3.1 Biological Molecules

Question 1

What is a monomer?

Answer 1

Smaller units from which larger molecules are made

Question 2

Name 3 examples of a monomer

Answer 2

• monosaccharides
• amino acids
• nucleotides

Question 3

What is a polymer?

Answer 3

Molecules made from a larger number of monomers joined together

Question 4

What is a condensation reaction?

Answer 4

A reaction that:
- JOINS two molecules together with a formation of a chemical bond
- involving the ELIMINATION of a water molecule

Question 5

What is a hydrolysis reaction?

Answer 5

A reaction that:
- BREAKS two molecules together with a formation of a chemical bond
- involving the USE of a water molecule

Question 6

What is a monosaccharide?

Answer 6

Monomers from which larger carbohydrates are made

Question 7

How do monosaccharides join together?

Answer 7

Condensation reaction

Question 8

What is the bond formed between two monosaccharides?

Answer 8

Glycosidic bond

Question 9

Name 3 common monosaccharides

Answer 9

• glucose
• galactose
• fructose

Question 10

How are disaccharides formed?

Answer 10

Condensation reaction of two monosaccharides

Question 11

Name 3 types of disaccharides:

Answer 11

• maltose
• sucrose
• lactose

Question 12

Glucose + glucose =

Answer 12

Maltose (+ water)

Question 13

Glucose + fructose =

Answer 13

Sucrose (+ water)

Question 14

Glucose + galactose

Answer 14

Lactose (+ water)

Question 15

What are the two isomers of glucose?

Answer 15

• alpha glucose
• beta glucose

Question 16

How are polysaccharides formed?

Answer 16

The condensation of many glucose units

Question 17

How are glycogen and starch formed?

Answer 17

Condensation of ALPHA glucose

Question 18

How is cellulose formed?

Answer 18

Condensation of BETA glucose

Question 19

What are the properties of starch?

Answer 19

-It is a compact coiled chain so can be stored in small spaces
-Insoluble in water so doesn’t affect water potential and osmosis
-Branched meaning enzymes so glucose monomers are released rapidly

Question 20

What is the test for starch?

Answer 20

• add iodine
• positive result is blue black

Question 21

What are the properties of glycogen?

Answer 21

• Insoluble so does not affect osmosis and does not diffuse out of cells
• Compact so can be stored in a small space
• Branched so glycogen is more rapidly broken down to form glucose monomers

Question 22

Why is it important that glycogen is more highly branched than starch?

Answer 22

Animals have a higher metabolic rate and respiratory rate than plants because they are more active

Question 23

What are the properties of cellulose?

Answer 23

• long, straight, unbranded chains of beta glucose
• chains are linked by hydrogen bonds and form strong fibres called microfibrils
• microfibrils allow cellulose to provide structural support for cells ( eg in plant cell walls)

Question 24

What is the test for reducing and non-reducing sugars?

Answer 24

• Benedict’s solution
• positive result is brick red

Question 25

What is a triglyceride?

Answer 25

- a type of lipid - have one molecule of glycerol with three fatty acids attached

Question 26

Describe the structure of a fatty acid

Answer 26

- long ‘tails’ made of hydrocarbons - these are hydrophobic ~ they repel water molecules - lipids are insoluble in water - all fatty acids have same basic structure but hydrocarbon tail varies

Question 27

How are triglycerides formed?

Answer 27

- fatty acid joined to glycerol - ester bond formed & molecule of water is released = condensation reaction - happens twice to form a triglyceride

Question 28

What is the difference between a saturated and unsaturated fatty acid?

Answer 28

- saturated fatty acids don’t have any double bonds between their carbon atoms - unsaturated have at least one double bond between their carbon atoms

Question 29

What is a phospholipid?

Answer 29

- they have 2 fatty acid and a phosphate group - phosphate group is hydrophilic - fatty acid tails are hydrophobic

Question 30

How does the structure of a triglyceride relate to its function?

Answer 30

- used as energy storage molecules - long hydrocarbon tails contain lots of chemical energy ~ energy is released when they’re broken down - insoluble ~ don’t affect the water potential of the cell and cause cells to move in by osmosis

Question 31

How does the structure of a phospholipid relate to its function?

Answer 31

- make up bilayer of cell membrane ~ control what enters and leaves a cell - heads are hydrophilic and tails are hydrophobic ~ form a double layer with their heads facing out to the water on either side - centre of the bilayer is hydrophobic ~ water-soluble substances can’t easily pass through it ~ membrane acts as a barrier

Question 32

What is the test for lipids and the positive result?

Answer 32

- shake the test substance with ethanol for about a minute so it dissolves, then pair the solution into water - any lipid will show up as a milky white emulsion - more lipid = more noticeable the milky colour

Question 33

What are the monomers of proteins?

Answer 33

Amino acids

Question 34

What is a dipeptide?

Answer 34

Two amino acids joined together

Question 35

What is a polypeptide?

Answer 35

More than two amino acids joined together

Question 36

What is protein made of?

Answer 36

One or more polypeptides

Question 37

Describe the structure of an amino acid

Answer 37

- a carboxyl group ~ -COOH - amine group ~ -NH2 - R group ~ variable side group

Question 38

How many amino acids do living things share?

Answer 38

20

Question 39

How are polypeptides formed?

Answer 39

- amino acids are linked together by condensation reactions - molecule of water is released - bond formed is a peptide bond

Question 40

Describe the primary structure of proteins

Answer 40

A sequence of amino acids in a polypeptide chain

Question 41

Describe the secondary structure of a protein

Answer 41

- hydrogen bonds form between amino acids in the chain - either coil into an ALPHA (α) helix - or fold into a BETA (β) pleated sheet

Question 42

Describe the tertiary structure of a protein

Answer 42

- coiled or folded structure in secondary is often coiled or folded further - more bonds form between parts of the chain ~ hydrogen or ionic - disulfide bridges form when two molecules of cysteine are close together - single chain proteins = tertiary structures is the final 3D structure

Question 43

Describe the quaternary structure of a protein

Answer 43

- for proteins made of several different polypeptide chains - proteins made of more than one chain (haemoglobin, insulin, collagen) the quaternary structure is the final 3D shape