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AQA A level Biology > 1.4.1 Proteins > Flashcards

1.4.1 Proteins Flashcards

1
Q

What are the 4 atoms that make up proteins

A
  • Carbon
  • Hydrogen
  • Oxygen
  • Nitrogen
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2
Q

What element do some proteins contain, in their R group

A

Sulfur

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3
Q

What element is present in proteins but not in lipids or carbohydrates

A

Nitrogen

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4
Q

Are proteins polymers

A

Yes

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5
Q

What are the monomers of protein

A

Amino acids

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6
Q

What type of reaction creates the bonds between the amino acids

A

Condensation reaction

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7
Q

What is the name of the bond that is formed during the condensation reaction to form a protein

A

A peptide bond

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8
Q

What is different about a peptide bond from the bonds formed in lipids and carbohydrates

A

Peptide bonds don’t contain an oxygen bridge

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9
Q

When amino acids combine, what do they make up

A

A polypeptide

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10
Q

When polypeptides combine what is formed

A

A protein

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11
Q

How many different naturally occurring amino acids are there

A

20

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12
Q

What are the 7 functions of proteins

A
  • Contractile
  • Enzyme
  • Hormonal
  • Receptors
  • Structural
  • Antibody
  • Respiratory
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13
Q

What are the 4 groups attached to the central carbon in a protein

A
  • Amino group
  • Carboxyl group
  • R / Variable group
  • H atom
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14
Q

What is the molecular formula for the amino group in a protein

A

NH2

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15
Q

What is the molecular formula for the carboxyl group in a protein

A

COOH

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16
Q

What are the 4 different structures of proteins

A
  • Primary
  • Secondary
  • Tertiary
  • Quaternary
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17
Q

When forming a peptide bond where does the water molecule come from

A

The OH in the carboxyl group and a H from the amino group

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18
Q

What is the primary structure of any protein

A

The sequence of amino acids in a polypeptide chain

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19
Q

What does the primary structure of a protein ultimately determine

A

The shape and hence the function

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20
Q

What might happen if a single amino acid was changed in the primary structure of a protein

A

It may stop carrying out it’s function

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21
Q

What is the secondary structure of any protein

A

Twisting of primary structure into a regular arrangement

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22
Q

What are the 2 types of secondary structures in a protein

A
  • Alpha helix
  • Beta-pleated sheet
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23
Q

What bonds hold a secondary structure protein together

A

Hydrogen bonds

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24
Q

In a secondary structure protein, where do the hydrogen bonds form

A

The OH of the carboxyl group and the H in the amino group

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25
Q

What is a tertiary structure protein in any protein

A

The further folding of the secondary structure to form a unique 3D shape

26
Q

What are the 3 bonds that hold tertiary structure proteins in place

A
  • Ionic bonds
  • Hydrogen bonds
  • Disulphide bridges
27
Q

Are disulphide bridges in a tertiary structure protein strong or weak

A

Fairly strong, so not broken easily

28
Q

What must be present to form disulphide bridges, and where in the amino acids

A

Sulfur must be in the R group

29
Q

What is a quaternary structure protein in any protein

A

A protein made up of more than 1 polypeptide chain

30
Q

Name an example of a quaternary structure protein

A

Haemoglobin

31
Q

Name 2 examples of fibrous proteins

A
  • Collagen
  • Keratin
32
Q

What is the function of fibrous proteins

A

Structural functions

33
Q

In a fibrous protein, is the primary structure polypeptide chain branched or unbranched

A

Unbranched

34
Q

In a fibrous protein, like collogen, how many polypeptide chains are in the quaternary structure

35
Q

Explain why the quaternary structure of collogen makes it a suitable molecule for a tendon

A

It has 3 polypeptide chains wound together to form a strong, rope-like structure that has strength in the direction of pull of a tendon

36
Q

Suggest how the cross-linkages between the amino acids of polypeptide chains increase the strength and stability of a collagen fibre

