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AQA Biology A level > Carbohydrates and Lipids > Flashcards

Carbohydrates and Lipids Flashcards

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1
Q

What is a condensation reaction?

A

The formation of polymers through polymerisation which produce water

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2
Q

What is a hydrolysis reaction?

A

Polymers that are broken down with the addition of water

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3
Q

What is metabolism?

A

All chemical processes that take place in living organisms

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4
Q

What is a monomer?

A

Smaller units from which larger molecules are made

-e.g- Monosaccharide, Amino Acids, Nucleotides

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5
Q

What is a polymer?

A

Molecules made from a large number for monomers joined together

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6
Q

What is the basic monomer of carbohydrates?

A

Monosaccharide

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7
Q

What is the product formed from combining 2/multiple monosaccharides?

A

Disaccharide

Polysaccharide

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8
Q

What are common monosaccharides?

A

Glucose
Galactose
Fructose

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9
Q

What does a condensation reaction between two monosaccharides form?

A

Glycosidic bond

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10
Q

How are these disaccharide formed:
Maltose
Sucrose
Lactose

A

Maltose - Condensation reaction between two glucose molecules

Sucrose - Condensation reaction between a fructose and glucose molecule

Lactose - Condensation reaction between a galactose and glucose molecule

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11
Q

What is the test for reducing sugars? + What is reduction?

A

Reduction - chemical reaction which involves the gain of electrons/hydrogen

A reducing sugar can donate electrons to another chemical

When a reducing sugar is heated with Benedict’s Solution, the solution will turn a brick red precipitate of copper oxide

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12
Q

How is the reducing sugars test carried out?

A
  • 2cm^3 of food solution in a test tube (in liquid form)
  • Add an equal volume of Benedict’s Solution
  • Heat solution for 5 minutes
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13
Q

What is the test for non-reducing sugars?

+ give examples of non reducing sugars

A

Some disaccharides are non-reducing sugars (maltose)

Benedict’s test is used but they do not change the colour of Benedict’s Solution
when heated with it. As a result, the non-reducing sugar should be hydrolysed into monosaccharides first.

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14
Q

How is the test for non-reducing sugars carried out?

A
  • Sample must be in liquid form
  • Add 2cm^3 of food sample and 2cm^3 of Benedict’s solution in test tube
  • Heat for 5 minutes, if it does not change colour then a reducing sugar is not present
  • Add 2cm^3 of food sample to dilute hydrochloric acid and heat test tube for 5 minutes (this hydrolyses disaccharide into its monosaccharides)
  • Add hydrogencarbonate to test tube to neutralise hydrochloric acid + test pH of solution to check if it is alkaline
  • Re-test the food solution by adding same volume with Benedict’s solution + heating it
  • If a non-reducing sugar was present, solution will turn a brick red
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15
Q

How are polysaccharides formed and what are their properties?

A

Formed by combining many monosaccharides, joined by glycosidic bonds from condensation reactions

Properties:

  • Very large -> insoluble therefore good for storage
  • (Cellulose) -> gives structural support in plants

When hydrolysed they are broken down into monosaccharides or disaccharides

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16
Q

What is the test for starch?

A

Iodine is added to starch solution, if starch is present, solution will change from yellow to blue-black

17
Q

How is the test for starch carried out?

A
  • Add 2cm^3 of sample into a test tube
  • Add two drops iodine solution and shake/stir
  • Solution will turn blue-black if starch is present
18
Q

What is the structure of starch and why is it important?

A

Starch is made up of chains of alpha glucose monosaccharides joined by glycosidic bonds, formed by condensation reactions
-may be branched or unbranched (unbranched chains are tightly coiled to become compact)

19
Q

What is the role of starch? and how does it structure help this?

A

-Mainly energy storage

Structure:

  • Insoluble -> does not affect water potential -> water does not move into cell by osmosis
  • Large/insoluble -> does not diffuse out of cells
  • Compact -> a lot can be stored in a small space
  • Forms alpha glucose when hydrolysed -> easily transported and used in respiration
  • Branched form has many ends -> easily acted on by enzymes to readily/rapidly release glucose monomers
20
Q

What is the role of starch? and how does it structure help this?

