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IB Biology > A1 > Flashcards

A1 Flashcards

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1
Q

Why is water essential for life? (including examples)

A
  • Cells and living organisms did not evolve until temperatures were appropriate for liquid water on earth
  • The first cells arose from oceans, as a result of water being the solvent for these building blocks
  • Cytoplasm of cells are water based
  • Water based blood in animals which transports materials between cells
  • These aqueous solutions are essential for life and all living processes
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2
Q

Why is water as a solvent important?

A
  • Significant, because it’s properties make it able to dissolve many different solutes
  • Examples: Cytoplasm of cells, Intracellular fluid, blood streams, habitats such as lakes, oceans and rivers
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3
Q

Why does water show cohesive properties?

A
  • The oxygen of a water molecule has a slight negative
  • The hydrogen of another water molecule has a slight positive
  • This causes them to be attracted to one another, and form a weak hydrogen bond between the two water molecules
  • The bonds between different water molecules are an example of COHESION
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4
Q

Why does water show adhesive properties?

A

When water forms hydrogen bonds/ is attracted to other polar molecules or surfaces, this is known as ADHESION

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5
Q

What is polarity?

A
  • When electrons are not equally shared in a molecule- instead are pulled more closely to one element than the other
  • This creates a slight/ partial charge in the elements
  • The molecule bends with a positive and negative pole
  • This creates a molecule with two poles of opposite charges= POLAR
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6
Q

What is cohesion?

A

When two polar molecules form weak bonds between them (known as hydrogen bonds)

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7
Q

What is capillary action?

A

The ability of fluid/ water to move against gravity up a narrow thin tube without any force.

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8
Q

What is adhesion?

A

When the slight positive charge of one molecule is attracted to the slight negative charge of a different molecule. This causes two different polar molecules to form hydrogen bonds.

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9
Q

What is a solvent?

A
  • The substance that solutes can dissolve into
  • Larger volumed substances, able to chemically dissolve solutes to create a solution
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10
Q

How does water form hydrogen bonds?

A
  • If two water molecules are in close proximity to each other, the slight negative charge on the oxygen of one molecule is attracted to the slight positive of the hydrogen of the other molecule
  • This forms a weaker, temporary bond between them called a HYDROGEN BOND
  • The bond is weaker than covalent and ionic bonds and is readily broken by heat or distance
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11
Q

How does the cohesion of water molecules create surface tension?

A
  • At the surface of a body of water there are hydrogen bonds between the molecules next to and below it but no bonds pulling up
  • This is because the attraction to water is much less pulling it closer to the other water molecules instead
  • This means the sideways and below bonds are actually stronger and more force is needed to break them that other cohesive bonds in water
  • Those stronger cohesive bonds at the surface are called surface tension
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12
Q

How do reptiles use surface tension?

A
  • The force of surface tension means that light objects can float on the surface of water without breaking those hydrogen bonds
  • This gives water a solid-like quality IF
    1. There is strong surface tension
    2. The object is light
    3. It moves quickly
  • Animals e.g insects use this to walk along the surface of the water- need light legs (many) and able to move quickly
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13
Q

How does water’s cohesive and adhesive properties allow the transport of water through xylem tissue?

A
  • Plants must transport water from soil to leaves without force
  • The tubes water travels in= xylem (like many tiny straws)
  • Cohesion- as water molecules leave the leaf, other molecules are pulled up, so water continuously moves upward
  • Adhesion- attraction between polar cellulose of cell wall and polar water molecules also pulls water up
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14
Q

What is an aqueous solution?

A
  • Any solution that has water as its solvent
  • Examples include the cytoplasm of cells, intercellular fluids and the blood stream
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15
Q

What does hydrophilic mean?

A

Water loving
A hydrophilic substance can either:
* Readily dissolve in water
* Be a polar substance that does not dissolve in water but has an attraction to water
Any substances that have charges that react with water in any way= HYDROPHILIC

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16
Q

What does hydrophobic mean?

A

A substance that is not attracted to water
Hydrophobic substances can either:
* Repel water
* Not be attracted to water

They do not dissolve in water and are attracted to other non-polar molecules instead

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17
Q

What is the buoyant force?

A

The buoyant force is the upwards force exerted on an object when it is placed in a medium (usually water)

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18
Q

Why are objects buoyant?

A
  • The pressure of the water below is greater than the pressure of the air above
  • If the density of the object is less than the buoyancy force, the object will FLOAT
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19
Q

What is viscosity?

A
  • Viscosity is the ‘stickiness’ of a fluid, that determines how easily it can flow
  • It comes from the friction when one part of a fluid moves relative to another
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20
Q

What is water’s viscosity and why?

