2.1.2 Biological Molecules

Question 1

Define a carbohydrate

Answer 1

• Contains carbon, hydrogen, and oxygen

Question 2

Explain how carbohydrates are classified and give examples

Answer 2

Sugars
- monosaccharides - glucose, fructose, galactose
- disaccharides - sucrose, maltose, lactose

Polysaccharides
- storage - glycogen, starch
- structural - cellulose

Question 3

Characteristics of a monosaccharide?

Answer 3

• are soluble in water
• have a sweet taste
• form crystals

Question 4

Explain how the amount of carbons ina sugar correlates to the type of monosaccharide

Answer 4

• if they have 3 carbons they are triose sugars
• 5 carbons = pentose sugar
• 6 carbons = hexose sugar

Question 5

What is the general formula of a monosaccharide?

Answer 5

(CHO2O)n, where n is >= to 3

Question 6

Explain how you distinguish between a-glucose and b-glucose

Answer 6

• In a-glucose the OH group on carbon 1 is below the plane of the ring
• In b-glucose the OH group on carbon 1 is above the plane of the ring

Question 7

How does glucose contasing lots of bonds relate to it’s function?

Answer 7

It can contain lots of energy

Question 8

What is a disaccharide?

Answer 8

Sugars composde of two monosaccharides bopnded together by a glycosidic bond

Question 9

What monosaccharides make up:
- maltose
- sucrose
- lactose

Answer 9

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

Question 10

How is a a-1,4-glycosidic bond formed?

Answer 10

• between carbon 1 of one glucose molecule and carbon 4 of another glucose molecule
• two OH groups bond to form a water molecule (H2O)
• O boned to carbon in one molecule and carbon in another
• C-O-C link formed

Question 11

What are the two types of storage polysaccharides and in which spieces are they found

Answer 11

• starch - plants
• glycogen - animals

Question 12

What are the two different polysaccharides that make up starch?

Answer 12

• amylose (coiled)
• amylopectin (coiled and branched)

Question 13

What bonds do amylose and amylopectin use?

Answer 13

• amylose = a-1.4-glycosidic bonds
• amylopectin = a-1,4glycosidic + a-1,6 glycosidic bonds

Question 14

Give key points about starch

Answer 14

• carbohydrate consiting of two polysacchardies, amylose and amylopectin
• stored in chloroplast and elsewhere in plants
• stored in cells as starch grains
• can be broken down into a-glucose which are respired to produce ATP

Question 15

Explain the structure of glycogen

Answer 15

• a-1,4glycosidic + a-1,6 glycosidic bonds
• same overall satrucutre as amylopectin, but signifficantly more branching and 1,4 chains are smaller

Question 16

Where and how is glucose stored?

Answer 16

• stored as glycogen granules
• found in large amounts in the liver + skeletal muscles

Question 17

Give key points about glycogen

Answer 17

• polymer of a-1,4 glycosidic bonds
• many side chains due to a-1,6 glycosidic bonds
• insoluble, compact, energy dense
• does not affect water poetion of cell
• branches for rapid hydrolysis by enzymes

Question 18

How do storage polysacchrides’s structures and properties relate to their function?

Answer 18

Structure
- both are made by bonding thousands of a-glucose molecules together (condenstation reactions)
- a-glucose stored is used in respiration

Function
- compact - lots of energy stored in small volume (energy dense)
- metagbolically inactive (doesn’t take part in metabolic reactions)
- insoluble in water - do not dissolve in water, so does not affect cell water potential
- chain molecules - glkucose held by chains which can be hydrolysed by enzymes
- branched - branches ahve ends where enzymes can add or remove glucose - can be quickly hydrolysed

Question 19

Give an example of a structural polysaccharide and it’s properties

Answer 19

cellulose - high tensdile strength + insoluble

Question 20

Explain the structure of the cell wall, and the glucose used

Answer 20

• beta glucose
• forms cellulose fibres, which form microfibril, which form macrofibril, which form the wall
• alternate beta glucose molectules roatet 180 degress - forms hydrogen bonds between OH groups

Question 21

Give exampels of lipids

Answer 21

triglycerides, phospholipids and steroid alcohols

Question 22

Explain the key functions of lipids

Answer 22

Triglycerides
- enmergy storage and source
- insulation
- protection of organms

Phospholipds
- plasma membrane

Sterols
- make up some hormones

Question 23

Explain the structure of a triglyceride

Answer 23

• made from 1 glyercol + 3 fatty acids
• not built from repeating units - not a polymer
• macromlecule - a large molecule