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biology year 1 aqa a level > biological molecules > Flashcards

biological molecules Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

Describe the structure of sucrose and explain how it is formed.

A

sucrose is a disaccharide and it is made up of glucose and fructose via a condensation reaction.

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2
Q

Test of non-reducing sugars?

A

Benedict’s test.

  1. Heat with Benedict’s = no change
  2. add dilute hydrochloric acid to hydrolyse the glycosidic bond.
  3. add sodium hydrogen carbonate to neutralise the solution.
  4. Heat with Benedicts = brick red.
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3
Q

Glycogen is a polysaccharide. Describe its structure and how it is related to its function.

A
  1. It is insoluble so i doesnt diffuse out of cells and does not allow water into the cells via osmosis.
  2. It is compact so a lot of it can be stored in one place therefore animals can store excess glucose.
  3. It is highly branched so there’s many more ends exposed for enzymes to act simultaneously on it and more glucose can be released quickly for energy.
  4. It is made from a-glucose and has 1,6 glycosidic bonds.
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4
Q

Test for proteins?

A

Biuret test.

  • add sodium hydroxide and copper sulfate solution.
  • if a protein is present it will go from blue - purple.
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5
Q

Describe an enzymes tertiary structure and how it relates to its properties.

A

The tertiary structure is the final 3D resting shape of the polypeptide chain.
It is formed by hydrogen bonds, ionic bonds and disulfide bridges. it determines the active site of an enzyme which makes the enzyme specific.

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6
Q

What happens when an enzyme is denatured?

A

The shape of the active site changes and the enzymes active site is longer complementary to the substrate.

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7
Q

Name 3 polysaccharides

A
  1. starch
  2. glycogen
  3. cellulose
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8
Q

3 Monosaccharides ?

A

glucose
galactose
fructose

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9
Q

what are the 3 disaccharides and what monosaccharides are they made from?

A
  1. glucose + glucose = maltose
  2. glucose + galactose = lactose
  3. glucose + fructose = sucrose
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10
Q

describe the structure of starch

A
  • it is insoluble so it does not diffuse out of cells or affect the water potential.
  • It is made of long, unbranched chains of a-glucose.
  • it is coiled and compact
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11
Q

describe the structure of amylopectin

A
  • long, branched chains of a-glucose.
  • it is branched so enzymes can get to the glycosidic bond easily.
  • insulbe so it doesn’t affect the water potential
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12
Q

describe the structure of cellulose

A
  • long, unbranched chains of b-glucose.
  • linked by h-bonds to form microfibrils
  • each glucose is alternate to the other (180 degrees)
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13
Q

what is the test for starch?

A

add potassium iodide and it turns black/blue

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14
Q

what is a phospholipid made up of?

A

2 fatty acids, glycerol and a phosphate

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15
Q

describe the structure of a phospholipid

A
  • hydrophobic tail which is an energy store because lots of chemical energy can be stored in the tails.
  • hydrophilic head
  • insoluble so it doesn’t affect the water potential.
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16
Q

Test for lipids

A

emulsion test

  • add ethanol
  • shake
  • add water
  • milky white
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17
Q

what is the phospholipid bilayer

A
  • double layer which makes up the membrane and water soluble substances cant pass due to the hydrophobic tails.
  • acts as a barrier
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18
Q

what are triglycerides made up of?

A

3 fatty acids and glycerol via a condensation reaction

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19
Q

bond in triglycerides?

A

ester bond

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20
Q

bond in proteins?

A

peptide bond

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21
Q

bond in carbohydrates?

A

glycosidic bond

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22
Q

structure of amino acids?

A

NH2CH(R)COOH

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23
Q

how many amino acids in living things and why are they universal?

A

20 and they are universal because they are the same in all living things

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24
Q

what does degenerate mean?

A

The same amino acid can be coded for by multiple different codons

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25
Q

describe the structure of proteins

A

primary - sequence of amino acids

secondary - H-bonds form between amino acids and it coils into either alpha helix or beta pleated sheets

tertiary - hydrogen, ionic and disulfide bridges form and the polypeptide chain goes into its final 3D resting shape.

quaternary - several different polypeptide chains.

