B1.2 Proteins

Question 1

Outline the number and type of bonds carbon can form with other atoms.

Answer 1

Carbon can for 4 covalent bonds with other atoms

Question 2

State common functional groups.

Answer 2

Hydroxyl
Carboxyl
Ester

Question 3

Outline the cause and consequence of covalent bonds between atoms in a carbon

Answer 3

Because carbon have 4 electrons on their outer shell it allows them to form 4 covalent bonds, because of these covalent bonds it makes these bonds the most stable bond

Question 4

List the four major classes of carbon compounds used by living organisms.

Answer 4

1. Carbohydrates
2. Lipids
3. Proteins
4. Nucleic Acids

Question 5

List example molecules with branched chain, unbranched chain, single ring or multiple rings.

Answer 5

Branched Chain : Triglycerides
Unbranched Chain : Fatty Acids
Single Rings : Glucose
Multiple Rings : Cholesterol

Question 6

Define monomer and polymer.

Answer 6

Monomers are single units which join to form polymers

Question 7

Describe condensation reactions.

Answer 7

Condensation reaction combines two molecules through the release of a water molecule

Question 8

State that energy from ATP is needed to produce macromolecules by condensation reactions.

Answer 8

Energy from ATP is needed to produce macromolecules by condensation reaction

Question 8

Outline the condensation reactions that form polysaccharides, polypeptides and nucleic acids.

Answer 8

Polysaccharides 1,4 - glycosidic bond
Nucleic acids 3,5 - phosphodiester bond
Polypeptides : Peptide bonds

Question 9

Describe hydrolysis reactions.

Answer 9

Hydrolisis reactions involve the addition of a water molecule to break down a large molecule.

Question 10

Outline the hydrolysis reactions that digest polysaccharides, polypeptides and nucleic acids.

Answer 10

Polysaccharides 1,4 - glycosidic bond
Nucleic acids 3,5 - phosphodiester bond
Polypeptides : Peptide bonds

Question 11

Define monosaccharide.

Answer 11

A carbohydrate consisting of a single sugar unit

Question 11

Define polysaccharide.

Answer 11

Polysaccharides are composed of many sugar molecules combined through a series of condensation reactions.

Question 12

Outline the properties of glucose referring to solubility, transportability, stability, and energy yield from oxidation.

Answer 12

Glucose is soluble within water because it is polar
Transportability Since it is oluble it is easily transported through body fluids
Chemical stability It is relatively stable compound, meaning it doesn’t degrade as it is transported
Energy yield : Glucose us the primary fuel for respiration in cells. It can be repeatedely oxidized to produce a net gain of up to 36 ATP molecules

Question 13

Compare the structure and function of amylose, amylopectin, and glycogen.

Answer 13

Amylose : long chains of alpha glucose with glycosidic bonds between carbon 1 and carbon 4
Amylopectin : long chains of alpha glucose with glycosidic bonds between carbon 1 and carbon 4 with branching chains at every 20th glucose which bonds at C6
Glycogen : long chains of alpha glucose with bonds between C1 and C4, There are also branching chains at C6

Question 14

Discuss the benefit of polysaccharide coiling and branching during polymerization.

Answer 14

It allows the polyssacharide to be more compact

Question 15

Explain how condensation or hydrolysis of alpha-glucose monomers build or mobilize energy stores.

Answer 15

The condensation allows the glucose to be stored and the hyrdolisis allows the starch being stored to be used as energy

Question 16

Compare the structure of alpha-glucose and beta-glucose.

Answer 16

Alpha glucose has the OH group attached to C1 at the bottom whereas Beta glucose has the OH group attached to C1 at the top

Question 17

Describe the structure of cellulose microfibrils.

Answer 17

Cellulose is composed of beta molecules linked through a 1,4 glycosidic bond. Also every second beta glucose is flipped, resulting in straight chains of cellulose molecules. Cellulose chains are held together through hydrogen bonds to form microfibrils

Question 18

Discuss the consequences of the strength of cellulose in the plant cell wall.

Answer 18

They have high tensile strength allowing them to maintain the structural integrity of the plant.

Question 19

State the function of glycoproteins in the cell membrane.

