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A-level AQA Biology > Chapter 1: Carbohydrates/Lipids > Flashcards

Chapter 1: Carbohydrates/Lipids Flashcards

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1
Q

What is the theory of evolution?

A

the theory that all organisms on Earth are descended from one COMMON ancestor and that they have changed over time

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2
Q

How can biochemistry be used as evidence for the theory of evolution?

A

this is because all animals share same biochemistry, no matter how diverse they are, so it proved that animals and plants have a common ancestor.

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3
Q

What are the definitions of monomers and polymers?

A

monomer- a small, basic molecular unit

polymer- a large chain made up of small repeating units

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4
Q

What is an isomer?

A

molecules with the same formula but are arranged in different ways

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5
Q

What is the general formula of a monosaccharide?

A

(CH₂O)ₙ

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6
Q

How are biological polymers formed?

A

by condensation reactions, which forms a chemical bond between monomers
releases a water molecule

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7
Q

How are biological polymers broken down?

A

by hydrolysis reactions
breaks the chemical bond between monomers
uses a water molecule

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8
Q

What are the monomers of carbohydrates?

A

monosaccharides

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9
Q

What are the two types of glucose?

A

alpha glucose
beta glucose
(need to be able to draw their structures!!!!)

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10
Q

Glucose is a _____ sugar?

A

hexose- a monosaccharide with six carbon atoms in each molecule

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11
Q

What type of bond is formed between two monosaccharides?

A

glycosidic bonds

1-4 is because the bond is formed between the first and the fourth carbon atom of the glucose mol.

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12
Q

How are the disaccharides maltose, sucrose and lactose produced?

A

(α) glucose + glucose == maltose (found in wheat)
(α) glucose + fructose == sucrose (1-2 glycosidic bond)
(β) glucose + galactose == lactose (1-4 glycosidic bond)

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13
Q

What are the two classifications of sugars?

A

reducing and non-reducing
this is dependent on their ability to donate electrons when in a copper sulfate solution (present in Benedict’s solution)
(ketone and aldehyde ability to donate electrons)

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14
Q

How to test for reducing sugars?

A

add Benedict’s solution to sample
HEAT it in a water bath
if positive, solution goes from blue to green/yellow/orange/brick-red (red being the most concentrated) (a red PRECIPITATE will be observed)

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15
Q

How to test for non-reducing sugars?

A

heat sample with dilute HCl
neutralise sol. with sodium hydrogencarbonate
then heat with Benedict’s reagent to the sample
if positive, colour change from blue to green/yellow/orange/brick-red

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16
Q

What is the test for starch (polysaccharide)?

A

add a few drops of iodine in potassium iodide solution to the sample
if starch present, solution will turn blue/black

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17
Q

Why do you add HCl in test for non-reducing sugar?

A

to allow ACID HYDROLYSIS to occur

breaks down bonds using acid

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18
Q

What are three properties of fructose?

A

its a simple sugar (monosaccharide)

  • very soluble
  • found in fruits
  • sweeter than glucose
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19
Q

What are three properties of galactose?

A
  • not as soluble as glucose

- has a role in the production of glycolipids and glycoprotein

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20
Q

What are two examples of pentose sugars?

A

ribose and deoxyribose

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21
Q

What is the function of starch and what two components make up starch?

A

it is used as an energy storage molecule in plants

  • amylopectin
  • amylose
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22
Q

What is amylose?

A
  • it is a long ,UNbranched chain of alpha - glucose mol.
  • coiled, helical structure
  • compact (so it can store more mol. in the same place)
  • joined by several alpha 1-4 glycosidic bonds
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23
Q

What is amylopectin?

A
  • long, branched chain of alpha - glucose
  • many branches means enzymes can reach glycosidic bonds quicker- so gl. can be released quicker
  • has 1-4 (for chains) and 1-6 (for branches) alpha glycosidic bonds
  • 1-6 bonds allow branches to be formed
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24
Q

How does starch affect water potential in cells?

A

it does not affect water potential because it is insoluble, makes it good for storage

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25
Q

What is cellulose used for?

A

it is used in plants for structural support
it is very strong and prevents cells from bursting
makes up the cell wall as it has great TENSILE stength

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26
Q

What is the structure of cellulose?

A

its a long, unbranched chain of BETA glucose mol.

forms 1-4 glycosidic bonds by every other monomer rotating 180°
the chains are linked by HYDROGEN bonds which then forms strong fibres-microfibrils, forms a MATRIX

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27
Q

What things make cellulose strong?

