Lipids & Proteins

Question 1

Examples of macromolecules

Answer 1

Triglycerides, phospholipids

Question 2

Structure of a triglyceride

Answer 2

Three fatty acids bonded to one glycerol by ester bonds which form through condensation reactions

Question 3

How do ester bonds form in triglycerides?

Answer 3

Hydroxyl groups on glycerol and fatty acids interact with each other, form three water molecules (One for each fatty acid)

Question 4

Name of the process of triglycerides forming

Answer 4

Esterification

Question 5

Structure of fatty acids

Answer 5

A carboxyl group with a hydrocarbon chain attached

Question 6

What does it mean if a fatty acid is saturated?

Answer 6

• carbon atoms have maximum number of hydrogen atoms bonded to them.
• NO double bonds

Question 7

Monounsaturated

Answer 7

One double bond

Question 8

What do double bonds in fatty acids cause?

Answer 8

Kinks and bends

Question 9

Effect of kinks and bends in a fatty acid

Answer 9

They can’t pack so closely together.

Question 10

How do triglycerides form?

Answer 10

Ester bonds form when the hydroxyl groups of the glycerol and the fatty acids interact, three water molecules form

Question 11

How do you break down triglycerides?

Answer 11

Three water molecules are supplied which reverse esterification in a hydrolysis reaction.

Question 12

Structure of phospholipids

Answer 12

Non-polar and hydrophobic tail (The fatty acids), charged and hydrophilic head (Phosphate group)

Question 13

How the properties of phospholipids relate to their purpose?

Answer 13

Act as surfactants
* hydrophilic head will be in water
* hydrophobic fatty acid tails won’t, in

• phospholipid bilayers the hydrophobic tails point towards the centre of the sheet
• bilayer allows it to form cell membranes in aqueous environments

Question 14

Functions of phospholipids

Answer 14

Surfactants, phospholipid bilayers in cell membranes

Question 15

What is cholesterol?

Answer 15

Sterol

Question 16

Structure of cholesterol

Answer 16

Hydrophobic four carbon ring, hydrophilic hydroxyl groups

Question 17

How do the properties of cholesterol link to its function?

Answer 17

Hydrophilic hydroxyl group at the periphery of a membrane regulates the fluidity

Question 18

Functions of lipids

Answer 18

Membrane formation, hormone production, electrical insulation, waterproofing, thermal insulation, cushioning of vital organs, buoyancy

Question 19

Example of lipids being used in waterproofing

Answer 19

Bird feathers, plant leaves

Question 20

Example of lipids being used in thermal insulation

Answer 20

Penguins

Question 21

Example of lipids being used in buoyancy

Answer 21

Whales

Question 22

How do dipeptides form?

Answer 22

• Hydroxyl in the carboxylic acid group of one amino acid reacts with hydrogen in an amine group of another amino acid
• peptide bond forms
• water released (condensation reaction)

Question 23

How do polypeptides form?

Answer 23

• Amino acids joined together by peptide bonds
• catalysed by peptidyl transferase in ribosomes,
• different R groups interact with each other to form different kinds of bonds

Question 24

What are the levels of protein structure?

Answer 24

Primary, secondary, tertiary, quaternary

Question 25

What is the primary structure of a protein?

Answer 25

* sequence of amino acids in the polypeptide * influences how the protein will fold * Only peptide bonds are involved

Question 26

What is the secondary structure of a protein?

Answer 26

* interaction of the oxygen, nitrogen and hydrogen atoms of the amino acids * in the carboxylic acid group and the amine group.

Question 27

Secondary structure

Answer 27

* interaction of H, O, N atoms of amino acids * in carboxylic group and amine group * structure: a-helix and b-pleated sheets

Question 28

How do alpha helices form?

Answer 28

Hydrogen bonds form within the chain, pulling it into a coil shape.

Question 29

How do beta pleated sheets form?

Answer 29

* polypeptide chains lie parallel to each other * join by hydrogen bonds * pattern formed by amino acids causes structure to look pleated.

Question 30

What causes secondary structure?

Answer 30

Hydrogen bonding which depends on the amino sequences of the long protein molecules

Question 31

What is the tertiary structure of a protein?

Answer 31

* Folding of a protein into its final shape * caused by coiling and folding into the secondary structure

Question 32

Examples of interactions that can occur between amino acid R groups

Answer 32

Hydrophobic/Hydrophilic Interactions, hydrogen bonds, ionic bonds, disulphide bonds

Question 33

Cause of hydrophobic/hydrophilic interactions between amino acid R groups

Answer 33

Interactions between polar and non-polar R groups

Question 34

Cause of ionic bonds between amino acid R groups

Answer 34

Oppositely charged R groups

Question 35

Cause of disulphide bonds between amino acid R groups

Answer 35

Covalent bonds form between R groups of amino acid that contain sulfur atoms.

Question 36

Examples of globular proteins

Answer 36

Haemoglobin, catalase, insulin

Question 37

General structure of globular protein

Answer 37

Compact, water soluble, roughly spherical, hydrophobic R-groups on the amino acids are kept away from the aqueous environment, hydrophilic R-groups on the outside of the protein

Question 38

Structure of insulin

Answer 38

Made up of two polypeptide chains that are linked together by disulphide bonds. Both chains are alpha helices.

Question 39

Structure of catalase

Answer 39

Quarternary protein with four haem prosthetic groups.

Question 40

Structure of haemoglobin

Answer 40

Quarternary protein made up of two alpha polypeptides and two beta polypeptides, each of which has a haem group containing an Fe^2+ ion.

Question 41

Function of insulin

Answer 41

To regulate blood glucose concentration.

Question 42

Conjugated proteins

Answer 42

Globular proteins with a prosthetic group

Question 43

Prosthetic groups

Answer 43

Non-protein attachments to a globular protein

Question 44

Function of haemoglobin

Answer 44

To transport oxygen around the body

Question 45

Function of catalase

Answer 45

To speed up the breakdown of hydrogen peroxide

Question 46

Examples of fibrous proteins

Answer 46

Collagen, keratin, elastin

Question 47

General structure of fibrous proteins

Answer 47

Long, insoluble molecules, high proportion of amino acids with hydrophobic R groups, limited range of amino acids, repetitive primary structure leading to organised structures

Question 48

Properties of keratin

Answer 48

Strong, inflexible, insoluble

Question 49

Function of keratin

Answer 49

To form hair, skin and nails, to help epithelial cells maintain integrity.

Question 50

Properties of collagen

Answer 50

Flexible, strong

Question 51

Function of collagen

Answer 51

To be a connective tissue in skin, tendons, ligaments and the nervous system.

Question 52

Properties of elastin

Answer 52

High resilience for large strains, low stiffness, flexible

Question 53

Function of elastin

Answer 53

To give structures like the walls of blood vessels and the lining of the lungs the flexibility to expand when needed.