Topic 1: Biological molecules

Question 1

What is a condensation reaction

Answer 1

Two molecules (like monomers) are joined together, resulting in the loss of water.

Question 2

What is hydrolysis

Answer 2

When a molecule of water is added to a reaction to breat apart the bonds of something.

Question 3

Name three monosaccharides

Answer 3

• glucose
• fructose
• galactose

Question 4

Name three disaccharides

Answer 4

• maltose
• sucrose
• lactose

Question 5

Name threee polysaccharides

Answer 5

• starch
• glycogen
• cellulose

Question 6

Whar is the difference between alpha glucose and beta glucose

Answer 6

alpha glucose - OH on bottom
beta glucose - OH at top

Question 7

How do you test for reducing sugars

Answer 7

Add benedicts to the solution, heat gently for 5 minutes, positive result changes to brick red

Question 8

What is a disaccharide

Answer 8

Made of two monosaccharides, joined together by a glycosidic bond between the monomers

Question 9

Name the components and products of the three disaccharides

Answer 9

Glucose + Glucose = Maltose + Water
Glucose + Fructose = Sucrose +Water
Glucose + Galactose = Lactose + Water

Question 10

Explain how glycosidic bonds are formed

Answer 10

Formed by condensation reactions,
between the hydroxide groups (OH). One hydroxide group joins with one hydrogen to form water, and the monomers are held together by a single oxyen which becomes the glycosidic bond

Question 11

Where is starch found, and what is its function

Answer 11

Found in plants,
Storage of glucose

Question 12

Where is glycogen found and what is its function

Answer 12

Found in animals
Storage of glucose

Question 13

Where is cellulose found and what is its function

Answer 13

Found in plants
To provide structural strength to the cell wall

Question 14

What two polymers form starch

Answer 14

Amylose and amylopectin

both made from alpha glucose

Question 15

Explain the structure of starch

Answer 15

The amylose is straight because of the 1,4 glycosidic bonds, making the starch helical.
The amylopectin can form 1,4 and 1,6 glycosidic bonds, making it branched.

Question 16

Explain the strucure of glycogen

Answer 16

Highly branched polymer, yet still easily compactible

Question 17

Where is starch and glycogen found

In animal and plants

Answer 17

starch - in grains in plant cells, e.g in chloroplasts
glycogen - in liver and muslce cells within the human body

Question 18

How is glycogen adapted for its function

Answer 18

Glycogen is highly branched
Enzymes can only work on the glycosidic bond linking the outermost monomer.
By having many branches, glycoge increases the surface area for enzymes to act on, so it can easily be hydrolysed when necessary

Question 19

Why is cellulose needed in the cell wall

Answer 19

It provides strength and supoort when the cell becomes turgid with water, preventing it from bursting

Question 20

What is a fibril

Answer 20

When long chains of cellulose are held together by hyrogen bodning they form a fibril of cellulose. This fibril lays perpendicular to other fibrils to provide added strength.

Question 21

Explain the importance of insolubility in glucose, starch, and cellulose

Answer 21

Insolubility means that they can be stored in cells without being dissolved.
This is important as the polysaccharides will not affect the water potential of the cell, and therefore will not cause osmosis to occur.
This allows for storage and structure.

Question 22

What is food test for starch

Answer 22

Add iodine to the sample
positive result turns blue/black

Question 23

What holds together (the reaction) the monomers bonds in lipids

Answer 23

Condensation reactions