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A Level > Biology: Section 1 (biomolecules) > Flashcards

Biology: Section 1 (biomolecules) Flashcards

1
Q

what is a condensation reaction?

A

a reaction where water is produced as the bond forms.

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2
Q

what is a hydrolysis reaction?

A

adding water to break bonds.

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3
Q

what do the following reactions result in?

1) glucose + glucose
2) glucose + fructose
3) glucose + galactose

A

1) maltose
2) sucrose
3) lactose

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4
Q

how do you test for reducing sugars?

A
  • add benedicts solution to the sample
  • it goes from blue to brick red
  • this is because it forms an insoluble precipitate of copper (II) oxide.
  • it’s a reduction reaction as electrons are gained.
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5
Q

how do you test for non-reducing sugars?

A
  • heat with hydrochloric acid.
  • neutralise the acid by adding an alkaline.
  • test with benedict’s solution
  • it goes from blue to brick red if non-reducing sugars are present.
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6
Q

how do you test for starch?

A

add iodine to the solution, it turns blue/black in the presence of starch.

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7
Q

how is starch adapted for its function?

A
  • long, branched chains means that there’s lots of space for enzyme action.
  • it’s compact so it can be packed into small spaces
  • doesn’t change the water potential of the cell as it’s insoluble.
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8
Q

how is glycogen adapted for its function?

A
  • found in small amounts in the muscles and liver as fat is the main storage molecule.
  • it has many branched chains, it takes up some space but it’s easily hydrolysed for quick energy release.
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9
Q

how is cellulose related to its function?

A
  • made of beta glucose.
  • joined together by 1,4 glycosidic bonds.
  • every 2nd b-glucose molecule is rotated 180 degrees as it makes the bonds stronger.
  • they’re straight, they can line up along eachother to form hydrogen crosslinks in order to make stems semi-rigid.
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10
Q

what is a triglyceride and what’s it made of?

A
  • it’s an ester of fatty acids and glycerol.
  • fatty acids and glycerol joined by a condensation reaction.
  • 1 glycerol, 3 fatty acids.
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11
Q

how does the structure of triglycerides make them useful in living organisms?

A
  • energy source: insoluble, long term reserves of energy in plants, animals etc.
  • insulation: poor conductor of heat, prevents heat loss.
  • molecules: steroids and some hormones are lipids.
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12
Q

what is a phospholipid?

A
  • made of glycerol and 2 fatty acid molecules.
  • polar molecule.
  • hydrophilic head, hydrophobic tail.
  • used in emulsifiers and in membrane bilayers
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13
Q

how do you test for lipids?

A

emulsion test

  • mix ethanol and sample in equal volumes.
  • shake to dissolve lipids
  • add an equal volume of water and mix
  • a white suspension indicates the presence of lipids
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14
Q

what is the primary structure of a protein?

A

the order of amino acids.

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15
Q

what is the secondary structure of a protein?

A

the chain begins to coil into a helix

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16
Q

what is the tertiary structure of a protein?

A

the chain coils further into a shape.

17
Q

what is the quaternary structure of a protein?

A

when 2 or more polypeptide chains join together.

18
Q

what makes enzymes specific?

A

their active site is complementary to the substrate because of its tertiary structure

19
Q

what does the lock and key hypothesis state?

A

it states that the active site is only specific to one substrate, the reaction doesn’t take place with a different substrate, similar to a lock and key.

20
Q

what does the induced fit model show?

A
  • when the substrate binds to the active site, the shape of the active site changes slightly as it moves around the substrate.
  • this puts pressure on the bonds holding it together, breaking them
  • this increases the rate of reaction
21
Q

what factors affect the activity of enzymes?

A
  • temperature: enzyme action slows at low temperatures, but they become denatured at high temperatures as their tertiary structures change and the active site is no longer complementary to the substrate.
  • pH: it can also cause denaturation, enzymes have an optimum pH
  • conc. of enzyme: rate increases as there are more active sites.
  • conc. of substrate: it becomes constant when all active sites are occupied.
  • inhibitors
22
Q

what do non-competitive inhibitors do?

A

they bind to the allosteric site, this changes the shape of the active site so it’s no longer complementary to the substrate.

23
Q

what do competitive inhibitors do?

A

they compete with the substrate for the active site. it’s complementary to the active site so the reaction can’t happen once it’s inhibited as it doesn’t fit.

24
Q

what are nucleotides made of?

A
  • pentose sugar (deoxyribose for DNA, ribose for RNA)
  • organic base (A,T,C OR G)
  • phosphate group.
25
Q

how is the structure of DNA adapted for its function?

A
  • sugar-phosphate backbone protects the chemically reactive bases.
  • weak hydrogen bonds hold the bases together, makes semi-conservative replication easy.
26
Q

what is the structure of RNA?

A
  • ribose sugar.

- thymine is replaces by uracil

27
Q

describe the process of semi-conservative replication

A
  • DNA helicase breaks the hydrogen bonds which holds the double-helix together
  • it halves and it results in 2 separate strands.
  • free nucleotides bind to their complementary bases.
  • a sugar phosphate backbone forms.
  • it results in 2 double-helical strands of DNA.
28
Q

what is ATP made of?

A
  • adenosine

- 3 phosphate groups

29
Q

how is energy released from ATP?

A

the phosphate group is snapped off, which releases energy. this is also used in active transport as the carrier protein is phosphorylated to change its shape.

30
Q

how is ATP adapted for its function?

A

-the phosphate can be reattached to the ADP so that the reaction can happen again.

31
Q

what are the functions of water?

A

-dipolarity and hydrogen bonding: oxygen carries a small negative charge, hydrogen carries a small positive charge. it has no net charge as they’re balanced.

solvent properties: ions and polar molecules readily dissolve in water due to the polarity of their molecules

A Level (36 decks)

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