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Biology 3.1 - Biological molecules > Carbohydrates > Flashcards

Carbohydrates Flashcards

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1
Q

What is a monosaccharide?

A

monomers from which larger carbohydrates are made

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2
Q

Give three examples of monosaccharides.

A

glucose, fructose and galactose

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3
Q

What is a disaccharide?

A

Two monosaccharides joined by a glycosidic bond through a condensation reaction

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4
Q

Give three examples of disaccharides

A

maltose, lactose and sucrose

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5
Q

What is maltose formed from?

A

two glucose monosaccharides

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6
Q

What is lactose formed from?

A

glucose and galactose

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7
Q

What is sucrose formed from?

A

glucose and fructose

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8
Q

What is a polysaccharide?

A

a large molecule formed from the condensation reaction of many glucose units joined by glycosidic bonds

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9
Q

What are the two isomers of glucose?

A

a glucose and b glucose

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10
Q

How does a and b glucose differ?

A

a glucose has two hydroxide groups facing downward whereas b glucose has one hydroxide facing upward and one facing downward

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11
Q

What are the three polysaccharides?

A

Starch, glycogen and cellulose

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12
Q

What is the structure of starch?

A
  • starch is formed of amylose and amylopectin
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13
Q

What is the structure of amylose?

A
  • amylose is an unbranched chain of glucose molecules joined by 1.4 glycosidic bonds.
  • This means it is unbranched and coiled, compact
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14
Q

What is the structure of amylopectin?

A
  • branched and made up of 1,4 and 1,6 glycosidic bonds
  • contains many side chains which can be acted upon by enzymes
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15
Q

What are the properties of starch?

A
  • it is insoluble so it does not affect the osmotic potential of cells
  • it is large and insoluble so it doesn’t diffuse out of cells
  • compact, can be stored
  • it has branched ends which enzymes can act on so it can be easily broken down
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16
Q

What is the structure of glycogen?

A
  • a main storage molecule for animals
  • joined of many a - glucose monosaccharides joined by 1,4 and 1,6 glycosidic bonds
  • a large number of branches
17
Q

What are the properties of glycogen?

A
  • insoluble, doesn’t affect osmotic potentials
  • compact
  • highly branched so can be easily acted upon by enzymes and used as an energy source In animals
18
Q

What is the structure of cellulose?

A
  • it is made of b - b-glucose monomers
  • straight unbranched chains
  • Chains of cellulose have each b glucose monomer inverted by 180 degrees
  • the chains run parallel to one another which forms hydrogen cross-links between adjacent chains
19
Q

What are the properties of cellulose?

A
  • a main component of cell walls
  • chains of cellulose form microfibrils which then group to form fibres
  • This increases the strength of cell walls, reducing the chance of the cell wall bursting from osmotic pressure
  • cellulose also exerts inward pressure, stopping the influx of water and helping cells remain turgid
20
Q

How does cellulose help plants?

A

By exerting inward pressure, cells remain turgid and this helps to maximise the surface area of plants for photosynthesis

21
Q

What is the test for reducing sugars?

A
  • All monosaccharides are reducing sugars and some disaccharides are ( maltose)
  1. Add benedicts reagent to the sample
  2. heat
  3. The colour change if negative will remain blue
  4. If there is a reducing sugar the colour change is green, yellow, orange to brick red
22
Q

What is the test for non-reducing sugars?

A
  • Add your sample and an equal volume of benedicts reagent and warm in a water bath
  • if the colour change isn’t from blue to brick red, there is no reducing sugar present
  • add 2cm of dilute HCL and the same volume of your sample and place the test tube in another water bath
  • The HCL will hydrolyse the disaccharides and polysaccharides into monosaccharides
  • add sodium hydro carbonate to neutralise the test tube
  • repeat the benedicts test and there should be a colour change from blue to brick red
23
Q

What is the test for starch?

A
  • Add 2cm of your sample to a test tube
  • add 2 drops of iodine to the test tube
  • a positive test is orange to blue - black

Biology 3.1 - Biological molecules (10 decks)

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