2.3 - Biological Molecules

Question 1

State the general formula of a carbohydrate

Answer 1

Cₓ(H₂O)ᵧ

Question 2

State the three main groups of carbohydrates

Answer 2

• Monosaccharides
• Disaccharides
• Polysaccharides

Question 3

What is a monosaccharide?

Answer 3

A simple sugar with the general formula (CH₂O)ₙ where ₙ can be 3-7.
They are examples of monomers.
e.g. glucose, fructose, ribose

Question 4

What are disaccharides?

Answer 4

‘Double sugars’ formed from two monosaccharides.

e.g. lactose, sucrose

Question 5

What are polysaccharides?

Answer 5

Large molecules formed from many monosaccharides.

e.g. glycogen, cellulose, starch

Question 6

How many carbons are contained in one molecule of pentose?

Answer 6

5 carbons.

Question 7

How do ribose and deoxyribose differ?

Answer 7

Ribose has one H atom and one -OH group on Carbon-2, whereas deoxyribose has 2 H atoms and no -OH group on Carbon-2.

Question 8

What type of sugar is glucose?

Answer 8

It is a hexose sugar.

Question 9

What is the difference between alpha and beta glucose?

Answer 9

On alpha glucose the -OH group is BELOW Carbon-1.

On beta glucose the -OH group is ABOVE Carbon-1.

Question 10

What reaction occurs when two monosaccharides join to form a disaccharide?

Answer 10

Condensation reaction.

Question 11

What reaction is used to break apart polysaccharides and disaccharides?

Answer 11

Hydrolysis reaction.

Question 12

How is maltose formed?

Answer 12

Two glucose molecules joined by an Alpha 1-4 Glycosidic bond.

Question 13

How is sucrose formed?

Answer 13

One glucose molecule and a fructose molecule joined by an Alpha 1-4 glycosidic bond.

Question 14

How is lactose formed?

Answer 14

Glucose and galactose joined by a Beta 1-4 glycosidic bond.

Question 15

What is the major polysaccharide in animals?

Answer 15

Glycogen.

Question 16

What is the major polysaccharides in plants?

Answer 16

Cellulose and starch.

Question 17

What is starch made from?

Answer 17

Amylose and amylopectin polysaccharides.

• 30% amylose (1-4 bonds)
• 70% amylopectin (1-4 and 1-6 bonds)

Question 18

How is starch stored in plants?

Answer 18

Stored as intracellular grains in plastids.

Question 19

What is cellulose made from?

Answer 19

Long chains of beta glucose molecules joined by beta 1-4 glycosidic bonds.

Question 20

How is cellulose structured?

Answer 20

Long glucose chains form rope-like microfibrils forming a network.

Question 21

What is glycogen made from?

Answer 21

Many alpha 1-6 glycosidic bonds producing a branched network.

Question 22

How is glycogen stored?

Answer 22

Small granules in the muscles an liver.

Question 23

How does the metabolic properties of glycogen differ from starch?

Answer 23

Glycogen is less dense and more soluble than starch - meaning it can be broken down more rapidly.

Question 24

What elements are proteins made from?

Answer 24

CHONS

Question 25

What functions do proteins provide?

Answer 25

- Structure (connective tissue, skeletal fibre, hair, etc.) - Body regulation (enzymes and hormones) - Immunity (antibodies) - Energy

Question 26

Outline the basic structure of an amino acid

Answer 26

- Amine group - R-Group - Carboxyl Group

Question 27

What kind of bond joins two amino acids together?

Answer 27

Peptide bond.

Question 28

What is a polypeptide?

Answer 28

10 or more amino acids in a chain.

Question 29

What is a protein?

Answer 29

One or more polypeptide chains folded into a highly specific 3D shape.

Question 30

What does primary structure of a protein involve?

Answer 30

Simple long chains with no intermolecular bonds/interactions.

Question 31

What does secondary structure of a protein involve?

Answer 31

Hydrogen bonds from causing the molecule to either fold or coil. Forms either an alpha helix or beta pleating sheet.

Question 32

What does tertiary structure of a protein involve?

Answer 32

- Hydrophilic/hydrophobic interactions - Hydrogen bonds - Ionic bonds - Disulphide bridges

Question 33

What does quaternary structure of a protein involve?

Answer 33

Same as tertiary but with two or more separate polypeptide chains interlinked. e.g. haemoglobin (4 chains), insulin (12 chains).

Question 34

How do proteins become denatured?

Answer 34

Changes in temperature, pH or salt concentration can break the bonds which maintain the protein's specific shape.

Question 35

What happens when proteins become denatured?

Answer 35

- Bonds which maintain protein's specific shape are broken. - Fibrous proteins lose their structural strength. - Globular proteins become insoluble and inactive.

Question 36

Outline the properties of a globular protein.

Answer 36

- Soluble - Metabolically active - Mostly alpha helix - Forms globules (enzymes, hormones etc.)

Question 37

Outline the properties of a fibrous protein.

Answer 37

- Insoluble - Structural - Mostly beta pleating sheet - Forms fibres (collagen, keratin etc.)

Question 38

Outline the structure and properties of haemoglobin.

Answer 38

- Globular - 4 polypeptide subunits (2 alpha, 2 beta) - Most of structure is alpha helix - Each haem group (prosthetic group) contains Fe²⁺ which is responsible for the colour. - Each molecule binds to 4 O₂ molecules.

Question 39

Outline the structure and properties of collagen.

Answer 39

- Fibrous - Very strong - 3 polypeptide chains wound around each other - Each of the chains are coils held together by H bonds. - Each collagen molecule forms strong covalent bonds with other collagen molecules - Form collagen fibrils. Many collagen fibrils make a collagen fibre.

Question 40

Why is collagen so strong?

Answer 40

- Glycine is small allowing close packing between molecules. - Collagen chains form a tight coil - they lie close to each other. - Many H bonds between R-Groups hold chains together very closely. - Strong covalent bonds with adjacent molecules - Staggered ends to parallel fibres prevent lines of weakness.

Question 41

Which elements do lipids contain?

Answer 41

CHO

Question 42

What is the most common form of lipid?

Answer 42

Triglyceride.

Question 43

How many water molecules are formed in the formation of a triglyceride?

Answer 43

3

Question 44

Why are some lipids liquids (oils) at room temperature?

Answer 44

They have unsaturated fatty acid chains. Double bonds cause kinks in the chains meaning there are fewer intermolecular forces between chains.

Question 45

Where in the cell do lipids play a major role?

Answer 45

The plasma membranes.

Question 46

Outline the functions of lipids.

Answer 46

- Energy and metabolic water source - Buoyancy aid - Heat insulation - Waterproofing on hair/feathers - Electrical insulation - Protection of internal organs

Question 47

Outline the structure and function of cholesterol.

Answer 47

- Small narrow molecule - 4 Carbon ring-based structure. - Regulates the fluidity of a membrane