Biological Molecules - Carbohydrates

Question 1

What molecules are carbohydrates made up of?

Answer 1

Carbon, hydrogen and oxygen.

Question 2

What is a single monomer in a carbohydrate called?

Answer 2

Monosaccharide.

Question 3

What is a carbohydrate with a pair of monomers called?

Answer 3

Disaccharide.

Question 4

What does the combining of many monosaccharides result in?

Answer 4

The formation of a polysaccharide.

Question 5

What bonds are monosaccharides joined together by?

Answer 5

Glycosidic bonds.

Question 6

How are polysaccharides and disaccharides formed and broken down?

Answer 6

Condensation reaction
Hydrolysis

Question 7

What is glucose?

Answer 7

A monosaccharide pintos sugar and is the main substrate for respiration. It has two isomers alpha and glucose.

Question 8

What is the difference in structure between alpha and beta glucose?

Answer 8

In alpha glucose, the OH is on the bottom and in beta glucose the OH is on the top.

Question 9

Give some examples of common monosaccharides.

Answer 9

Glucose, galactose and fructose.

Question 10

What is the general formula of monosaccharides?

Answer 10

(CH2O)n

Question 11

Give us some examples of disaccharides and what monosaccharides they are formed by.

Answer 11

Maltose is a disaccharide formed by the condensation reaction of two glucose molecules.

Sucrose is a disaccharide formed by a condensation reaction of glucose and fructose .

Lactose is a disaccharide formed by condensation of glucose and galactose.

Question 12

What are the two polysaccharides formed by the condensation reaction of many alpha glucose molecules?

Answer 12

Glycogen and starch.

Question 13

What is the polysaccharide formed from many beta glucose molecules?

Answer 13

Cellulose.

Question 14

What is mainly glycogen for?

Answer 14

The main energy store molecule in animals.

Question 15

Which bonds is alpha glucose joined together to form glycogen?

Answer 15

1, 4 and 1, 6 acidic bonds.

Question 16

Give other factors of glycogen structure.

Answer 16

• It has a large number of side branches, meaning that energy can be released quickly as enzymes connect simultaneously on these branches.
• It is large, but compact maximising the amount of energy can store.
  -it is insoluble meaning it will not affect the water potential of cells and cannot diffuse out of cells.

Question 17

What are the two forms of starch?

Answer 17

Amylose and Amylopectin.

Question 18

Describe the structure of Amylose.

Answer 18

-unbranched chain of glucose molecules.
-joined by 1, 4 acidic bonds.
- Therefore it is coiled and very compact storing a lot of energy.

Question 19

Describe the structure of amylopectin.

Answer 19

– It is branched.
– Joined by 1, 4 and 1, 6 glycosidic bonds.
– due to many side branches these can be acted upon simultaneously by enzymes and thus broken down to release energy.

Question 20

What are some key properties of starch that make it suitable?

Answer 20

• It is insoluble: it will not affect cell water potential.
• It is compact: a lot of energy can be stored in a small space and when it is hydrolysed the released Alpha glucose can be transported easily.

Question 21

What is starch for?

Answer 21

Energy source in plants.

Question 22

What is cellulose question?

Answer 22

It is a component of cell wall in plants to provide rigidity and strength and structural support.

Question 23

What is the structure of cellulose?

Answer 23

– Long unbranched chains of beta glucose joined by glycosidic bonds.
- Microfibrils are strong threads which are made of long cellulose chains running parallel to one another that are joined together by hydrogen bonds forming cross linkages.

Question 24

What is cellulose function?

Answer 24

Cellulose is important in stopping the cell wall from bursting under osmotic pressure. This is because it exerts inward pressure that stops the influx of water. This means that cell detergent and rigid helping them to maximise the surface area of plants photosynthesis.

Question 25

How do you test for reducing sugars?

Answer 25

1. Add 2 cm³ of the food sample to be tested.
2. Add 2 cm³ of Benedict reagent.
3. Heat the mixture gently in a water bath for five minutes up to 100°C if the solution turns brick red orange then reducing sugar is present.

Question 26

How do you test for non-reducing sugars?

Answer 26

1. 2 cm³ of the food sample is added to 2 cm³ of Benedict reagent this is then placed in a water bath at 100°C for five minutes to gently warm.
2. If the colour does not change from blue to brick red, then red reducing sugar is not present.
3. 2 cm³ of the food sample is then taken and 2 cm³ of dilute hydrochloric acid is added. The test tube is then place in a water bath for five minutes.
4. After this some sodium hydrogen carbonate is added in order to neutralise the test tube as the Benedict reagent will not work in acidic conditions. (Can check if the solution is neutralised).
5. The solution can be retested by adding 2 cm³ of Benedict reagent and placed in the same water bath for five minutes.
6. If a reducing sugar is present then a colour change from the blue to brick red.

Question 27

What is the chemical test for starch?

Answer 27

Potassium iodide is added to the sample if the solution turns blue/black in colour then starch is present.

Question 28

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