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AS AQA Biology > Topic 1 - Biological Molecules > Flashcards

Topic 1 - Biological Molecules Flashcards

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1
Q

What is a condensation reaction?

A

This is a reaction joining two molecules together to form a larger molecule through the formation of a glycosidic bond and involving the elimination of a water molecule.

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2
Q

What is a hydrolysis reaction?

A

This is a reaction that breaks a chemical bond between two molecules through the use of a water molecule

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3
Q

Which monosaccharides make up maltose?

A

Glucose + Glucose

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4
Q

Which monosaccharides make up sucrose?

A

Glucose + Fructose

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5
Q

Which monosaccharides make up lactose?

A

Glucose + Galactose

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6
Q

What type of bonds make up the disaccharides: maltose, sucrose and lactose?

A

1-4 glycosidic bonds

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7
Q

Describe the structure and function of cellulose.

A
  • Makes up plant cell walls
  • Made up of beta-glucose
  • Made of glycosidic bonds
  • Unbranched/straight chain structure
  • Every other beta glucose flips 180º so that the OH molecules are next to each other
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8
Q

How is cellulose adapted to its function in the plant cell wall?

A

Cellulose is very strong to prevent cells from bursting when they take in excess water - they’re strong because glucose chains form rope-like microfibrils, layered to form a network with hydrogen bonds between these layers

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9
Q

What two units is starch arranged into?

A

Amylose and amylopectin

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10
Q

Describe the structure of amylose.

A
  • 1-4 glycosidic bonds of alpha glucose in an unbranched and coiled shape
  • It’s insoluble so it doesn’t affect water potential so no effect on osmosis
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11
Q

Describe the structure of amylopectin.

A
  • 1-4 + 1-6 glycosidic bonds of alpha glucose in highly branched chains to increase the SA so it can be hydrolysed more quickly
  • Insoluble so no effect on water potential or on osmosis
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12
Q

Describe the structure and function of glycogen.

A
  • Stored as energy in animals in the form of small granules in muscles/liver
  • Made up of many 1-6 glycosidic bonds producing a really branched structure to increase the SA
  • Insoluble so has no effect on water potential or on osmosis
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13
Q

What’s the test for reducing sugars?

A

1) Add Benedict’s solution (blue)
2) Heat sample in water bath to 100°
3) If sugar present - turns red

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14
Q

What’s the test for non-reducing sugars?

A

1) Add some HCl
2) Boil in water bath
3) Test again for reducing sugars :
- If it turns red - non-reducing sugar
- If it stays same (blue) - no sugar/carbohydrate

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15
Q

What are the two types of lipids?

A

Triglycerides and phospholipids

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16
Q

Definitions of:

  • Saturated
  • Mono-unsaturated
  • Polyunsaturated
A

Saturated - No double bonds between carbons
Mono-unsaturated - One double bond between carbon atoms
Polyunsaturated - More than one double bond between carbon atoms

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17
Q

What are triglycerides made up of?

A

Glycerol and fatty acids

18
Q

Describe the structure of triglycerides.

A

Glycerol and 3 fatty acids joined together by and ester bond via a condensation reaction

19
Q

Describe some features of triglycerides.

A
  • Their main function is energy storage
  • They’re long polymers with lots of bonds
  • Insoluble so have no effect on water potential or osmosis
  • Form insoluble droplets - have hydrophobic tails on the inside
20
Q

Describe the structure of phospholipids.

A
  • 1 glycerol molecule and 2 fatty acids
  • Polar phosphate group is attached to the third hydroxyl group on the glycerol molecule
  • Fatty acid ‘tails’ are hydrophobic
  • Phosphate ‘head’ is hydrophilic
  • Has amphipathic nature
21
Q

What is the function of phospholipids?

A

They have a vital role in the cell membrane controlling what goes in or out of a cell
It’s called the phospholipid bilayer

22
Q

Why is it difficult for water to diffuse in and out of cells?

A

The middle is hydrophobic due to the fatty acid tails and since water is polar it makes diffusion difficult due to repulsion

23
Q

What are glycolipids and how are they formed?

A

Glycolipids are important in the cell membrane for cell recognition and are formed by combining phospholipids with carbohydrates

24
Q

What does amphipathic mean?

A

It’s a molecule that has both hydrophilic and hydrophobic sections

25
Q

What are the main roles of lipids (adipose tissue) ?

A

They’re stored in adipose tissue
⭐︎Heat insulation - in mammals, adipose tissue underneath the skin helps to reduce heat loss
⭐︎Protection - Adipose tissue around delicate organs such as kidneys act as a cushion against impacts
⭐︎Source of energy

26
Q

Why do lipids dissolve in ethanol but not water?

A

Ethanol is also a non-polar molecule whereas water is polar

27
Q

What is the test for lipids known as?

A

The emulsion test

28
Q

Describe the emulsion test.

A

1) Mix 2cm³ of test sample to 5cm³ of ethanol and shake in order to dissolve any lipid in the sample
2) Add 5cm³ of water and shake gently
3) Observe - Milky layer if lipid is present
- No milky layer = no lipids

29
Q

What is a protein?

A

A polymer built up of one or more amino acids with specific shapes essential to their function

30
Q

What’s an amino acid?

A

The monomer that makes up proteins (polypeptides)

31
Q

What makes up an amino acid chemically?

A

○Amino group (-NH2) - a basic group form which the amino part of the name amino acid is derived
○Carboxyl group (-COOH) - an acidic group which makes up the acid part of the name amino acid
○Hydrogen atom (-H)
○R (side) group - a variety of different chemical groups. Each amino acid has a different R group which means the R group is the only difference in the 20 naturally occurring animo acids

32
Q

What bond joins amino acids together?

A

Peptide bonds

33
Q

What are the main biological roles of proteins?

A

⭐︎Structural - main component of body tissues e.g. muscle, skin, ligaments, hair
⭐︎Catalytic - all enzymes are proteins, catalysing biochemical reactions
⭐︎Signalling - many hormones and receptors are proteins
⭐︎Immunological - all antibodies are proteins

34
Q

Describe the primary structure of proteins

A

A sequence of amino acids in a polypeptide chain

35
Q

Describe the secondary structure of a protein

A

Weak hydrogen bonds are formed between amino acids which caused the long polypeptide chain to be twisted into a 3D shape such as the coil known as an alpha-helix

36
Q

Describe the structure of a tertiary protein

A

The alpha helixes can be twisted or folded to make the structure more complex and specific. This structure is maintained by a number of different bonds. Where these bonds occur is down to the primary structure of the protein

37
Q

Name and describe the bonds in a tertiary protein

A
  • Disulfide bridges - fairly strong and nit easily broken
  • Ionic bonds - are formed between any carboxyl and amino groups that are not involved in forming peptide bonds. They are weaker than disulfide bridges and are easily broken by changes in pH
  • Hydrogen bonds - numerous but easily broken
38
Q

Describe the structure of a quarternary protein

A

Large proteins often form complex molecules containing a number of individual polypeptide chains that are linked in various ways. There also may be prosthetic groups associated with the molecules such as the iron-containing haem group in haemoglobin.

39
Q

What’s a prosthetic group

A

Non-protein group

40
Q

Name and describe the test for proteins

A

Biuret test to detect peptide bonds

  1. Place a sample of the solution to be tested in a test tube and add an equal volume of sodium hydroxide solution at room temperature
  2. Add a few drops of very dilute (0.05%) copper (ll) sulfate solution and mix gently
  3. A purple coloration indicates the presence of peptide bonds and hence a protein. If solution remains blue there is no presence

AS AQA Biology (10 decks)

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