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AQA A-level Biology > Chapter 1 - Biological Molecules > Flashcards

Chapter 1 - Biological Molecules Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What are biological molecules?

A

Particular groups of chemicals that are made up and used by living organisms

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2
Q

What is covalent bonding?

A

When atoms share one or more pairs of electrons in their outermost shell

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3
Q

What is ionic bonding?

A

The electrostatic force of attraction between two or more oppositely charged ions

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4
Q

What is hydrogen bonding?

A

Weak electrostatic bond caused when the negative region of one polarised molecule is attracted to the positively charged region of another

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5
Q

What is a polar molecule?

A

A molecule with an uneven distribution of charge

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6
Q

What are monomers?

A

Small, basic molecular unit that builds polymers

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7
Q

What are polymers?

A

Molecule made up of large numbers of monomer sub-units joined together

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8
Q

What is polymerisation?

A

Process of making polymers by joining monomers together

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9
Q

Give examples of industrial made polymers

A

Polythene and polyester

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10
Q

Give examples of naturally occurring polymers

A

Polysaccharides, polypeptides and polynucleotides

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11
Q

What is a condensation reaction?

A

A reaction that releases a molecule of water when it links molecules together.

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12
Q

What is a hydrolysis reaction?

A

A reaction that hydrolyses the chemical bond between monomers by the addition of water

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13
Q

What does the term metabolism mean?

A

All the chemical processes/reactions that take place in a living organism

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14
Q

Define mole

A

The amount of a substance that contains as many particles as there are atoms

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15
Q

What is a molar solution?

A

A solution that contains one mole of solute in each litre of solution

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16
Q

What is an ion?

A

A charged atom that has received or lost an electron

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17
Q

What is an isotope?

A

Atoms of the same element that have a different number of neutrons which results in a difference in mass

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18
Q

What three elements are carbohydrates made from?

A

Carbon, hydrogen and oxygen

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19
Q

What are the monomers that make up carbohydrates called?

A

Monosaccharides

20
Q

What are monosaccharides and give examples

A

Simple sugars i.e. glucose, galactose and fructose

21
Q

What are the isomers of glucose?

A

Alpha glucose and beta glucose

22
Q

What are disaccharides?

A

Pairs of monosaccharides joined together by a glycosidic bond in a condensation reaction

23
Q

Give examples of disaccharides

A

Maltose (glucose+glucose)
Lactose (glucose+galactose)
Sucrose (glucose+fructose)

24
Q

What are polysaccharides?

A

Large molecules formed from combining many monosaccharides together by glycosidic bonds formed in a condensation reaction

25
Q

Give examples of some polysaccharides

A

Starch, cellulose and glycogen

26
Q

What is a reducing sugar?

A

A sugar that can donate electrons to (or reduce) another chemical

27
Q

How do you test for reducing sugars?

A

Benedict’s Test

  • Add equal amounts of sample and Benedict’s reagent, mix gently and heat for 5 mins
  • Positive reaction=red precipitate formed of copper oxide
28
Q

How is the test for reducing sugars semi-quantitative?

A

Has variation in the colour of the precipitate formed depending on how much reducing sugar is present

  • Blue = none
  • Green = very low
  • Yellow = low
  • Orange = medium
  • Red = high
29
Q

How do you test for non reducing sugars?

A
  1. Do the Benedict’s test and get a negative reaction
  2. Add equal volumes of food sample and dilute hydrochloric acid
  3. Heat for 5 mins (acid hydrolyses any disaccharides)
  4. Slowly add sodium hydrogen carbonate solution and check pH with pH paper to ensure solution is alkaline
  5. Re-test with Benedict’s reagent and heat for 5 mins
  6. Orange-brown precipitate formed when a non-reducing sugar is present
30
Q

Where is starch located in organisms?

A

Found only in plants in the form of small grains and large amounts are found in the seeds and storage organs

31
Q

What is the role of starch?

A

It’s main role is energy storage as plants store excess glucose as starch

32
Q

How is starch produced?

A

Chains of alpha glucose monomers joined together by glycosidic bonds formed in a condensation reaction

33
Q

Starch is a mixture of…

A

2 polysaccharides of alpha-glucose: amylose and amylopectin

34
Q

Describe the structure of amylose

A

Long, unbranched chain of alpha-glucose that is wound into a tight coil

35
Q

Describe the structure of amylopectin

A

Long, branched chain of alpha-glucose monomers

36
Q

Describe how the structure of starch relates to its function

A
  1. Insoluble - doesn’t affect water potential
  2. Large - does not diffuse out of cells
  3. Compact (when coiled) - lots of energy stored in small spaces
  4. Amylopectin branches - provide more area for enzymes to act on and break down the glycosidic bonds easily so glucose is released rapidly
37
Q

Alpha glucose molecules are formed by what type of glycosidic bonds?

A

1,4 and 1,6 glycosidic bonds

38
Q

Where is glycogen located in organisms?

A

Found in animals and bacteria and is stored as small granules in the liver and muscles

39
Q

Describe glycogen’s structure

A

Shorter and more highly branched polysaccharide chains of alpha-glucose

40
Q

Describe how glycogen’s structure relates to its function

A
  1. Insoluble - does not affect water potential or diffuse out of the cell
  2. Compact - lots stored in small spaces
  3. Lots of branches and shorter chains - more area for enzymes to act on so stored glucose can be released very quickly, important for animals with high metabolic and respiratory rates
41
Q

Describe the test for starch

A

Add iodine solution to a sample and if it reacts with starch it produces a blue-black colouration from yellow

42
Q

Describe the structure of cellulose

A

Long, straight, unbranched chains of beta-glucose that run parallel to each other that allows hydrogen bonds to form cross-linkages between chains which results in the formation of microfibrils that group together in parallel to make fibres

43
Q

What is the purpose of cellulose?

A

Provides rigidity and support to plant cells as it is a major component in the cell wall

44
Q

How does cellulose prevent the cell from bursting as water enters the cell by osmosis?

A

Experts an inwards pressure that stops any influx of water so it makes the plant cell turgid

45
Q

Why is it important that stems and leaves are in a turgid state?

A

To provide maximum surface area for photosynthesis

AQA A-level Biology (4 decks)

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