Biological molecules 1 (Water and Carbohydrates)

Question 1

What percentage of water makes up a living cell?

Answer 1

80%

Question 2

Roles of water

Answer 2

1. biological solvent
2. regulates temperature
3. transport medium
4. site of chemical reactions
5. used in hydrolysis
6. acts as a cooling mechanism (sweat evaporating)
7. provides habitats

Question 3

Properties of water

Answer 3

1. polar molecule
2. individual bonds provide stability
3. high specific heat capacity
4. hydrogen bonding
5. ice is less dense than liquid water
6. water is a good solvent (polar molecule)

Question 4

Water is a polar molecule, what properties does this provide?

Answer 4

1. makes it cohesive

2. a good solvent

Question 5

Define Cohesive

Answer 5

the attraction between molecules of the same type of type meaning they sick together, this allows water to be a great transport mechanism

Question 6

How does polarity allow water to be a good solvent?

Answer 6

The slightly positive end will be attracted to the negative ion and the slightly negative end will be attracted to the positive ion, allowing ions to dissolve as they become surrounded

Question 7

Polar

Answer 7

A partial positive charge on one side and a partially negative charge on the other

Question 8

Charge of oxygen molecule in water

Answer 8

slightly negative

Question 9

Charge of hydrogen molecule in water

Answer 9

slightly positive

Question 10

Define hydrogen bonding

Answer 10

primarily electrostatic force of attraction between a hydrogen atom which is covalently bound to a more electronegative atom

Question 11

What properties does hydrogen bonding account for in water?

Answer 11

1. High specific heat capacity

2. High latent heat of evaporation

Question 12

Specific heat capacity

Answer 12

The energy needed to raise the temperature of 1g of substance by 1℃

Question 13

Specific heat capacity of water

Answer 13

H bonds between molecules absorb at lot of energy therefore water takes a lot of energy to heat it up.

Question 14

High latent heat of evaporation

Answer 14

It takes a lot of heat energy to break the H bonds in water, this is useful for organisms as it allows water to be a good cooling mechanism (e.g sweating)

Question 15

Water is less dense when it freezes, describe the structure

Answer 15

Molecules are held further apart in ice because each molecule forms 4 H bonds to other molecules making a lattice structure. Less dense than L water allowing it to float

Question 16

Elements in carbohydrates

Answer 16

Carbon, hydrogen and oxygen

Question 17

In what three sugars do carbohydrates exist in?

Answer 17

Modnosaccarides, disaccaride and polysaccharides

Question 18

How many carbon atoms in a polysaccharide?

Answer 18

8 or more

Question 19

Glucose

Answer 19

An abundant monosaccharide, containing six carbon atoms (hexose sugar) and is highly soluble

Question 20

Two structural isomers of glucose

Answer 20

Alpha and beta

Question 21

Alpha glucose

Answer 21

Hydrogen above the OH on C1

Question 22

Beta glucose

Answer 22

Hydrogen below the OH on C1

Question 23

Condensation reaction

Answer 23

A reaction between two monosaccharides to from a disaccharide, a hydrogen atom on one monosaccharide bonds to an OH group releasing a molecule of water

Question 24

Opposite of condensation reaction

Answer 24

Hydrolisis

Question 25

What bond is formed in alpha glucose following a condensation reaction?

Answer 25

1-4 glycosidic bond

Question 26

How does b-glucose join during a condensation reaction?

Answer 26

Every other one gets turn upside down in order to join chains

Question 27

Pentose sugars

Answer 27

Pentose monosaccharides contain 5 carbon atoms and are long enough to form a ring (e.g maltose, sucrose and lactose)

Question 28

Maltose

Answer 28

Formed from two glucose alpha 1-4 glycosidic bonds

Question 29

Sucrose

Answer 29

Formed from glucose + fructose and forms alpha 1-2 glycosidic bonds

Question 30

Lactose

Answer 30

Formed from galactose and glucose joined by a 1-4 glycosidic bond

Question 31

Define polysaccharide

Answer 31

Polymers containing many monosaccharides linked via glycosidic bonds and are formed via condensation reactions

Question 32

Examples of polysaccharides

Answer 32

Starch, cellulose and glycogen

Question 33

Glycosidic bond

Answer 33

A type of covalent bond that joins and carbohydrate to another molecule

Question 34

Starch

Answer 34

1. Used for medium term storage in plants (NEVER ANIMALS) 2. can be broken down to a-glucose 3. found in seeds and tubers 4. insoluble 5. compact

Question 35

Molecular structure of starch

Answer 35

Made of both amylose and amylopectin

Question 36

Amylose

Answer 36

Made of condensations between alpha glucose, the are linked 1-4 , NO branches

Question 37

Amylopectin

Answer 37

Long chains of a-glucose, straight chains linked 1-4 and branches linked 1-6

Question 38

Glycogen

Answer 38

1. Medium term storage for animals 2. similar to starch, shorter chains and more branches 3. more readily hydrolysed 4. contains chains and branches 5. insoluble 6. does not diffuse out of cells (too big) 7. a-glucose

Question 39

Why does glycogen have short chains and many branches?

Answer 39

Easier for enzymes to access 'free ends' on the branches

Question 40

Cellulose

Answer 40

1. NOT storage provides structural purposes only 2. made of b-glucose 3. to form a straight chain each monomer rotates 180 4. straight unbraced chains 5. the H bonds alone are very weak but together create a stronger structure 6. difficult to hydrolyse

Question 41

What does Benedict's test for?

Answer 41

Reducing sugars

Question 42

Benedict's test method

Answer 42

1. Place sample in boiling tube 2. add equal volume of Benedict's reagent 3. heat mixture gently in water bath for 5 minutes

Question 43

Benedict's test result

Answer 43

Positive = Brick red precipitate, Negative = Blue copper ions remain

Question 44

Reducing sugar

Answer 44

any sugar that is capable of acting as a reducing agent all monosaccharides (glucose) and some disaccharides (maltose and lactose)

Question 45

Non-reducing sugar

Answer 45

For example sucrose

Question 46

Reagent test stops for non-reducing sugar

Answer 46

1. add HCl (to hydrolyse the bond and break down to monosaccharides of sucrose) and heat in a water bath 2. neutralise the solution with sodium hydrogen carbonate 3. then carry out Benedict's procedure and record observations

Question 47

Test strips for glucose

Answer 47

The test strips are coated in a reagent. They are dipped into a test solution and compared to a colour chart

Question 48

Iodine to test for stach

Answer 48

Add iodine dissolved in potassium iodide solution, if starch is present it will change form browny-orange to blue-black