Proteins (biochemistry) Flashcards

1
Q

What elements do proteins contain?

A

Carbon, Hydrogen , Oxygen, Nitrogen (and Sulfur)

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2
Q

What are proteins polymers of?

A

amino acids

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3
Q

How many different types of amino acids are there?

A

20

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4
Q

What is an R group?

A

the variable group in an amino acid

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5
Q

What do all amino acids contain?

A

an amine group, a carboxyl group, an variable group, alpha Carbon + hydrogen

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6
Q

What is a zwitter ion?

A

when H from COOH has moved to the lone pair on the N in the NH2 group

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7
Q

What is it called when 2 amino acids are linked?

A

Dipeptide

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8
Q

What reaction enables formation of a dipeptide?

A

condensation reaction

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9
Q

What bond is formed between 2 amino acids?

A

peptide bond

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10
Q

How is a peptide bond broken?

A

Hydrolysis

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11
Q

Where does the peptide bond form during condensation reaction of 2 amino acids?

A

the peptide bond forms between the C atom of the carboxyl group of one amino acid and the Nitrogen Atom of the amine group of the adjacent amino acid

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12
Q

What is a polypeptide?

A

consists of a chain of amino acids linked by peptide bonds

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13
Q

What do the ends of a polypeptide look like?

A

at one end there is an amine group at the other end there is a carboxyl group

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14
Q

What are the 4 structures that a protein can show?

A

primary
secondary
tertiary
quaternary

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15
Q

What is primary structure in a protein?

A

the type, number, and sequence of amino acids in a polypeptide linked by peptide bonds only, forming a linear chain

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16
Q

What is the most common secondary structure in a protein?

A

most common is alpha helix formed by hydrogen bonding

17
Q

Where do hydrogen bonds from in alpha helix structure?

A

between oxygen atoms of carboxyl groups and hydrogen atoms of amine groups

18
Q

what is another secondary structure of proteins?

A

a beta-pleated sheet

19
Q

What is tertiary structure of a protein?

A

the folding of the alpha helix as shown by globular proteins, to form very specific 3-d shapes. (one polypeptide)

20
Q

What other bonds forms in a tertiary structure?

A

disulfide bridges, ionic bonds, hydrogen bonds (secondary), hydrophobic interactions

21
Q

What is quaternary structure?

A

Where 2 or more polypeptide chains in tertiary form combine to form complexes

22
Q

What is an example of a protein with quaternary structure?

A

Haemoglobin

23
Q

What are the 2 groups of proteins?

A

globular and fibrous

24
Q

What is the function of a globular protein?

A

metabolism (soluble)

25
What is the function of a fibrous protein?
structural (insoluble)
26
What is the molecular shape of a globular protein?
Spherical in tertiary or quaternary structure
27
What is the molecular shape of a fibrous protein?
Chains in secondary structure
28
What are examples of globular proteins?
Enzymes (lysozome), insulin
29
What are examples of fibrous proteins?
keratin, collagen
30
What is the function of keratin?
strengthens hair, nails, scales, feathers etc.
31
What is the function of collagen?
strengthens bones, tendons, ligaments, skin
32
What is elastin?
elastic fibrous tissue that allows many tissues in the body to resume their shape after stretching or contracting
33
What does elastin do?
helps skin to return to its original position when it is stretched
34
What test is used for proteins?
Biuret test
35
What is a negative result for biuret test?
blue
36
What is a positive result for biuret test?
violet