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Alevel Bio > Biological Molecules > Flashcards

Biological Molecules Flashcards

1
Q

What does organic mean?

A

Contains the element carbon, organic compounds always contain carbon-carbon bonds

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2
Q

What are the 4 types of organic compounds found in organisms?

A

Carbohydrates, amino acids, lipids and nucleic acid

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3
Q

What conditions are needed for hydrogen bonds to form?

A

Between a d+ hydrogen and d- Nitrogen, Oxygen or Fluorine with an electron pair

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4
Q

Why do hydrogen bonds form between water molecules?

A
  • water molecules are polar, hydrogen is d+ while Oxygen is d-
  • opposite partial charges of different water molecules causes these hydrogen bond (intermolecular forces)
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5
Q

How do polar molecules interact with water?

A

Polar molecules dissolve readily in water being hydrophilic, eg salts, sugars and amino acids

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6
Q

How do uncharged molecules interact with water?

A

Non-polar molecules do not dissolve in water and are called hydrophobic, eg lipids

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7
Q

Why is it important for life that water molecules have high cohesive properties?

A

For long water columns in Transpiration and so insects can walk on water

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8
Q

Give 3 examples of monosaccharides, disaccharides and polysaccharides:

A

Mono: glucose, fructose, galactose
Di: sucrose, maltose, lactose
Poly: starch, glycogen, cellulose

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9
Q

What is the monosaccharide formula? And what type of sugar is glucose?

A

(CH2O)n when n is 3-7

Glucose is a hexose sugar

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10
Q

What is an isomer? Give 2 isomers of glucose

A

Same chemical formula, different structural formulae

-galactose and fructose

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11
Q

Name 3 pentose sugars:

A

Ribose, deoxyribose and ribulose (occurs in photosynthesis)

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12
Q

How are disaccharides formed?

A

2 monosaccharides join together forming a glycosidic bond (C-O-C) in a condensation reaction releasing a water molecule

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13
Q

Structure of sucrose, lactose and maltose:

A

Sucrose- glucose and fructose
Maltose- glucose and glucose
Lactose- glucose and galactose

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14
Q

Describe a glucose molecule:

A
  • Hexagonal shape
  • 5 OH groups
  • 1 (c-o-c) bond in top right
  • carbon methyl group on top left with OH
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15
Q

Describe a glycerol: or draw

A
  • 3 carbon molecule
  • each carbon contain OH group
  • C3H803
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16
Q

Describe or draw the structure of a fatty acid:

A
  • Polar carboxylic acid group at one end
  • non-polar hydrocarbon chain which varies in length (14-22)
  • written as R-COOH
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17
Q

How does the bond form between glycerol and fatty acid to form triglyceride?

A
  • Glycerol loses OH group
  • Carboxyl group of fatty acid loses H
  • Ester bond forms (C-O-C)
  • Therefore, polymerisation reaction=condensation reaction
18
Q

What are triglycerides used for and why cant they be mobilised easily?

A
  • protection, insulation and energy storage in fatty tissues

- They are insoluble so cant be mobilised to respiring tissues easily

19
Q

Properties of saturated fatty acids:

A
  • contain no C=C in hydrocarbon chain
  • higher melting point, and solid at room temp (fats) eg butter, lard
  • found in warm blooded animals
20
Q

Properties of unsaturated fatty acids (Poly-unsaturated, mono-unsaturated):

A
  • contain C=C
  • more than one C=C is poly unsaturated
  • found in cold blooded animals and plants
  • lower melting point (oils at room temp)
21
Q

Describe of draw a phospholipid:

A
  • contains a phosphate group replacing a fatty acid
  • phosphate group produces a polar hydrophilic head (negatively charged phosphate group)
  • 2 non polar hydrophobic tails
22
Q

What is a liposome?

