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A-Level Biology AQA > 3.1 Biological Molecules > Flashcards

3.1 Biological Molecules Flashcards

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1
Q

What is a monomer?

A

Smaller units from which larger molecules are made

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2
Q

Name 3 examples of a monomer

A
  • monosaccharides
  • amino acids
  • nucleotides
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3
Q

What is a polymer?

A

Molecules made from a larger number of monomers joined together

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4
Q

What is a condensation reaction?

A

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

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5
Q

What is a hydrolysis reaction?

A

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

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6
Q

What is a monosaccharide?

A

Monomers from which larger carbohydrates are made

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7
Q

How do monosaccharides join together?

A

Condensation reaction

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8
Q

What is the bond formed between two monosaccharides?

A

Glycosidic bond

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9
Q

Name 3 common monosaccharides

A
  • glucose
  • galactose
  • fructose
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10
Q

How are disaccharides formed?

A

Condensation reaction of two monosaccharides

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11
Q

Name 3 types of disaccharides:

A
  • maltose
  • sucrose
  • lactose
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12
Q

Glucose + glucose =

A

Maltose (+ water)

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13
Q

Glucose + fructose =

A

Sucrose (+ water)

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14
Q

Glucose + galactose

A

Lactose (+ water)

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15
Q

What are the two isomers of glucose?

A
  • alpha glucose
  • beta glucose
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16
Q

How are polysaccharides formed?

A

The condensation of many glucose units

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17
Q

How are glycogen and starch formed?

A

Condensation of ALPHA glucose

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18
Q

How is cellulose formed?

A

Condensation of BETA glucose

19
Q

What are the properties of starch?

A

-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

20
Q

What is the test for starch?

A
  • add iodine
  • positive result is blue black
21
Q

What are the properties of glycogen?

A
  • 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
22
Q

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

A

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

23
Q

What are the properties of cellulose?

A
  • 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)
24
Q

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

A
  • Benedict’s solution
  • positive result is brick red
25
Q

What is a triglyceride?

A
  • a type of lipid
  • have one molecule of glycerol with three fatty acids attached
26
Q

Describe the structure of a fatty acid

A
  • 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
27
Q

How are triglycerides formed?

A
  • fatty acid joined to glycerol
  • ester bond formed & molecule of water is released = condensation reaction
  • happens twice to form a triglyceride
28
Q

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

A
  • saturated fatty acids don’t have any double bonds between their carbon atoms
  • unsaturated have at least one double bond between their carbon atoms
29
Q

What is a phospholipid?

A
  • they have 2 fatty acid and a phosphate group
  • phosphate group is hydrophilic
  • fatty acid tails are hydrophobic
30
Q

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

A
  • 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
31
Q

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

A
  • 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
32
Q

What is the test for lipids and the positive result?

A
  • 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
33
Q

What are the monomers of proteins?

A

Amino acids

34
Q

What is a dipeptide?

A

Two amino acids joined together

35
Q

What is a polypeptide?

A

More than two amino acids joined together

36
Q

What is protein made of?

A

One or more polypeptides

37
Q

Describe the structure of an amino acid

A
  • a carboxyl group ~ -COOH
  • amine group ~ -NH2
  • R group ~ variable side group
38
Q

How many amino acids do living things share?

A

20

39
Q

How are polypeptides formed?

A
  • amino acids are linked together by condensation reactions
  • molecule of water is released
  • bond formed is a peptide bond
40
Q

Describe the primary structure of proteins

A

A sequence of amino acids in a polypeptide chain

41
Q

Describe the secondary structure of a protein

A
  • hydrogen bonds form between amino acids in the chain
  • either coil into an ALPHA (α) helix
  • or fold into a BETA (β) pleated sheet
42
Q

Describe the tertiary structure of a protein

A
  • 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
43
Q

Describe the quaternary structure of a protein

A
  • 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

A-Level Biology AQA (16 decks)

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