Chapter 3 Biological Molecules

Question 1

State the elements present in carbohydrates

Answer 1

Carbon, Hydrogen, Oxygen

Question 2

State the elements present in lipids

Answer 2

Carbon, Hydrogen, Oxygen

Question 3

State the elements present in proteins

Answer 3

Carbon, Hydrogen, Oxygen, Nitrogen and Sulfur

Question 4

State the elements present in nucleic acids

Answer 4

Carbon, Hydrogen, Oxygen, Nitrogen, Phosphorus

Question 5

Describe the structure of water

Answer 5

One atom of Oxygen covalently bonded to two atoms of Hydrogen
The hydrogen atom is slightly positive while the oxygen atom is slightly negative making the molecule polar
Therefore, the slightly negatively charged oxygen is attracted to the slightly positively charged hydrogen atom of neighbouring water molecules
This forms a hydrogen bond

Question 6

State the primary properties of water

Answer 6

-Solvent
-High specific heat capacity
-High latent heat of vaporisation
-Cohesive and adhesive
-Water is less dense than ice

Question 7

Describe how water acts as a solvent and why is this is useful

Answer 7

Water is able to dissolve ions due to its polarity, this is because the slightly positive hydrogen atom will attract the negative ions and the slightly positive oxygen atom will attract the positive ion.

This is useful as water is able to act as a transport medium for soluble substances.
Acts as a medium for chemical reactions helps to transport dissolved compounds into and out of cells
Water is able to act as a habitat means organisms are able to survive and reproduce

Question 8

Describe how water has a high specific heat capacity and why is this useful

Answer 8

The hydrogen bonds between the water molecules can absorb a lot of energy meaning the waters temperature is difficult to raise
This means water doesn’t experience rapid temperature changes and remains a constant temperature

This is useful as it provides a stable habitat for organisms to survive and reproduce

Question 9

Describe how water has a high latent heat of evaporation and why is this useful

Answer 9

A lot of energy is required to break the hydrogen bonds between water molecules meaning a lot of energy is used to evaporate water.

This is useful for organisms as only a little amount of water needs to be evaporated from the skin for the organism lose a large amount of heat providing a cooling effect. - sweating

Question 10

Describe how water is able to act cohesively and why is this useful

Answer 10

Waters polarity allows neighbouring water molecules to move together as a result of hydrogen bonding.

This is useful as it allows water to flow helping water to be drawn up the xylem during transpiration
Provides surface tension between the upper layer of water molecules

Question 11

Describe how water is able to act adhesively and why is this useful

Answer 11

Waters polarity allows water molecules to bond to other molecules like cellulose

Useful to move molecules up the xylem for transpiration

Question 12

Describe how water can be less dense than ice and why is this useful

Answer 12

Water molecules are held further apart as a solid in an open lattice structure making ice less dense and allowing it to float

This is useful as it forms an insulating layer so the water below does not freeze and temperatures remain fairly stable
This also provides a habitat underneath for organisms to survive and reproduce when temperatures drop.

Question 13

State the two different types of glucose molecules

Answer 13

Alpha
Beta

Question 14

State and explain a property of glucose

Answer 14

Glucose is polar and soluble in water, this is due to the hydrogen bonds that are able to form between the -OH group and water molecules.
This is useful for glucose to be easily transported.

Question 15

Describe the structure of glucose

Answer 15

Hexose monosaccharide composed of 6 carbon atoms arranged in a ring structure.
C6H12O6

Question 16

Describe the structure of ribose

Answer 16

Pentose monosaccharide as it is made up of five carbon atoms arranged in a ring structure.

Question 17

Describe the structure of lactose

Answer 17

Disaccharide composed of the monosaccharides galactose and glucose

Question 18

Describe the structure of sucrose

Answer 18

Disaccharide composed of the monosaccharides fructose and alpha glucose

Question 19

Describe the structure of maltose

Answer 19

Disaccharide composed of the monosaccharides alpha glucose and alpha glucose

Question 20

State the bond that forms between two monosaccharides

Answer 20

Glycosidic bond

Question 21

What is a condensation reaction?

Answer 21

Two molecules join to form a larger molecules and release water in the process.

Question 22

What is a hydrolysis reaction?

Answer 22

When a larger molecules breaks down into smaller molecules as a result of water.

Question 23

State the bond that forms when maltose is made

Answer 23

1,4- glycosidic bond

Question 24

Describe the structure of starch

Answer 24

Starch is a polysaccharide composed of amylose and amylopectin.
Amylose is made up of long unbranched chains of alpha glucose joined together by 1-4 glycosidic bonds. Coils are induced by the glycosidic bonds.
Amylopectin is made up of long branched chains of alpha glucose joined by 1-6 and 1-4 glycosidic bonds

Question 25

Describe how the structure of starch relates to its function

Answer 25

The structure of amylose allows it to be stored compactly, more is able to fit in a small space
The structure of amylopectin has side branches that allows the enzymes that break down the molecule to reach the glycosidic bonds easily meaning glucose can be released quickly.
The structure of starch makes it good for storage as it is insoluble in water

Question 26

Describe the structure of glycogen

Answer 26

Composed of long highly branched chains of alpha glucose

Question 27

Describe how the structure of glycogen relates to its function

Answer 27

Highly branched chains means stored glucose can be released quickly
Branching allows the molecule to be stored compactly

Question 28

What is the function of starch?

Answer 28

Plants store excess glucose as starch to release energy when required.

Question 29

What is the function of glycogen?

Answer 29

Animal and Fungi store excess glucose as glycogen to release energy when required

Question 30

Describe the structure of cellulose

Answer 30

Long unbranched chains of beta glucose joined by 1-4 glycosidic bonds forming straight cellulose chains.
The cellulose chains are linked by hydrogen bonds to form strong fibres called microfibrils.

Question 31

Describe how the structure of cellulose is related to its function

Answer 31

The strong fibres means cellulose provides structural support for cells.

Question 32

State the important properties of starch and glycogen

Answer 32

-Insoluble
-Compact
-Free ends for long branching chains so glucose can be added or removed

Question 33

State how two beta glucose molecules are able to join

Answer 33

Beta glucose molecules join together if alternate beta glucose molecules are turned upside down

Question 34

Describe the structure of a triglyceride lipid

Answer 34

One molecule of glycerol with three fatty acids.
The tails are hydrophobic and are composed of hydrocarbons.

Question 35

Draw the basic structure of a fatty acid

Answer 35

O

C—R
//
HO

Question 36

Describe the process of esterification

Answer 36

A condensation reaction between each fatty acid and the glycerol molecule forming water in the process.

Question 37

State the different forms of fatty acids

Answer 37

Saturated
Unsaturated

Question 38

Describe how a saturated fatty acid is structured

Answer 38

The hydrocarbon chain only has single bonds in straight chains

Question 39

Describe how a unsaturated fatty acid is structured

Answer 39

The hydrocarbon chains contains at least one carbon to carbon double bond
Causing the chain to kink meaning the molecules cannot pack closely together