Proteins Flashcards

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1
Q

What are the monomers from which proteins are made called?

A
  • Amino acids.
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2
Q

How many types of amino acids are there in all organisms?

A
  • 20 amino acids
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3
Q

How is peptide bond formed?

A
  • Peptide bond formed by condensation reaction between two amino acids.
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4
Q

What are dipeptides formed by?

A
  • Dipeptides formed by condensation reaction of two amino acids.
  • Peptide bond forms between OH of carboxyl group (on amino acid) and H of the amine group.
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5
Q

What are polypeptides formed by?

A
  • Polypeptides are formed by the condensation of many amino acids.
  • Peptide bond forms between OH (of carboxyl group) and H of the amine group.
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6
Q

What is the only part of the amino acid monomer that changes depending on the type of amino acid?

A
  • The R (variable) group.
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7
Q

What are the components of an amino acid monomer, ie. the groups in an amino acid monomer?

A
  • C and H atom in centre
  • Amine group (NH₂)
  • Carboxyl group (COOH)
  • R- group (variable) side chain.
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8
Q

What type of protein contains one or more polypeptides?

A
  • Functional protein may contain one or more polypeptides.
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9
Q

What is a hydrogen bond?

A
  • Chemical bond often between slight negative oxygen atoms and slight positive hydrogen atoms (in water.) (oxygen = slightly negative as it has more electrons than hydrogen.)

() - extra info for clarification

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10
Q

What are the 4 levels of structure in proteins?

A

1.) Primary
2.) Secondary
3.) Tertiary
4.) Quaternary

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11
Q

Definition of primary structure of protein.

A
  • The sequence of amino acids in a polypeptide chain.
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12
Q

Definition of secondary structure of a protein.

A
  • Sequence of amino acids (ie. primary structure) are bent into alpha helix shapes or folded into beta pleated sheets (this is known as secondary structure.)
  • Hydrogen bonds hold the secondary structure of protein.
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13
Q

Where are hydrogen bonds formed in the secondary structure of a protein?

A
  • Hydrogen bonds form between the C=O groups (part of peptide bond of 1 amino acid) and the NH group (in the peptide bond of another amino acid.)
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14
Q

Definition of** tertiary structure** of proteins.

A
  • The further folding of the secondary structure (forms the tertiary structure.)
  • Folding forms a unique 3D shape.
  • Tertiary structure held in place by ionic, hydrogen and disulphide bonds/ bridges.
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15
Q

What 3 types of bonds hold the tertiary structure of proteins in place?

A
  • Ionic
  • Hydrogen
  • Disulphide
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16
Q

Where are ionic and disulphide bonds formed in the tertiary structure?

A
  • Ionic/ disulphide bonds = formed between the R groups of different amino acids.
17
Q

True or False

Disulphide bonds/ bridges are always present in the tertiary structure of a protein.

A
  • False.
  • Disulphide bridges only sometimes occur (when there is a sulphur in the R groups of the amino acids.)
18
Q

Definition of **quarternary structure ** of protein.

A
  • More than one polypeptide chain.
19
Q

What happens to the tertiary structure of a protein when it is **denatured? **

A
  • The bonds which hold the tertiary structure in place break (ionic/ hydrogen bonds break) and therefore the unique 3D shape is lost/ collapses back into the secondary structure.
20
Q

Two conditions that would denature a protein:

A

1.) Too high temperature ( too much kinetic energy - of amino acids - can cause bonds to break.)
2.) Too high/ low a pH (ie. too many H+ or OH- : will lead to imbalance in charge which can break the bonds.)

21
Q

What is the importance of the primary structure of a protein?

A
  • Primary structure: sequence of amino acids.
  • If sequence of amino acids changes (ie. from a mutation), it will cause the ionic/ hydrogen/ disulphide bonds to form in different locations (in the tertiary structure.)
  • This will result in a different 3D shape.
22
Q

What is the issue with the shape of a 3D protein (ie. enzymes/ carrier proteins) changing ?

A
  • Enzymes: will have different shapes active site (will be non-functioning.)
  • Carrier proteins: will have different shapes binding site (molecules = no longer complementary/ cannot be transported across membranes.)
23
Q

What is the test for proteins?

A
  • Add Biuret (solution) to sample.
  • A positive result = Biuret goes from blue to purple.
24
Q

Atoms involved in peptide bond?

A

– COHN

25
Q

How does the charge of amino acids affect the protein?

A
  • Change in charge of an amino acid may change the tertiary structure of the protein.
  • Ie. Ionic bond only between positively-charged/ negatively-charged amino acids. Mutation (change in amino acid to another amino acid) may change the charge so the ionic bond will break.