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3.1 Biological Molecules > 3.1.4.1 General properties of proteins > Flashcards

3.1.4.1 General properties of proteins Flashcards

1
Q

EQ: Protein test- lactase from lactose solution

A
  • Add Biuret reagent to both solutions
  • lactase (enzyme) will give purple
  • lactose (reducing sugar) will remain blue
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2
Q

What are proteins?

A

Molecules made up of one or more polypeptide chain

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3
Q

What are example of proteins?

A

Amylase, maltase, lipase, collagen, keratin, insulin

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4
Q

Amino acids

Definition

A

the monomers from which proteins are made

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5
Q

Amino acids

Structure

A 
Amine group (NH2)
Carbon chain
Side chain (R) 
Carboxyl group (COOH)
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6
Q

What is the H₂N group called?

A

The amine/amino group

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7
Q

What is the COOH group called?

A

The carboxyl group

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8
Q

What is the R group called?

A

The carbon containing R Group

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9
Q

What are three examples of amino acids?

A

Glycine, alanine and cysteine

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10
Q

Number of amino acids that are common in all organisms

A

20

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11
Q

The twenty amino acids that are common in all organisms differ only in…

A

their side group

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12
Q

What do proteins contain

A

Carbon,
Hydrogen,
Oxygen,
Nitrogen

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13
Q

A condensation reaction between two amino acids forms…

A

a peptide bond

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14
Q

peptide bond formation

A

A condensation reaction between two amino acids

between the carboxyl group of one and amine group of another

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15
Q

Dipeptide formation

A

the condensation of two amino acids

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16
Q

Polypeptide formation

A

the condensation of many amino acids

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17
Q

What may a functional protein contain

A

one or more polypeptides

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18
Q

Bends involved in the structure of proteins

A

Hydrogen
Ionic
Disulphide

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19
Q

Types of protein function

A 
Structural
Enzymes / Hormones
Transport
Protective
Contractile
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20
Q

Protein Function - Structural

A

Keratin - skin, feathers, hair

Collagen - connective tissue, bone, tendons

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21
Q

Protein Function - Enzymes / Hormones

A

Digestive enzymes
Insulin
Glucagon

22
Q

Protein Function - Transport

A

Haemoglobin

23
Q

Protein Function - Protective

A

Antibodies etc

24
Q

Protein Function - Contractile

A

Myosin, Actin - moving muscle tissue

25
Q

Primary structure

Definition

A

The unique sequence of amino acids that makes up a protein/polypeptide chain

26
Q

Primary structure

Structure/formation

A

Amino acids joined with peptide bonds in enzyme catalysed condensation reactions

27
Q

Primary structure

Bonds involved

A

Peptide bond

28
Q

Secondary structure

Definition

A

The way in which the primary structure of a polypeptide chain folds

29
Q

Secondary structure

Structure/formation

A

Alpha helixes

Beta pleated sheets

30
Q

Secondary structure

Bonds involved

A

Hydrogen bonds

31
Q

Tertiary structure

Definition

A

The final 3D structure of a protein, entailing the shaping of the secondary structure
Held together by different chemical bonds (Hydrogen [weakest], Ionic, Disulphide bridges [strongest])
-Tertiary structure depends on the primary structure

32
Q

Tertiary structure

Structure

A

Globular

Fibrous

33
Q

Fibrous protein

A

Parallel polypeptide chains are cross linked at intervals to form long fibres or sheets

34
Q

Fibrous protein

Examples

A

collagen and keratin

35
Q

Globular protein

A

Polypeptide chain - tightly folded to form a spherical shape

Soluble proteins with a specific 3D shape

36
Q

Globular protein

Examples

A

enzymes, hormones, antibodies, haemoglobin

37
Q

Tertiary structure

Bonds/interactions involved

A 
Held by bonds/interactions
Ionic
└2 oppositely charged r groups
Disulphide
└between two cysteine amino acids
Hydrogen
Hydrophobic/phallic
38
Q

Quaternary structure

Definition

A

The structure formed when 2 or more polypeptide chains join together, sometimes with an inorganic component, to form a protein

39
Q

Quaternary structure

Structure/formation

A

Inorganic component
└prosthetic group
└e.g. haem in haemoglobin

40
Q

Quaternary structure

Examples

A

Collagen (3 chains)
Antibodies (3 chains)
Haemoglobin (4 chains)

41
Q

Test for proteins

A

biuret test

42
Q

biuret test

A

-add biuret reagent
Positive result- light purple
Negative result- blue

43
Q

EQ: The type of bond that joins amino acids together in a polypeptide

A

-peptide

44
Q

EQ: Name the type of bond hydrolysed when the short chain of amino acids is removed.

A

Peptide (bond)

45
Q

EQ: Competitive inhibition- why a high concentration of galactose slows down the breakdown of lactose by lactase

A

galactose is a similar shape to lactose, so are both complimentary to the active site

  • galactose therefore fits into the active site of the enzyme
  • this prevents the substrate binding with the active site so less e-s complexes are made
46
Q

EQ: Effect of temperature on reaction- graph explanation (high temp)

A
  • the enzyme becomes denatured as hydrogen bonds holding the tertiary structure are broken
  • meaning there is a change in the active site of the enzyme
  • so the substrate no longer fits into the active site and fewer e-s complexes are formed
  • more enzyme molecules are denatured as temperature increased
47
Q

EQ: How the students make sure pH doesn’t change

A

Use a buffer

48
Q

EQ: Why an enzyme catalyses only one reaction- enzyme specificity

A
  • enzyme has an active site

- and only the substrate fits the active site

49
Q

EQ: Why maltase:

  • only breaks down maltose
  • allows this reaction to take place at normal body temperature.
A
  • the 3D shape of the enzyme (tertiary structure) means
  • the active site is complimentary to the substrate (maltose)
  • as shown in the induced fit model
  • the enzyme is a catalyst
  • and lowers activation energy (as it provides alternative pathway for the reaction at a lower energy level)
  • by forming an e-s complex(which stresses the bonds so they are more easilt broken)
50
Q

EQ: Describe competitive and non-competitive inhibition of an enzyme

A

-Inhibitors reduce binding of enzyme to substrate / prevent formation of ES complex
Competitive inhibition:
-inhibitor similar shape to substrate
-binds in to active site of enzyme
-Inhibition can be overcome by more substrate
-so max product will eventually be formed/ max rate of reaction will be reached
Non-competitive inhibition:
-Inhibitor binds to site on enzyme other than active site
- Prevents formation of active site / changes shape of active site
-Cannot be overcome by adding more substrate
-so max product will not be formed/ max rate of reaction will not be reached

51
Q

EQ: Maltose is hydrolysed by the enzyme maltase. Explain why maltase catalyses only this reaction

A
  1. Active site (of enzyme) has (specific) shape/tertiary structure / active site complementary to substrate/maltose;
  2. (Only) maltose can bind/fit;
  3. To form enzyme substrate complex;
52
Q

EQ: Sometimes trypsin can become activated inside a pancreatic cell. A competitive inhibitor in the cell then binds to the trypsin and stops it working. Explain how the competitive inhibitor stops trypsin working.

A
  1. Inhibitor is a similar shape to the substrate;
  2. (Inhibitor) blocks active site/is complementary to the active site/binds to the active site (of trypsin);
  3. Substrate can’t bind to active site / no/fewer ES complexes formed;

3.1 Biological Molecules (10 decks)

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