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Biology A-level > Biological molecules > Flashcards

Biological molecules Flashcards

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1
Q

What is the molecular formula of glucose?

A

C6H12O6

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2
Q

How are monosaccarides joined together?

A

Condensation reaction

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3
Q

What bond forms between two monosaccarides?

A

glycosidic bond

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4
Q

What is the name of two monosaccarides joined together?

A

disaccaride

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5
Q

What is sucrose made up of?

A

a glucose and a fructose molecule

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6
Q

What is lactose made up of?

A

a glucose and galactose molecule

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7
Q

What test can be used to test for reducing sugars and what are the results?How do you carry the test out?

A

Benedicts test
Add Benedictus reagent (blue) and heat in a water bath that’s been brought to boil if the test positive it will form a coloured precipitate.
The colour of the precipitate changes from blue to green to yellow to orange, the further on the colour the higher the concentration of the reducing sugar.

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8
Q

What test can be used to test for non-reducing sugars and what are the results?How do you carry the test out?

A

If Benedictus test is negative then you probably have a non-reducing sugar.
Add hydrochloric acid to break the sugars down into monosaccarides.
Heat in a water bath that’s been brought to boil.
neutralise it with sodium hydrogen carbonate.
Then carry out the Benedictus test.

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9
Q

What is a polysaccaride?

A

Many sugars joined together

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10
Q

How do plants store excess glucose?

A

In starch

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11
Q

What two polysaccharides is starch a mixture of?

A

alpha glucose-amylose and amylopectin

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12
Q

What makes starch a good storage molecule?

A

The amylose has a coiled structure so its compact meaning you can fit lots of it into a small space.
The amylopectin is branched so enzymes that break down the molecule have easy access to the glycosidic bonds meaning glucose can be released quickly.

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13
Q

What test is used for starch?

A

The iodine test.
Add iodine dissolved in potassium iodide solution to the test sample, if starch is present the sample changes from browny-orange to blue-black.

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14
Q

What is the main energy storage material in animals?

A

Glycogen

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15
Q

What is the monomer of starch and glycogen?

A

alpha-glucose

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16
Q

What make glycogen a good storage molecule?

A

It has many branches so glucose can be quickly released.

It is a compact molecule so is good for storage.

17
Q

What monomer is cellulose made from?

A

beta-glucose

18
Q

Describe the structure of cellulose

A

The beta-glucose form straight chains, the chains are linked together by hydrogen bonds to form strong fibres called microfibrils.The strong fibres mean that cellulose provides structural support for cells.

19
Q

Name a type of lipid

A

Triglyceride

20
Q

What are triglycerides made up of?

A

One glycerol molecule with three fatty acids attached to it.

21
Q

Name a property of fatty acids

A

Insoluble in water.
Fatty acids have long hydrocarbon ‘tails’ which are hydrophobic.All fatty acids have the same basic structure however the hydrocarbon tail varies.

22
Q

What type of reaction occurs when a glycerol molecule joins with a fatty acid? What bond is formed?

A

A condensation reaction and an ester bond.

23
Q

What do unsaturated fatty acids have that saturated fatty acids don’t?

A

a carbon-carbon double bond

24
Q

Describe the structure of a phospholipid.

A

a glycerol molecule joined to two fatty acids and one phosphate group. The phosphate grouping hydrophilic.

25
Q

What makes triglyceride molecules good energy storage molecules?

A
  • The long hydrocarbon chains of the fatty acids contain lots of chemical energy which is released hone there are broken down.
  • They’re insoluble so don’t affect water potential of the cell and don’t cause water to enter the cell by osmosis.The triglycerides clump together as insoluble droplets because the hydrophobic tails face inwards shielding themselves from water with their glycerol heads.
26
Q

What test can be used for lipids?

A

The emulsion test.

  • Shake the test substance with ethanol for about a minute until it dissolves then pour the solution into water.
  • Any lipid will show up as milky emulsion.
  • the more lipid there is the more noticeable the milky colour will be.
27
Q

What are the monomers of proteins?

A

Amino acids

28
Q

What reaction forms polypeptides?What bonds are between amino acids?

A
  • Condensation reaction

- Peptide bonds

29
Q

Describe the secondary structure of proteins:

A

-Hydrogen bonds form between the amino acids in the chain.This makes it automatically coil into an alpha helix or fold into beta pleated sheet.

30
Q

Describe the tertiary structure of proteins:

A
  • The coiled or folded chain of amino acids is often coiled or folded further.
  • More bonds form between different parts of the polypeptide chain, including hydrogen and iconic bonds.
  • Disulfide bridges also form whenever two molecules of cysteine come close together.
31
Q

Describe the quaternary structure of proteins:

A
  • some proteins are made of several different polypeptide chains held together by bonds.
  • the quaternary structure is how these chains are assembled together.
32
Q

What is the test used for proteins? What is a positive result?

A

The Biuret test

  • Add a few drops of sodium hydroxide solution
  • then add some copper sulfate solution
  • if a protein is present it turns purple
33
Q

Give 5 properties of water:

A
  • good metabolite
  • high latent heat of vaporisation
  • buffers changes in temperature
  • good solvent
  • strong cohesion between molecules
34
Q

Explain the fact that water is a good metabolite:

A
  • Many metabolic reactions involve a condensation or hydrolysis reaction.
  • A hydrolysis reaction requires a water molecule to break a bond and a condensation reaction releases water as a bond is formed.
35
Q

Explain the fact that water has a high latent heat of vaporisation:

A
  • It takes a lot of energy to break the hydrogen bonds between water molecules
  • This means a lot of energy is needed to evaporate water.
  • This means organisms can use water loss through evaporation to cool down without loosing too much water.
36
Q

Explain the fact that water buffers changes in temperatures:

A
  • The hydrogen bonds between molecules absorb a lot of energy.
  • So water has a high specific heat capacity.
  • This means that water doesn’t experience rapid temperature changes.
  • This means water is a good habitat as the temperature is more stable that on land.
  • Also water inside organisms help maintain a constant body temperature.
37
Q

Explain the fact that water is a good solvent:

A
  • A lot of important substances in metabolic reactions are ionic.
  • because water is a polar molecule both positive and negative ions are attracted to it.
  • this means ions will get surrounded by water molecules (they’ll dissolve)
38
Q

Explain the fact that there is a strong cohesion between water molecules:

A
  • Strong cohesion helps water flow making it great for transporting substances e.g in. the xylem
  • The cohesion also means water has a high surface tension causing it to from droplets of sweat helping organisms to cool down and it also allows organisms to walk on the surface of water.
39
Q

Describe the structure of ATP:

A

made up of adenine a ribose sugar and three phosphate groups

Biology A-level (10 decks)

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