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biology year 12 > carbs & lipids > Flashcards

carbs & lipids Flashcards

1
Q

what is a monomer ?

A

a monomer is a smaller / repeating) unit / molecule from which larger molecules / polymers are made

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2
Q

a starch molecule has a spiral shape. Explain why this shape is important to its function in cells.

A

compact/occupies small space/tightly packed

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3
Q

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

A

long, straight, unbranched chains of Beta glucose
(joined by) many WEAK hydrogen bonds
form microfibrils / macrofibrils
provide rigidity/strength/support

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4
Q

give one feature of starch and explain how this feature enables it to act as a storage
substance

A

helical / spiral So compact / tightly packed / can fit (lots) into a small space
insoluble So no osmotic effect / does not leave cell / does not affect water potential
large molecule / long chain (So) does not leave cell / contains large number of glucose units
branched chains (So) rapid hydrolysis to remove glucose for respiration

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5
Q

hydrogen bonds are important in cellulose molecules, explain why

A

holds chains/cellulose molecules together/forms cross links between chains/cellulose molecules/forms microfibrils
providing strength/rigidity (to cellulose/cell wall)
weak Hydrogen bonds provide strength in large numbers

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6
Q

describe how lactose is formed and where in the cell it would be attached to a polypeptide to form a glycoprotein

A

glucose and galactose
joined by condensation
joined by glycosidic bond
added to polypeptide in Golgi

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7
Q

describe how the student would show that reducing sugars were present in a solution

A
  1. add Benedict’s;
  2. heat to 95°C;
  3. red/range/yellow/green precipitate (shows reducing sugar present);
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8
Q

describe how you would test a sample of food for the presence of starch.

A
  1. (mix / shake sample) with ethanol, then water and shake
  2. cloudy White / milky (emulsion)
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9
Q

omega-3 fatty acids are unsaturated
what is an unsaturated fatty acid?

A

double bond(s)
(bonds) between carbon atoms within the hydrocarbon chain

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10
Q

describe how an ester bond is formed in a phospholipid molecule

A
  1. condensation (reaction) OR loss of water
  2. between of glycerol and fatty acid
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11
Q

some seeds contain lipids
describe how you could use the emulsion test to show that a seed contains lipids (3)

A
  1. crush/grind
  2. with ethanol/ alcohol, to dissolve the lipid
  3. then add water then shake
  4. forms a white emulsion / goes white
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12
Q

what are the differences between a triglyceride and a phospholipid ?

A
  1. fatty acid removed
  2. replaced with a phosphate group
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13
Q

compare and contrast the structure and properties of triglycerides and phospholipids

A

both contain ester bonds
both contain glycerol
fatty acids on both may be saturated or unsaturated
both are insoluble in water
both contain C, H and O but phospholipids are also contain P
triglyceride has three fatty acids and phospholipids have two fatty acids plus phosphate group
triglycerides are hydrophobic/non-polar and phospholipids have hydrophilic and hydrophobic region
phospholipids form monolayer/micelle/bilayer but triglycerides don’t.

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14
Q

describe the biochemical tests you would use to confirm the presence of lipid, non-reducing sugar and amylase in a sample

A

lipid
1. add ethanol/alcohol then add water and shake/mix OR Add ethanol/alcohol and shake/mix then pour into/add water
2. white/milky emulsion OR emulsion test turns white/milky

non-reducing sugar
3. do Benedict’s test and stays blue/negative
4. boil with acid then neutralise with alkali
5. heat with Benedict’s and becomes red/orange (precipitate)

amylase
6. add biuret (reagent) and becomes purple/violet/mauve/lilac
7. add starch, (leave for a time), test for reducing sugar/absence of starch

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15
Q

A student carried out the Benedict’s test

suggest a method, other than using a colorimeter, that this student could use to measure the quantity of reducing sugar in a solution

A
  1. filter and dry (the precipitate)
  2. find mass/weight
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16
Q

What is a polymer? (1)

A

Polymers are large molecules made from joining 3 or more similar monomers together

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17
Q

What is a condensation reaction? (1)

A

removal of one water molecule which forms a bond

SPEC - joins two molecules together with the formation of a chemical bond and involves the elimination of a molecule of water.

