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a level biology aqa > Carbohydrates > Flashcards

Carbohydrates Flashcards

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AP® Biology flashcards
1
Q

Contain

A

Only carbon, hydrogen, oxygen

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2
Q

General formula

A

Cx (H2O) y

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3
Q

3 groups

A

Monosaccharides - single sugars eg galactose, fructose, glucose

Disaccharides - two sugars eg maltose, sucrose, lactose

Polysaccharides - many sugars eg starch, cellulose, glycogen

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4
Q

Condensation reaction

A

Two monosaccharides join to from a disaccharides, water is also produced and a glycosidic bond forms

Many monosaccharides join in many condensation reactions to form a polysaccharide

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5
Q

Most common monosaccharide

A

a Glucose - C6H12O6

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6
Q

Isomer

A

Molecule with the same molecular formulae but a different arrangement of atoms

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7
Q

Optical isomerism

A

When the bonds in the molecules can rotate in space to give a different form of the molecule (glucose to B glucose)

B glucose - the hydroxyl group rotates 180 around carbon 1

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8
Q

Fructose and galactose formulae + structure

A

C6H12O6 - makes it a structural isomer of A and B glucose (different arrangement of atoms, same molecular formulae)

Hexose sugars - 6 carbon atoms

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9
Q

Monosaccharides use

A

Make ATP - respiration
Formation of other carbohydrates
Formation of other molecules (DNA & RNA)

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10
Q

Properties of monosaccharides

A

Small, can move across membranes with channel or transport proteins

Soluble in water, easily transportable and diffuse around living organisms to be used as a respiratory substrate

Lower water potential

Reducing sugars

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11
Q

Test for reducing sugars

A

Add Benedicts reagent, heat

Present - red/brown/orange/green
Absent - blue

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12
Q

Reducing sugars , quantitative

A

Use standard solution, a colorimeter and calibration curve

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13
Q

Reducing properties come from

A

The aldehyde or ketone group within the molecule

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14
Q

Disaccharides

A

Maltose, sucrose, lactose

Bond formed when 2 monosaccharides join by a condensation reaction with a glycosidic bond

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15
Q

Maltose + formulae

A

Disaccharides formed by condensation of A glucose & A glucose

C12H22O11 as there are 2x glucose and - water since it is a condensation reaction

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16
Q

Sucrose + formulae

A

disaccharides formed by condensation of A glucose & fructose

C12H22O11 as there are 2x glucose and - water since it is a condensation reaction

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17
Q

Lactose + formulae

A

Disaccharides formed by condensation of A glucose & galactose

C12H22O11 as there are 2x glucose and - water since it is a condensation reaction

18
Q

Use of disaccharides

A

Make polysaccharides

Hydrolysed to make monosaccharides for respiration

19
Q

Properties of disaccharides

A
  • soluble in water
  • need to be hydrolysed before the monosaccharides produced can be transported across membranes
  • lower water potential
  • maltose + lactose are both reducing sugars
  • sucrose is a non-reducing sugar
20
Q

Lactose and maltose and the reducing sugar test

A
  • if you perform benedicts test on lactose or maltose you get a precipitate
  • if you add lactase to lactose or maltase to maltose then perform benedicts test you get double the precipitate
21
Q

Non-reducing sugars test sucrose

A

Sucrose will give a blue colour

22
Q

Test for non-reducing sugars

A
  • add acid, boil
  • neutralise
  • add benedicts reagent
  • heat

Present - red/brown/ orange/ green
Absent - blue

23
Q

Non-reducing sugars, semi-quantitative

A

Using standard solutions, a colorimeter and a calibration curve

24
Q

Maltose hydrolysed

A

By maltase which is produced by epithelial cells of the ileum

25
Q

Sucrose hydrolysed

A

By sucrase which is produced by epithelial cells of the ileum

26
Q

Lactose hydrolysed

A

By lactase which is produced by epithelial cells of the ileum

27
Q

Polysaccharides

A

Chains of many monosaccharides joined together by condensation reactions with many glycosidic bonds

Three important : starch, cellulose, glycogen

28
Q

Properties of polysaccharides dependent on

A
  • number of monosaccharide molecules in the chain
  • type of monosaccharide in the chain
  • how they are joined together (branched or un-branched
  • overall shape of the molecule
29
Q

Starch

A

Polymer of A glucose molecules

  • all atoms lie upwards
  • found only in plants, storage polysaccharides (acting as a store of glucose)
  • insoluble and doesn’t affect water potential of the cell or solution
  • 1-4 and 1-6 glycosidic bonds
30
Q

Describe structure of starch

A
  • large insoluble chains of A-glucose
  • helix
  • branched with 1-4 and 1-6 glycosidic bonds
  • consists of 2 polysaccharides amylose and amylopectin
31
Q

Structure related to function starch

A

Large and insoluble - doesn’t affect water potential, cannot pass across the cell membrane and move out of the cell

Helix - will compress/compact into starch grains which take up less space

Branched - more ends so larger surface area for faster hydrolysis by enzymes to release glucose for respiration

32
Q

test for starch

A

iodine or potassium iodide solution

present - blue/black
absent - orange/yellow/brown

33
Q

food in the stomach

A

when food is swallowed the enzyme is denatured by the acid in the stomach or hydrolysed by the endopeptidase, pepsin in the stomach

34
Q

stomach acid pH

A

1-2

35
Q

glycogen features

A
  • all atoms lie in 1 direction
  • polymer formed by the condensation of A glucose molecules
  • found only in animals and fungi and is a storage polysaccharide (acting as a store of glucose)
  • glycogen is insoluble and doesn’t affect water potential of the cell or solution
  • 1-4, 1-6 glycosidic bonds
36
Q

structure of glycogen

A

large and insoluble - doesn’t affect water potential, cannot move past cell membrane and move out of the cell

helix - will compress/compact which takes up less space

branched - more ends, larger surface area, for faster hydrolysis by enzymes to release glucose for respiration

37
Q

why is glycogen more branched than starch

A

only found in animals so the more ends increases surface area for faster hydrolysis of glucose by enzymes for respiration.

38
Q

cellulose features

A
  • polymer formed by condensation of B glucose molecules
  • found only in plants and is a structural polysaccharide found in plant cell walls
  • cellulose is insoluble and doesn’t affect water potential of the cell or solution
  • atoms alternate up and down
  • only 1-4 glycosidic bonds
39
Q

structure of cellulose

A

long unbranched parallel chains of B-glucose cross-linked by hydrogen bonds to form microfibrils

40
Q

how is cellulose adapted for its role as a structural polysaccharide

A

long unbranched chains of B-glucose lie parallel (as there are only 1-4 glycosidic bonds)

allows hydrogen bonds to form between them so they are cross-linked to microfibrils

individual hydrogen bonds are weak however many of them together makes the strong structure that gives them strength and rigidity to the molecule important in cell walls

a level biology aqa (29 decks)

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