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AQA A level Biology > 1.4.1 Proteins > Flashcards

1.4.1 Proteins Flashcards

(60 cards)

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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
What is a tertiary structure protein in any protein
The further folding of the secondary structure to form a unique 3D shape
26
What are the 3 bonds that hold tertiary structure proteins in place
- Ionic bonds - Hydrogen bonds - Disulphide bridges
27
Are disulphide bridges in a tertiary structure protein strong or weak
Fairly strong, so not broken easily
28
What must be present to form disulphide bridges, and where in the amino acids
Sulfur must be in the R group
29
What is a quaternary structure protein in any protein
A protein made up of more than 1 polypeptide chain
30
Name an example of a quaternary structure protein
Haemoglobin
31
Name 2 examples of fibrous proteins
- Collagen - Keratin
32
What is the function of fibrous proteins
Structural functions
33
In a fibrous protein, is the primary structure polypeptide chain branched or unbranched
Unbranched
34
In a fibrous protein, like collogen, how many polypeptide chains are in the quaternary structure
3
35
Explain why the quaternary structure of collogen makes it a suitable molecule for a tendon
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
Suggest how the cross-linkages between the amino acids of polypeptide chains increase the strength and stability of a collagen fibre
They prevent the individual polypeptide chains from sliding past one another and so they gain strength because they act as a single unit
37
Explain why this arrangement of collagen molecules is necessary for the efficient functioning of a tendon
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
What are the 5 main roles of globular proteins
- Enzymes - Hormones - Receptors - Pigments - Antibodies
39
Name an example of a globular protein
Haemoglobin
40
What happens to a protein when it gets denatured
It changes shape because the bonds break
41
What type of bond breaks in high temperature in a protein
Hydrogen bonds
42
What type of bonds break in extreme pH in a protein
Ionic bonds
43
What impact does denaturing proteins have on fibrous proteins
They lose structural strength
44
What impact does denaturing proteins have on globular proteins
Become inactive and/or insoluble
45
True or false: Collagen and keratin are globular proteins
False, they are fibrous proteins
46
True or false: Peptide bonds and hydrogen bonds are the only bonds that maintain a protein's shape
False, there are also ionic and disulphide bridges
47
True or false: Polypeptides are made by hydrolysis reactions between amino acids
False, its condensation reactions
48
True or false: Primary structure is the number, type and sequence of amino acids in a polypeptide chains
True
49
True or false: Changing a single amino acid in a polypeptide may stop the protein from working properly
True
50
True or false: All proteins have quaternary structure
False, they can be secondary and tertiary too
51
True or false: The function of globular proteins rely on their 3D shape
True
52
True or false: Denaturing a fibrous protein makes it insoluble
False, it makes it lose it structural stength
53
True or false: Enzymes, hormones, pigments and antibodies are all examples of proteins
True
54
True of false: Alpha helices and beta-pleated sheets can both occur within a single polypeptide chain
True
55
Describe the primary structure of all proteins (2 marks)
- Sequence of amino acids - Joined by peptide bonds
56
Describe how the structure of a protein depends on the amino acids it contains. (5 marks)
- 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
Define genome and proteome (2 marks)
Genome: complete set of gens in a cell Proteome: Range of proteins coded for by the cell's genome
58
Describe how one amino acid is added to a polypeptide that is being formed at a ribosome during translation (3 marks)
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
Describe the role of a ribosome in the production of a polypeptide. Do not include transcription in your answer (3 marks)
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
Explain the importance of amino acids to an organism
- 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 (43 decks)

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