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MTM > Proteins And Their Functions > Flashcards

Proteins And Their Functions Flashcards

1
Q

Stop codons ?

A

UAA
UGA
UAG

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2
Q

Start codon?

A

AUG
Codes for aa methionine

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3
Q

What structure requires the lowest energy

A

Tertiary

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4
Q

Homomer quaternary structure

A

Made from same polypeptide chain

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5
Q

Heteromer quaternary structure

A

Different polypeptide chains

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6
Q

Technologies used to look at protein structure in fine detail

A
  • X-ray crystallography
  • Nuclear magnetic resonance
  • Cryo-EM
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7
Q

Are proteins rigid structures?

A

No. Conformation is dynamic.
Induced fit hypothesis

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8
Q

Regulation of proteins (4 steps)

A
  1. Synthesis
  2. Localisation
  3. Modification
  4. Degradation
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9
Q

When may synthesis of proteins occur? Examples

A
  • immune response
  • differentiation
  • in response to signalling
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10
Q

What directs a protein to a desired organelle

A

Sorting signal

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11
Q

3 methods of protein transport

A

Nuclear pores
Across membranes
Transport by vesicles - RER to Golgi appa to final organelle

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12
Q

Secretory pathway?

A

Proteins transported between compartments via transport vesicles

Specialised cells have secretory vesicles which store hormones and enzymes for future use

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13
Q

Types of secretion (2)

A

o Constitutive secretion:
unregulated
secretion occurs continuously no external signals required
o Regulated secretion:
requires extracellular signal

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14
Q

Difference between secretory and transport vesicles

A

Secretory contain materials that are to be excreted from the cell

Transport move molecules within the cell

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15
Q

Protein modification?

A

• Most proteins are post translationally modified in the endoplasmic reticulum (rER)
• Includes disulphide bonds and glycosylation (i.e. sugars added)
• Further modified in the Golgi apparatus

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16
Q

Regulation of proteins?

A
  • Phosphorylation. Phosphate attached covalently to aa side chains.

Can inhibit or activate protein
Induces conformational change

17
Q

What protein catalyses phosphorylation

A

Protein kinase

18
Q

Protein that catalyses dephosphorylation

A

Protein phosphatase

19
Q

What is the unfolded protein response?

A

Homeostatic response
Excessive accumulation of misfolded proteins triggers response
Expands ER enabling proper folding
If ER cannot cope then translation inhibited and apoptosis

20
Q

Example of UPR?

A

DIABETES
Insulin resistance. More insulin produced to compensate and ER reaches max capacity

21
Q

Cytoplasmic signalling

A

Adapter protein binds to phosphorylated receptor
And Ras G protein then binds to adaptor protein.

22
Q

Growth factor signalling

A

Tyrosine kinase receptor becomes activated by GF
Leads to phosphorylation an d dimerisation of the receptor

23
Q

Degradation of proteins ?

A

Misfolded/damaged proteins are transported to lysosomes & endosomes for degradation

24
Q

Three stop codons

A

UAG
UAA
UGA

25
Q

What does every protein sequence start with

A

Met amino acid

26
Q

What is a sorting signal

A

A signal which causes a newly manufactured protein from the RER to move to the correct site in a cell via transporters

27
Q

What makes proteins so diverse

A

Variation in side chains of the proteins

28
Q

What is the synthesis of proteins

A

Ribosomes are responsible for the synthesis of proteins. Proteins destined for intracellular use are produced in free ribosomes, whereas proteins for extracellular export are produced in the rER. These processes are regulated.

29
Q

What is protein localisation

A

It is important that proteins get to where they are needed. Proteins have a sorting signal which allows them to be moved in transport vesicles to their correct destination. They can be taken into organelles via protein transporters

30
Q

What is protein modification

A

Proteins are modified in the ER and golgi apparatus. Modifications involve glycolysation (adding stability) and phosphorylation (conformational change) among others. Kinases are involved in phosphorylation. This is a regulated process.

31
Q

What is protein degradation

A

Proteins are folded in the ER. The ER is responsible for the homeostatic control of the balance between folding and endoplasmic reticulum associated degradation (ERAD) . If too many unfolded proteins are produced, it produces a signal which inhibits further production of that protein. This is a regulated process.

MTM (12 decks)

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