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A Level Biology > Biological Molecules > Flashcards

Biological Molecules Flashcards

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1
Q

How many bonds can a carbon atom form?

A

4

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2
Q

How many bonds can a nitrogen atom form?

A

3

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3
Q

How many bonds can an oxygen atom form?

A

2

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4
Q

How many bonds can hydrogen form?

A

1

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5
Q

What are calcium ions essential for?

A

Nerve impulse transmission

Muscle contraction

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6
Q

What are sodium ions essential for?

A

Nerve impulse transmission

Kidney function

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7
Q

What are potassium ions needed for?

A

Nerve impulse transmission

Stomata opening

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8
Q

What’s the hydrogen ions needed for?

A

Catalysis of reactions

PH determination

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9
Q

What are ammonium ions used for?

A

Production of nitrate ions by bacteria

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10
Q

What are nitrate ions needed for?

A

Nitrogen supply to plants for amino acid and protein formation

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11
Q

What are hydrogen carbonate ions essential for?

A

Maintenance of blood pH

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12
Q

What are chloride ions essential for?

A

Balance positive charge of sodium and potassium ions in cells

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13
Q

What are phosphate ions needed for?

A

Cell membrane formation
Nucleus acid and ATP formation
Bone formation

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14
Q

What are hydroxide ions needed for?

A

Catalysis of reactions

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15
Q

What does polar mean?

A

Has regions of positivity and negativity

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16
Q

Name a polar molecule

A

Water

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17
Q

What bonds form in polar molecules?

A

Hydrogen bonds abs they are relatively weak interactions which break and reform.

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18
Q

What are the characteristics of water?

A

High boiling point
Water less dense as a solid
Cohesive

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19
Q

Why does water have a high boiling point?

A

Hydrogen bonding means that it takes a lot of energy to break all the hydrogen bonds (so many) and therefore evaporate the liquid

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20
Q

Why is ice less dense than water?

A

Due to the bonding pattern of hydrogen bonds at a certain temperature. Produces giant rigid and open structure with every oxygen at the centre of a tetrahedral arrangement

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21
Q

Why does water have cohesive properties?

A

Water molecules attracted to each other due to polarity.

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22
Q

Why is water vital for life?

A

Acts as a solvent

Very efficient transport medium

Acts as a coolant

Surface tension

Does not change temp very easily

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23
Q

Why can water demonstrate capillary action?

A

As it shows cohesive and adhesive properties water can be taken up by plants by the force of gravity

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24
Q

What is the general formula of carbohydrates?

A

Cx(H2O)y

25
Q

Are glucose molecules polar and soluble in water?

A

Yes

26
Q

What type of bond forms between two glucose molecules?

A

Glycosidic bonds

27
Q

What does the reaction for the joining of 2 glucose molecules produce?

A

Maltose and water

28
Q

What do galactose and glucose form?

A

Lactose

29
Q

What do fructose and glucose form?

A

Sucrose

30
Q

How is amylose formed?

A

Alpha glucose molecules joined by 1-4 glycosidic bonds.

31
Q

What shape is amylose and why?

A

Amylose forms a helix shape due to the angle of the 1-4 glycosidic bonds which makes the chain twist to form a helix which is further stabilised by hydrogen bonding.

32
Q

What are the characteristics of amylose?

A

More compact and less soluble than glucose

33
Q

How is amylopectin formed?

A

With 1-4 and 1-6 glycosidic bonds between alpha glucose molecules formed by condensation reactions.

34
Q

What structure does amylopectin have?

A

Branched structure because of the 1-6 bonds,l. Branches every 25 glucose subunits.

35
Q

Why is glycogen better for storage than amylopectin?

A

It has more branches which makes it more compact and less soluble.

36
Q

How is glucose released for respiration or other processes?

A

By hydrolysis reactions catalysed by enzymes.

37
Q

Structure of cellulose?

A

Alternate beta glucose molecules turned upside down to form 1-4 glycosidic bonds. Forms a straight chain molecule called cellulose.

38
Q

How are microfibrils formed?

A

When cellulose makes hydrogen bonds with each other.

39
Q

What do microfibrils do?

A

Join together to form macrofibrils which combine to produce fibres. These fibres are strong and insoluble and are used to make cell walls.

40
Q

How to carry out a Benedicts test for reducing sugars?

A

Place the sample to be tested into a boiling tube. ( if it’s not liquid, grind it up or blend it in water)

Add an equal volume of Benedict’a Reagent.

Heat the mixture gently in a boiling water bath for 5 mins.

41
Q

What results will be seen and why?

A

Reducing sugars react with copper ions in Benedicts. This results in the addition of electrons to the blue Cu2+ ions, reducing them to red brick Cu+ ions. A red brick precipitate forms indicating a positive result.

42
Q

What kind of test is the Benedict’s test for reducing sugars?

A

Qualitative

43
Q

What is the most common non reducing sugar?

A

Sucrose

44
Q

What result will sucrose show on a reducing sugar Benedicts test?

A

None. The solution will stay blue after warming indicating a negative result.

45
Q

How can you get sucrose to show a positive result?

A

Boil sucrose with dilute hydrochloric acid. This will hydrolyse the sucrose into glucose and fructose with are both reducing sugars.

46
Q

Explain the iodine test for starch?

A

Mix a few drops of iodine dissolved in potassium iodide solution with a sample.
If the solution changes colour from yellow / brown to purple / black then starch is present.

47
Q

What can manufactured reagent strips be used for?

A

Can be used to test for the presence of reducing sugars most commonly glucose

48
Q

How to work a colorimeter?

A

Place a filter in the colorimeter.
Calibrate colorimeter using distilled water.
Perform Benedict’s test.
Filter out the precipitate of the resulting solutions.
The % transmission of each glucose solution measured by colorimeter.
Plot calibration curve

49
Q

Are lipids polar?

A

No

50
Q

Are lipids soluble?

A

No

51
Q

What is a triglyceride?

A

One glycerol and 3 fatty acids

52
Q

What group is glycerol a member of?

A

Alcohols

53
Q

What group are fatty acids a member of?

A

Carboxylic acids, consist of a carboxyl group and a hydrocarbon chain attached

54
Q

How does a triglyceride form?

A

The hydroxyl groups (OH) interact forming 3 water molecules and bonds between the fatty acids and glycerol molecule, these are called ester bonds.

55
Q

What is a saturated fatty acid?

A

Fatty acid chains that have no double bonds present, all the carbons have already formed all 4 of their bonds and therefore cannot bond with anymore.

56
Q

What is an unsaturated fatty acid?

A

A fatty acid with double bonds between some of the carbon atoms.

57
Q

Why are unsaturated fats kinked or bent in their structure?

A

The presence of double bonds causes the molecule to kind or bend which means that they cannot pack as closely together. As a result, they’re liquid at room temperature.

58
Q

What are phospholipids?

A

Modified triglycerides that contain phosphorus as well as carbon hydrogen and oxygen. Inorganic phosphate ions are found in cytoplasm of every cell. These have extra electrons and are therefore negatively charged.

A Level Biology (22 decks)

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