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Biology > Pack 1 - Biological Molecules > Flashcards

Pack 1 - Biological Molecules Flashcards

1
Q

Name 6 biologically important types molecules found in all living organisms.

A
  • Carbohydrates
  • Lipids
  • Proteins
  • Nucleic Acids
  • ATP
  • Water
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2
Q

What does a common biochemistry of all living organisms suggest indirectly about EVOLUTION?

A

All organisms were derived from a COMMON ancestor.

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3
Q

Describe, in 4 steps, hydrogen bonding.

A
  1. ELECTRONS in a molecule are not evenly DISTRIBUTED.
  2. Causes the molecule to become POLARISED (e.g. one part is more negatively charged)
  3. Slightly negatively charged areas attract slightly positively charged areas, forming an ELECTROSTATIC bond.
  4. Many WEAK bonds COLLECTIVELY can affect molecules properties.
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4
Q

Name the type of reaction JOINING molecules together and in doing so, a WATER MOLECULES IS LOST.

A

Condensation Reaction

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5
Q

Name the type of reaction SEPARATING molecules by the ADDITION of a WATER MOLECULE.

A

Hydrolysis (Hydro=water; lysis=breaking up)

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6
Q

Name the MONOMER of the following POLYMERS:

  1. Protein
  2. Polysaccharide
  3. DNA
  4. RNA
A
  1. Amino Acid
  2. Monosaccharide
  3. DNA Nucleotide
  4. RNA Nucleotide
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7
Q

What does metabolism mean?

A

All chemical processes that take place collectively in an organism.

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8
Q

What is a carbohydrate?

A

A molecule containing HYDROGEN, CARBON and OXYGEN (Carbo=Carbon; Hydr=Hydrogen; ate; oxygen).

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9
Q

What feature of CARBON atoms makes it useful in forming different types of molecules?

A

Carbon bonds readily with other carbon atoms.

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10
Q

What is the general formula for MONOSACCHARIDES.

A

CnH2nOn

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11
Q
  1. What is the difference between α-glucose and β-glucose?

2. They are isomers, what is an isomer?

A
  1. The -H and -OH groups are the opposite way round on Carbon-1.
  2. An isomer has the same atoms but arranged differently.
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12
Q

What are monosaccharides mainly used for?

A
  1. Respiratory substrate

2. Structural components in plasma membrane

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13
Q

What is a reducing sugar?

A

A sugar that can donate electrons to another molecule.

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14
Q

What types of carbohydrates are reducing sugars?

A
  • All monosaccharides

* Some disaccharides (e.g. maltose and lactose)

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15
Q

What is the test for reducing sugars?

A

Benedicts Test

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16
Q

Describe Benedict’s test in three steps and a positive result.

A
  1. Add 2cm³ of liquid sample to a test tube.
  2. Add an equal volume of Benedict’s reagent.
  3. Heat the mixture in a gently boiling water bath for 5 minutes.
    Positive result = orange-brown
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17
Q

Why is Benedict’s test semi-quantitative?

A

The difference in colours produced mean the concentration of reducing sugar can be estimated (e.g. green = very low; yellow = low; orange = medium; red = high).

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18
Q

Why does Benedict’s reagent turn red when heated with a reducing sugar?

A

The reducing sugar reacts with the copper(II) sulphate forming a copper(I) oxide precipitate.

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19
Q

Name the monosaccharides of MALTOSE.

A

α-glucose x2

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20
Q

Name the monosaccharides of LACTOSE.

A

α-glucose + galactose

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21
Q

Name the monosaccharides of SUCROSE.

A

α-glucose + fructose

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22
Q

What type of bond is formed when monosaccharides join together?

A

Glycosidic bond

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23
Q

What type of glycosidic bond is formed in the formation of maltose, lactose and sucrose?

A

1-4 glycosidic bond

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24
Q

What are disaccharides mainly used for?

A

Respiration

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25
Q

Which disaccharide is commonly found in fruit?

A

Sucrose

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26
Q

Which disaccharide is commonly found in milk?