Answer 19

To act as an antigen, allowing it to perform the roles of :

1. Cell to Cell Adhesion
2. Receptors
3. Cell to Cell communication
4. Immune Response

Question 20

Compare the structure of the A, B and O glycoproteins on the red blood cell membrane.

Answer 20

A : antigen present A antibody present B
B : antigen present B antibody present A
AB : antigen present A and B no antibody present
O : no antigen present antibody present A and B

Question 21

Discuss the consequences of the presence of A, B and O glycoproteins during blood transfusion.

Answer 21

If your blood type has an antibody against the antigen of another bloodtype you can’t receive blood from that person

Question 22

Explain why lipids are hydrophobic.

Answer 22

Because of their non polar structure

Question 23

Outline the structure and function of fats, oils, waxes and steroids.

Answer 23

Fats are triglycerides that store concentrated form of energy, they provide insulation and cushioning for organs and act as a source of fatty acids

Oils are also triglycerides however are liquid at room temperature as they have a higher proportion of unsaturated fatty acids they are used as cooking and frying mediums.

Waxes are esters of long chain fatty acids and long chain alcohols with a highly hydrophobic nature due to their non-polar structure they’re used as protective coatings on the surface of animals, plants and insects. They help reduce water loss, dehydration, provide protection against environmental factors, aid structuring features like feathers, fur and exoskeletons

Steroids are composed of four interconnected carbon rings. They have various functional groups attached to the rings, some act as hormones, others are essential to the cell membrane

Question 24

Explain the condensation reaction connecting fatty acids and glycerol to form a triglyceride.

Answer 24

3 condensation reactions between glycerol and 3 fatty acids, releasing 3 water molecules

Question 25

Explain the condensation reaction connecting fatty acids, glycerol and a phosphate group to form a phospholipid.

Answer 25

two condensation reactions with two fatty acids

one condensation reaction with a phosphate head

Question 26

Describe the structure of a generalized fatty acid.

Answer 26

A carboxyl group linked to a hydrocarbon chain linked to a methyl group at the end

Question 27

Compare and contrast the structures and properties of saturated and unsaturated (mono- or poly-) fatty acids.

Answer 27

Saturated fatty acids have no double bonds between the carbons

Unsaturated fatty acids have 1 or more double bonds between the carbons leading to a bend in the fatty acid

Question 28

Distinguish between the structure and properties of cis- and trans-unsaturated fatty acids.

Answer 28

A cis- unsaturated fatty acid has both hydrogen atoms linked to the carbon with a double bond on the same side causing a bend whereas a trans has the hydrogen atoms on opposite sides causing a straighter line.

Question 29

Outline properties of triglycerides that make them suitable for long-term energy storage.

Answer 29

High energy density

Low solubility

Insulation and protection

Question 30

State the function of adipose tissue.

Answer 30

To store energy in the form of triglycerides and release it when needed

Question 31

Discuss the adaptation of a thick adipose tissue layer as a thermal insulator.

Answer 31

The adaptation made is due to the properties of ATP as it has :
- low thermal conductivity
- layered organization
- metabolic heat production

Question 32

Define hydrophilic, hydrophobic and amphipathic.

Answer 32

hydrophillic = water loving
hydrophobic = water fearing
amphiphatic = hydropohillic parts and hydrophobic parts

Question 33

Outline the amphipathic properties of a phospholipid.

Answer 33

The phospholipid at the same time contains a hydrophillic phosphate head and a hydrophobic fatty acid tails which makes it amphipathic

Question 34

Explain why phospholipids form bilayers in water, with reference to hydrophilic phosphate heads and two hydrophobic hydrocarbon tails.

Answer 34

Phospholipids form bilayers in water because their structure allows their head to face the water while their tails don’t creating a circular barrier with water trapped inside facing a hydrophillic head and the water outside also touching a hydrophillic head however unable to pass through as their are hydrophobic tails.

Question 35

State why steroid hormones are able to pass directly through the phospholipid bilayer.

Answer 35

Steroids are hydrophobic and can therefore pass through a phospholipid bilayer as they are able to disolve in hydrophobic fatty acid tails on the inside of the bilayer