Chapter 3: Biological molecules

Question 1

anions

Answer 1

*Nitrate - Nitrogen supply to plants and protein formation
*Hydrogen carbonate - maintenance of blood pH
*Chloride - balance sodium and potassium ions in cells
* Phosphate - cell membrane formation, nucleic acid and ATP formation, bone formation
Hydroxide - Catalysts and pH determination

Question 2

cations

Answer 2

Calcium - Nerve impulses and muscle contraction
Sodium - Nerve impulse transmission and kidney function
Potassium - Nerve impulse transmission and stomatal opening
Hydrogen - catalysis of reactions and pH determination
Ammonia - Production of nitrate ions by bacteria

Question 3

water

Answer 3

water is important as:
*its a metabolite
*able to do electrolysis

Question 4

props of water?

Answer 4

*excellent solvent
*High SHC
*High latent heat of vaporisation
*less dense when solid
*high surface tension and cohesion
*acts as a reagent

Question 5

water (2)

Answer 5

*104.5 bond angle
*covalent bond
*it is a polar molecule as it has charge but is specifically a dipole meaning it has both a slight negative and slight positive charge
*oxygen has the slight negative charge
hydrogen has the slight positive charge
*oppositely charged atoms on each molecule are attracted to eachother and form hydrogen bonds

Question 6

glucose

Answer 6

*a hexose monosaccharide
*fundamental within carbs

Question 7

glycosidic bonds

Answer 7

*formed by condensation reaction which produces water
*broken by hydrolisis

Question 8

alpha-glucose

Answer 8

starch:
*amylose - straight chain therefore only 1-4 glycosidic bonds
*amylopectin - has branches aswell so has 1-4 and 1-6 glycosidic bonds
Glycogen (animals) : like amylopectin but more branched
-Branched means that it can be more compact and therefore more stable

Question 9

carbohydrates

Answer 9

a group of substances used as both energy sources and structural materials in organisms
*carbohydrates - H,O,C element atoms only

Question 10

monosaccharides

Answer 10

*monosaccharides are simple: galactose, fructose, glucose
* they are bonded together in a condensation reaction to form disaccharides
* bond formed is a glycosidic bond

Question 11

disaccharides formed from monosaccharides

Answer 11

maltose: 2 x glucose
sucrose: glucose and fructose
lactose: glucose and galactose

Question 12

What’s the general formula of carbohydrates?

Answer 12

Cx(H2O)y

Question 13

What’s the bond angle of water?

Answer 13

104.5

Question 14

Where is the OH group on a glucose which is different to b glucose?

Answer 14

Alpha has OH on bottom on first carbon whereas Beta has OH on top of first carbon.

Question 15

What reaction is it called when a glycosidic bond is formed?

Answer 15

Condensation reaction and water is released

Question 16

What type of bond is a glycosidic bond?

Answer 16

Covalent bond

Question 17

What is starch?

Answer 17

Many alpha glucose molecules joined by glycosidic bonds.
Glucose which is stored in plants is known as starch.

Question 18

What is amylose?

Answer 18

Is a polysaccharide in starch.
Is formed by alpha glucose molecules and only has 1-4 glycosidic bonds.
Is much more compact as it forms a helix shape.

Question 19

What is amylopectin?

Answer 19

Is the other polysaccharide of starch.
Contains 1-4 and 1-6 glycosidic bonds.
1-6 glycosidic bonding means amylopectin has branches.
1-6 branch occurs approximately every 25 glucose sub units

Question 20

What is glycogen?

Answer 20

Is the functionally equivalent storage molecule to starch in animals and fungi.
Forms more branches than amylopectin, therefore is more compact and this is ideal for storage.

Question 21

What are the key properties of amylopectin and glycogen?

Answer 21

They are insoluble, branched and compact

Question 22

How is glucose released from starch or glycogen for respiration?

Answer 22

They undergo hydrolysis.
Is catalysed by enzymes.

Question 23

What is cellulose made from and how?

Answer 23

Cellulose is made from Beta glucose molecules.
Every other beta glucose molecule is inverted so that condensation reactions between the oh groups can occur.

Question 24

How are cellulose fibres formed from cellulose molecules?

Answer 24

Cellulose molecules form hydrogen bonds with each other to form microfibrils.
Microfibrils join to form macrofibrils.
Macrofibrils combine to produce cellulose fibres.

Question 25

What do cellulose fibres make?

Answer 25

Cell wall

Question 26

What are properties of cellulose fibres?

Answer 26

Strong and insoluble

Question 27

How do you test for reducing sugars? What is the positive test result?

Answer 27

1) place sample in boiling tube. If not liquid, grind it up and mix with water.
2) add equal vol of Benedict’s reagent
3) heat gently in boiling water bath for 5 mins

Blue to brick red

Question 28

How do you test for non reducing sugars using Benedict’s?

Answer 28

Same as reducing sugars but has to be boiled with dilute HCl first.

Question 29

How do you test for starch using iodine? What is the positive result?

Answer 29

Dissolve a few drops of iodine solution with potassium iodide.

Yellow to purple/black

Question 30

What is another way to test for reducing sugars?

Answer 30

Manufactured reagent test strips

Question 31

What are fats?

Answer 31

Fats are lipids that are solid at room temp

Question 32

What are oils?

Answer 32

Are lipids that are liquid at room temp

Question 33

Are lipids polar or non polar?

Answer 33

Non polar and so insoluble in water

Question 34

What is a triglyceride made from?

Answer 34

A glycerol and three fatty acid tails.

Question 35

What are the bonds between a glycerol and fatty acid tails called? What is the reaction called?

Answer 35

The bonds are ester bonds and the reaction is called esterification.

Question 36

What is esterification an example of

Answer 36

A condensation reaction.

Question 37

How much water is used when triglycerides are broken down? What is the reaction called?

Answer 37

Three water molecules are released.
Hydrolysis