A
  1. hydrogen bonds that join the chains
  2. every other monomer is rotated
  3. microfibril fibres are very strong
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28
Q

What is glycogen used for?

A

energy store of glucose in animals

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29
Q

What is the structure of glycogen?

A
  • it is made of alpha glucose mol.
  • forms 1-6 glycosidic bonds
  • very branched structure, so stored glucose can be released quicker because enzymes can act on glycosidic bonds easier
  • its also a compact mol. so good for storage
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30
Q

Where is glycogen stored?

A

it is stored as small granules in the liver and muscles

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31
Q

How can you compare glycogen to starch?

density, solubility & rate of breakdown

A

-glycogen is less dense
-glycogen is also more soluble
-it is broken down quicker than starch
this proves that animals have higher metabolic requirements

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32
Q

Why is starch a good storage mol.?

A
  • it is unbranched and coiled so compact, can fit more in smaller space
  • insoluble
  • large mol. so it can fit many glucose molecules into a smaller space
  • amylopectin is highly branched so enzymes can have quicker access to the bonds, release the glucose faster
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33
Q

Why is it important to have two differing forms of glucose?

A

more biochemical advantages
greater diversity for chemical reactions as each isomer has its own advantages in reactions
e.g- alpha-gl, is better with storage
beta-gl. is better for structural support

34
Q

What are two similarities between structure of starch and cellulose?

A
  1. both contain glycosidic bonds
  2. both are polysaccharides
  3. both have 1-4 links
35
Q

What functional groups are inverted in cellulose?

A

the hydroxyl and hydrogen groups on every other monomer is inverted

36
Q

What sugars are reducing sugars?

A

ALL monosaccharides and some disaccharides (e.g- maltose, lactose)

37
Q

What is an example of a non-reducing sugar?

A

sucrose

38
Q

What are two structural differences between glycogen and starch?

A
  • starch is made up of amylose and amylopectin, but glycogen is just alpha-glucose
  • glycogen is more highly branched
  • *(optional)-glycogen has more terminal ends than starch
39
Q

Describe how you could separate a mixture of monosaccharides in solution?

A

paper chromatography
a spot of sol. on chrom. paper and paper is suspended in a solvent
larger mol. move slower up the paper, travel less distance
sep. out into different spots

40
Q

What is a serial dilution?

A

when you create a set of solutions that decrease in concentration by the same factor each time

41
Q

What are the roles of lipids (5)?

A
  • plasma membranes
  • energy storage
  • insulation
  • protects delicate organs
  • waterproofing- waxy cuticles -conserve water
42
Q

What are triglycerides made of?

A

one glycerol molecule

3 fatty acids

43
Q

What is the formula for glycerol?

A

C₃H₈O₃

44
Q

What is the structure of a fatty acid?

A

long chain hydrocarbons

  • contain a carboxylic group (COOH- double C=O bond)
  • a varied hydrocarbon tail
45
Q

What are the two types of fatty acids?

A

saturated- all single C-C bonds in the fatty acid chain
unsaturated- one or more C=C bonds in the fatty acid chain
mono-unsaturated (one C=C bond)
poly-unsaturated (two or more C=C bond)

46
Q

What state are unsaturated fatty acids in?

A

liquid because of the double bond, they have a kink in their structure which means that they can’t be packed closely together (NOT A STRAIGHT chain)
saturated fatty acids have straight chains so all the mol. can pack closely together

47
Q

How many types of fatty acids are there?

A

around 70 and they affect the triglyceride’s properties

48
Q

How are triglycerides formed?

A

by condensation reactions, the fatty acids join to the glycerol and form an ESTER bond
the reaction happens between the carboxyl (fatty acids) and hydroxide (glycerol) groups

49
Q

What is the structure of a phospholipid?

A
  • 1 glycerol
  • 2 fatty acids
  • 1 phosphate group
50
Q

What is a property of the fatty acid chains and the phosphate group?

A

fatty acid= non-polar: hydrophobic

phosphate group= polar: hydrophilic

51
Q

What is the function of a phospholipid?

A

found in the cell membrane

makes up the phospholipid bi-layer membrane

52
Q

What type of molecule is a phospholipid?

A

amphipathic (have a hydrophobic and hydrophilic part)

53
Q

What are the properties of a triglyceride that help it carry out its function?

A
  • function: energy storage molecule
  • large fatty acid chain- many bonds that release energy when broken down/ high energy
  • insoluble in water so it does no affect water potential
54
Q

What are the properties of phospholipids that aid their function?