A

Lactose

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27
Q

Is sucrose a reducing or non-reducing sugar?

A

Non-reducing

28
Q

What type of reaction is the formation of a glycosidic bond?

A

Condensation

29
Q

What type of reaction is the breaking of a glycosidic bond?

A

Hydrolysis

30
Q

Describe the test for a non-reducing sugars. Explain how it works.

A
  1. Add 2cm³ of liquid sample to a test tube.
  2. Add an EQUAL volume of HYDROCHLORIC ACID.
  3. Heat the mixture in a gently boiling water bath for 5 minutes.
  4. Slowly add some SODIUM HYDROGEN-CARBONATE solution to the test tube until the solution is ALKALINE.
  5. Test with pH paper.
  6. Perform Benedict’s Test.

Adding Hydrochloric acid and heating will hydrolyse the non-reducing sugar into its constituent monosaccharides.
The hydrolysed solution must be alkaline in order for Benedict’s Test to work.

31
Q

What is the monosaccharide of glycogen?

A

α-glucose

32
Q

What is the monosaccharide of starch?

A

α-glucose

33
Q

What is the monosaccharide of cellulose?

A

β-glucose

34
Q

What is the function of glycogen?

A

Energy storage in animals.

35
Q

What is the function of starch?

A

energy storage in plants.

36
Q

What is the function of cellulose?

A

Strengthen plant cell walls.

37
Q

Describe the test for starch.

A
  • Place 2cm³ of the liquid sample into a test tube.
  • Add 2 drops of iodine in potassium iodide solution and shake.
  • Presence of starch is indicated by a change to blue-black colour.
38
Q

Give 5 ways the structure of starch is linked to its function.

A
  • Insoluble - does not affect the water potential - no osmotic effect.
  • Large/long chain - does not diffuse out of the cell.
  • Compact/coiled tightly - lots can be stored in a small space.
  • 1-6 glycosidic branches - enzymes can act on many ends simultaneously - glucose released rapidly.
  • Hydrolysed to glucose monomers - easily transported ready for use.
39
Q

Where and in what form is glycogen mainly found?

A

In the liver and muscles; granules

40
Q

Where and in what form is starch largely found?

A

Plant seeds (many other parts as well); grains

41
Q

Give 4 ways the structure of glycogen is linked to its function.

A
  • Insoluble - does not affect the water potential - no osmotic effect.
  • insoluble/large - does not diffuse out of the cell.
  • Compact - lots can be stored in a small space.
  • MORE 1-6 glycosidic branches then starch - enzymes can act on many ends simultaneously - glucose released more rapidly.
42
Q

Why is is it useful for glycogen to be more highly beached than starch?

A

Animals have a higher metabolic rate and therefore repiritory rate as they are more active. Therefore animals require more glucose in a shower amount of time so more branches means more glucose can be released by enzyme action in the same amount of time.

43
Q

What is the name of an -OH group?

A

Hydroxyl

44
Q

Describe the structure of cellulose molecules.

A
  • Cellulose is a polymer of β-glucose
  • Every other β-glucose is rotated 180° so the hydroxyl groups line up forming 1-4 glycosidic bonds.
  • Each polymer chain is very straight due to the structure of β-glucose.
  • Unbranched
  • Chains run parallel to each other forming WEAK hydrogen bonds between the Carbon-2s of DIFFERENT molecules. Together the hydrogen bonds add lots of strength to cellulose fibres.
45
Q

Describe the structure of cellulose fibres.

A
  • Molecules are grouped together to form microfibrils.

* These are arranged to form fibres.

46
Q

Give 5 ways the structure of cellulose is linked to its function.

A
  • Long chains - forms microfibrils.
  • H-bonds crosslink molecules - forms microfibrils
  • NO side chains - molecules lie close together.
  • Provide rigidity to the plant cell.
  • Resist osmotic pressure - makes cells turgid and cells push against each other - non-woody plants become semi-rigid.
47
Q

Which types of organism produce cellulase?

A

Bacteria and fungi

48
Q

Describe 4 general characteristics of Lipids.

