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Bio PPQs > Bio Molecules > Flashcards

Bio Molecules Flashcards

1
Q

Describe how the structure of a protein depends on the amino acid it contains.

(5 marks)

A
  • Structure depends on R group interactions (hydrogen bonds, disulphide bridges, ionic bonds)
  • Primary structure is sequence/ number of amino acids
  • Secondary stucture based on hydrogen bonds between amino acids (forms alpha helixes or beta pleated sheets)
  • Tertiary structure based on R group ionic, hydrogen and disulphide bridge bonds
  • Creates active site in enzymes
  • Quaternary structure is more than 1 polypeptide chain
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2
Q

Name 2 similarities between dipeptides.

(2 marks)

A
  • Amine group at one end
  • Carboxyl group at other end
  • 2 R groups
  • All contain C and N and H and O
  • Joined by peptide bond

(Max 2)

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3
Q

Name 1 difference between dipeptides.

(1 mark)

A
  • R group

(Max 1)

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4
Q

What are the differences between competitive and non-competitive inhibitors?

(4 marks)

A
  • Competitive binds to A.Sbut non competitive binds to allosteric site
  • Competitive does not change shape of enzyme A.S but non competitive changes conformational shape which changes A.S shape
  • Increasing substrate conc. helps overcome competitive and increases likelihood of successful collisions but has no effect on non-competitive
  • At high inhibitor concs. enzyme is still available for competetive but not for non-competitive

(ALWAYS compare both sides of both subjects in ONE point)

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5
Q

How does the active site of an enzyme cause a high ROR?

(3 marks)

A
  • Lowers activation energy
  • Induced fit causes active site to change shape
  • ES complex distresses and distorts bonds and causes them to break

(ALWAYS mention ES complex when writing about enzymes)

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6
Q

Why might a set of results not be accurate/ reliable?

A
  • Test only tested on one sample
  • Test only done once instead of multiple times w/ mean
  • Used subjective measure of values instead of quantative
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7
Q

How is the structure of glycogen related to its function?

(4 marks)

A
  • Coiled so more compact
  • Polymer of glucose so easily hydrolysed
  • Branched, more ends, faster hydrolysis
  • Made from glucose which provides substrate for respiration for energy
  • Insoluble so does not affect water potential

(Any 4)

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8
Q

Why can 2 proteins have the same number and types of amino acids but different tertiary structures?

(2 marks)

A
  • Different sequence of amino acids
  • Forms ionic, disulphide, hydrogen bonds in different places

(Whenever talking about bonds BE SPECIFIC to their names)

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9
Q

Why is a buffer solution added to an experiment?

(2 marks)

A
  • To maintain a constant PH
  • So changes in PH does not affect ROR
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10
Q

In an enzyme reaction, what colour would a biurets solution test go and why?

(3 marks)

A
  • Lilac/ purple
  • Enzyme is a protein
  • Not used up in reaction/ still present at the end of the reaction
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11
Q

How is the structure of starch related to its function?

(3 marks)

A
  • Helical/ coiled so compact
  • Insoluble so does not affect water potential
  • Branched so glucose easily released for respiration
  • Large so cannot leave cell

(Any 3)

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12
Q

How is the structure of cellulose related to its function?

(3 marks)

A
  • Long, straight unbranched chains of Beta Glucose
  • Layers joined by weak hydrogen bonds
  • Forms micro/macro fibrils
  • This provides rigidity and strength

(Any 3)

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13
Q

Describe the induced fit model of enzyme action and how an enzyme acts as a catalyst.

(3 marks)

A
  • Substrate binds to active site/ enzyme-substrate complex forms
  • Active site changes shape so it is complementary to substrate
  • Reduces activation energy
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14
Q

Describe how amino acids join to form a polypeptide so there is always NH2 at one end and COOH at the other end.

(2 marks)

A
  • One amine group joins to a carboxyl group to form a peptide bond
  • So there is a free amine at one end and a free carboxyl at the other end/ each amino acid is oriented in the same direction in the chain
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15
Q

Suggest two variables a biochemist controlled when investigating the effect of temp on the rate of breakdown of a protein by protease.

(1 mark)

A
  • Initial substrate concentration
  • Enzyme concentration
  • pH
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16
Q

Describe how a triglyceride molecule is formed.

(3 marks)

A
  • One glycerol and three fatty acids
  • Condensation and removal of three molecules of water
  • Ester bonds formed

GLYCEROL (not glycerine)

17
Q

Describe a biochemical test to show that a solution contains a non-reducing sugar.