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18
Q

What is a hydrolysis reaction? (1)

A

addition of one water molecule to break a bond

SPEC - breaks a chemical bond between two molecules and involves the use of a water molecule.

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19
Q

Give 2 examples of monomers (2)

A

Alpha/Beta glucose
Nucleotides
Amino acids

20
Q

Give 2 examples of polymers (2)

A

Nucleic Acids
Cellulose
Starch
Protein

21
Q

Name the bond formed between two monosaccharides within a condensation reaction (1)

A

Glycosidic bond

22
Q

Draw the structure of alpha glucose (1)
Draw the structure of beta glucose (1)

A

https://www.aqa.org.uk/subjects/science/as-and-a-level/biology-7401-7402/subject-content/biological-molecules/carbohydrates

23
Q

Which monosaccharides form maltose and which enzyme is used to hydrolyse maltose? (2)

A

Alpha Glucose and Alpha
Glucose
Enzyme - Maltase

24
Q

Which monosaccharides form lactose and which enzyme is used to hydrolyse lactose? (2)

A

Alpha Glucose and Galactose
Enzyme - Lactase

25
Q

Which monosaccharides form sucrose and which enzyme is used to hydrolyse sucrose? (2)

A

Alpha Glucose and Fructose
Enzyme - Sucrase

26
Q

Give three features of starch and explain how these enable it to act as a storage substance. (3)

A

Helical so compact
Insoluble so doesn’t affect water potential
Large molecule so does not leave cell
Branched chains (1:4 and 1:6 glycosidic bonds) so rapid hydrolysis to remove glucose for respiration

27
Q

Describe how a student would show that a non-reducing sugar is present in the solution (5)

A

Complete Benedict’s test and observe negative
result
Add HCI to sugar solution AND heat to 95C
Neutralise with alkali
Add equal volume of Benedict’s solution
Heat again to 95C
Red/Orange/Green PRECIPITATE formed

28
Q

What is a triglyceride made from and what bond is formed between them? (1)

A

3 fatty acids bonded via an ester bond to one glycerol molecule

29
Q

What is a saturated fatty acid? (1)

A

Do not have double bonds between carbon atoms within the hydrocarbon chain

30
Q

Explain how the digestion of starch in the small intestine leads to an increase in the
concentration of glucose in the blood. Details of co-transport are not required. (3)

A

Starch is hydrolysed by amylase
Produces glucose
Small enough to cross the gut wall into the blood

31
Q

Describe the structure of glycogen (2)

A
  1. Polymer of alpha glucose
  2. joined by glycosidic bonds
32
Q

Suggest how glycogen acts as a store of energy (2)

A
  1. Hydrolysed
  2. Glucose used in respiration
33
Q

What are monosaccharides

A

are the monomers from which larger carbohydrates are made. Glucose, galactose and fructose are common monosaccharides.

34
Q

What does the condensation of two monosaccharides form

A

Disaccharides

35
Q

What are the 3 disaccharides

A

Maltose
Sucrose
Lactose

36
Q

How is maltose the disaccharide formed

A

Formed by condensation of two glucose molecules

37
Q

How is sucrose the disaccharide form

A

Formed by condensation of a glucose molecule and a fructose molecule

38
Q

How is the lactose disaccharide formed

A

Formed by a condensation of a glucose molecule and a glucose molecule

39
Q

What are the two isomers of glucose

A

a-glucose
β-glucose

40
Q

What are polysaccharide’s

A

Polysaccharides are formed by the condensation of many glucose units

41
Q

What does the condensation of a-glucose
lead to

A

Glycogen and starch

42
Q

What does the condensation of β-glucose lead to

A

Cellulose

43
Q

What are 2 groups of lipids

A

Triglycerides
Phospholipids

44
Q

How are triglycerides formed

A

By the condensation of one molecule of glycerol & 3 molecules of fatty acid

45
Q

What forms an ester bond

A

A condensation reaction between glycerol and a fatty acid (RCOOH) forms an ester bond

46
Q

The R-group of a fatty acid can be what

A

Saturated or unsaturated

47
Q

What happens in a phospholipid

A

One of the fatty acids of a triglyceride is substituted by a phosphate-containing group

biology year 12 (20 decks)

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