Chapter 5.3-5.4 - Proteins

Question 1

7 functions of protein

Answer 1

1. Enzymes
2. Structure
3. Movement
4. Signalling
5. Transport
6. Regulation
7. Defence

Question 2

Enzymatic proteins regulate metabolism by acting as:

Answer 2

Catalysts

Question 3

Catalyst

Answer 3

Chemical agents that selectively speed up chemical reactions without being consumed by the reaction

Question 4

Building blocks of proteins are:

Answer 4

Monomers: amino acids
Polymers: peptides, polypeptides

Question 5

What shape do proteins take

Answer 5

A unique 3D structure

Question 6

Proteins are constructed from:

Answer 6

The same set of 20 amino acids, linked in unbranched polymers

Question 7

Peptide Bond

Answer 7

The covalent bond between amino acids formed by a dehydration reaction (occurs on the ribosome)

Question 8

Polypeptide

Answer 8

A polymer of amino acids

Question 9

Protein

Answer 9

A biologically functional molecule made up of one or more polypeptides, each coiled and folded into a specific 3D structure important for its function

Question 10

Amino acids differ in their:

Answer 10

R Groups! These determine properties.

Some R groups are hydrophobic (nonpolar)
Some R groups are hydrophilic (polar)
Some R groups carry charge (+ or -) at cellular pH

Question 11

Amino Acid

Answer 11

An organic molecule with both an amino group and a carboxyl Group. They are the building blocks of protein.

*see diagram in notes

Question 12

Amino Acid Diagrams and Groups

Answer 12

SEE TEXTBOOK P. 85

Question 13

Protein functions result from:

Answer 13

Exquisite Molecular Order

Question 14

Four Levels of Superimposed Structure

Answer 14

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

Question 15

Primary Structure (3)

Answer 15

1. Linear chain of amino acids
2. Unravelled depiction of amino acids
3. Ex: transthyretin in textbook!!!!

Question 16

Secondary Structure (4)

Answer 16

1. Hydrogen bonds between atoms of backbone
2. Within the backbone, the oxygen atoms have a partial negative charge, while the hydrogen atoms attached to the nitrogen’s have a partial positive charge.
3. Can be depicted in ribbon models of protein
4. Toxic proteins may undergo helix to sheet transitions

Question 17

Tertiary Structure (4)

Answer 17

1. Polypeptides fold into a specific shape determined by primary structure
2. Interactions among R Groups of amino acids stabilizes the tertiary structure of a protein
3. Covalent Bonds called disulphide bridges may further reinforce the shape of a protein
4. SEE TEXTBOOK

Question 18

Quaternary Structure (4)

Answer 18

1. Two or more polypeptides (subunits) May interact (aggregate)
2. Globular Protein; e.g, hemoglobin (textbook p. 89)
3. Non-covalent interactions between polypeptides
4. Can often be predicted from primary structure

Question 19

Methods to determine protein structure (2)

Answer 19

1. X-Ray Crystallography

2. Nuclear Magnetic Resonance Spectroscopy

Question 20

Protein Structure Depends on (3)

Answer 20

1. Temperature
2. pH
3. Salt Concentration

Question 21

What could happen if temp, pH or salt concentration are altered?

Answer 21

Denaturation

Question 22

Denaturation

Answer 22

When the weak chemical bonds and interactions within a protein are destroyed, causing the protein to unravel and lose its shape

Question 23

Renaturation

Answer 23

Reversal of denaturation

Question 24

Chaperonins

Answer 24

Protein molecules that assist the proper folding of other proteins

Question 25

Importance of Protein Structure (3)

Answer 25

1. Each protein folds into a unique shape (tertiary structure) that determines its specific function 2. The shape of a protein is determined by its primary structure 3. The side chains of amino acids determine the interactions that occur within and between proteins

Question 26

Neurodegenerative diseases attributed to protein misfolding: (4)

Answer 26

1. Alzheimer’s 2. Huntington’s disease 3. Parkinson’s 4. Prion

Question 27

Why can misfolded proteins cause disease?

Answer 27

Due to the production and accumulation of misfolding proteins that aggregate and damaged nerves

Question 28

CTE or Chronic Traumatic Encephalopathy:

Answer 28

A progressive degenerative brain disease in individuals with a history of repetitive brain injury (common in contact sports). Associated with memory loss, aggression, impaired judgement etc.

Question 29

Diagnosis of CTE:

Answer 29

Hallmark is accumulation of an abnormal variant of tau protein

Question 30

Normal Function of Tau Protein (2)

Answer 30

1. Binds to microtubules (a component of cytoskeleton) in axons of neurons 2. Stabilizes and promotes polymerization of microtubules in axons

Question 31

Normal Structure of Tau Protein (3)

Answer 31

1. Globular, naturally disordered, soluble protein 2. Low content of secondary structure 3. Folds into stable structure when bound to microtubules via repeat regions in C terminus

Question 32

Protein Phosphorylation (2)

Answer 32

1. Phosphorylated amino acids are usually theronine, serine and tyrosine. 2. Site of phosphorylation is influenced by surrounding amino acids *diagrams in notes*

Question 33

Hyperphosphorylated Tau

Answer 33

Adopts a beta sheet conformational and changes secondary and tertiary structure of ptau

Question 34

Ptau

Answer 34

Improperly folded or damaged Tau. See drawings in notes!

Question 35

Severity of CTE in relation to PTau

Answer 35

Severity is determined by measuring ptau accumulation in brain tissue sections. CTE is classified as either mild or severe based on amount of ptau deposition

Question 36

Oligomerization of Ptau

Answer 36

1. Misfolding of ptau results in formation of aggregates (oligomers) that are toxic to cell.

Question 37

Ptau Fibrils (3)

Answer 37

1. Beta sheets are stacked in tau oligomers 2. Oligomers polymerize to form fibrils 3. Fibrils have a high tensile strength *see drawings in notes!

Question 38

Head injury does what to the brain

Answer 38

It causes it to oscillate in skull