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Flashcards in 2: Water and Life Deck (25):
1

State 4 unusual but very useful types of properties of water.

1. cohesive
2. adhesive
3. thermal
4. solvent

2

How can the 4 'unusual but useful' types of properties of water be explained? What is this a good example of?

- using the theories of dipolarity and hydrogen bonding
- theories being used to explain natural phenomena

3

Explain the 'cohesive' properties of water in terms of hydrogen bonding and dipolarity. Give an example of a benefit to living organisms this property provides.

Explanation:
- water molecules cohere because of hydrogen bonds that form between them

Example:
- strong pulling forces exerted to suck columns of water up to the tops of the tallest trees in tubes called xylem vessels. These columns rarely break

4

Explain the 'adhesive' properties of water in terms of hydrogen bonding and dipolarity. Give an example of a benefit to living organisms this property provides.

Explanation:
- dipolarity of water molecules makes them adhere to surfaces that are polar and therefore hydrophilic

Example:
- adhesive forces between water and cellulose in cell walls in the leaf
- cause water to be drawn out of xylem vessels, keeping the cell walls moist and able to act as a gas exchange surface

5

Explain the 'thermal' properties of water in terms of hydrogen bonding and dipolarity. Give an example of a benefit to living organisms this property provides.

Explanation:
- due to hydrogen bonding, water has high melting and boiling points, high latent heat of vaporization and high specific heat capacity

Example:
- thermal properties cause water to be liquid in most habitats on earth = suitable for living organisms
- high specific heat capacity makes its temp change slowly so it is a stable habitat
- high heat of vaporization makes it an effective coolant in leaves or in sweat

6

Explain the 'solvent' properties of water in terms of hydrogen bonding and dipolarity. Give an example of a benefit to living organisms this property provides.

Explanation:
- many substances dissolve in water due to its polarity, including those composed of ions or polar molecules

Example:
- most chemical reactions take place with all of the substances involved in the reaction dissolved in water, so water is the medium for metabolic reactions

7

What happens in a condensation reaction?

two molecules are joined together to form a larger molecule plus a molecule of water

8

What sort of reactions are anabolic reactions?

condensation reactions

9

What is a dimer?

a pair of monomers - single sub-units - bonded together

10

What is a polymer composed of?

a long chain of monomers

11

What would you call two amino acids joined together?

a dipeptide

12

What sort of reaction joins two amino acids together?

a condensation reaction

13

What would a long chain of amino acids be called?

a polypeptide

14

What bond links amino acids together?

a peptide bond

15

Draw a condensation reaction between two amino acids. (p19)

-

16

Name three macromolecules that are built through condensation reactions.

1. proteins
2. carbohydrates
3. lipids

17

What is the basic sub-unit of carbohydrates?

monosaccharides

18

What would a condensation reaction between two monosaccharides form?

a disaccharide + H2O

19

What does a long chain of monosaccharides form?

a polysaccharide

20

What are glycerides made from?

fatty acids and glycerol

21

What is the maximum number of fatty acids that can be added to glycerol? What does this form?

3 - a triglyceride + 3 water molecules

22

What happens in a hydrolysis reaction?

a large molecule is broken down into a smaller molecule

23

What is used up in a hydrolysis reaction?

water

24

How is water used in a hydrolysis reaction?

1. -H and -OH split (hence lysis = splitting)
2. -H and -OH needed to make new bonds after a bond in the macromolecule has been broken

25

Give 3 examples of hydrolysis reactions.

1. polypeptides + H2O --> dipeptides or amino acids
2. polysaccharides + H2O --> disaccharides or monosaccharides
3. glycerides +H2O --> fatty acids + glycerol

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