A
  • when phospholipids interact with water they form droplet spheres
  • a phospholipid bilayer creates a sphere trapping water in the center (aqueous compartment) from the outside
23
Q

Describe the structure of an amino acid:

A
  • central carbon (alpha carbon) with 4 different chemical groups
  • basic amino group (NH2)
  • acidic carboxyl group (COOH)
  • hydrogen
  • variable R group (which determines the type of amino acid)
24
Q

How is a peptide bond formed?

A
  • OH from carboxyl group and H from amino group form a water molecule
  • this forms a dipeptide and peptide bond (C-N)
  • polymerisation reaction = condensation reaction
25
Q

What is the free COOH group and NH2 group at either end of a polypeptide chain called?

A 
COOH = C-terminus
NH2  = N-terminus
26
Q

Where does polymerisation of amino acids occur?

A

In the ribosomes, this is also called protein synthesis

27
Q

What is the primary structure?

A

The sequence of amino acids in a polypeptide chain which determines the rest of the protein structure

28
Q

What is the secondary structure?

A

A basic level of protein folding occurs due to the hydrogen bonds between carboxyl groups and amino groups, forming either a:
Alpha helix or beta pleated sheet

29
Q

What is the tertiary structure?

A

This is the compact globular structure due to the folding of a whole polypeptide chain
Includes hydrogen bonds and disulphides bridges between 2 cysteine amino acids

30
Q

Why are the tertiary structures of protein different?

A

The tertiary structure is held together by bonds between R groups of the amino acids, and so depends on the sequence of amino acids (primary structure)

31
Q

What is the quaternary structure?

A

The arrangement of the different chains

32
Q

Give 3 examples of a quaternary structure protein:

A

1) haemoglobin- 4 chains in a tetrahedral shape each with an Fe group
2) Antibodies- 4 chains arranged in a Y shape
3) Enzymes
4) collagen- 3 chains in a triple helix structure
5) Actin- hundreds of glubular chains arranged in double helix

33
Q

Globular and fibrous proteins, what’s the difference?

A

Globular- compact ball shaped, usually enzymes, membrane proteins, receptors and storage proteins
Fibrous proteins- long thin rope-like, usually structural roles like collagen (bone), keratin (hair), actin (muscle)

34
Q

What happens when a protein is denatured?

A

Under high temps or pH changes the hydrogen bonds break, since the the secondary, tertiary and quaternary structures are large sly held together by them, the polypeptide chains just fold up into a random coil and lose their function and shape

35
Q

Test for starch?

A

Add a few drops of potassium iodide solution into the sample.
Blue/black colour change from yellow = positive
-Black starch-polyiodide complex is formed

36
Q

Reducing sugars test?

A

Add a few mL of Benedictus reagent to sample, shake and heat at 95 degrees C in a water bath

  • the colour and density of precipitate indicates amount of reducing sugar present
  • Blue solution-> green precipitate->brick red precipitate (lots of reducing sugar)
  • this test is semi-quantitive
37
Q

Test for non reducing sugars?

A
  • test sample for reducing sugars
  • using a separate sample add dilute hydrochloride acid for a few mins to hydrolyse the glycosidic bond
  • neutralise the solution by gently adding solid sodium hydrogen carbonate until stops fizzing
  • repeat test for reducing sugars
38
Q

How does the test for non reducing sugars work?

A

There is no direct test for non-reducing sugars eg sucrose so:
Hydrolyse the di/polysaccharide into its constituent monosaccharides then test for reducing sugars

39
Q

Test for lipids?

A

Emulsion test- lipids are insoluble in water but dissolve in ethanol

  • add a sample to 4mL of ethanol and shake vigorously
  • decant the liquid into a second test tube of water leaving undissolved substances behind
  • a precipitate of lipids will form in the water forming white cloudy emulsion
40
Q

Test for proteins?

A

Biuret test: add a few mL of biuret solution to the sample, shake and if solution turns lilac/purple proteins are present

Alevel Bio (7 decks)

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