A
  • Pure water has a higher viscosity than other pure fluids e.g alcohol
  • This is because of the hydrogen bonds
  • Note: the addition of solutes increases viscosity- sea water has a higher viscosity than pure water
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21
Q

What is thermal conductivity?

A

The rate at which heat passes through a material

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22
Q

What is water’s thermal conductivity and why is it important?

A
  • Water has a relatively high thermal conductivity compared to air and fats
  • This has implications for aquatic organisms who lose heat, but is also helpful for being used to transfer heat
    (e.g blood can move heat towards the surface of our bodies to remove heat from the body)
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23
Q

What is specific heat capacity?

A

How much heat can be absorbed without changing temperature.

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24
Q

What is water’s specific heat capacity and why is it important?

A
  • Water has a high specific heat capacity- it will take a lot of absorbed heat before it will raise a degree celcius
  • This is important for aquatic life as it means water does not rapidly change temperature
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25
Q

What are some examples of hydrophilic molecules in living organisms?

A
  • Salt- an ionic compound that dissolves in water
  • Glucose- a polar covalent compound that dissolves in water
  • Cellulose- a large polar compound that water forms adhesive bonds with water
26
Q

What are some examples of hydrophobic molecules in living organisms?

A

Fats, including:
* Body fats
* Lipids that make up our cell membrane (phospholipid bilayer)
* Hormones- fat based
* Cuticles on leaves which prevent water loss

27
Q

What is the difference between buoyancy in water and air?

A
  • Water- reasonably high buoyancy force- if objects have a lower density, they could float
  • Air- almost no buoyancy force so nothing can effectively float in air

DUE TO: Hydrogen bonds and cohesion in water, little to no cohesion in air

28
Q

What is the difference between viscosity in water and air?

A
  • Water- has some viscosity due to H bonds- e.g swimming requires muscular force
  • Air- Almost no viscosity, objects move through with little resistance

DUE TO: Hydrogen bonds and cohesion in water, little to no cohesion in air

29
Q

What is the difference between thermal conductivity in water and air?

A
  • Water- has a high thermal conductivity- organisms lose heat to water
  • Air- lower thermal conductivity- better able to sustain temperature
30
Q

What is the difference between specific heat capacity in water and air?

A
  • Water- high heat capacity- requires lots of heat/ energy to raise temperature- stable temps for aquatic organisms
  • Air- lower heat capacity- air temp is highly variable
31
Q

How do black throated loon and ringed seals adapt to buoyancy?

A
  • Loon- light enough to float on the surface
  • Seal- allows head to stay above water and breathe oxygen
32
Q

How do black throated loon and ringed seals adapt to viscosity?

A
  • Loon- webbed feet and streamlined shape to combat viscosity- to move and dive for food
  • Seal- paddle feet and streamlined shape to combat viscosity- to swim for food and avoid predators
33
Q

How do black throated loon and ringed seals adapt to thermal conductivity?

A
  • Loon- has an oil gland, uses to coat its feathers with oil to repel water and prevent heat loss
  • Seal- thick layer of blubber to reduce heat loss
34
Q

How do black throated loon and ringed seals adapt to heat capacity?

A
  • Loon- sitting on water can help regulate temp during extremes
  • Seal- helps during extreme air temps- cold arctic air
35
Q

What does extraplanetary mean?

A
  • Outside of Earth and its orbit
  • Occuring in outer space outside of a planet
36
Q

What is an asteroid?

A
  • Small, hydrated rocks that orbit the sun
  • Often rotate and move erratically, leading for collisions
37
Q

What is the asteroid theory in relation to water on Earth?

A
  • Hydrated rocks moving erratically in space, relatively close to Earth
  • Can collide with surface of Earth- at collision, break apart and release liquid water
38
Q

What is the evidence for the asteroid theory as the way water got on Earth?

A
  • Evidence of lots of large asteroid collisions long ago- around formation of Earth
  • Heavy water (one extra neutron) which is found in asteroids- found on Earth
39
Q

What has enabled water to stay on Earth?

A
  1. Gravitational pull- Earth’s mass means it has a large gravitational pull, so holds water close to surface- in bodies of water
  2. Temperature- Earth’s temperature suits liquid form with some state changes (never boils and only a little bit is frozen)
40
Q

What is the ‘goldilocks zone’ concept in relation to water and life?

A
  • Temperature must be just right for water to stay in liquid form
  • Must be the right distance from a star- cannot be too close (hot) or too far (cold)
  • Earth is the right distance to maintain liquid water
41
Q

How does the ‘goldilocks zone’ concept assist with the search for extraterrestrial life?

