Biological Molecules

Question 1

Give two properties of lipids

Answer 1

-insoluble in water (non-polar)
-high in energy (rich in C - H bonds)

Question 2

What is a saturated fatty acid?

Answer 2

a fatty acid that contains the maximum number of hydrogens and no C=C double bonds

Question 3

How is a saturated fatty acid different from unsaturated?

Answer 3

-only C-C single bonds
-Usually solid at room temp
-higher melting point
-doesn’t contain any kinks

Question 4

What is the structure of a triglyceride?

Answer 4

a glycerol molecule joined to three fatty acid molecules. join by a condensation reaction and form an ester bond (esterification)

Question 5

Give 5 functions of triglycerides

Answer 5

-Energy source
-Energy store
-Insulation
-Buoyancy
-Protection

Question 6

How do you test for a lipid?

Answer 6

1. Mix sample thouroughly with an eqaul volume of ethanol
2. Filter
3. pour filtrate into water
4. will form a cloudy emulsion if lipids are present

Question 7

What is the structure of a phospholipid?

Answer 7

a glycerol molecule joined to two fatty acid molecules and one phosphate group.

Question 8

What does amphipathic mean?

Answer 8

molecules that contain both hydrophobic and hydrophilic parts

Question 9

What is the function of cholesterol?

Answer 9

Cholesterol regulates and maintains the fluidity of the membrane - at high temperatures it raises the meltiing point and at low temperatures it intercalates between phospholipids and prevents clustering (makes it more fluid)

Question 10

What is the structure of proteins?

Answer 10

A chain of amino acids joined by peptide bonds

Question 11

Give 7 functions of proteins

Answer 11

1. Essential component of cell membranes
2. all enzymes are proteins
3. Antibodies
4. Haemaglobin
5. collagin
6. keratin
7. form structural components

Question 12

What is the structure of an amino acid?

Answer 12

Question 13

What protein has the simplest R group?

Answer 13

glycine (H)

Question 14

What is a buffer?

Answer 14

A substance that helps to reduce large changes in pH

Question 15

What is the primary structure of a protein?

Answer 15

A sequence of amino acids held together by peptide bonds

Question 16

What is the secondary structure of a protein?

Answer 16

The folding of an amino acid chain into a beta pleated sheet or an alpha helix due to hydrogen bonding between amino acids.

Question 17

What is the tertiary structure of a protein?

Answer 17

The folding of the secondary structure to form a specific 3D shape, 4 different types of bond hold this structure together - ionic bonds, disulphide bonds, hydrogen bonds, hydrophilic / hydrophobic interactions.

Question 18

What is the quaternary structure of a protein?

Answer 18

A protein which is made up of two or more polypeptide chains, held together by ionic bonds, disulphide bonds, hydrogen bonds, hydrophilic / hydrophobic interactions.

Question 19

Give three examples of fibrous proteins

Answer 19

-Collagen
-Elastin
-Keratin

Question 20

Give two examples of globular proteins

Answer 20

-Enzymes
-Haemoglobin

Question 21

What is a monomer?

Answer 21

A small molecule which binds to other identical molecules to form a polymer

Question 22

What is a condensation reaction?

Answer 22

This occurs when molecules are joined together with the removal of water and a covalent bond is formed.

Question 23

What is a hydrolysis reaction?

Answer 23

Splitting a polymer apart with the addition of water so a covalent bond is broken.

Question 24

What is a polar molecule?

Answer 24

A molecule that has an uneven charge distribution, it has partial positive and negative charges which do not cancel out

Question 25

What are the 7 properties of water?

Answer 25

1. Liquid at room temperature 2. Ice is less dense than water 3. Solvent for polar molecules 4. water pushes non-polar molecules together (helps formation of PLbilayer) 5. Cohesion and surface tension 6. High specific heat capacity 7. High latent heat of vaporisation

Question 26

What are the 4 functions of carbohydrates?

Answer 26

1. Energy source 2. Energy store 3. structural role (e.g cellulose) 4. part of larger molecules

Question 27

what are three properties of monosaccharides?

Answer 27

-Soluble in water -Insoluble in non-polar solvents -Taste sweet

Question 28

What is a disaccharide?

Answer 28

Formed from two monosaccharides in a condensation reaction and a glyosidic bond is formed

Question 29

What are three properties of disaccharides?

Answer 29

-Taste sweet -Soluble -Some are reducing and some are non-reducing

Question 30

Which disaccharide is non-reducing?

Answer 30

Sucrose

Question 31

Which disaccharide is reducing?

Answer 31

-Maltose -Lactose -Cellubiose

Question 32

What enzyme is needed for hydrolysis of a disaccharide?

Answer 32

Maltase

Question 33

What bond is formed in the condensation reaction of two alpha glucose molecules?

Answer 33

A 1,4 glyosidic bond

Question 34

Are all monosaccharides reducing or non-reducing?

Answer 34

They are all reducing

Question 35

How do you test for a reducing sugar?

Answer 35

Benedict's Test- -Add Benedict's solution and heat in a water bath at 80*C for 3 mins -If a reducing sugar is present a green / yellow/ orange/ brick red precipitate will form -If a reducing sugar is not present the solution will remain blue

Question 36

How do you test for a non-reducing sugar?

Answer 36

-Carry out normal reducing sugar test -Boil the solution with 1cm^3 of hydrochloric acid and anti-bumping granules -Cool the solution and add sodium hydrogen carbonate powder to neutralise -Carry out reducing sugar test again

Question 37

What is the equation for finding the volume of stock solution required in a proportional dilution?

Answer 37

Volume of stock solution required = (total volume wanted / conc. of stock solution) X conc. wanted

Question 38

What is starch made up of?

Answer 38

Amylose and Amylopectin

Question 39

How do you test for starch?

Answer 39

-Add iodine solution -Will turn from orangey brown to blue black if starch is present

Question 40

What is cellulose made up of?

Answer 40

Beta glucose molecules - every other beta glucose molecule is rotated by 180*, held together by glyosidic bonds