Carbohydrates Chapter 3.3

Question 1

General formula

Answer 1

Cx(H20)y

Question 2

Monosaccharides

Answer 2

Glucose, Fructose, Ribose

Question 3

Disaccharides

Answer 3

Sucrose, Lactose, Maltose

Question 4

Lactose

Answer 4

Glucose+Galactose

Question 5

Sucrose

Answer 5

Glucose+Fructose

Question 6

Maltose

Answer 6

Glucose+Glucose

Question 7

Polysaccharides

Answer 7

Starch, Glycogen, Cellulose

Question 8

Glucose is a hexose monosaccharide

Answer 8

This means it’s composed of 6 carbons

Question 9

Structural variations of glucose

Answer 9

There is alpha glucose and beta glucose, both have hydroxyl groups in different places

Question 10

Properties of glucose

Answer 10

It is polar and soluble. This is down to the hydrogen bonds between the hydroxyl groups. They are polar so are easily attracted to each other because of the partially positive and negative regions.

Question 11

Condensation reaction

Answer 11

Happens when two hydroxyls from alpha glucose molecules join together and form a glycosidic bond as well as water which is why it’s called that.

Question 12

Hydrolysis Reaction

Answer 12

Occurs when glucose is need by the organism and is taken from the glucose store (either starch or glycogen), water is added for this to happen which breaks the glycosidic bond.

Question 13

Amylose

Answer 13

Chain of alpha glucose molecules joined together which twist to form a helix. They also have hydrogen bonds in between the 2 strands and is less soluble than glucose.

Question 14

Amylopectin

Answer 14

This is like amylose except there are bonds between carbon 1 and carbon 6 that occur every 25 glucose subunits. This results in branching, this makes it more compact. It’s insoluble.

Question 15

Glycogen

Answer 15

Forms more branches than amylopectin, but same structure. This is because it has to be more compact for animals as they are mobile and need room for other things. It also has free ends on the branches for glucose to be added or take away.

Question 16

Cellulose

Answer 16

A chain of beta glucose except every alternate one is turned 180 degrees. This can only form straight chains with no branches and it’s insoluble.

Question 17

Reducing sugars

Answer 17

All monosaccharides and some disaccharides are reducing sugars because they can donate electrons easily.

Question 18

Testing for reducing sugars

Answer 18

Add Benedicts reagent that contains Cu2+ ions to your sample and heat gently. If there are reducing sugars it will turn brick red because the Cu2+ ions have become reduced to Cu+ ions. The most common non-reducing sugar is sucrose.

Question 19

Testing for starch

Answer 19

Add a few drops of iodine to potassium iodide solution and add that to your sample. If it goes from yellow/brown to blue/black, it contains starch

Question 20

Manufactured reagent test strips

Answer 20

These can be used on your sample to test for glucose normally. These will turn a specific colour and you can compare that colour to find a concentration

Question 21

Colorimeter

Answer 21

These are used to tell you the % transmission or % absorbance of your sample. You can then work out the concentration from that. The more concentration your sample has, the more absorbance and less transmission

Question 22

Which disaccharide is a non-reducing sugar and how do you make it reducing?

Answer 22

Sucrose is the most common but if you add hydrochloric acid and boil it, it will undergo a hydrolysis reaction which will break the sucrose into glucose and fructose.