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26
Q

what are enzymes?

A

biological catalysts that speed up the rate of reaction by lowing the activation energy required for the reaction to occur and providing an alternate route

they don’t get used up

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27
Q

how does an enzyme-substrate complex lower the activation energy?

A
  • if 2 substrates need to be joined, being attached to the enzyme holds them closer together, reducing repulsion so they can bond together more easily.
  • fitting into the active puts strain on the bonds spo they break more easily.
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28
Q

what is the lock and key model?

A

The active site is rigid so only exactly complementary substrates bind to form E-S complexes.

29
Q

what is the induced fit model model?

A

the active site is able to change shape as it is flexible so the substrate binds and then the active site changes shape so the substrate fits exactly to for E-S complexes

30
Q

what can alter the tertiary structure and therefore the active site shape?

A

a change in Ph and temperature

31
Q

how can the primary structure be altered? how does that affect the active site of an enzyme?

A

by a mutation. altering the primary structure would alter the tertiary structure which in turn would change the shape of the active site.

32
Q

How can you measure enzyme activity?

A
  • how fast the product is made

- how fast the substrate is broken down

33
Q

how does temp affect enzyme activity?

A
  • temp increases
  • kinetic energy increases
  • molecules move faster
  • increases the chance of successful collisions
  • increases the chance of forming ES complexes
  • which increases rate of reaction
  • until it reaches the optimum (40 degrees)
  • then the bonds in the tertiary structure break
  • and the enzyme denatures
34
Q

How does Ph affect enzyme activity?

A

if the Ph moves away from the optimum, the the bonds in the tertiary structure break and it loses its active site shape.
the enzyme denatures and you cannot form ES complexes

35
Q

what does increasing the substrate conc do?

A
  • increases the chance of successful collisions
  • which increases the chance of successful ES complexes
  • which increases the rate of reaction

this increases until all the enzyme active sites are full

36
Q

what does increasing the enzyme conc do?

A
  • increases the chance of successful collisions
  • which increases the chance of successful ES complexes
  • which increases the rate of reaction

continues until all the substrates are used up.

37
Q

what are competitive inhibitors ?

A

they have a similar shape to the substrate and so they bind to the active site and block it preventing ES complexes from forming.

38
Q

what are non-competitive inhibitors?

A

they bind to another binding site that is not the active site.
this causes the active site to change shape so the substrate cant bind.
this means less ES complexes are formed.

39
Q

how do you calculate the rate of reaction?

A
  • draw a tangent
  • gradient = change in y divided by change in x
  • remember units!!
40
Q

what are the monomers in DNA?

A

nucleotides

41
Q

what is a nucleotide made up from?

A

phosphate, pentose sugar, and a nitrogen containing base

42
Q

bond in polynucleotides?

A

phosphodiester bond

43
Q

What are the differences between DNA and RNA?

A

DNA has a deoxyribose sugar whereas RNA had a ribonucleic acid.
DNA is double stranded in a double helix whereas RNA is single stranded.
The bases in DNA are adenine, thymine, cytosine and guanine whereas in RNA they are adenine, uracil, cytosine and guanine.
DNA is longer whereas RNA is shorter

44
Q

what are the differences between tRNA and mRNA?

A

mRNA functions at the nucleus and the cytoplasm whereas tRNA functions only at the cytoplasm.

mRNA carries a codon sequence which is complementary to the codon sequence of the gene whereas tRNA carries an anticodon which is complementary to the codon on the mRNA.

tRNA is a clover shape whereas mRNA is linear in shape and is single stranded

45
Q

What is DNA?

A
  • 2 polynucleotide strands that are antiparallel to each other
  • with hydrogen bonds between complementary bases
  • the sugar-phosphate backbone protects the bases
46
Q

when does DNA replication occur?