A

the centre of the layer is hydrophobic so water soluble substances can’t easily pass through it- the membrane acts as a barrier to those substances

55
Q

What is the test for lipids?

A

emulsion test

  • shake the sample with some ethanol
  • then add some water to solution
  • any lipid will show up as a milky emulsion
  • the more lipid there is the more noticable the milky colour will be
56
Q

What does hydrophobic mean?

A

repels water or does not mix with water

57
Q

What substance (not an enzyme) is used to break down lipids?

A

water

water is needed in the reaction of hydrolysis

58
Q

What does emulsion mean?

A

a milky suspension of tiny droplets

59
Q

How should a sample be prepared for the emulsion test and why should it be prepared like this?

A

grind and crush sample into a powder to allow the lipids to be exposed to ethanol during shaking

60
Q

Why do phospholipids assemble in a bilayer?

A

because the hydrocarbon tails are hydrophobic (non-polar) so they arrange toe-to-toe to minimise contact with water

61
Q

How is glucose stored within the cell?

A

α-glucose mol. undergo a condensation reaction
1-4 glycosidic bonds to form chains
1-6 glycosidic bonds to form branches
condensation rxn. releases water molecules
and glycogen is formed
(When a question asks ‘how’ its asking for the PROCESS)

62
Q

What is the formula for maltose?

A

C₁₂H₂₂O₁₁

63
Q

What bond does a lactose molecule have ?

A

1-4 glycosidic bond

64
Q

What bond does a sucrose molecule have?

A

1-2 glycosidic bond

65
Q

What is the ideal temperature for an enzyme to work?

A

37℃

66
Q

Why is glycogen a good storage molecule? (4)

A
  • highly branched-so enzymes can reach glycosidic bonds faster and release glucose faster
  • insoluble so it doesn’t affect water potential
  • easily synthesised and broken down so it can respond rapidly to hormones (insulin and glucagon)
  • compact structure- can fit more into a small storage granule
67
Q

How are branched molecules advantageous for energy storage molecules?

A
  • allows enzymes to reach glycosidic bonds faster and release glucose faster when needed
  • allows for even more folding which gives it even more compactness
68
Q

What is the feature that allows cellulose to form long chains?

A

in every other monomer, it is inverted

this is because in beta glucose, the -OH and -H are inverted

69
Q

What is the product of incomplete digestion of cellulose?

A

methane

70
Q

What is one similarity and a difference between glucose and fructose?

A

similarity: both are hexose sugars
difference: glucose has a six-atom ring
pentose has a 5-atom ring

71
Q

What two ways can glycosidic bonds be broken?

A

enzyme hydrolysis

acid hydrolysis- boil the solution in a test tube with the acid

72
Q

Why are storage molecules such as starch advantageous compared to glucose?

A
  • insoluble so does not affect water potential
  • highly folded so its a compact structure
  • can easily be broken down
73
Q

What is an unsaturated fatty acid?

A
  • a long hydrocarbon chain
  • one or more C=C double bonds in the chain
  • it has a terminal COOH- group
74
Q

What groups of lipids are present in nuts?

A

phospholipids and triglycerides

75
Q

What does the R mean in COOHR-?

A

R means the hydrocarbon chain

76
Q

Why is a white emulsion formed in the emulsion test?

A

because a triglycerides have non-polar fatty chains
therefore, it is hydrophobic
forms micelles in water

77
Q

How is a phospholipid bilayer formed?

A

phospholipids have a polar (hydrophilic) head -phosphate group
phosphate groups can form hydrogen bonds with the water
fatty acids hidden from the water
to form a bilayer

78
Q

Why can some substances not pass the phospholipid membrane?

A

hydrophilic
polar
substance is too large

79
Q

What effects do double bonds have on intermolecular forces?

A

they disrupt intermolecular forces

80
Q

How can you measure the quantity of glucose after a benedict’s test?

A

use a colorimeter

or filter out the precipitate and weigh it

81
Q

Give two ways in which the structure of starch is different from cellulose

A

starch is a polymer of alpha glucose (not beta)
starch is helical but cellulose is not
starch contains 1-6 glycosidic bonds (cellulose 1-4)

82
Q

Explain how cellulose is adapted for its function in plant cells?

A

cellulose chains are LONG and STRAIGHT, which are linked by MANY hydrogen bonds, which forms fibrils, which have high tensile strength so cellulose can support the cell wall

A-level AQA Biology (6 decks)

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