A

They prevent the individual polypeptide chains from sliding past one another and so they gain strength because they act as a single unit

37
Q

Explain why this arrangement of collagen molecules is necessary for the efficient functioning of a tendon

A

The junctions between adjacent collagen molecules are points of weakness. If they all occurred at the same point in a fibre, this would be a major weak point at which the fibre might break

38
Q

What are the 5 main roles of globular proteins

A
  • Enzymes
  • Hormones
  • Receptors
  • Pigments
  • Antibodies
39
Q

Name an example of a globular protein

A

Haemoglobin

40
Q

What happens to a protein when it gets denatured

A

It changes shape because the bonds break

41
Q

What type of bond breaks in high temperature in a protein

A

Hydrogen bonds

42
Q

What type of bonds break in extreme pH in a protein

A

Ionic bonds

43
Q

What impact does denaturing proteins have on fibrous proteins

A

They lose structural strength

44
Q

What impact does denaturing proteins have on globular proteins

A

Become inactive and/or insoluble

45
Q

True or false: Collagen and keratin are globular proteins

A

False, they are fibrous proteins

46
Q

True or false: Peptide bonds and hydrogen bonds are the only bonds that maintain a protein’s shape

A

False, there are also ionic and disulphide bridges

47
Q

True or false: Polypeptides are made by hydrolysis reactions between amino acids

A

False, its condensation reactions

48
Q

True or false: Primary structure is the number, type and sequence of amino acids in a polypeptide chains

49
Q

True or false: Changing a single amino acid in a polypeptide may stop the protein from working properly

50
Q

True or false: All proteins have quaternary structure

A

False, they can be secondary and tertiary too

51
Q

True or false: The function of globular proteins rely on their 3D shape

52
Q

True or false: Denaturing a fibrous protein makes it insoluble

A

False, it makes it lose it structural stength

53
Q

True or false: Enzymes, hormones, pigments and antibodies are all examples of proteins

54
Q

True of false: Alpha helices and beta-pleated sheets can both occur within a single polypeptide chain

55
Q

Describe the primary structure of all proteins (2 marks)

A
  • Sequence of amino acids
  • Joined by peptide bonds
56
Q

Describe how the structure of a protein depends on the amino acids it contains. (5 marks)

A
  • Structure is determined by (relative) position of amino acid/R group/interactions;
  • Primary structure is sequence/order of amino acids
  • Secondary structure formed by hydrogen bonding (between amino acids);
  • Tertiary structure formed by interactions (between R groups)
  • Creates active site in enzymes
  • Quaternary structure contains >1 polypeptide chain
57
Q

Define genome and proteome (2 marks)

A

Genome: complete set of gens in a cell
Proteome: Range of proteins coded for by the cell’s genome

58
Q

Describe how one amino acid is added to a polypeptide that is being formed at a ribosome during translation (3 marks)

A
  1. tRNA brings specific amino acid (to ribosome);
  2. Anticodon (on tRNA) binds to codon (on
    mRNA);
  3. Amino acids join by condensation reaction
    (using ATP)
    OR
    Amino acids join to form a peptide bond (using
    ATP);
59
Q

Describe the role of a ribosome in the production of a polypeptide. Do not include transcription in your answer (3 marks)

A
  1. mRNA binds to ribosome;
  2. Idea of two codons/binding sites;
  3. (Allows) tRNA with anticodons to bind/associate;
  4. (Catalyses) formation of peptide bond between
    amino acids (held by tRNA molecules);
  5. Moves along (mRNA to the next
    codon)/translocation described;
60
Q

Explain the importance of amino acids to an organism

A
  • Amino acids are the monomers of proteins, whiich are essential for the structure and function of cells
  • Amino acids are involved in enzyme production, facilitating metabolic reactions
  • Some amino acids are used to synthesise important molecules like neurotransmitters and hormones

AQA A level Biology (41 decks)

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