A

during interphase

47
Q

outline the process of semi-conservative replication

A
  • DNA helicase breaks H-Bonds between bases
  • this separates the double strand
  • free nucleotides do complementary base pairing with the template strand
  • DNA polymerase joins the free nucleotides to the template strand via a condensation reaction and H-bonds reform.
48
Q

Evidence for SCR

A
  • replicated 15N (heavy) and 14N (light)

- replicated both together and instead of finding 2 different densities, they found a medium one

49
Q

What is ATP?

A

Adenosine triphosphate

50
Q

what is the structure of ATP?

A

1 adenosine and 3 phosphates

  • condensation reaction using ATP Synthase
  • ATP carries energy in its bonds
  • hydrolyses reaction using ATP Hydrolase
  • releases energy from its bonds
51
Q

Why is ATP a good source of energy?

A
  • it is an immediate source as only 1 weak bond needs to be broken
  • it is a manageable source as only a small amount is released.
52
Q

equation for formation of ATP using ATP Synthase?

A

ADP + Pi = ATP

53
Q

equation for hydrolysis of ATP?

A

ATP = ADP + Pi

54
Q

what does adding a phosphate do to other compounds?

A

makes it more reactive

55
Q

what are the properties of water?

A
  • it acts as a metabolite
  • it acts as a solvent so it can dissolve substances together due to its polarity
  • it is cohesive meaning the molecules can stick together which helps it to flow = transport
  • habitat
  • Has high hydrostatic pressure - when pressurized it has a strong physical pushing force which helps mass flow and turgidity.
  • high specific heat capacity which is the energy needed to raise 1 gram of substance by 1 degree
  • high latent heat of evaporation so it takes a lot of energy away with it when it evaporates from the surface helps maintain a constant body environment e.g sweating which cools the surface (homeostasis).
56
Q

what is an inorganic ion?

A

something that doesn’t contain carbon

such as salts, minerals, ions

57
Q

suggest why ATP hydrolysis can be coupled up to the action of DNA helicase

A

ATP can provide energy to DNA helicase and allow the reaction to occur so it can unwind the double helix by breaking the H-bonds

58
Q

How can Na+ ions dissolve in water?

A

Na+ ions can dissolve in water due to water being a polar molecule and so the slightly negative oxygen can attract the Na+ redulting the Na+ being surrounded by water molecules, causing it to dissolve.

59
Q

give 2 types of molecules from which ribosomes are made

A
  • ribosomal RNA

- protein

60
Q

Describe the role of a ribosome in the production of a polypeptide, DO NOT include transcription in your answer.

A
  • mRNA binds to the ribosome
  • tRNA binds with the correct anticodon
  • It forms a peptide bond between amino acids
  • mRNA moves along to the next codon
61
Q

How does mRNA differ from pre-mRNA

A

In pre-mRNA there’s introns and in mRNA the introns are spliced and removed.
Therefore, mRna is shorter and pre-mRNA is loner.

62
Q

Suggest 1 advantage of showing the genetic coce as base sequences on mRNA rather than triplets on DNA

A
  • DNA has 2 strands with different base sequences
63
Q

Suggest the role of mRNA base triplets UGA, UAG, UAA

A
  • to stop translation

- which results in the detachment of polypeptide chains from the ribosome

64
Q

Lactose + _________ = glucose + ________ ?

A
  1. water

2. galactose

65
Q

Hydrolysis and condensation are important in the formation of new adult proteins. explain how ?

A
  • hydrolysis breaks down the proteins

- protein synthesis involves condensation

66
Q

After lactose has been broken down, there’s a higher conc of reducing sugar.
why?

A

theres 2 products (galactose and glucose)

67
Q

describe how proteins are digested in the human gut

A
  • by the hydrolysis of peptide bonds
  • endopeptidases break polypeptide chains into smaller peptide chains
  • exopeptidases remove terminal amino acids
  • dipeptidases break down dipeptides into amino acids
68
Q

what sugars/reducing sugars would you expect to produce during chewing?

A
  • maltose
  • because salivary glands produce amylase
  • which breaks down starch
69
Q

what enzyme is needed for the complete digestion of starch?

A

maltase

biology year 1 aqa a level (7 decks)

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