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DS1101 - S1 Y1 > Protein - Week 2 > Flashcards

Protein - Week 2 Flashcards

1
Q

What is an Amino Acid

A

A compound that contains both an Amino group and a carboxyl group. Where there are different side chains attached to the alpha carbon which gives the molecule its characteristics

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2
Q

What is Chirality

A

A molecule which contains a single bonded carbon bonded to 4 different groups (functional groups) is Chiral.
Such molecules are not superimposable on its mirror molecule

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3
Q

What is L Form

A

Where the amino group (-NH2) lies on the left side of a Fischer projection

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4
Q

What is D form

A

Where the amino group -NH2 lies on the right side of a Fischer projection

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5
Q

What is the zwitterion

A

AA with a neutral charge

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6
Q

What impacts the net charge of an AA

A

The pH of the solution
High pH makes the AA have a net negative charge as the increased -OH removed a H+

Low pH makes the AA have a net positive charge as the increase H30+ adds a H+ to NH2 to make it NH3+

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7
Q

What is the Isoelectric point and what is use for

A

The point along the pH scale at which a molecule exists with a neutral charge.

The more neutrally charged the AA is the less soluble it is and the more likely it is to precipitate out of solution

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8
Q

If a protein has a pI of 7 what is its charge at a low pH

A

Positive

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9
Q

If a protein has a pI of 7 what is its charge at a high pH

A

negative

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10
Q

How does pH change the charge of a protein

A

Causes the protein to under go hydrolysis where either the amino group will deprotonate or the carboxyl group will protonate changing the net charge of the protein. (NOTE: the side chain will impact this) (NOTE: only acidic and basic functional groups will be affected)

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11
Q

What is a peptide

A

A short chain of AA held together by peptide bonds (2-10 AA) - di peptide, tri peptide
By convention peptides are written from left beginning with the free -NH3+ (N-terminal) to the right ending with the free -COO- (C-terminal)

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12
Q

What is a Protein

A

A chain of many AA (more than 30)

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13
Q

Example of non polar AA

A

Alanine* (methane side chain)
Glycine (hydrogen)
Valine (methyl-ethane)

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14
Q

Example of polar AA

A

Serine* (methanol)
Cysteine* (CH2SH)
Threonine

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15
Q

Example of acidic AA

A

Aspartate* (ethanoic acid)
Glutamate (propanoic acid)

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16
Q

Example of basic AA

A

Lysine* (butamine)
Arginine
Histidine

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17
Q

What are the functions of Proteins (8)

A
  • Structure
  • Catalysts
  • Movement
  • Transport
  • Signaling
  • Protection
  • Storage
  • Regulation
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18
Q

Example of Protein Function: Structure

A

Collagen - supports skin, bone, teeth
Keratin - component of hair and nail

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19
Q

Example of Protein Function: Catalyst

A

Enzymes (Pyruvate kinase) - increases rate of organic reactions

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20
Q

Example of Protein Function: Movement

A

Myosin an Actin - protein in muscles

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21
Q

Example of Protein Function: Transport

A

Hemoglobin - transports oxygen from the lungs to cells

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22
Q

Example of Protein Function: Signaling

A

Insulin - regulates the production of glucose and lipids

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23
Q

Example of Protein Function: Protection

A

Fibrinogen - split apart into the active protein fibrin and then join to create an insoluble mesh which stabilises blood clots

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24
Q

Example of Protein Function: Storage

A
  • Casein(kay-seen) is a protein in milk which stores nutrients for newborns
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25
Q

Example of Protein Function: Regulation

A

Transcription factors - involves proteins which control the expression of genes into RNA

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26
Q

What are the 3 classes of Proteins

A
  • Fibrous Proteins
  • Globular proteins
  • Membrane proteins
27
Q

What are Fibrous Proteins

A
  • Simple chain primary structures
  • mostly simple beta sheet or triple helix secondary structures
    E.g. Collagen, Silk Fibroin, A-keratin
28
Q

What are Globular proteins

A
  • Complex primary and tertiary structures
  • Completes complex roles 5-8
    e.g. Hemoglobin
29
Q

What are the types of membrane proteins

A
  • Integral membrane protein (intrinsic)
  • Peripheral Protein
30
Q

What are integral membrane protein

A
  • Proteins bounded to the into the cell membrane (reaches both sides)
  • functions as ion channels which transport small molecules across the membrane
  • Also functions as receptors where other noncellular molecules can attatch to
    eg. Lactose permease which transports sugar across the membrane???
31
Q

What are Peripheral proteins

A
  • Proteins which is only attatched to the surface of the cell membrane
  • functions to carry electrons
    e.g. Cytochrome C - moves electrons in the final
32
Q

What is the Primary structure of Proteins

A

initial sequence of amino acids in a polypeptide chain linked together by peptide bonds

