2.5 Carbohydrates

Question 1

What function do carbohydrates serve in all organisms?

Answer 1

quick fuel and short-term energy storage

Question 2

In what organisms do carbohydrates play a structural role?

Answer 2

woody plants, bacteria, animals such as insects

Question 3

What are carbohydrates on cell surfaces involved in?

Answer 3

cell-to-cell recognition

Question 4

What are carbohydrate molecules characterized by?

Answer 4

the presence of the atomic grouping H-C-OH in which the ration of H atoms to O atoms is 2:1

Question 5

Why is the term “hydrates of carbon” used?

Answer 5

the ratio of H atoms to O atoms in the atomic grouping in carbohydrates is the same ratio as water

Question 6

What is glucose?

Answer 6

a hexose sugar in our blood used as an immediate source of energy in our blood

Question 7

What does “hexose” mean? Name some common hexoses.

Answer 7

hexose is a 6-carbon sugar

ie. fructose, galactose, glucose

Question 8

How are hexose sugars similar

Answer 8

they all occur as ring structures with the molecular formula C6H12O6 (glucose)

Question 9

How do hexose sugars differ?

Answer 9

the exact shape of the ring differs, as does the arrangement of the hydrogen (–H) and hydroxl (–OH) groups attached to the ring

Question 10

What is a monosaccharide?

Answer 10

a simple sugar in which the number of carbon atoms i a molecule is between 3 and 7

Question 11

What is fructose?

Answer 11

hexose sugar found in fruits

Question 12

What is galactose?

Answer 12

hexose sugar found in constituents of milk

Question 13

What is a disaccharide?

Answer 13

two monosaccharides that joined during a dehydration reaction

Question 14

What is maltose?

Answer 14

a disaccharide formed when two glucose molecules bond together

Question 15

What can break a bond between two monosaccharides?

Answer 15

our hydrolytic digestive juices

Question 16

What is sucrose?

Answer 16

a disaccharide formed when glucose and fructose join and is used to sweeten food

ie. comes from sugarcane and sugar beets

Question 17

What is lactose?

Answer 17

a disaccharide formed by glucose combined with galactose and is found in milk

Question 18

What is a polysaccharide?

Answer 18

many monosaccharides joined together, long polymers that contain glucose subunits

Question 19

What is starch?

Answer 19

a polysaccharide of up to 4000 glucose subunits that is a large storage form of glucose found in plants

*has fewer side branches (chains of glucose) that branch off the main chain than glycogen does

Question 20

What happens after we eat starchy foods?

Answer 20

starch is hydrolyzed into glucose which will then enter the bloodstream

Question 21

What is glycogen?

Answer 21

a polysaccharide that is a large form of glucose found in animals and humans

liver stores glucose as glycogen

Question 22

What is the concentration percentage of blood glucose in the body?

Answer 22

in between meals, the liver releases glucose so that the blood glucose concentration is always about 0.1%

Question 23

What is cellulose?

Answer 23

a polysaccharide that helps strengthen plant cell walls which allows non-woody plants to stand upright as long as they have an adequate supply of water

Question 24

Why can’t humans digest cellulose?

Answer 24

the oxygen atoms in the linked glucose units are in an alternating up/down position

Question 25

What is the importance of cellulose in our diet?

Answer 25

cellulose passes through our digestive tract as fibre or roughage

• necessary for good health
• may help prevent colon cancer

Question 26

Who/what can digest cellulose?

Answer 26

herbivores can break it down and use it as glucose

Question 27

What is chitin?

Answer 27

a structural polysaccharide found in the exoskeleton (shell) of crabs and related animals

• can be made into thread/suture material

Question 28

What is deoxyribose?

Answer 28

a monosaccharide needed to make protein in DNA

Question 29

What is ribose?

Answer 29

a monosaccharide needed to make protein in RNA

Question 30

What test do you use to detect the presence of simple sugars? What colours does it change to and from?

Answer 30

Benedict’s solution

peacock blue to orange or brick red

Question 31

What test do you use to detect the presence of complex sugars? What colours does it change to and from?

Answer 31

Lugol’s Iodine

orange to black