Carbohydrates

Question 1

What is one calorie?

Answer 1

• one calorie is the quantity of heat energy required to raise the temperature of 1cm³ of water by 1°C

Question 2

What is a kilocalorie?

Answer 2

• 1 kc = 1000 calories
• food labels normally display units of 1000 calories, called kilocalories

Question 3

How many joules are in one calorie?

Answer 3

4.18 Joules = 1 calorie

Question 4

What is a kilojoule?

Answer 4

1 kJ = 1000 Joules

Question 5

What is a condensation reaction?

Answer 5

• A condensation reaction is a chemical reaction in which two molecules join together forming a larger molecule and release a smaller molecule such as water in the process.
• it is an anabolic reaction

Question 6

What is hydrolysis?

Answer 6

• hydrolysis is a chemical reaction that breaks a chemical bond between two molecules by adding water
• is the opposite of a condensation reaction
• (is basically the addition of water to break a chemical bond)

Question 7

What is a glycosidic link?

Answer 7

• the glycosidic link (or bond) is the bond that forms between two sugar units when they are joined through a condensation reaction

Question 8

What are monosaccharides, disaccharides and polysaccharides?

Answer 8

• a monosaccharide is one single sugar unit
• a disaccharide is the molecule that is formed when two monosaccharides are joined together through a condensation reaction
• a polysaccharide is a long chain of saccharides bonded together by glycosidic links

Question 9

What is the general formula for carbohydrates?

Answer 9

the general formula for carbohydrates is Cx(H2O)n

Question 10

What does carbohydrate mean?
What are the atoms that make up a carbohydrate?

Answer 10

• the term carbohydrate means ‘hydrated carbon’ and hydration means adding water
• carbohydrate are made up of carbon, hydrogen and oxygen atoms

Question 11

What are sugars with six carbons called? What are sugars with 3 carbons called?

Answer 11

• sugars with 6 carbons are called hexose sugars
• sugars with 3 carbons are called triose sugars

Question 12

What are three common monosaccharides and where are they found? (need to know the structures of all of these)

Answer 12

• glucose = is found in blood and used by all cells for respiration
• galactose = occurs in our diet and is found in milk (it is part of the disaccharide lactose)
• fructose = occurs naturally in fruit, honey and some vegetables. (Its sweetness attracts animals which helps with seed dispersal)

Question 13

What are three common disaccharides and what are the monosaccharides that make them?

Answer 13

• sucrose = glucose + fructose
• maltose = glucose + glucose
• lactose = galactose + glucose

Question 14

What does sucrose contain? What is it linked by?

Answer 14

• sucrose contains a molecule of glucose and a molecule of fructose linked by a 1,2 glycosidic bond

Question 15

What does maltose contain? What is it linked by?

Answer 15

• maltose contains two molecules of glucose linked by a 1,4 glycosidic bond

Question 16

What does lactose contain? What is it linked by?

Answer 16

• lactose contains a molecule of glucose and a molecule of galactose linked by a 1,4 glycosidic bond

Question 17

What are some features of mono/disaccharides?

Answer 17

• sweet
• crystalline
• small (can diffuse out of cell)
• soluble

Question 18

What are some features of polysaccharides?

Answer 18

• non-sweet
• non-crystalline
• large (cannot diffuse out of cell)
• insoluble (no osmotic effect on the cell)

Question 19

What are some examples of polysaccharides?

Answer 19

• starch
• glycogen
• cellulose
• amylose
• amylopectin

Question 20

What do starch and glycogen act as?

Answer 20

• starch and glycogen act as an energy storage molecule within cells

Question 21

What is starch? What is it made up of?

Answer 21

• starch is the storage carbohydrate found in plants
• its made up of a mixture of two molecules: amylose and amylopectin

Question 22

What is amylose?

Answer 22

• amylose is composed of a straight chain of between 200 and 5000 glucose molecules with 1,4 glycosidic bonds between adjacent glucose molecules
• the position of the bonds causes the chain to coil in a spiral shape

Question 23

What is amylopectin?

Answer 23

• amylopectin is also a polymer of glucose but it has side branches
• a 1,6 glycosidic link holds each side branch onto the main chain

Question 24

What is used instead of starch as an energy store?

Answer 24

• glycogen is used by bacteria, fungi and animals instead of starch as an energy store

Question 25

What is glycogen? Where is it stored?

Answer 25

• glycogen is another polymer composed of glucose molecules
• its numerous side branches mean that it can be rapidly hydrolysed, giving easy access to stored energy
• In humans glycogen is stored in the liver and muscles

Question 26

What are the two forms that glucose comes in? How are they different?

Answer 26

• glucose comes in two forms: alpha (a) and beta (B)
• Alpha glucose has the H above carbon 1 and the Oh group below (Alpha = (H) Above)
• beta glucose has the H below carbon 1 and the OH group above (Beta = (H) Below)

Question 27

What is the main function of monosaccharides?

Answer 27

• the main function of monosaccharides is to store energy within their bonds
• when the bonds are broken during respiration energy is released

Question 28

How is the structure of monosaccharides related to their function?

Answer 28

• it is soluble so can be transported easily
• it has many covalent bonds which store energy

Question 29

What bond forms between disaccharides/ polysaccharides?

Answer 29

• disaccharides and polysaccharides form a strong covalent bond called the glycosidic bond

Question 30

How do 1,4 glycosidic bonds form? How do 1,6 glycosidic bonds form?

Answer 30

• If the OH groups are located on carbon 1 of one monosaccharide and carbon 4 of the other a 1,4 glycosidic bond forms
• if the OH groups are located on carbon 1 of one monosaccharide and carbon 6 of the other, a 1,6 glycosidic bond forms

Question 31

What reaction forms a glycosidic bond? As a result, what reaction breaks a glycosidic bond?

Answer 31

• the glycosidic bonds are formed by condensation reactions
• the glycosidic bond is broken when water is added in a hydrolysis reaction

Question 32

What is the function of disaccharides?

Answer 32

• the function of disaccharides is to provide the body with a quick-release source of energy
• they are easily broken down by enzymes in the digestive system into their respective monosaccharides and then absorbed into the bloodstream

Question 33

Are disaccharides soluble? Why?

Answer 33

• disaccharides are easily soluble in water due to the presence of a large number of hydroxyl groups
• these hydroxyl groups form hydrogen bonds with the water molecules when dissolved in aqueous solutions

Question 34

What increases the rate at which polysaccharides can be broken down?

Answer 34

• polysaccharides may be branched or unbranched
• being branched increases rate at which polysaccharides can be broken down

Question 35

What happens if polysaccharides are straight or coiled?

Answer 35

• being straight makes the molecules suitable for constructing cellular structures e.g. cellulose
• being coiled makes a molecule more compact and suitable for storage e.g. amylose in starch

Question 36

What are useful storage polysaccharides and why?

Answer 36

• starch and glycogen are useful as storage polysaccharides:
• they are compact = large quantities can be store
• they are insoluble = they will have no osmotic effect