3.1.4.1 General Properties of Proteins Flashcards

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1
Q

what are proteins also referred to as?

A

polypeptides

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2
Q

what are polypeptides made from (ie. monomers?)

A

amino acids

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3
Q

how many amino acids are there and how many of these are naturally occurring?

A

100 identified, 20 of which are naturally occuring

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4
Q

describe the general structure of an amino acid and draw it

A

(check diagram against notes)
amine group (NH₂)
carboxyl group (COOH)
central carbon (C)
hydrogen atom (H)
R group (R)

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5
Q

what can 2 amino acids bond together to form and which mechanism does this involve?

A

two amino acids can bond together to form a dipeptide, and this happens through a condensation reaction, (molecule of H₂O removed and a bond is made.)

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6
Q

what sort of bond is formed when a dipeptide is made and where is it?

A

peptide bond forms between the C-N

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7
Q

if condensation reactions are repeated after a dipeptide then what is formed?

A

polypeptide

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8
Q

place in order of decreasing strength: ionic, hydrogen, covalent bonds

A

STRONGEST
covalent
ionic
hydrogen
WEAKEST

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9
Q

give 3 examples of tertiary proteins

A

enzymes, antibodies and hormones

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10
Q

give 4 examples of quaternary proteins and 2 of their prosthetic groups (PG)

A

chlorophyll (PG = Mg)
haemoglobin (PG = Fe)
collagen
antibodies

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11
Q

what is an R group?

A

an R group is a carbon containing side chain
it is what differs between amino acids

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12
Q

state the 5 functions of polypeptides within an organism and give examples

A
  1. STRUCTURE eg. collagen, keratin, actin
  2. ENZYMES eg. carbohydrase, protease
  3. TRANSPORT eg. haemoglobin
  4. HORMONES eg. oestrogen, testosterone
  5. ANTIBODIES
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13
Q

name and describe the chemical test for proteins

A

BIURET TEST:
- place sample of solution into test tube
- add equal volume of sodium hydroxide
- add few drops of copper (II) sulphate
- mix gently

+ve result = purple/mauve
-ve result = remains blue

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14
Q

describe the differences between globular and fibrous proteins

A

fibrous: elongated shape, insoluble, structural roles eg. collagen, keratin, myosin, actin

globular: spherical shape, soluble in water, metabolic roles eg. haemoglobin, enzymes, hormones

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15
Q

describe the primary structure of a protein (3 points)

A
  • a singular polypeptide chain
  • only contains peptide bonds
  • the order and number of amino acids in the chain determines the structure and function of a protein
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16
Q

describe the secondary structure of a protein (3 points)

A
  • hydrogen bonding between H⁺ and O⁻
  • causes the polypeptide chain to fold and twist into a 3D structure
  • results in the formation of an alpha helix or a beat pleated sheet
17
Q

where do the H⁺ and O⁻ originate from when forming a secondary protein?

A

hydrogen in -NH is delta positive and oxygen in C=O is delta negative

18
Q

give 2 examples of secondary structure proteins

A

keratin and collagen

19
Q

describe the structure of a tertiary structure protein (3 points)

A
  • further twisting and folding of a secondary structure
  • results in a 3D SPECIFIC structure
  • the number and location of ionic, covalent and hydrogen bonds determine and maintain this structure of the tertiary protein
20
Q

describe the strength of hydrogen bonds and what they can be broken by?

A

numerous and weak so easily broken by temperature changes

21
Q

describe the strength of ionic bonds and what they can be broken by?

A

formed between the carboxyl and amine groups that are not involved in the peptide bond. easily broken by pH and are weaker than covalent but stronger than hydrogen

22
Q

describe the strength of covalent bonds and what they can be broken by? given an example

A

a sulphide bridge is a very strong covalent bond caused by interactions between the R group of the amino acid and cysteine. not easily broken

23
Q

describe the structure of a quaternary protein (2 points)

A
  • a protein consisting of more than one polypeptide chain linked together
  • possible prosthetic group