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Molecular and cell biology > Protein biochemistry > Flashcards

Protein biochemistry Flashcards

Semester 1 year 1

1
Q

What does the wide range of structural properties of proteins allow for?

A

A wide range of functions - versatile

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2
Q

What are hormones?

A

Small proteins that travel in blood + bind to specific receptors elsewhere in the body

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3
Q

What are antibodies?

A

Recognise foreign material, allowing the immune system to respond

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4
Q

What are DNA binding proteins?

A

Bind to specific DNA sequences + affect gene expression

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5
Q

What is porin?

A

-sits in outer membrane of bacteria
-allows diffusion of certain molecules into cell

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6
Q

What is ferritin?

A

Stores, transports + releases iron

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7
Q

What are enzymes?

A

-proteins that accelerate rate of chemical reactions
-don’t change final equilibrium
-reduce energy needed to carry out reaction

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8
Q

What are the 4 levels of protein structure?

A

-primary
-secondary
-tertiary
-quaternary

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9
Q

What is different in amino acid side chains?

A

-shape + size
-electric charge
-polarity

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10
Q

Describe the primary structure of a protein

A

-order of amino acids in the polypeptide
-protein sequence determined by gene sequence

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11
Q

What is a residue?

A

An amino acid in a polypeptide chain

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12
Q

How are amino acids joined in the primary structure?

A

-lose a water molecule to form peptide bond
-amino terminus + carboxyl terminus of 2 amino acids join
-no rotation around peptide bond

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13
Q

What are unfolded and folded polypeptide chains called?

A

-unfolded = denatured
-folded = native

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14
Q

Describe the stability of unfolded and folded chains

A

-unfolded = thermodynamically unstable
-folded = thermodynamically stable

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15
Q

How do chains go from unfolded to folded?

A

-some spontaneously, determined by primary sequence
-others require secondary protein - chaperone

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16
Q

Describe the secondary structure of an amino acid

A

-regular, repeating structures
-many weak hydrogen bonds between amino acids close together
-can fold into alpha helix or beta sheet

17
Q

What stabilises the secondary structure of a protein?

A

Hydrogen bonds

18
Q

Describe the alpha helix structure

A

-H bonds between amino + carboxyl terminals 4 residues apart
-side chains on outside of helix

19
Q

Describe the beta sheet structure

A

H bonds between amino + carboxyl groups on different strands

20
Q

What 2 forms can the beta sheet be in?

A

-parallel - adjacent strands run in same direction
-anti parallel - opposite directions

21
Q

Describe the tertiary structure of a protein

A

-tightly packed, thermodynamically stable 3D structure
-determined by non-covalent interactions between side chains

22
Q

How do amino acids with hydrophilic side chains interact with water?

A

Can form hydrogen bonds + ionic interactions

23
Q

How do amino acids with hydrophobic side chains interact with water?

A

-non polar
-can’t form hydrogen bonds + ionic interactions

24
Q

Which amino acids tend to be on the inside of the tertiary structure and why?

A

-hydrophobic amino acids
-polar residues on outside to interact with water
-non polar residues on inside, away from aqueous environment

25
Q

How are disulfide bridges formed?

A

-interactions between sulphur atoms in cysteine amino acids
-oxidation occurs between 2 sulphurs
-forms crosslinks between different parts of primary sequence

26
Q

What is the purpose of disulphide bridges?

A

Strengthen tertiary structure

27
Q

What can proteins fold into?

A

Several domains - regions that fold tightly

28
Q

What separates domains?

A

Flexible regions that are less tightly folded

29
Q

What do domains do?

A

Often carry out a specific part of a proteins function

30
Q

Describe the quaternary structure of a protein

A

-complex structure composed of 2 or more subunits
-subunits can be identical or different

31
Q

What are post-translational modifications?

A

Removal of specific parts of the sequence after sticking the amino acids together

32
Q

What does adding molecules to proteins do and give examples?

A

-modulates protein function
-methylation
-glycosylation
-ubiquitination

33
Q

What is phosphorylation?

A

-reversible addition of phosphate by kinases
-phosphorylation of amino acids in/around active site can change properties + alter substrate binding

34
Q

How are proteins carried to where they’re needed?

A

-many contain short signal or localisation sequence showing where to go
-some completely synthesised in cytoplasm then delivered to location

35
Q

How are proteins targeted to the cell membrane?

A

-via the secretory pathway
-uses ribosomes associated with ER

36
Q

What posttranslational modifications can occur to anchor proteins to the membrane?

A

Additional hydrophobic groups added to sequence

Molecular and cell biology (29 decks)

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