

Define hydrophobic (3)

Answer 14

substances not attracted to water

more attracted to other hydrophobic substances

insoluble in water

Question 15

Examples of hydrophobic substances (2)

Answer 15

non-polar molecules (not positive or negative)

lipids

Question 16

Metabolism in water solvent property (2)

Answer 16

solutes can move + interact

allows for substrates to touch the active sites of enzymes

Question 17

Thermal conductivity as a property of water

Answer 17

high thermal conductivity = good at absorbing/transferring heat

Question 18

Define thermal conductivity

Answer 18

the rate at which heat passes through a material

Question 19

Applications of water’s thermal conductivity

Answer 19

high water content in blood –> can carry heat from parts of body to parts that need more heat or parts that dissipate heat

Question 20

Define specific heat capacity

Answer 20

energy required to raise the temperature of 1g of material by 1 C

Question 21

Specific heat capacity as a characteristic of water (2)

Answer 21

increase in temperature must have hydrogen bonds broken with energy

must lose an equal amount of energy to cool down

Question 22

Applications of specific heat capacity of water (2)

Answer 22

aquatic habitats are more thermally stable

helps mammals maintain constant body temperatures

Question 23

Why water is able to be retained on earth (2)

Answer 23

distance between sun and earth = temperatures are not high enough to vaporize water

strong gravity = oceans is held to surface, gases kept within atmosphere

Question 24

Define the Goldilocks Zone (2)

Answer 24

habitable zone around a star

location depends on size of star, amount of energy it emits, size of planet

Question 25

Parts of nucleotides (3)

Answer 25

pentose sugar with 5 carbon atoms

phosphate group : acidic and negatively charged part of nucleic acids

base that contains nitrogen - has either 1 or 2 rings of atoms in its structure

Question 26

Phosphate group nucleotide diagram

Answer 26

O-
|
O- – P – O –
||
O

Question 27

Deoxyribose sugar nucleotide diagram

Answer 27

– CH2
| O
CH CH – N
CH CH
| |
OH OH

Question 28

How are nucleotides linked together

Answer 28

covalent bonds formed between phosphate of one nucleotide and the pentose sugar of another

Question 29

What is the DNA and RNA backbone made of

Answer 29

chain between sugar and phosphate

Question 30

Bases in DNA (4)

Answer 30

Adenine (A)

Cytosine (C)

Guanine (G)

Thymine (T)

Question 31

Bases in RNA (4)

Answer 31

Adenine (A)

Cytosine (C)

Guanine (G)

Uracil (U)

Question 32

Links between bases of DNA (2)

Answer 32

Adenine forms hydrogen bonds with thymine

guanine forms hydrogen bonds with cytosine

Question 33

Strands of DNA nucleotides in relation to each other (2)

Answer 33

(anti)parallel - parallel but run in opposite directions

one strand ends with phosphate group other ends with deoxyribose (pentose sugar)

Question 34

Differences between DNA and RNA (3)

Answer 34

DNA is double-stranded, RNA is single-stranded

RNA has uracil instead of thymine in DNA

pentose sugar of DNA is deoxyribose, pentose sugar of RNA is ribose

Question 35

How do RNA nucleotide join together

Answer 35

condensation reaction - molecules combine while losing water

Question 36

What happens in DNA replication (3)

Answer 36

2 strands of double helix separate

newly made strand should be complementary to the original

changes 1 DNA molecule into 2 identical ones

Question 37

Number of possible combinations of DNA bases (2)

Answer 37

4^n

where n is the number of bases