A

When looking for ET life, must look for habitable zones with distance from a star allowing liquid water- in a GOLDILOCKS ZONE

42
Q

What is a nucleotide?

A
  • Building blocks of nucluic acids including DNA and RNA
  • Repeated units that form nucleic acids
  • Made of 3 parts- pentose sugar, phosphate group and nitrogen base
43
Q

What is a polymer?

A
  • Large molecules made up of many repeated units
  • Building blocks of polymers= monomers
  • Monomers are chemically joined to make polymers
  • DNA/RNA= polymer, nucleotide= monomer
44
Q

What is a hydroxyl group?

A
  • Common chemical group made of 1x Oxygen and 1x Hydrogen connected to a larger molecule
  • This is the difference between DNA (deoxyribose) and RNA (ribose) sugars, as RNA has an OH, but DNA only has a H
45
Q

What is a condensation reaction?

A

A reaction that joins 2 monomers together

46
Q

What are covalent bonds and their role in nucleic acids?

A
  • Covalent bonds are strong and relatively difficult to break
  • They are the bonds between the phosphate and the 3rd carbon on the pentose sugar that join nucleotides and form the backbone of the DNA/ RNA
47
Q

What are hydrogen bonds and their role in nucleic acids?

A
  • They are much weaker than covalent bonds
  • Formed between the bases in a double stranded DNA
  • Their weakness is important, as these bonds need to be broken for DNA replication and transcription to make proteins
48
Q

How do nitrogen bases differ in DNA and RNA?

A

DNA- Adenine, Thymine, Guanine, Cytosine
RNA- Adenine, Uracil, Guanine, Cytosine

49
Q

What are the types of RNA?

A

mRNA- Messenger RNA
tRNA- Transfer RNA
rRNA- Ribosomal RNA

50
Q

What is another type of nucleic acid in organisms other than DNA and RNA?

A

Adenosine Triphosphate, or ATP

51
Q

What are the complimentary base pairings for DNA?

A

A—T
C—G

52
Q

How does DNA provide the code for proteins?

A
  • A gene= DNA that codes for a single protein
  • Length and base sequence of gene gives order for the amino acids that make the proteins
  • Every 3 base sequences- a triplet codon- codes for 1 amino acid
  • Note: structure of protein defines function
53
Q

Why is DNA universal?

A
  • The same base sequences code for the same amino acids in all living organisms
  • This is important as evidence for evolution, and also has implications for genetic technology
54
Q

What are the similarities between DNA and RNA?

A
  • Both made of nucleotides
  • Both form strong covalent phosphodiester bonds between nucleotides
  • Share 3 bases: Adenine, Guanine and Cytosine
55
Q

What are the differences between DNA and RNA?

A

DNA
* Deoxyribose sugar (-1 oxygen)
* Adenine is complimentary to THYMINE
* Double helix with 2 anti-parallel backbone strands that are bonded by H bonds b/w complimentary bases

RNA
* Ribose sugar (OH)
* Adenine is complimentary to URACIL
* Generally exists in a single stranded form, as a mRNA, tRNA or rRNA

56
Q

What are histones and how do they organise DNA?

A
  • Histones- proteins used to organise DNA
  • 8 histones and a long histone called H1 clump together and DNA wraps around 2 times (146 base pairs)
  • Forms the chromosome shape
57
Q

What is directionality?

A
  • The alignment of the nucleotides- whether the phosphate is up or down
  • DNA strands run in opposite directions
    5’—3’ or 3’—5’
    ‘right side up’= 5’—3’
    ‘upside down’= 3’—5’
    5’ and 3’ refer to the carbon number
58
Q

What is replication?

A

The process where one double stranded DNA is split into 2 single strands, and then each strand is replicated to produce 2 double stranded DNAs

New strands always produced 5’—3’

59
Q

What is transcription?

A

The process of DNA being copied in the nucleus to make mRNA for protein synthesis

Will always be 5’—3’, so 3’—5’ becomes template

60
Q

What is translation?

A

Translating the RNA at ribosome

Translation runs from 5’—3’ end

61
Q

What are the differences between purines and pyrimidines?

A
  • Nitrogen bases differ according to chemical makeup and size
  • Larger double ringed (hexagon and pentagon) nucleotides= PURINES ex: Adenine and Guanine
  • Smaller single ringed (hexagon only) nucleotides= PYRIMIDINES ex: Thymine, Uracil and Cytosine

Remember, CUTs are not pure

62
Q

Why is it essential for a pyrimidine and a purine to be paired together?

A

For DNA to maintain its consistent shape and for the hydrogen bonds to form.

IB Biology (9 decks)

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