Biological molecules

Question 1

What are the four main carbon-based molecules common to all life?

Answer 1

carbohydrates, lipids, proteins, nucleic acids

Question 2

What are monomers?

Answer 2

small units that make up larger molecules

Question 3

What are polymers?

Answer 3

large molecules made up of a large number of monomers

Question 4

Name some examples of monomers

Answer 4

monosaccharides, amino acids, nucleotides

Question 5

What is a condensation reaction?

Answer 5

joining of two molecules forming a chemical bond, with the elimination of a water molecule, forming polymers

Question 6

What is hydrolysis?

Answer 6

chemical bond between two molecules broken using a water molecule

Question 7

What are the monomers of the disaccharide sucrose?

Answer 7

glucose and fructose

Question 8

What are the monomers of the disaccharide maltose?

Answer 8

glucose and glucose

Question 9

What are the monomers of the disaccharide lactose?

Answer 9

glucose and galactose

Question 10

What type of bond forms between the condensation reaction between two monosaccharides?

Answer 10

glycosidic bond

Question 11

What are the two isomers of glucose?

Answer 11

α-glucose and β-glucose

Question 12

Draw the structure of an α-glucose isomer

Answer 12

H
OH

Question 13

Draw the structure of a β-glucose isomer

Answer 13

OH
H

Question 14

How are polysaccharides formes?

Answer 14

by the condensation of many glucose units

Question 15

How are the polysaccharides glycogen and starch formed?

Answer 15

condensation of α-glucose

Question 16

How is the polysaccharide cellulose formed?

Answer 16

condensation of β-glucose

Question 17

Where is glycogen found?

Answer 17

in animal cells

Question 18

Where is cellulose and starch found?

Answer 18

in plant cells

Question 19

Describe the structure of starch

Answer 19

unbranched= amylose
branched= amylopectin
amylose is wound into a tight coil, makes molecule compact

Question 20

Describe the role of starch in energy storage

Answer 20

large and insoluble, compact, amylopectin has many ends which can be acted on by enzymes

Question 21

Describe the structure of glycogen

Answer 21

similar in structure to starch but has shorter chains and is more highly branched

Question 22

Describe how glycogen’s structure suits it for storage

Answer 22

insoluble, compact, has more ends acted on by enzymes so rapidly broken down to glucose monomers (respiration)

Question 23

Describe the structure of cellulose

Answer 23

made of β-glucose monomers , straight, unbranched chains, chains run parallel with hydrogen bonds (strong)

Question 24

Describe the role of cellulose

Answer 24

support and rigidity in plant cells, prevents bursting (inward pressure)= turgid- surface area- photosynthesis

Question 25

Describe the test for reducing sugars

Answer 25

1. Add 2 cm^3 of food sample in test tube (grind in water) 2. Add equal volume of Benedict's solution 3. Heat in water bath. If reducing sugar present solution turns orange-brown

Question 26

Describe the test for non-reducing sugars

Answer 26

1. Grind sample in water 2. Add 2 cm^3 of food sample being tested to 2 cm^3 of Benedict's solution in test tube and filter 3. Place test tube in water bath 5 mins. If Benedict's solution doesn't change colour (blue) then reducing sugar not present. 4. Add another 2 cm^3 of food sample to 2 cm^3 of dilute HCl acid in test tube and place in water bath 5 mins 5. Add some sodium hydrogencarbonate solution to test tube to neutralise HCl acid. Test with pH paper to check solution alkaline 6. Re-test solution by heating it with 2 cm^3 of Benedict's solution in water bath 5 mins. If non-reducing sugar present, turn orange-brown

Question 27

Out of the disaccharides maltose, sucrose and lactose, which one is the non-reducing sugar?

Answer 27

sucrose

Question 28

Describe the test for starch

Answer 28

1. Place 2 cm^3 of sample in test tube 2. Add 2 drops iodine solution 3. If starch present turns blue-black

Question 29

What are the two groups of lipids?

Answer 29

triglycerides and phospholipids

Question 30

How are triglycerides formed?

Answer 30

condensation of three fatty acids (R-COOH) and one glycerol

Question 31

Which bonds form between glycerol and fatty acids?

Answer 31

ester bond

Question 32

What are the 2 forms the R-group of a fatty acid may be?

Answer 32

saturated or unsaturated

Question 33

What makes a lipid unsaturated?

Answer 33

carbon-carbon double bonds

Question 34

What type of lipid is common in plasma membranes?

Answer 34

phospholipids

Question 35

Which molecules are phospholipids made of?

Answer 35

two fatty acids, one phosphate group and one glycerol

Question 36

How are phospholipids formed?

Answer 36

one of the fatty acids of a triglyceride is substituted by a phosphate-containing group

Question 37

Describe the emulsion test for lipids

Answer 37

1. Take dry and grease-free test tube 2. To2 cm^3 of sample, add 5 cm^3 of ethanol 3. Shake tube (bung) 4. Add 5 cm^3 of water and shake. Lipid present if a milky-white emulsion forms 5. As a control, repeat method using water (clear)

Question 38

Why are triglycerides insoluble in water?

Answer 38

they are non-polar

Question 39

What two parts are a phospholipid made up of?

Answer 39

a hydrophillic head and a hydrophobic tail (polar),

Question 40

Which biological molecule often functions as an enzyme?

Answer 40

protein

Question 41

Which biological molecules are involved in making proteins?

Answer 41

nucleic acids

Question 42

Which two biological molecules are the main respiratory substrates?

Answer 42

carbohydrates and lipids

Question 43

What are amino acids?

Answer 43

monomers of which proteins are made

Question 44

How do the twenty amino acids that are common in all organisms differ?

Answer 44

differ in their side group (R group)

Question 45

What are the two groups common to all amino acid molecules?

Answer 45

amine group and carboxyl group

Question 46

What does the R group on an amino acid represent?

Answer 46

a side group

Question 47

What type of bond is formed when two amino acids join via condensation reaction?

Answer 47

peptide bond

Question 48

What is a molecule called that is made up of two amino acids via condensation reaction?

Answer 48

dipeptide

Question 49

What is a molecule called that is made up of many amino acids via condensation reaction?

Answer 49

polypeptide

Question 50

What is a functional protein?

Answer 50

contains one or more polypeptides (haemoglobin)

Question 51

What type of bond is involved in secondary structure formation of proteins?

Answer 51

hydrogen bond

Question 52

What is the role of hydrogen bonds?

Answer 52

form between some amino acids to either pleat or twist a polypeptide

Question 53

Which three bonds can form between polypeptides in tertiary protein structures creating their shape?

Answer 53

hydrogen, ionic, disulfide bonds (bridge)

Question 54

Describe the tertiary structure

Answer 54

α-helices of the secondary structure twisted and folded even more

Question 55

What does a protein with a primary structure look like?

Answer 55

a polypeptide chain, no extra bonding

Question 56

What two forms can secondary structures of a protein take?

Answer 56

alpha helix or beta-pleated sheet

Question 57

Describe the quaternary structure of proteins

Answer 57

separate polypeptides linked together