A

-Mainly energy storage

Structure:

  • Insoluble -> does not affect water potential -> water does not move into cell by osmosis
  • Large/insoluble -> does not diffuse out of cells
  • Compact -> a lot can be stored in a small space
  • Forms alpha glucose when hydrolysed -> easily transported and used in respiration
  • Branched form has many ends -> easily acted on by enzymes to readily/rapidly release glucose monomers
21
Q

What is the difference between starch and glycogen?

A

Glycogen:
Found in animal cells only
Shorter chains and more branched than starch
Stored as small granules in muscles + liver

22
Q

How does the structure of glycogen help its role?

A

Role: storage

  • Insoluble -> does not affect water potential -> water does not move into cell by osmosis
  • Large/insoluble -> does not diffuse out of cells
  • Compact -> a lot can be stored in a small space
  • More highly branched than starch -> more ends that can be acted on simultaneously by enzymes + is rapidly broken down into glucose monomers for respiration (as animals have a higher metabolic rate than plants due to being more active they need glucose more readily available)
23
Q

What is the structure of cellulose?

A
  • Made of monomers of beta glucose
  • Straight, unbranched chains
  • Chains run parallel to each other and are cross linked by hydrogen bonds (for strength)
  • Grouped to form microfibrils, forming fibres for strength
24
Q

What are the differences/similarities between starch and cellulose?

A

Similarities

  • Polysaccharides
  • Made from glucose monomers
  • Insoluble
  • In plants

Differences

  • Starch is made of alpha glucose
  • Cellulose is made of beta glucose
  • Starch is the main energy store in plants
  • Cellulose forms microfibrils for structural support
25
Q

What are the main properties of lipids?

+ The two main groups of lipids

A
  • Contain hydrogen, carbon and oxygen
  • Proportion of oxygen to carbon and hydrogen is smaller compared to carbohydrates
  • Insoluble in water
  • Soluble in organic solvents like alcohol
  • Main group of lipids is triglycerides + phospholipids
26
Q

What are the roles of lipids?

A
  • In cell membranes -> allow flexibility and transfer of lipid soluble substances
  • Source of energy -> when oxidised release twice the energy that a carbohydrate would as well as water
  • Waterproofing -> Plants/insects have waxy cuticles to limit water loos
  • Insulation -> Slow conductors of heat and retain body heat
  • Protection -> Fat is stored around delicate organs
27
Q

How are triglycerides formed?

A

Condensation reaction of one molecule of glycerol and three fatty acids

28
Q

What is the difference between a saturated and unsaturated fatty acid?

A

Saturated - no carbon-carbon double bonds (all carbon atoms are linked to all H atoms)

Unsaturated:
Poly-unsaturated: More than one double bond between carbon atoms
Mono-unsaturated: One double bond between carbon atoms

29
Q

How is the structure of triglycerides related to its properties?

A
  • High ratio of energy-strong carbon-hydrogen bonds to carbon atoms -> good source of energy
  • Low mass to energy ratio
  • > good for storage
  • Large and insoluble -> do not affect osmosis/water potential
  • High ratio of hydrogen to oxygen atoms -> release water when oxidised (important source of water)
30
Q

What is the difference between a phospholipid and a triglyceride?

A

Phospholipids have the same structure as triglycerides but one fatty acid is replaced by a phosphate group

31
Q

What is the structure of a phospholipid?

A
  • Hydrophilic head
  • Hydrophobic tail

The phosphate group attracts water where as fatty acids repel water

32
Q

What does polar mean?

A

Molecules with two ends that behave differently

33
Q

How is the structure of phospholipids related to its properties?

A
  • Polar -> In aqueous environment, form a bilayer in membranes so a hydrophobic barrier is formed between outside and inside of the cell
  • Hydrophilic heads -> hold at the surface of membrane
  • Phospholipid structure -> Can form glycolipids when combined with carbohydrates (important for cell recognition)
34
Q

What is the test for lipids ?

A

Emulsion test:

  • 2cm^3 of sample with 5cm ^3 of ethanol
  • Shake test tube to dissolve any lipid in sample
  • Add 5cm^3 of water
  • Milky-white solution will form if lipid is present

AQA Biology A level (13 decks)

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