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A Level Biology > Proteins > Flashcards

Proteins Flashcards

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1
Q

What are the type of bonds formed between amino acids

A

Peptide bonds

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2
Q

What are proteins composed of

A

Carbon
Hydrogen
Oxygen
Nitrogen
Sometimes sulphur and phosphorus to

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3
Q

Name the different examples of proteins

A
  • enzymes
  • cell membranes
  • structural protein (e.g collagen)
  • hormones
  • antibodies
  • transport (e.g haemoglobin)
  • muscle contraction (actin and myosin proteins)
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4
Q

What is the general structure of an amino acid

A

Amine group (NH2)
Central carbon and hydrogen
R group
Carboxyl group

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5
Q

What is an R group

A

It is the variable group which differs with the 20 different amino acids

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6
Q

How do different R groups change the properties of amino acids

A
  • non-polar
  • polar
  • acidic
  • bases / basics
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7
Q

How do peptide bonds form

A

A condensation reaction between 2 amino acids form a peptide bond

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8
Q

What forms when a condensation reaction occurs between 2 amino acids?

A

One water molecule
Dipeptide chain

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9
Q

What always forms at either end of a dipeptide/polypeptide chain?

A

An amine group is ALWAYS at one end and a carboxyl group is ALWAYS at the other end.

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10
Q

How do you test for proteins

A

Add a few drops of biuret reagent(1 - sodium hydroxide) and a few drops of biuret reagent(2 copper sulphate) this should look blue. When added to the test solution, if a purple/lilac colour develops, it indicates the presence of protein

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11
Q

What is biuret reagent p composed of?

A

Copper sulphate
Sodium hydroxide

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12
Q

Why won’t an amino acid show a positive result in the biuret test?

A

The biuret test - tests for peptide bonds which are not present in a single amino acid

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13
Q

What does a semi-quantitative test mean?

A

It means that with observation, you can determine that the concentration is higher or lower.

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14
Q

How do you make a semi-quantitative food test more accurate?

A

Use a colorimeter to measure colour

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15
Q

What is the primary structure of proteins?

A

The sequence of amino acids found in a proteins polypeptide chain.

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16
Q

What is the secondary structure of proteins

A

The primary structure is pulled into the secondary structure due to the hydrogen bonds forming between the double bonded oxygen and single bonded hydrogen of nearby peptide bond. This forms an Alpha helix or Beta pleated sheet

17
Q

What does the secondary structure form?

A

Alpha helix
Beta pleated sheet

18
Q

What’s the tertiary structure of protein

A

R group interactions pull the secondary structure into a more complex 3D shape held in place by disulphide bridges, ionic bonds, hydrogen bonds and hydrophobic/hydrophilic interactions

19
Q

What is a disulphide bridge?

A

A bond which forms between 2 sulphur molecules in the R-group of amino acids. This causes bends/folds in the structure

20
Q

What is an ionic bond in the tertiary structure?

A

A bond which forms between a positive and negative charge of the R-group.
This also causes folds/turns in the structure

21
Q

What is the hydrogen bond in the tertiary structure?

A

A bond which forms between nearby peptide bonds (between O and H)

22
Q

How do hydrophobic and hydrophilic interactions affect the structure of proteins?

A

Hydrophobic molecules fold inwards to avoid contact with water. Hydrophilic molecules push out due to the attraction with water

23
Q

What is the quaternary structure of proteins?

A

When 2 or more polypeptide chains are bonded together. Prosthetic groups may also be present to form large, complex protein molecules.

24
Q

How does the tertiary structure impact the function of a protein?

A

The tertiary structure aids to determine the shape of the molecule which affects its function (e.g enzymes active site)

25
Q

What are the two types of proteins?

A

Globular
Fiborous

26
Q

What function does a globular structure give proteins

A

It forms a :
spherical shape
Compact structure
And aids metabolic function

27
Q

Name 2 globular proteins

A

Enzymes
Haemoglobin

28
Q

What structure does haemoglobin have?

A

Has a quaternary structure as 4 polypeptide chains are bonded together around an iron ion

29
Q

What function does a fibrous protein have?

A

The long strands/chains which run parallel to one another are linked by cross bridges which make them strong and stable, they are also insoluble

30
Q

Name a fiborous protein

A

Collagen (structural function like bones)

31
Q

Why are globular proteins soluble in water?

A

The hydrophobic R-groups flood in and cluster on the inside while the hydrophilic R-groups push towards the outside to make attractions with the water molecules

A Level Biology (13 decks)

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