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A-Level Biology > Carbohydrates + Lipids > Flashcards

Carbohydrates + Lipids Flashcards

1
Q

Chemical formula for alpha glucose

A

C6H12O6

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2
Q

Maltose structure

A

Glucose + Glucose

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3
Q

Sucrose structure

A

Glucose + Fructose

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4
Q

Lactose

A

Glucose + Galactose

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5
Q

Enzyme suffix

A

-ase

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6
Q

What 2 subcategories are carbohydrates divided into?

A

Sugars (mono +di)
Polysaccharides (storage + structural)

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7
Q

Name 2 storage polysaccharides

A

Starch (plants)
- AmylOse
- Amylopectin
Glycogen (humans)

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8
Q

Name a structural polysaccharide

A

Cellulose (beta-glucose)

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9
Q

Describe amylOse structure (STARCH)

A
  • Long straight chains of alpha glucose
  • COil into a helix (amylOse)
  • Compact so good for storage
  • Insoluble so doesn’t affect water potential
  • Large so cannot diffuse out of cell
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10
Q

Describe amylopectin structure (STARCH)

A

BRANCHED chain of alpha glucose
- Large surface area for rapid hydrolysis by enzymes (to release glucose for respiration)
- Insoluble so doesn’t affect water potential
- Large so cannot diffuse out of cells

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11
Q

Describe glycogen structure

A

Similar to starch, however:
- Shorter chains
- More highly branched
- Larger surface area

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12
Q

Explain advantage of glycogen being more highly branched

A

Glycogen hydrolysed more rapidly into glucose to be used in respiration (as animals require glucose faster than plants can hydrolyse starch)

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13
Q

Describe cellulose structure

A
  • Long straight unbranched chains of beta-glucose
  • Every other beta-glucose molecule inverts 180 degrees to form 1-4 glycosidic bond.
  • Several chains joined together in layers by MANY WEAK h-bonds to form micro/macrofibrils
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14
Q

What is cellulose found in?

A

Plant cell wall

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15
Q

Starch use and location

A

Storage and plant

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16
Q

Glycogen use and location

A

Storage and animal

17
Q

Cellulose use and location

A

Structure and plant

18
Q

The structure of cellulose is related to its role in plant cell walls. Explain how (3)

A
  • Long straight chains of beta-glucose
  • Joined by many weak hydrogen bonds
  • To form micro/macrofibrils
  • To provide integrity/rigidity
19
Q

Hydrogen bonds are important in cellulose molecules. Explain why (3)

A
  • Join cellulose chains together to form micro/macrofibrils
  • Providing rigidity/integrity to cell wall
  • Weak bonds provide strength in larger numbers`
20
Q

Describe benedicts test for reducing suagr

A
  • Add equal volume of benedicts reagent to solution
  • Heat to 95 celcius
  • Red precipitate indicates sugar present
21
Q

Describe how a student would show that a non-reducing sugar was present in a solution (6)

A
  • Complete benedicts test and observe negative result (blue precipitate)
  • Add acid (HCL) to solution AND heat to 95 celcius
  • Neutralise with alkali
  • Add equal volume of benedicts reagent
  • Heat again to 95 celcius
  • Observe red precipitate formed as reducing sugar is now present
22
Q

What is an arbitary unit?

A

A scale of measurement to show the ratio of amount of substance to a predetermined reference measurement

23
Q

Describe how you would produce a calibration curve for a reducing sugar of unknown concentration and use it to obtain results (5)

A
  • Make up several known concentrations of glucose
  • Perform benedicts test on each sample
  • Use colorimeter to measure colour intensity of each solution AND plot calibration curve
  • Plot known conc. on X-axis and aborbance on Y-axis
  • Find concentration of unknown sample using calibration curve
24
Q

Describe how you would test a food sample for starch

A
  • Add potassium iodide solution to food sample
  • Turns purple in presence of starch
25
Q

Name the 2 types of lipids

A
  • Triglycerides
  • Phospholipids
26
Q

Triglyceride structure

A

ONE glycerol molecule bonded to 3 fatty acid tails via ester bonds.

27
Q

Are triglycerides polymers?

A

No (not made up of repeating units)

28
Q

Define unsaturated fatty acid

A

Have double bonds between adjacent carbon atoms within the hydrocarbon chain

29
Q

Describe the emulsion test for a lipid (liquid)

A
  • Add ethanol
  • Mix
  • Add water and shake again
  • Cloudy white emulsion forms in lipid presence
30
Q

Describe how you could use the emulsion test to show that a seed contains lipids (3)

A
  • Crush
  • Mix with ethanol and shake
  • Add water and shake
  • Forms cloudy white emulsion in lipid presence
31
Q

What do phospholipids form in water?

32
Q

Describe similarities and differences between triglycerides and phospholipids (5)

A

DIFFERENCE:
- PPL has 2 fatty acid tails, 3rd replaced with hydrophillic phosphate head whereas TRI has 3 fatty acid tails and no phosphate head
- PPL form bilayer in water whereas TRI do not

SIMILARITIES:
- Both contain ester bonds between fatty acid tails and glycerol
- Both contain glycerol and fatty acid tails
- Both fatty acid tails can be saturated or unsaturated

A-Level Biology (12 decks)

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