3.2 - Water Flashcards

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1
Q

How do hydrogen bonds form between water molecules?

A

• water is polar, O is more electronegative than H so attract electron density in a covalent bond more strongly
• forms O delta negative and H delta positive
• there are intermolecular forces of attraction between a lone pair on O delta negative of one molecule & hydrogen delta positive on an adjacent molecule

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2
Q

State 7 biologically important properties of water

A

• reaches maximum density at 4°c
• high surface tension
• incompressible
• metabolite solvent for chemical reactions in the body
• high specific heat capacity
• high latent heat of vaporisation
• cohesion between molecules

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3
Q

Why is the incompressible nature of water important for organisms?

A

• provides turgidity to plant cells
• provides hydrostatic skeleton fot some small animals eg. Earth worms

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4
Q

Explain why ice floats on water?
Why is this important for organisms?

A

• ice is less dense than water because H bonds hold molecules in fixed positions further away from each other
• insulates water in arctic climates so aquatic organisms can survive
• water acts as a habitat

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5
Q

Why is the high surface tension of water important for organisms?

A

• slows water loss due to transpiration in plants
• water rises unusually high in narrow tubes lowering demand on root pressure
• some insects can skim across the surface of water

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6
Q

Why are the high specific heat capacity and latent of vapourisation of water important for organisms?

A

• acts as a temperature buffer which enables endothermic to resist fluctuations in core temperature to maintain optimum enzyme activity
• cooling effect when water evaporates from skin surface as sweat/ mouth when panting

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7
Q

Define monomer and give a example

A

•monomer = smaller units that join together to form larger molecules
•Eg. Monosaccharides ( glucose, fructose, galactose, ribose )
• amino acids
• nucleotides

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8
Q

Define polymer and give examples

A

•Polymer = molecules formed when many monomers join together
• polysaccharides
• proteins
• DNA/RNA

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9
Q

What happens in condensation and hydrolysis reactions?

A

• condensation- chemical bond forms between 2 molecules and a molecule of water is produced
• hydrolysis- water molecule is used to break a chemical bond between 2 molecules eg. Peptide bonds in protein,
Ester bonds between fatty acids and glycerol in lipids

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10
Q

What is a transport medium and give a example

A

Water is a transport medium and transports substances such as glucose and oxygen

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11
Q

What is specific heat capacity?

A

Amount of thermal energy required to rise the temperature of 1Kg of a substance by 1°c

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12
Q

What is waters specific heat capacity

A

4200 J/kg °c

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13
Q

Why is waters specific heat capacity so high ?

A

• many hydrogen bonds - takes a lot of thermal energy to break these bonds and a lot of energy to build them thus the temperature of water does not fluctuate greatly

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