(3 marks)

A
  • Boil with acid and neutralise
  • Heat with Benedict’s solution in heat bath to 90 degrees
  • Red precipitate

(Remember neutralisation and that it forms a PRECIPITATE)

18
Q

Why would the use of a colorimeter improve the repeatability of results?

(1 mark)

A
  • Quantative/ colour change is subjective
  • Standardises the method

(1 max)

19
Q

Describe the structure of glycogen.

(2 marks)

A
  • Polysaccharide/ polymer of alpha glucose
  • Joined by glycosidic bonds
20
Q

Describe how glycogen acts as a source of energy.

(2 marks)

A
  • Hydrolysed to glucose
  • Glucose used in respiration
21
Q

Describe how a phosphodiester bond is formed between two nucleotides within a DNA molecule.

(2 marks)

A
  • Condensation/ loss of water
  • Between phosphate and deoxyribose
  • Catalysed by DNA polymerase

Max 2

22
Q

Describe the chemical reactions involved in the conversion of polymers to monomers and monomers to polymers giving 2 named examples.

(5 marks)

A
  • Condensation joins monomers and forms a chemical bond and releases water
  • Hydrolysis breaks a chemical bond between monomers and uses water
    Two of:
  • Nucleotide and polynucleotide (Phosphodiester)
  • Alpha glucose and starch/glycogen (Glycosidic)
  • Beta glucose and cellose (Glycosidic)
  • Amino acid and polypeptide (Peptide)
  • One of the above named bonds
23
Q

Explain 5 properties that make water important for organisms

(5 marks)

A
  • Metabolite: Used in chemical reactions such as photosynthesis, respiration, hydrolysis, condensation
  • Solvent: So metabolic reactions can occur
  • High specific heat capacity: Buffers change in temperature
  • Large specific latent of vaporisation: Provides a cooling effect
  • Cohesion: Supports columns of water
  • Cohesion: Provides surface tension supporting small organisms

5 max

24
Q

When three amino acids are placed on filter paper with a positive and negative electrode on either side, explain the result.

(3 marks)

Positive electrode [ | * * ] Negative electrode

A
  • Moved to negative electrode because positively charged
  • Move different distances because amino acids have different charge/ mass
  • Two spots because 2 amino acids have same charge/ mass
25
Q

Suggest why the ROR lowers when a sugar called Lyxose is added to an enzyme reaction

(3 marks)

(Part of an application question)

A
  • Binding alters the tertiary structure of the enzyme
  • Which causes the active site to change shape
  • So less successful E-S compexes form
26
Q

Certain enzyme-catalysed reactions can only take place if substrates have been phosphorylated. Explain why

(1 marks)

A
  • Phosphorylation makes substrate more reactive
27
Q

ATR is an enzyme responsible for phosphorylating other enzymes that repair DNA but also phosphorylates the required substrate. When it phosphorylates other enzymes, they become able to bind to their substrates. Explain why

(2 marks)

A
  • Changes tertiary structure of enzyme
  • Active site is formed/ becomes complementary
28
Q

An enzyme called ATM stops cell division of broken DNA until it is repaired. What are the possible effects of having a non-functional form of ATM?

(3 marks)

A
  • ATM will not bind to broken DNA
  • DNA not repaired
  • Cell division continues/ tumour forms
29
Q

Explain how a scientist can stop an enzyme reaction

(2 marks)

A
  • Add high concentration of inhibitor
  • Enzyme-substrate complex cannot be formed
30
Q

Describe how an ATP molecule is formed from its component molecules

(4 marks)

A
  • Adenine, pentose, three phosphates (for 2 marks)
  • Condensation
  • ATP synthase
31
Q

ATP is an energy source used in many cell processes. Give two ways in which ATP is a suitable energy source for cells to use.

(2 marks)

A
  • Little energy lost as heat
  • Releases energy instantaneously
  • Phosphorylates other compound, making them more reactive
  • Can be rapidly resynthesised
  • Not lost from cells
32
Q

Describe how ATP is resynthesised in cells

(2 marks)

A
  • From ADP and phosphate
  • By ATP synthase
  • During respiration/ photosynthesis
33
Q

Give 2 ways in which the hydrolysis of ATP in used in cells

(2 marks)

A
  • To provide energy for active transport (or other names processes)
  • To phosphorylate other substances and make them more reactive

Bio PPQs (7 decks)

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