33
Q

What is the secondary structure of proteins

A

The connection/folding of the primary structure to create the backbone structure of a protein.
Created from the hydrogen bonds between the amide hydrogens and the carbonyl oxygens of the peptide bonds

34
Q

Main types of secondary structures

A

alpha-helix
beta-pleated sheet

35
Q

Example of a alpha helix

A

Alpha-keratin - fibrous protein

36
Q

Example of a beta-pleated sheet

A

silk fibroin - antiparallel b-sheet

37
Q

What are the tertiary structure of proteins

A

the 3D shape of the entire peptide chain where the regions of the secondary structure further fold on themselves.
Created by the bonds/ forces between the side chains

38
Q

What are the bonds/forces which create tertiary structures of proteins

A
  • Covalent bonds (disulphide bonds between 2 sulphides - cysteine (-CH2SH))
  • Hydrogen bonding - H bonds - HFONs
  • Salt bridges/ionic bonds - forces between oppositely charged side chain group (-NH3+ and -COO-)
  • Hydrophobic interactions/ Dispersion forces - temporary dipole attractions between hydrophobic/ nonpolar side chains
39
Q

Types of Tertiary Structures

A
  • beta saddle
  • beta Barrel
40
Q

What are quaternary structures of Proteins

A

Some proteins are made up of multiple polypeptide chains also known as subunits, where when these subunits come together they give the protein its quaternary structure

e.g. Hemoglobin

41
Q

What is the primary structure of collagen

A

Gly - X - Pro
Gly - Glycine
X = Any AA
Pro = Proline

42
Q

What is collagen

A
  • Fibrous Protein
  • Most abundant protein in vertebrates (bones, connective tissues)
  • provides structure and stability
43
Q

What is the quaternary structure of collagen

A

Tertiary structure - triple helix

44
Q

What is silk fibroin

A
  • fibrous protein
  • insoluble protein secreted by silkworm
45
Q

What is the secondary structure of silk fibroin

A
  • antiparallel beta-sheet
  • using hydrogen bonds to hold the peptide chains together
46
Q

What is alpha keratin

A
  • fibrous fiber
  • found in hair, nails and epithelial cells (gives skin colour)
47
Q

Types of protein folding (2)

A
  • spontaneous folding
  • assisted folding
48
Q

What is spontaneous folding

A
  • proteins self assembling slowly using dispersion forces as they come out of the ribosome
  • then interactions between side chains will create the secondary and tertiary structures
49
Q

What is assisted folding

A
  • uses chaperones (protein complex) which takes incorrectly folded proteins and assembles them into the right structure
50
Q

What is protein denaturation

A

The process of destroying the structure of a protein by either chemical or physical means

51
Q

Examples of protein denaturation using cellular organelles

A
  • In Lysosomes (contains acid enzymes which breaks down protein)
  • In Proteasomes (has a molecular channel which feeds protein to its enzymes)
52
Q

How can protein be broken down into

A
  • amino acids which can be re used again
  • or AA further broken down through protein catabolism to create energy
53
Q

Examples of protein denaturation using denaturing agents (7)

A
  • Heat
  • 6M aq Urea
  • Surface-active agents (sodium dodecylsulfate)
  • Reducing agents
  • Heavy metal ions
  • Alcohol
  • Extreme pH
54
Q

How does heat denature a protein

A

Increases vibrational motion inside the molecule which breaks the hydrogen bonding which holds the peptide chains together

55
Q

How does 6M aq Urea denature a protein

A

C=O and NH2 form hydrogen bonds with the protein in turn weakening the strength of the hydrogen bonds between the AA chains

56
Q

Impact of alcohol to a protein

A

The -OH hydroxyl group of the alcohol will disrupt and weaken the hydrogen bonds between the amino acid chain. Denaturing the protein

57
Q

Impact of Hg, Pb (heavy metal ions) on proteins

A

Forms insoluble salts with Sulphur in turn disrupting the desulphated bridges - denaturing proteins

58
Q

Give an example of a widely used therapeutic peptide

A

Oxytocin - a peptide hormone which reduces blood pressure and cotisol levels

59
Q

How does the structure of hemoglobin relate to its function

A

Hemoglobin contains 4 globin subunits that provides its overall 3D structure. There is a heme group in each subunity and as a result there are 4 iron atoms in a molecule of hemoglobin, this allows it to have 4 binding sites for oxygen which means it can bind 4 molecules of oxygen at once.

60
Q

Example to essential amino acids

A

Phenylalanine(fee -nile - a - luh - neen), lysine

61
Q

What is the function of proteins such as lysozyme and lactoperoxidase in toothpaste

A

Lysozme breaks down bacteria cell walls in toothpaste, fighting against oral bacteria. WHile lactoperoxidase generates antimicrobial compounds in saliva, aiding in the prevention of bacteria growth in the mouth.

62
Q

Example of a peripheral protein

A

Cytochrome C - transports electrons

63
Q

What is the average life span of a protein

A

3 days

DS1101 - S1 Y1 (63 decks)

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