A
  • Contain Carbon, Hydrogen and Oxygen
  • The proportion of OXYGEN to carbon and hydrogen is LOWER than in carbohydrates.
  • Insoluble in water
  • Soluble in organic solvents such as alcohols and acetone.
49
Q

Name 7 uses of lipids in living organisms.

A
  • Cell membrane structure
  • Insulation
  • Waterproofing
  • Protection (e.g. organs)
  • Source of energy
  • Hormones
  • Buoyancy
50
Q

Describe the structure of triglycerides.

A

Three fatty acids (type of carboxylic acid) bonded with an. ESTER bond to one glycerol oxygen. Hydroxyl group (-OH) of the glycerol is bonded to the carboxylic group (-COOH) of the fatty acids.

51
Q

What type of reaction is the formation of an ester bond between glycerol and fatty acids?

A

Condensation.

52
Q

Where does the variation between triglycerides happen ?

A

In the fatty acid carbon skeleton.

53
Q 
What is the difference between:
   • Saturated;
   • mono-unsaturated and
   • polyunsaturated
Lipids?
A
  • Saturated - no C=C double bonds
  • mono-unsaturated - one C=C double bonds
  • polyunsaturated - more than one C=C double bonds
54
Q

Give 4 ways the structure of triglycerides are related to their function.

A
  • High C-H bond ratio - excellent source of energy.
  • Low mass to energy ratio - efficient storage of energy.
  • Insoluble in water - no osmotic effect
  • High hydrogen to oxygen ratio - release water when oxidised.
55
Q

Describe the structure of a phospholipid. How does this make is a polar molecule.

A

Same as triglyceride, except, one fatty acid is replaced with a phosphate molecule (from phosphoric acid).

  • It forms a hydrophilic ‘head’ (phosphate).
  • It forms a hydrophobic ‘tail’ (fatty acids).
56
Q

Give 2 ways the structure of phospholipids are related to their function.

A
  • Polar - in an aqueous environment phospholipids form a bilayer within cell-surface membranes.
  • Allow formation of glycolipids within cell membrane.
57
Q

Test for Lipids (Emulsion) in 6 steps.

A
  1. Take a dry grease-free test tube.
  2. Add 5cm of ethanol to 2cm of the sample.
  3. Shake to fully dissolve lipid.
  4. Add 5cm of water and shake.
  5. A cloudy-white colour indicates lipids presence.
  6. As a control repeat using water instead of the sample.
58
Q

Why is a water molecule described as dipolar?

A

Although overall the molecule has zero charge, the oxygen atom has a slightly negative charge and the hydrogen atoms have a slightly positive charge. Therefore is has both negative and positive poles so is described as dipolar.

59
Q

What type of bonding does the polarity of water cause?

A

Hydrogen bonding

60
Q

Give 4 properties of water due to hydrogen bonding and explain why these are useful.

A
  • High specific heat capacity - water is less susceptible to sudden changes in temperature, it is liquid at room temperature.
  • Latent heat of vaporisation - large cooling effect (e.g. sweat)
  • Cohesion and Adhesion - water can be pulled up through xylem tubes.
61
Q

Give 5 ways water is useful in living organisms.

A
  • Used in metabolism (hydrolysis)
  • Solvent
  • Cooling
  • Not easily compressed - support
  • Transparent (aquatic life)
62
Q

Give 2 functions of phosphate ions in living organisms.

A
  • Structural component in DNA

* Energy storage in ATP

63
Q

What is co-transport?

A

TWO substances are moved across a membrane SIMULTANEOUSLY by ONE protein.

64
Q

How are sodium ions used in co-transportation?

A

Glucose can only bind to the protein if sodium is also bound. This allows the transport of glucose.

65
Q

Describe the structure of haemoglobin (3 parts).

A
  • 2 α-polypeptide chains
  • 2 β-polypeptide chains
  • 4 iron ions (one in each polypeptide chain)
66
Q

What is the role of iron ions in haemoglobin?

A

To transport oxygen.

Biology (18 decks)

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