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Biology OCR > Carbohydrates > Flashcards

Carbohydrates Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What is a organic molecule?

A

A molecule containing carbon and hydrogen

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2
Q

Describe hydrolysis

A

the breaking down of polymers into monomers by the addition of water and the breaking of a covalent bond.

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3
Q

Describe condensation

A

the joining of monomers into polymers by the removal of a water molecule to form a covalent bond

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4
Q

What is the general formula for a monosaccaride?

A

(CH2O)n

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5
Q

Are monosaccarides polar, if so explain why?

A

Yes, because they contain OH groups so they are polar and can dissolve in water.

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6
Q

What is an isomer?

A

Isomers are molecules with the same chemical formula but different structure e.g. glucose and fructose.

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7
Q

Give an example of a triose (C3H6O6)

A

Glyceraldehyde triose phosphate - used in photosynthesis and respiration

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8
Q

Give an example of a pentose (C5H10O5)

A

ribulose 1,5 biphosphate - used in photosynthesis. Ribose. Deoxyribose - DNA

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9
Q

Give an example of a hexose (C6H12O6)

A

glucose - transport sugar. Fructose - found in plants. Galactose - milk sugar.

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10
Q

What are the two isomers of glucose and describe the difference between them.

A

Alpha and Beta glucose. The location of of the OH group bonded to carbon-1. On alpha-glucose the OH group sits below the ring, while beta has the OH group above the ring. (ngl easier just to look at a picture)

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11
Q

What bonds form between monomers of carbohydrates?

A

Glycosidic

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12
Q

Describe the disaccaride maltose.

A

Maltose is 2 alpha glucoses forming a 1,4 glycosidic bond. Reducing sugar

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13
Q

Draw the complete structure of a alpha glucose - and explain how the carbons are numbered.

A

ngl I would add a photo here but since we need brainscape pro it aint happening but just make sure u can do dat.

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14
Q

Describe sucrose and its function.

A

alpha glucose and fructose. Non-reducing sugar.

Found in plant phloem.

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15
Q

Describe lactose and its function

A

beta glucose and galactose. Reducing sugar. Milk sugar. 1,4 glycosidic bonds where monomers are flipped with respect to each other.

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16
Q

Describe the test for reducing sugars.

A

Benedicts test.

  1. Place sample in clean test tube.
  2. Add equal volume of Benedicts solution (CuSO4) (Blue) with pippette.
  3. Heat solution at 100’C in water bath for 3 minutes.
17
Q

Describe positive result of Benedicts test for reducing sugars.

A

Depending on the concentration of reducing sugars the results are Blue(none), Green(trace), yellow, orange, brick-red(high) precipitate.

18
Q

Explain the chemistry of the results.

A

Reducing sugars oxidise (donate electrons) so when they are put into a solution with Cu2+ they form C+ ions which bond to form Cu2O - a brick-red precipitate.

19
Q

Test for non-reducing sugars e.g. sucrose

A
  1. Add 1 mol. HCl to sample in test tube and swirl.
  2. Heat at 100’C for 5 minutes in water bath
  3. Neutralise solution by adding NaHCO3
  4. Carry out Benedicts test
20
Q

Describe reagent test for reducing sugars and give a use.

A
  1. Dip testing strip into sample
  2. Compare colour change to calibration card
    Used to test urine samples for diabetes
21
Q

Describe test using a colorimeter

A

place sample in colorimeter and record the absorbance of red light. More light absorbed the lower the concentration of reducing sugars. disclaimer: i dont rly get this colorimeter stuff so u might want to check yrself - soz.

22
Q

Describe test for starch.

A
  1. Add sample to clean test tube
  2. Add potassium iodide solution and swirl
  3. If starch is present solution will change from yellow brown to blue black
23
Q

Explain why starch turns blue black when tested with iodine

A

The iodine molecules enter the helix of amylose - blocking light travelling through

24
Q

Describe the structure of amylose and give properties

A
  • alpha glucose
  • 1,4 glycosidic bonds
  • coils to form helix by intramolecular hydrogen bonds
  • makes up 20% of starch
  • Mr around 50,000 and composed of 300 monomers
25
Q

Describe the structure of amylopectin and give properties

A
  • alpha glucose
  • 1,4 and every around 24 monomers a 1,6 glycosidc bond
  • branches highly
  • Mr and no. of monomers is 500,000 and 3000
26
Q

Describe the structure and properties of glycogen

A
  • alpha glucose
  • 1,4 and frequent 1,6 glycosidic bond (more than amylopectin)
  • animal storage carbohydrate, particularly cells with high metabolic activity e.g. muscle cells
  • very highly branched
27
Q

Explain why starch (particularly amylopectin) and glycogen make good energy storage.

A
  • Very compact; high energy density, due to branches
  • Insoluble in water; doesn’t effect water potential of cells or cause osmotic swell
  • Glycogen and amylopectin are both highly branched which means enzymes can hydrolyse to release glucose monomers for respiration quickly
28
Q

Why do animals use glycogen as a energy storage carbohydrate?

A

Glycogen is more branched so it can more quickly release energy which is important as animals are more metabolically active as they perform high energy functions such as movement.

29
Q

What is the structure of cellulose?

A
  • Beta glucose
  • 1,4 glycosidic bonds
  • It is a straight and linear chain that does not coil due to alternating monomers are flipped respective of each other
  • chains of cellulose lie parallel to each other and form hydrogen bonds.
30
Q

Give properties of cellulose and explain why.

A
  • High tensile due to strong covalent glycosidic bonds and lots of hydrogen bonds.
  • around 80 chains join together to form microfibrils which run in lots of directions for support.
  • Plants use it as support as they don’t have skeletons
  • They are fully permeable however can be mixed with substances to make them impermeable - e.g. cutin, suberin and lignin
  • cellulose fibres stop plant cells bursting when turgid, this turgidity give cell support and strength
31
Q

Give two other examples of polysaccharides.

A
  • Chitin: cell wall of fungi and exokeletion of arthropods.

- Mucopoly

Biology OCR (8 decks)

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